Online Submission
Manuscript Tracking
Peer Review
Editor WorkMost Cited Articles
（The cited data comes from the whole network and is updated monthly.）
1
2020, 28(6): 1186-1192.
Abstract
3468KB
Humidification-dehumidification cycle is one of the main causes of engineering diseases in the loess area. It is of great theoretical and engineering significance to explore the mechanism of the humidification-dehumidification cycle to damage the loess structure. In this paper, the loess in Yan'an area is taken as the research object. The undisturbed loess humidification-dehumidification cycle tests with different water contents and different times are carried out to analyze the change rules of porosity, shear strength and parameters of loess induced by dry and wet cycles. NMR technology is used to obtain the damage evolution of crack development in loess. The results show that with the increase of the times of dry-wet cycling, the soil exhibits a gradual increase in porosity, a decrease in the liquid limit and plasticity index, and a basically constant plastic limit. The reason is the dynamic changes in the internal particles loess damage. The increase of dry-wet cycling times and water content weakens the cementation of the soil particles, which reduces the shear strength, cohesion, and internal friction angle. When the water content of the sample exceeds the plastic limit, the decline becomes more obvious. The NMR of the loess shows that with the increase of the times of dry-wet cycling, micropores smaller than 0.025 μm inside the sample gradually transits to small pore groups of 0.025~0.63 μm and new pores begin to occur.
Humidification-dehumidification cycle is one of the main causes of engineering diseases in the loess area. It is of great theoretical and engineering significance to explore the mechanism of the humidification-dehumidification cycle to damage the loess structure. In this paper, the loess in Yan'an area is taken as the research object. The undisturbed loess humidification-dehumidification cycle tests with different water contents and different times are carried out to analyze the change rules of porosity, shear strength and parameters of loess induced by dry and wet cycles. NMR technology is used to obtain the damage evolution of crack development in loess. The results show that with the increase of the times of dry-wet cycling, the soil exhibits a gradual increase in porosity, a decrease in the liquid limit and plasticity index, and a basically constant plastic limit. The reason is the dynamic changes in the internal particles loess damage. The increase of dry-wet cycling times and water content weakens the cementation of the soil particles, which reduces the shear strength, cohesion, and internal friction