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Editor Work2020 Vol. 28, No. 5
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2020, 28(5): 935-941.
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The freezing-induced moisture migration within saturated soft mucky clay with high moisture content in closed system is an important factor that affecting the frost heave rate. This pape aims to gain a better understanding of the effect of cooling temperature on moisture migration within coastal soft clayey soil. It carries out the unidirectional freezing tests of Shanghai Quaternary marine mucky clay in closed system. Different cooling temperatures of - 5 to - 20 ℃ are set. It measures the amounts of frost heave and the temperatures of samples along the direction of temperature gradient. From the variation of frost front with time,the critical temperature gradient,the water inflow flux and velocity are derived. The results show that the heights of frost front at different cooling temperatures are a function of time. It is expressed as X(t)=t(at+b)-1. A ratio value of the decrease of the temperature gradient in the frozen zone to the critical temperature gradient can be used to estimate the onset of moisture migration. The critical temperature gradient increases linearly with the decrease of cooling temperature. In the period of moisture migration,the water inflow velocity increases first and then decreases with time. Correspondingly,the water inflow flux-time curve gradually turns to linear from "S-shaped" as the cooling temperature decreases. The results of critical temperature gradient and cooling temperature,and the fitting formula of height of frost front on time,have great significance to predict the starting time of moisture migration during the unidirectional freezing process in closed system at a certain cooling temperature. This paper can promote the quantitative study of moisture migration within soft clayey soil with high moisture content under unidirectional freezing in closed system. It can be a valuable reference for the early warning of frost heaving during artificial ground freezing construction in coastal areas.
The freezing-induced moisture migration within saturated soft mucky clay with high moisture content in closed system is an important factor that affecting the frost heave rate. This pape aims to gain a better understanding of the effect of cooling temperature on moisture migration within coastal soft clayey soil. It carries out the unidirectional freezing tests of Shanghai Quaternary marine mucky clay in closed system. Different cooling temperatures of - 5 to - 20 ℃ are set. It measures the amounts of frost heave and the temperatures of samples along the direction of temperature gradient. From the variation of frost front with time,the critical temperature gradient,the water inflow flux and velocity are derived. The results show that the heights of frost front at different cooling temperatures are a function of time. It is expressed as X(t)=t(at+b)-1. A ratio value of the decrease of the temperature gradient in the frozen zone to the critical temperature gradient can be used to estimate the onset of moisture migration. The critical temperature gradient increases linearly with the decrease of cooling temperature. In the period of moisture migration,the water inflow velocity increases first and then decreases with time. Correspondingly,the water inflow flux-time curve gradually turns to linear from "S-shaped" as the cooling temperature decreases. The results of critical temperature gradient and cooling temperature,and the fitting formula of height of frost front on time,have great significance to predict the starting time of moisture migration during the unidirectional freezing process in closed system at a certain cooling temperature. This paper can promote the quantitative study of moisture migration within soft clayey soil with high moisture content under unidirectional freezing in closed system. It can be a valuable reference for the early warning of frost heaving during artificial ground freezing construction in coastal areas.
2020, 28(5): 942-950.
The Standard of Engineering Classification of Rock Masses(BQ system) is a classification method of multi-factors,multi-variables,and qualitative and quantitative combination. In this method,we select the rock saturation uniaxial compressive strength and rock integrity index to calculate the value of the rock mass basic quality [BQ]. The modification of rock mass is made considering the field conditions of engineering rock mass,which makes BQ classification method ensure the objectivity of classification,and also reduces the difficulty of the scene classification. However,in some complex geological conditions,such as layered rock mass,BQ classification has the limitation of qualitative evaluation of correction coefficient. The actual use of the subjective judgment due to different field engineers,in the junction of two types of rock classifications,often occurs classification phenomenon. This paper expounds the influence law of angle of bedding and confining pressure on mechanical parameters of layered rock mass based on laboratory mechanics test. Jaeger-Donath and Mogi-Coulomb strength criteria are used to propose the calculation formulas of structural surface shape correction K2 and initial ground stress state correction coefficient K3. Finally,we verify the modification by the calculation of surrounding rock classification of Muzhailing railway tunnel.
The Standard of Engineering Classification of Rock Masses(BQ system) is a classification method of multi-factors,multi-variables,and qualitative and quantitative combination. In this method,we select the rock saturation uniaxial compressive strength and rock integrity index to calculate the value of the rock mass basic quality [BQ]. The modification of rock mass is made considering the field conditions of engineering rock mass,which makes BQ classification method ensure the objectivity of classification,and also reduces the difficulty of the scene classification. However,in some complex geological conditions,such as layered rock mass,BQ classification has the limitation of qualitative evaluation of correction coefficient. The actual use of the subjective judgment due to different field engineers,in the junction of two types of rock classifications,often occurs classification phenomenon. This paper expounds the influence law of angle of bedding and confining pressure on mechanical parameters of layered rock mass based on laboratory mechanics test. Jaeger-Donath and Mogi-Coulomb strength criteria are used to propose the calculation formulas of structural surface shape correction K2 and initial ground stress state correction coefficient K3. Finally,we verify the modification by the calculation of surrounding rock classification of Muzhailing railway tunnel.
2020, 28(5): 951-958.
Soil-rock mixtures are widely distributed in the Three Gorges Reservoir area. The mechanical properties and deformation response of the soil-rock mixtures under external action have an important influence on the initiation or reactivation of landslide on the reservoir bank. The soil-rock mixture of typical landslide in the Three Gorges Reservoir area is selected for sampling,and the large scale direct shear tests on soil-rock mixture is carried out in laboratory. The deformation characteristics of soil-rock mixture under different rock contents are studied based on the method of drilling,wire inserting and sand filling. The results show that the stone content has an obvious control effect on the strength and deformation characteristics of the soil-rock mixture. When the content of stone is less than 20%,the effect of block stone on the sample is small,and the fine-grained soil is the dominant factor. The shear deformation of fine-grained soil is characterized by staggered shear deformation,and the strength depends on the strength of fine particles,and the specimen shows strain hardening characteristics. With the increase of stone content(20% ~80%),the block stone begins to contact and gradually forms the skeleton structure. In addition,because of interlocking of fine-grained soil,the dilatancy of samples are enhanced. The shearing process is characterized by the gnawing type shear deformation between the mixture,and the strength is affected by the joint action of the block stone and the fine particles. At the same time,the samples show strain softening characteristics gradually. When the stone content is more than 80%,the block stone in the sample is dominant,the structure effect of the sample is reduced,and the strength and deformation performance are weakened.
Soil-rock mixtures are widely distributed in the Three Gorges Reservoir area. The mechanical properties and deformation response of the soil-rock mixtures under external action have an important influence on the initiation or reactivation of landslide on the reservoir bank. The soil-rock mixture of typical landslide in the Three Gorges Reservoir area is selected for sampling,and the large scale direct shear tests on soil-rock mixture is carried out in laboratory. The deformation characteristics of soil-rock mixture under different rock contents are studied based on the method of drilling,wire inserting and sand filling. The results show that the stone content has an obvious control effect on the strength and deformation characteristics of the soil-rock mixture. When the content of stone is less than 20%,the effect of block stone on the sample is small,and the fine-grained soil is the dominant factor. The shear deformation of fine-grained soil is characterized by staggered shear deformation,and the strength depends on the strength of fine particles,and the specimen shows strain hardening characteristics. With the increase of stone content(20% ~80%),the block stone begins to contact and gradually forms the skeleton structure. In addition,because of interlocking of fine-grained soil,the dilatancy of samples are enhanced. The shearing process is characterized by the gnawing type shear deformation between the mixture,and the strength is affected by the joint action of the block stone and the fine particles. At the same time,the samples show strain softening characteristics gradually. When the stone content is more than 80%,the block stone in the sample is dominant,the structure effect of the sample is reduced,and the strength and deformation performance are weakened.
2020, 28(5): 959-965.
Saline soil is one of the geological environment problems encountered in the construction of project in the coastal area. This paper takes saline soil samples shallower than 5 m depth to test the content of dissolvable salt,and studies the distribution principle,salinization degree and its influential factors of saline soil. The experiment results show that the distribution of saline soil is parallel to the coastline. Medium and weak saline soils take the majority and strong saline soil distributes sporadically. Salinization degree varies greatly under the influences of sedimentary environment,climate,hydrogeological conditions and human activities. In the horizontal direction,salt content and salinization degree are more and more obvious toward the coastal line,and strongly in the north but weakly in the south. Strong saline soil is distributed in the clayed soil area of Lianyungang. Lithology and groundwater mineralization serve as dominant influential factors. In the vertical direction,salt accumulation is common in the surface layer. The zoning in Lianyungang area is not obvious. Dafeng and Nantong districts can be divided into 3 zones from the shallow ground to the deeper layer,with salt accumulation section,changeable salt content section,and salt solution section. Groundwater level and soil layer construction serve as dominant influential factors. With the rapid promotion of grand development of the coastal area,to avoid the secondary salinization,it shall pay attention to the ground elevation loss derived from land subsidence,which would induce seawater intrusion and thus enhance the salinization of topsoil. In the engineering development,it can set isolated layer to cut off the capillarity of underground water with high salinity.
Saline soil is one of the geological environment problems encountered in the construction of project in the coastal area. This paper takes saline soil samples shallower than 5 m depth to test the content of dissolvable salt,and studies the distribution principle,salinization degree and its influential factors of saline soil. The experiment results show that the distribution of saline soil is parallel to the coastline. Medium and weak saline soils take the majority and strong saline soil distributes sporadically. Salinization degree varies greatly under the influences of sedimentary environment,climate,hydrogeological conditions and human activities. In the horizontal direction,salt content and salinization degree are more and more obvious toward the coastal line,and strongly in the north but weakly in the south. Strong saline soil is distributed in the clayed soil area of Lianyungang. Lithology and groundwater mineralization serve as dominant influential factors. In the vertical direction,salt accumulation is common in the surface layer. The zoning in Lianyungang area is not obvious. Dafeng and Nantong districts can be divided into 3 zones from the shallow ground to the deeper layer,with salt accumulation section,changeable salt content section,and salt solution section. Groundwater level and soil layer construction serve as dominant influential factors. With the rapid promotion of grand development of the coastal area,to avoid the secondary salinization,it shall pay attention to the ground elevation loss derived from land subsidence,which would induce seawater intrusion and thus enhance the salinization of topsoil. In the engineering development,it can set isolated layer to cut off the capillarity of underground water with high salinity.
2020, 28(5): 966-972.
Cone penetration test(CPT) is usually performed vertically to identify subsurface soil stratification. However,due to time and budget constraints,the number of CPT soundings performed in a site is often limited,leading to a great challenge in properly interpreting CPT data and identifying stratification in unsounded area along horizontal direction. A Bayesian learning method is presented in this paper to address this difficulty. The method can predict soil classification and stratification in a two-dimensional(2D)vertical cross-section using a limited number of CPT soundings. The method consists of three components:(1)2D interpolation of CPT data using Bayesian learning; (2)determination of soil behavior type(SBT)using Robertson chart at every location in the 2D cross-section,including locations with and without CPT soundings; (3) and soil layer/zone delineation using an edge detection method. High-resolution CPT data and SBT information in the 2D vertical cross-section can be obtained. Soil layer/zone boundaries are delineated automatically. The method is illustrated using a simulated example. The results suggest that the method performs well even when only five sets of CPT soundings are available.
Cone penetration test(CPT) is usually performed vertically to identify subsurface soil stratification. However,due to time and budget constraints,the number of CPT soundings performed in a site is often limited,leading to a great challenge in properly interpreting CPT data and identifying stratification in unsounded area along horizontal direction. A Bayesian learning method is presented in this paper to address this difficulty. The method can predict soil classification and stratification in a two-dimensional(2D)vertical cross-section using a limited number of CPT soundings. The method consists of three components:(1)2D interpolation of CPT data using Bayesian learning; (2)determination of soil behavior type(SBT)using Robertson chart at every location in the 2D cross-section,including locations with and without CPT soundings; (3) and soil layer/zone delineation using an edge detection method. High-resolution CPT data and SBT information in the 2D vertical cross-section can be obtained. Soil layer/zone boundaries are delineated automatically. The method is illustrated using a simulated example. The results suggest that the method performs well even when only five sets of CPT soundings are available.
2020, 28(5): 973-981.
We utilized a self-made device to humidify an undisturbed and typical loess sample(column) to different degrees of saturation. During the humidification process,we analyzed the distribution of water at different locations in the soil sample. We conducted the collapsible test on samples after the humidification process. We defined the unsaturated humidified collapsible coefficient to discuss the different positions and total collapsibility of the sample under unsaturated humidified conditions. As the target water content of low-humidification samples increases over time,the water content of the upper layer decreases gradually,while the water content of the lower layer increases. The distribution of the water content in the loess column is uneven. In contrast,as the target water content of high-humidification samples increases over time,the water content of the upper layer decreases at an increasing rate,while the water content of the lower layer increases at an increasing rate. Furthermore,the distribution of the water content in the loess soil column is even,and the time required to achieve an even distribution is reduced. As the target water content increases,the unsaturated humidified collapsible coefficient of each layer of the loess column increases at a faster rate; moreover,the coefficients of the bottom layer and upper layer tend to become more similar. The total unsaturated collapsible coefficient of the loess column increases with pressure at an increasing rate. When the target water content is low,the time needed for humidification is longer,which leads to shorter unsaturated humidified collapsible coefficients. In contrast,when the target water content is high,the time needed for humidification is reduced,which leads to larger unsaturated humidified collapsible coefficients. Our study on the collapsible characteristics of the loess column shows that the construction of a large-thickness loess site cannot be evaluated by the collapsible coefficient; instead,consideration of the water content,time,and pressure is required. Our results provide important insights into the evaluation of the unsaturated collapsibility of loess.
We utilized a self-made device to humidify an undisturbed and typical loess sample(column) to different degrees of saturation. During the humidification process,we analyzed the distribution of water at different locations in the soil sample. We conducted the collapsible test on samples after the humidification process. We defined the unsaturated humidified collapsible coefficient to discuss the different positions and total collapsibility of the sample under unsaturated humidified conditions. As the target water content of low-humidification samples increases over time,the water content of the upper layer decreases gradually,while the water content of the lower layer increases. The distribution of the water content in the loess column is uneven. In contrast,as the target water content of high-humidification samples increases over time,the water content of the upper layer decreases at an increasing rate,while the water content of the lower layer increases at an increasing rate. Furthermore,the distribution of the water content in the loess soil column is even,and the time required to achieve an even distribution is reduced. As the target water content increases,the unsaturated humidified collapsible coefficient of each layer of the loess column increases at a faster rate; moreover,the coefficients of the bottom layer and upper layer tend to become more similar. The total unsaturated collapsible coefficient of the loess column increases with pressure at an increasing rate. When the target water content is low,the time needed for humidification is longer,which leads to shorter unsaturated humidified collapsible coefficients. In contrast,when the target water content is high,the time needed for humidification is reduced,which leads to larger unsaturated humidified collapsible coefficients. Our study on the collapsible characteristics of the loess column shows that the construction of a large-thickness loess site cannot be evaluated by the collapsible coefficient; instead,consideration of the water content,time,and pressure is required. Our results provide important insights into the evaluation of the unsaturated collapsibility of loess.
2020, 28(5): 982-988.
The fluid flow in rock fracture network exists widely in underground engineering,which has important influences on the safety of engineering construction and operation. Therefore,the study of flow in fracture network has important theoretical and practical significance. This paper is based on the flow model of intersecting fractures. The model is derived based on the cubic law and Forchheimer equation. It studies the nonlinear parameters of the flow model of planar intersecting fractures by numerical simulation and artificial neural network. Using the artificial neural network genetic algorithm,the paper explores the relationship between the geometry of the intersecting fractures and the nonlinear coefficient in the flow model. It proves that the nonlinear flow model of the plane intersecting fractures can adequately describe the flow characteristics of the intersecting fractures. It verifies the feasibility and accuracy of the neural network method in predicting the nonlinear coefficient. At the same time,it obtains the characteristics of the two methods of fitting numerical expression and artificial neural network.
The fluid flow in rock fracture network exists widely in underground engineering,which has important influences on the safety of engineering construction and operation. Therefore,the study of flow in fracture network has important theoretical and practical significance. This paper is based on the flow model of intersecting fractures. The model is derived based on the cubic law and Forchheimer equation. It studies the nonlinear parameters of the flow model of planar intersecting fractures by numerical simulation and artificial neural network. Using the artificial neural network genetic algorithm,the paper explores the relationship between the geometry of the intersecting fractures and the nonlinear coefficient in the flow model. It proves that the nonlinear flow model of the plane intersecting fractures can adequately describe the flow characteristics of the intersecting fractures. It verifies the feasibility and accuracy of the neural network method in predicting the nonlinear coefficient. At the same time,it obtains the characteristics of the two methods of fitting numerical expression and artificial neural network.
2020, 28(5): 989-999.
As a part of Yandang Mountain World Geopark, Fangshan scenic spot, located in Wenling City, Zhejiang Province, was built on the volcanic strata of Jiuliping formation of the early cretaceous Moshishan group. It is not only a beautiful scenery, but also a profound cultural heritage. However, field investigation shows that there are many hidden dangers of falling rocks in the steep cliffs around Fangshan Mountain and there are also rare hazards caused by falling icicles on the top of steep cliffs in the winter. For example, in the winter of 2017, there was an incident in which ice block from the steep cliff of the scenic spot of Liangyi pavilion smashed the main body of the pavilion and the stone pavement and stone railings on the ground. As Liangyi pavilion is one of the most important scenic spots in Fangshan scenic area, tourists often come here to enjoy the beautiful scenery and sit in the pavilion for a rest. Therefore, the phenomenon of falling rock and /or ice block along the steep cliffs in Liangyi pavilion can seriously threaten the travel safety. In order to ensure travel safety, according to the principle of engineering geology method of mountain tourism planning, the following countermeasures are put forward: under the condition that the viewing value of Liangyi pavilion is basically guaranteed, the route of the scenic spot is adjusted by scientific "avoidance" method, so as to achieve the purpose of eliminating the hidden danger of geological disaster caused by falling rock and /or ice blocks.
As a part of Yandang Mountain World Geopark, Fangshan scenic spot, located in Wenling City, Zhejiang Province, was built on the volcanic strata of Jiuliping formation of the early cretaceous Moshishan group. It is not only a beautiful scenery, but also a profound cultural heritage. However, field investigation shows that there are many hidden dangers of falling rocks in the steep cliffs around Fangshan Mountain and there are also rare hazards caused by falling icicles on the top of steep cliffs in the winter. For example, in the winter of 2017, there was an incident in which ice block from the steep cliff of the scenic spot of Liangyi pavilion smashed the main body of the pavilion and the stone pavement and stone railings on the ground. As Liangyi pavilion is one of the most important scenic spots in Fangshan scenic area, tourists often come here to enjoy the beautiful scenery and sit in the pavilion for a rest. Therefore, the phenomenon of falling rock and /or ice block along the steep cliffs in Liangyi pavilion can seriously threaten the travel safety. In order to ensure travel safety, according to the principle of engineering geology method of mountain tourism planning, the following countermeasures are put forward: under the condition that the viewing value of Liangyi pavilion is basically guaranteed, the route of the scenic spot is adjusted by scientific "avoidance" method, so as to achieve the purpose of eliminating the hidden danger of geological disaster caused by falling rock and /or ice blocks.
2020, 28(5): 1000-1006.
The low-resistance motion characteristics of subaqueous debris flow is an important topic to study the mechanism of subaqueous debris flow. The water pressure at the bottom of the subaqueous debris flow is an important factor to reduce the resistance. Rotating flume tests are performed to reproduce the low-resistance motion of subaqueous debris flow and to measure the reach angle of dense granular flow granular flow in the subaqueous debris flow. The newly developed measurement system is used to measure the water pressure at the bottom of the dense granular flow granular flow, and to evaluate the static and additional water pressure at the bottom of the dense granular flow granular flow. The experimental results and theoretical analysis show that the additional water pressure at the bottom of the subaqueous debris flow is related to the low resistance motion of the subaqueous debris flow. The maximum thickness of the dense granular flow granular flow is 12 mm, while the maximum additional water pressure is 69 Pa. This research provides an experimental method for revealing the mechanism of low resistance motion of subaqueous debris flow. The newly developed measurement system provides a new way for the water pressure measurement of debris flow with low resistance motion.
The low-resistance motion characteristics of subaqueous debris flow is an important topic to study the mechanism of subaqueous debris flow. The water pressure at the bottom of the subaqueous debris flow is an important factor to reduce the resistance. Rotating flume tests are performed to reproduce the low-resistance motion of subaqueous debris flow and to measure the reach angle of dense granular flow granular flow in the subaqueous debris flow. The newly developed measurement system is used to measure the water pressure at the bottom of the dense granular flow granular flow, and to evaluate the static and additional water pressure at the bottom of the dense granular flow granular flow. The experimental results and theoretical analysis show that the additional water pressure at the bottom of the subaqueous debris flow is related to the low resistance motion of the subaqueous debris flow. The maximum thickness of the dense granular flow granular flow is 12 mm, while the maximum additional water pressure is 69 Pa. This research provides an experimental method for revealing the mechanism of low resistance motion of subaqueous debris flow. The newly developed measurement system provides a new way for the water pressure measurement of debris flow with low resistance motion.
2020, 28(5): 1007-1015.
Landslide dam are naturally formed dams with the characteristics of the loose structure, poor stability and strong permeability. Once a landslide dam is formed, its high probability of breaching and the flood caused by its breaching may threaten the safety of people and property in local area. Therefore, a systematic and comprehensive study needs to be conducted to analyze the breaching characteristics of landslide dam. In this article, a detail review from model experimental studies on dam break of landslide dam is conducted. The results and limitations are analyzed and summarized. Moreover, the factors of particle size distribution, compactness, water content and bed slope of single dam break are also analyzed. Finally we discuss the relationship among the dam break factor and the failure mode, the characteristics of dam breaching, peak discharge, and downcutting process. On the basis of the systematic analysis of the breaching of landslide dams, it's suggested that further studies of model similarity theory, scaling effect, testing methods and the disposal of landslide dam may be carried out in the future.
Landslide dam are naturally formed dams with the characteristics of the loose structure, poor stability and strong permeability. Once a landslide dam is formed, its high probability of breaching and the flood caused by its breaching may threaten the safety of people and property in local area. Therefore, a systematic and comprehensive study needs to be conducted to analyze the breaching characteristics of landslide dam. In this article, a detail review from model experimental studies on dam break of landslide dam is conducted. The results and limitations are analyzed and summarized. Moreover, the factors of particle size distribution, compactness, water content and bed slope of single dam break are also analyzed. Finally we discuss the relationship among the dam break factor and the failure mode, the characteristics of dam breaching, peak discharge, and downcutting process. On the basis of the systematic analysis of the breaching of landslide dams, it's suggested that further studies of model similarity theory, scaling effect, testing methods and the disposal of landslide dam may be carried out in the future.
2020, 28(5): 1016-1027.
Earth fissure is one of main geological hazards in China. By 2015, 5002 earth fissures were discovered in more than 1, 500 localities across 22 provinces. These earth fissures caused huge economic loss. Based on a series of geological investigations including in surveying, mapping, trenching, drilling and monitoring, the spatial distribution and development rules of the earth fissures are summarized, and the movement characteristic of the earth fissures are revealed. The results show that the earth fissures mainly distribute in North China and South China, especially in the Fenwei Basin, Hebei Plain and Yangtze River Delta. The giant earth fissures, longer than 1 km, mainly distribute in the Fenwei Basin and Hebei Plain. These earth fissures exhibit the following five regular patterns: clustering along fault zones, distributing along geomorphic boundaries, appearing on the edge of subsidence areas, dispersing in loess collapsible area, and centralizing in larger and medium cities. The movement characteristics of the earth fissures can be divided into four types: tension type, tension-shear type, shear-tension type and shear type.
Earth fissure is one of main geological hazards in China. By 2015, 5002 earth fissures were discovered in more than 1, 500 localities across 22 provinces. These earth fissures caused huge economic loss. Based on a series of geological investigations including in surveying, mapping, trenching, drilling and monitoring, the spatial distribution and development rules of the earth fissures are summarized, and the movement characteristic of the earth fissures are revealed. The results show that the earth fissures mainly distribute in North China and South China, especially in the Fenwei Basin, Hebei Plain and Yangtze River Delta. The giant earth fissures, longer than 1 km, mainly distribute in the Fenwei Basin and Hebei Plain. These earth fissures exhibit the following five regular patterns: clustering along fault zones, distributing along geomorphic boundaries, appearing on the edge of subsidence areas, dispersing in loess collapsible area, and centralizing in larger and medium cities. The movement characteristics of the earth fissures can be divided into four types: tension type, tension-shear type, shear-tension type and shear type.
2020, 28(5): 1028-1038.
The prediction and evaluation of the change characteristics of non-homogeneous debris flow are an important content of debris flow control project planning and early warning and forecasting system construction. They are also a key issue that needs to be improved in the field of debris flow. By sorting out and analyzing the measured data of the mud level and velocity of the debris flow, a prediction model of the characteristic value of the non-homogeneous debris flow movement is constructed. Based on the previous results, the model can distinguish the change characteristics of the debris flow movement in the study area with fewer factors. Taking the mud-rock flow in Xiahuyang Gully, Lixian County, Longnan area as an example, the FLO-2D fluid model is used to simulate the movement characteristics of debris flow under precipitation conditions of once in 50 years(2% frequency) and once in 20 years(5% frequency). The results show that when the specific weight gravity of debris flow is 1.83t ·m-3, the characteristic value of debris flow movement in Xiahuyang Gully in 20 years is the smallest and the difference is not significant. When the specific weight gravity of debris flow is 1.97t ·m-3, the characteristic value of debris flow movement in Xiahuyang Gully is once in 50 years the biggest and the difference is huge. When the flow of debris flows of different scales reaches the peak, they all produce larger mud level depth. The simulation results of the debris flow movement characteristic value are further combined with the actual measured cross-sections for inspection and analysis. The peak flow rate of the debris flow event is inferred and is in good agreement with the actual situation, indicating that the results calculated by the prediction model of this paper are reliable. The results in this paper can provide a reference for the construction of debris flow disaster prevention and mitigation and debris flow monitoring and early warning demonstration areas.
The prediction and evaluation of the change characteristics of non-homogeneous debris flow are an important content of debris flow control project planning and early warning and forecasting system construction. They are also a key issue that needs to be improved in the field of debris flow. By sorting out and analyzing the measured data of the mud level and velocity of the debris flow, a prediction model of the characteristic value of the non-homogeneous debris flow movement is constructed. Based on the previous results, the model can distinguish the change characteristics of the debris flow movement in the study area with fewer factors. Taking the mud-rock flow in Xiahuyang Gully, Lixian County, Longnan area as an example, the FLO-2D fluid model is used to simulate the movement characteristics of debris flow under precipitation conditions of once in 50 years(2% frequency) and once in 20 years(5% frequency). The results show that when the specific weight gravity of debris flow is 1.83t ·m-3, the characteristic value of debris flow movement in Xiahuyang Gully in 20 years is the smallest and the difference is not significant. When the specific weight gravity of debris flow is 1.97t ·m-3, the characteristic value of debris flow movement in Xiahuyang Gully is once in 50 years the biggest and the difference is huge. When the flow of debris flows of different scales reaches the peak, they all produce larger mud level depth. The simulation results of the debris flow movement characteristic value are further combined with the actual measured cross-sections for inspection and analysis. The peak flow rate of the debris flow event is inferred and is in good agreement with the actual situation, indicating that the results calculated by the prediction model of this paper are reliable. The results in this paper can provide a reference for the construction of debris flow disaster prevention and mitigation and debris flow monitoring and early warning demonstration areas.
2020, 28(5): 1039-1048.
Two typical debris flow gullies in Hot Water River Basin, Laowa Gully and Fencha Gully are taken as research objects in this paper. The initiation mechanism of debris flow hazard is revealed by means of field engineering geological investigation and analysis of the formation and development conditions of debris flow. The topography of the debris flow formation areas is steep and its catchment areas are fan-shaped. There are rich loose deposits as source conditions in the gully slopes and trench beds. The abundant rainfall and hydrodynamic conditions in rainy season provide a good water source for the formation and development of debris flows, which causes the debris flow hazard. The efficiency of different debris flow hazard mitigation engineering is evaluated using the matrix discrete element numerical simulation software MatDEM. Specifically, 62.3% of the total energy carried by the debris flow source is dissipated as system heat energy and 37.7% is beared by the dam structure under the geotechnical engineering measures. While 70% of the total energy carried by the debris flow source is consumed by ecological engineering measures and the other 30% is beared by the dam structure under the ecological engineering and geotechnical engineering measures. Based on the above results, the debris flow prevention and mitigation schemes are proposed for these two typical debris flow gullies under the synergistic effect of ecological engineering and geotechnical engineering, which provides references for the establishment of debris flow hazard mitigation mode in small watershed in mountainous area.
Two typical debris flow gullies in Hot Water River Basin, Laowa Gully and Fencha Gully are taken as research objects in this paper. The initiation mechanism of debris flow hazard is revealed by means of field engineering geological investigation and analysis of the formation and development conditions of debris flow. The topography of the debris flow formation areas is steep and its catchment areas are fan-shaped. There are rich loose deposits as source conditions in the gully slopes and trench beds. The abundant rainfall and hydrodynamic conditions in rainy season provide a good water source for the formation and development of debris flows, which causes the debris flow hazard. The efficiency of different debris flow hazard mitigation engineering is evaluated using the matrix discrete element numerical simulation software MatDEM. Specifically, 62.3% of the total energy carried by the debris flow source is dissipated as system heat energy and 37.7% is beared by the dam structure under the geotechnical engineering measures. While 70% of the total energy carried by the debris flow source is consumed by ecological engineering measures and the other 30% is beared by the dam structure under the ecological engineering and geotechnical engineering measures. Based on the above results, the debris flow prevention and mitigation schemes are proposed for these two typical debris flow gullies under the synergistic effect of ecological engineering and geotechnical engineering, which provides references for the establishment of debris flow hazard mitigation mode in small watershed in mountainous area.
2020, 28(5): 1049-1056.
The Outang landslide is a giant complex ancient landslide in the Three Gorges Reservoir Region. It consists of multiple sliding zones and multiple sliding masses. Some obvious creeping slip of the landslide were found after the impoundment of the Three Gorges Reservoir. The landslide has a great threat to thousands of people's lives and properties nearby. In order to clarify the response characteristics and the failure mechanism of the landslide under the influence of water level fluctuation, a model test is done. The model test material development and the accurate control of the water level fluctuation can simulate the process of instability of the Outang landslide. Response characteristics and mechanical mechanism of the Outang landslide are discussed. Results indicate that the fast the speed of the water level fluctuation, the bigger deformation of the three phase sliding masses which compose Outang landslide. The influence of water level fluctuation is concentrated in the zone of the first phase mass. The rapid drawdown of the water level result in deformation of the slope, which makes the retrogressive sliding possibility of Outang landslide larger. The stabilities of the second phase mass and the third phase mass decline after the deformation of the first phase mass. Outang landslide is the hydrodynamic pressure landslide. The whole Outang landslide mass is less likely to destroy along the bed rock surface under water level fluctuation. The major failure mode of the Outang landslide under the water level fluctuation is the type of local buckling failure in the leading edge of the first phase sliding mass. This test reveals response characteristics and instability mechanism of the landslide under water level fluctuation, which provides reference for researching this kind of landslide.
The Outang landslide is a giant complex ancient landslide in the Three Gorges Reservoir Region. It consists of multiple sliding zones and multiple sliding masses. Some obvious creeping slip of the landslide were found after the impoundment of the Three Gorges Reservoir. The landslide has a great threat to thousands of people's lives and properties nearby. In order to clarify the response characteristics and the failure mechanism of the landslide under the influence of water level fluctuation, a model test is done. The model test material development and the accurate control of the water level fluctuation can simulate the process of instability of the Outang landslide. Response characteristics and mechanical mechanism of the Outang landslide are discussed. Results indicate that the fast the speed of the water level fluctuation, the bigger deformation of the three phase sliding masses which compose Outang landslide. The influence of water level fluctuation is concentrated in the zone of the first phase mass. The rapid drawdown of the water level result in deformation of the slope, which makes the retrogressive sliding possibility of Outang landslide larger. The stabilities of the second phase mass and the third phase mass decline after the deformation of the first phase mass. Outang landslide is the hydrodynamic pressure landslide. The whole Outang landslide mass is less likely to destroy along the bed rock surface under water level fluctuation. The major failure mode of the Outang landslide under the water level fluctuation is the type of local buckling failure in the leading edge of the first phase sliding mass. This test reveals response characteristics and instability mechanism of the landslide under water level fluctuation, which provides reference for researching this kind of landslide.
2020, 28(5): 1057-1065.
The movement law and impact performance of debris flows have decisive significance to the influence range and severity of debris flow disasters. This paper uses the discrete element simulation software EDEM 2018 and conducts a numerical simulation study on the debris flow flume test, taking into account the influence of the flume slope, barrier angle and particle size distribution. Based on the existing research results, the solid particle movement process and its impact performance have been systematically studied. The numerical simulation results are compared with the existing flume test data to verify the reliability of the numerical simulation method. On this basis, the following conclusions are drawn:(1)When the barrier angle and particle size distribution remain constant, the larger the flume slope, the greater the corresponding peak velocity and impact force; (2)For the model with the same flume slope and particle size distribution, the steeper the barrier, the more particles interact with it, and the faster the flow reaches the peak of velocity and impact force, and the corresponding peak of velocity and impact force is also greater.; (3)During the movement of debris flow, the debris flow of each particle gradation exhibit reverse order characteristics. And the fine particles are distributed in the lower part and the rear part of the sliding body, which improves the sliding speed of the sliding body and reduces the impact force. While the coarse particles have little effect on the moving speed and would increase the impact pressure on the barrier structure.
The movement law and impact performance of debris flows have decisive significance to the influence range and severity of debris flow disasters. This paper uses the discrete element simulation software EDEM 2018 and conducts a numerical simulation study on the debris flow flume test, taking into account the influence of the flume slope, barrier angle and particle size distribution. Based on the existing research results, the solid particle movement process and its impact performance have been systematically studied. The numerical simulation results are compared with the existing flume test data to verify the reliability of the numerical simulation method. On this basis, the following conclusions are drawn:(1)When the barrier angle and particle size distribution remain constant, the larger the flume slope, the greater the corresponding peak velocity and impact force; (2)For the model with the same flume slope and particle size distribution, the steeper the barrier, the more particles interact with it, and the faster the flow reaches the peak of velocity and impact force, and the corresponding peak of velocity and impact force is also greater.; (3)During the movement of debris flow, the debris flow of each particle gradation exhibit reverse order characteristics. And the fine particles are distributed in the lower part and the rear part of the sliding body, which improves the sliding speed of the sliding body and reduces the impact force. While the coarse particles have little effect on the moving speed and would increase the impact pressure on the barrier structure.
2020, 28(5): 1066-1068.
2020, 28(5): 1069-1075.
Investigation of karst voids is significant to the construction in the karst area. Cross-hole seismic tomography is an effective borehole geophysical method. We conduct an inversion study on cross-hole seismic karst voids detection based on the Eikonal equation. Multiple numerical scenarios are used to test the effectiveness of the proposed method. FDTD is applied to simulate cross-hole seismic detection. The arrival time of the first break is extracted from modeling recorded wave profile. The Eikonal equation traveling time inversion is used to image the underground velocity between boreholes. Four scenarios including single void, single fracture, fracture and void, and multiple voids are analyzed. The result shows that the Eikonal equation-based inversion method can image the location, size and orientation of the karst voids and fracture. The inversion is stable even in complex scenarios. The velocity difference between voids infill can be identified. However, the inverted velocity is slightly higher than the true velocity. The lateral resolution is lower than that in depth. The inversion method is not sensitive to the fracture anomaly. The Eikonal equation-based inversion method is robust and efficient in complex scenarios with multiple anomalies, and can be applied in practice to provide important geological information.
Investigation of karst voids is significant to the construction in the karst area. Cross-hole seismic tomography is an effective borehole geophysical method. We conduct an inversion study on cross-hole seismic karst voids detection based on the Eikonal equation. Multiple numerical scenarios are used to test the effectiveness of the proposed method. FDTD is applied to simulate cross-hole seismic detection. The arrival time of the first break is extracted from modeling recorded wave profile. The Eikonal equation traveling time inversion is used to image the underground velocity between boreholes. Four scenarios including single void, single fracture, fracture and void, and multiple voids are analyzed. The result shows that the Eikonal equation-based inversion method can image the location, size and orientation of the karst voids and fracture. The inversion is stable even in complex scenarios. The velocity difference between voids infill can be identified. However, the inverted velocity is slightly higher than the true velocity. The lateral resolution is lower than that in depth. The inversion method is not sensitive to the fracture anomaly. The Eikonal equation-based inversion method is robust and efficient in complex scenarios with multiple anomalies, and can be applied in practice to provide important geological information.
2020, 28(5): 1076-1083.
To investigate the anti-vibration structure design of precision instrument workshop, this article evaluates the micro-vibration level of a single-story light steel factory located in a high-tech electronic industrial plant of Suzhou by conducting field measurement and numerical simulation. We carried out the micro-vibration tests before and after the construction of the structure to reveal the effectiveness of the structure on vibration reduction. We built the dynamic finite element model of the plant by ANSYS software. Then we analyzed the sensitivity of design parameters by introducing the structural and foundation design parameters of Rayleigh damping and floor thickness. The investigation shows that, the vibration of the bottom structure meets the limitation requirements after the plant is completed. The pile-raft foundation of the factory building has great effect on vibration reduction. Damping and floor thickness have little effect on structure frequency, but have a greater impact on amplitude. The vibration amplitude of the structure decreases with the increase of Rayleigh damping, especially in the low frequency range of 1~3 Hz and 10~50 Hz, and also decreases as floor thickness increasing in the low frequency range(within 50 Hz). Therefore, in the anti-vibration design of the plant, properly increasing floor thickness and damping can reduce the middle and low frequency vibration(within 50 Hz) significantly and achieve a better vibration isolation effectiveness.
To investigate the anti-vibration structure design of precision instrument workshop, this article evaluates the micro-vibration level of a single-story light steel factory located in a high-tech electronic industrial plant of Suzhou by conducting field measurement and numerical simulation. We carried out the micro-vibration tests before and after the construction of the structure to reveal the effectiveness of the structure on vibration reduction. We built the dynamic finite element model of the plant by ANSYS software. Then we analyzed the sensitivity of design parameters by introducing the structural and foundation design parameters of Rayleigh damping and floor thickness. The investigation shows that, the vibration of the bottom structure meets the limitation requirements after the plant is completed. The pile-raft foundation of the factory building has great effect on vibration reduction. Damping and floor thickness have little effect on structure frequency, but have a greater impact on amplitude. The vibration amplitude of the structure decreases with the increase of Rayleigh damping, especially in the low frequency range of 1~3 Hz and 10~50 Hz, and also decreases as floor thickness increasing in the low frequency range(within 50 Hz). Therefore, in the anti-vibration design of the plant, properly increasing floor thickness and damping can reduce the middle and low frequency vibration(within 50 Hz) significantly and achieve a better vibration isolation effectiveness.
2020, 28(5): 1084-1090.
The horizontal ground heat exchangers(GHE) and particularly those deployed under pavement have gained increasing attention in recent years. One major advantage of the GHE under pavement is the significant amount of upfront cost that can be saved from drilling or excavation. In China, the potential for these GHE is immense due to the fact that there are more than 100, 000 km of infrastructural pavements being constructed each year. In this paper, we aim to study the thermal diffusion radius of horizontal GHE under pavement and the effect of air temperature fluctuation on the heat transfer capability. In order to achieve the research goal, we use the GeoCube thermal response test unit to conduct two in-situ thermal response tests(TRT), with 4 kW and 6 kW heating powers respectively on the GHE. In addition, a 3D numerical model is developed in COMSOL to simulate the heat transfer between the GHE and soil medium based on the experimental parameters of TRT with 4 kW heating power. The experimental result shows that the fluctuation in air temperature has a substantial adverse impact on the GHE′s heat transfer ability. Nonetheless, the adverse impact is weakened when the heating power of the TRT is increased. According to the experimental and numerical simulation results, the thermal diffusion radius of horizontal GHE under the pavement is found to be less than 0.75 m, thereby suggesting a minimum space to space distance between the GHE pipes to be 1.5 m to prevent thermal interference. The experimental validation also demonstrates that the numerical model can be utilized to simulate the heat transfer progress of a horizontal GHE under pavement and that the accuracy of simulation result is acceptable.
The horizontal ground heat exchangers(GHE) and particularly those deployed under pavement have gained increasing attention in recent years. One major advantage of the GHE under pavement is the significant amount of upfront cost that can be saved from drilling or excavation. In China, the potential for these GHE is immense due to the fact that there are more than 100, 000 km of infrastructural pavements being constructed each year. In this paper, we aim to study the thermal diffusion radius of horizontal GHE under pavement and the effect of air temperature fluctuation on the heat transfer capability. In order to achieve the research goal, we use the GeoCube thermal response test unit to conduct two in-situ thermal response tests(TRT), with 4 kW and 6 kW heating powers respectively on the GHE. In addition, a 3D numerical model is developed in COMSOL to simulate the heat transfer between the GHE and soil medium based on the experimental parameters of TRT with 4 kW heating power. The experimental result shows that the fluctuation in air temperature has a substantial adverse impact on the GHE′s heat transfer ability. Nonetheless, the adverse impact is weakened when the heating power of the TRT is increased. According to the experimental and numerical simulation results, the thermal diffusion radius of horizontal GHE under the pavement is found to be less than 0.75 m, thereby suggesting a minimum space to space distance between the GHE pipes to be 1.5 m to prevent thermal interference. The experimental validation also demonstrates that the numerical model can be utilized to simulate the heat transfer progress of a horizontal GHE under pavement and that the accuracy of simulation result is acceptable.
2020, 28(5): 1091-1098.
Subgrade settlement monitoring is one of the most fundamental work for safe construction and operation of highway engineering. The traditional roadbed monitoring methods are mostly point-based, simple and easy to operate, but have technical problems such as serious missed inspection. Recently, the high-spatial-resolution and accurate-microstrain-recognition distributed optical fiber technology has been widely used in various fields. It can provide more efficient subgrade monitoring method than the traditional methods. Therefore, this paper introduces an advanced distributed optical fiber sensing technology and its novel saw-tooth layout method for the subgrade settlement research and calculation analysis. Concurrently, a comparison research with the traditional detection methods is implemented. The results show that the saw-tooth optical fiber can generate more monitoring data and reflect the actual subgrade settlement with more detailed information. The three-dimensional cubic spline interpolation method based on MATLAB further confirms that the saw-tooth optical fiber can intuitively express the subgrade settlement in testing area. The distributed optical fiber sensing technology has simple operation, wide monitoring range and high accuracy, which makes it have better performance in settlement detection. This method and its novel layout can provide important technical support for practical engineering applications.
Subgrade settlement monitoring is one of the most fundamental work for safe construction and operation of highway engineering. The traditional roadbed monitoring methods are mostly point-based, simple and easy to operate, but have technical problems such as serious missed inspection. Recently, the high-spatial-resolution and accurate-microstrain-recognition distributed optical fiber technology has been widely used in various fields. It can provide more efficient subgrade monitoring method than the traditional methods. Therefore, this paper introduces an advanced distributed optical fiber sensing technology and its novel saw-tooth layout method for the subgrade settlement research and calculation analysis. Concurrently, a comparison research with the traditional detection methods is implemented. The results show that the saw-tooth optical fiber can generate more monitoring data and reflect the actual subgrade settlement with more detailed information. The three-dimensional cubic spline interpolation method based on MATLAB further confirms that the saw-tooth optical fiber can intuitively express the subgrade settlement in testing area. The distributed optical fiber sensing technology has simple operation, wide monitoring range and high accuracy, which makes it have better performance in settlement detection. This method and its novel layout can provide important technical support for practical engineering applications.
2020, 28(5): 1099-1105.
This paper aims to systematically and comprehensively extract relevant geological information from UAV aerial photography data and ensure that it can better assist in geological survey work. It introduces the method of geologic overall analysis and information acquisition of geological points, boundary, plane, objects based on photos and DEM made by UAV. At the same time, it forms a set of technical methods for assisting geological survey with UAV. It verifies the feasibility and efficiency of UAV in geological survey work through practical application in geological survey of landslide disaster. The study has certain guiding significance for effective acquisition of comprehensive and systematic geological data based on UAV aerial geological mapping and geological compre￣hensive survey.
This paper aims to systematically and comprehensively extract relevant geological information from UAV aerial photography data and ensure that it can better assist in geological survey work. It introduces the method of geologic overall analysis and information acquisition of geological points, boundary, plane, objects based on photos and DEM made by UAV. At the same time, it forms a set of technical methods for assisting geological survey with UAV. It verifies the feasibility and efficiency of UAV in geological survey work through practical application in geological survey of landslide disaster. The study has certain guiding significance for effective acquisition of comprehensive and systematic geological data based on UAV aerial geological mapping and geological compre￣hensive survey.
2020, 28(5): 1106-1115.
Diaphragm wall and internal support are commonly used forms of support for foundation pit engineering. The deformation of the foundation pit is generally considered during the excavation of the foundation pit, while the deformation in the stage of support removal is ignored. Based on the Shenzhen Vanke Coastal Foundation Pit Project, this paper mainly studies the impact of excavation and support removal of a foundation pit on the surrounding environment by finite element numerical simulation. The following conclusions are obtained. The deformation law of the support removal and the excavation is consistent, and it is obviously influenced by space-time effect. The amounts of deformation in the two stages are similar, and the sum of the deformation amounts accounts for more than 85% of the total deformation. The deformation of the bottom soil excavation and bottom support removal is the biggest. The reasons are as follows: firstly, the three supports are not equidistant, and the thickness of the bottom soil is large; Secondly, the thickness of granite residual soil varies greatly. Finally, after the support is removed, only the basement floor is provided with a change brace, which causes the cantilever section of the pile body to be long. The simulation results show that the lateral displacement at the top of the foundation pit, ground settlement and building settlement are basically consistent with the monitoring data. The results can provide reference for similar projects.
Diaphragm wall and internal support are commonly used forms of support for foundation pit engineering. The deformation of the foundation pit is generally considered during the excavation of the foundation pit, while the deformation in the stage of support removal is ignored. Based on the Shenzhen Vanke Coastal Foundation Pit Project, this paper mainly studies the impact of excavation and support removal of a foundation pit on the surrounding environment by finite element numerical simulation. The following conclusions are obtained. The deformation law of the support removal and the excavation is consistent, and it is obviously influenced by space-time effect. The amounts of deformation in the two stages are similar, and the sum of the deformation amounts accounts for more than 85% of the total deformation. The deformation of the bottom soil excavation and bottom support removal is the biggest. The reasons are as follows: firstly, the three supports are not equidistant, and the thickness of the bottom soil is large; Secondly, the thickness of granite residual soil varies greatly. Finally, after the support is removed, only the basement floor is provided with a change brace, which causes the cantilever section of the pile body to be long. The simulation results show that the lateral displacement at the top of the foundation pit, ground settlement and building settlement are basically consistent with the monitoring data. The results can provide reference for similar projects.
2020, 28(5): 1116-1122.
In the calculation of the support stiffness of the deep foundation pit retaining structure system with the top-down construction method, the structural deadweight and construction load are borne by the vertical support system, and the lateral bearing capacity Is ignored. The article intends to calculate the lateral stiffness of the vertical support system, and provides a method for calculating the lateral stiffness based on the results of numerical analysis. The method can be used to quickly calculate the lateral stiffness of various column structures in engineering. The lateral stiffness of steel pipe column and lattice column structure under different forms is numerically calculated. The corresponding lateral stiffness fitting calculation formula is given. The error between the fitting formula and the numerical calculation is between 2.50% ~9.26%. The calculation method of lateral stiffness proposed in the paper is reliable. It can be used in similar projects and can be used as a reference for deep foundation pit engineering design and construction personnel.
In the calculation of the support stiffness of the deep foundation pit retaining structure system with the top-down construction method, the structural deadweight and construction load are borne by the vertical support system, and the lateral bearing capacity Is ignored. The article intends to calculate the lateral stiffness of the vertical support system, and provides a method for calculating the lateral stiffness based on the results of numerical analysis. The method can be used to quickly calculate the lateral stiffness of various column structures in engineering. The lateral stiffness of steel pipe column and lattice column structure under different forms is numerically calculated. The corresponding lateral stiffness fitting calculation formula is given. The error between the fitting formula and the numerical calculation is between 2.50% ~9.26%. The calculation method of lateral stiffness proposed in the paper is reliable. It can be used in similar projects and can be used as a reference for deep foundation pit engineering design and construction personnel.
2020, 28(5): 1123-1131.
The lined high-pressure gas storage cavern has the advantages of high extraction rate and strong circulation capacity, and can withstand higher internal pressure. It overcomes many shortcomings of traditional compressed air energy storage systems and has a wide application. This paper takes the three most important layout parameters including cavern depth, inner diameter and space as influencing factors and uses ABAQUS finite element software to design simulation conditions based on orthogonal test and single-factor experiment. It calculates the displacements of key points and the areas of plastic zones. Suggestions for the optimal layout of caverns are put forward. The results show that the buried depth of the cavern is the most significant factor affecting the deformation of the surrounding rock and the area of the plastic zone, followed by the space and diameter. As the increase of the buried depth, the development area of the plastic zone is effectively restrained, and the plastic zone is mainly developed on the top of the cavern. The restraint effect of high internal pressure on the surrounding rock can be weakened by increasing the space. The maximum tensile stress of the lining is mainly distributed at the top and bottom of the cavern. The stability of the lining is improved when the buried depth increases or the height-to-diameter ratio reduces. The optimal layout of the caverns is that the depth, the diameter and the space are 400 m, 42 m and 60 m, respectively. The results provide a reference for the optimization of the layout and stability analysis of the lined high-pressure gas storage caverns.
The lined high-pressure gas storage cavern has the advantages of high extraction rate and strong circulation capacity, and can withstand higher internal pressure. It overcomes many shortcomings of traditional compressed air energy storage systems and has a wide application. This paper takes the three most important layout parameters including cavern depth, inner diameter and space as influencing factors and uses ABAQUS finite element software to design simulation conditions based on orthogonal test and single-factor experiment. It calculates the displacements of key points and the areas of plastic zones. Suggestions for the optimal layout of caverns are put forward. The results show that the buried depth of the cavern is the most significant factor affecting the deformation of the surrounding rock and the area of the plastic zone, followed by the space and diameter. As the increase of the buried depth, the development area of the plastic zone is effectively restrained, and the plastic zone is mainly developed on the top of the cavern. The restraint effect of high internal pressure on the surrounding rock can be weakened by increasing the space. The maximum tensile stress of the lining is mainly distributed at the top and bottom of the cavern. The stability of the lining is improved when the buried depth increases or the height-to-diameter ratio reduces. The optimal layout of the caverns is that the depth, the diameter and the space are 400 m, 42 m and 60 m, respectively. The results provide a reference for the optimization of the layout and stability analysis of the lined high-pressure gas storage caverns.
2020, 28(5): 1132-1139.
Cemented mine fills have been extensively used in subsurface mining worldwide for their superior environmental, mechanical and economic benefits. The stability of backfill systems hinges upon the evolution of pore water pressure in response to the coupled thermo-hydro-mechanical-chemical(THMC)effects during mine fill deposition. In this study, a multiphysics framework for cemented mine fills is first developed by extending Biot's classical poroelasticity, and a one-dimensional overpressure model is then derived for the thermo-chemical consolidation of accreting mine fills. The coupled THMC effects on overpressure evolution are demonstrated by scrutinizing the accretion of cemented mine fills under various sedimentation rates and thermal conditions.
Cemented mine fills have been extensively used in subsurface mining worldwide for their superior environmental, mechanical and economic benefits. The stability of backfill systems hinges upon the evolution of pore water pressure in response to the coupled thermo-hydro-mechanical-chemical(THMC)effects during mine fill deposition. In this study, a multiphysics framework for cemented mine fills is first developed by extending Biot's classical poroelasticity, and a one-dimensional overpressure model is then derived for the thermo-chemical consolidation of accreting mine fills. The coupled THMC effects on overpressure evolution are demonstrated by scrutinizing the accretion of cemented mine fills under various sedimentation rates and thermal conditions.
2020, 28(5): 1140-1146.
Based on the continuity equation and Darcy's law and the Bernoulli expression, the paper deduces the analytical formula of the water pressure at the key point of the uplift pressure of a check dam laid on horizontal soil in reasonable hypothesis condition. Comparing the results with numerical simulation(Autobank finite element program), the error between the analytical calculation result and the numerical analysis result in this paper is very small, basically less than 1%, which shows the analytical method reliable and stable. The application value of this method is further discussed. Based on the obtained water head, the hydraulic gradient at the downstream x location of the structure can be calculated, the type of seepage deformation of the soil laid on downstream of the structure can be judged, and the range to be treated and the design of the length of the protective tank can be estimated. Referring to the conclusions of relevant literatures, it is proposed that it is safer to use this analytical formula to calculate the uplift pressure of the foundation base of a check dam built on a sloping channel bed. Further study is needed about whether the influence of "effective depth of foundation" to the water pressure of the foundation base needs to be considered in the calculation of uplift pressure of a check dam.
Based on the continuity equation and Darcy's law and the Bernoulli expression, the paper deduces the analytical formula of the water pressure at the key point of the uplift pressure of a check dam laid on horizontal soil in reasonable hypothesis condition. Comparing the results with numerical simulation(Autobank finite element program), the error between the analytical calculation result and the numerical analysis result in this paper is very small, basically less than 1%, which shows the analytical method reliable and stable. The application value of this method is further discussed. Based on the obtained water head, the hydraulic gradient at the downstream x location of the structure can be calculated, the type of seepage deformation of the soil laid on downstream of the structure can be judged, and the range to be treated and the design of the length of the protective tank can be estimated. Referring to the conclusions of relevant literatures, it is proposed that it is safer to use this analytical formula to calculate the uplift pressure of the foundation base of a check dam built on a sloping channel bed. Further study is needed about whether the influence of "effective depth of foundation" to the water pressure of the foundation base needs to be considered in the calculation of uplift pressure of a check dam.
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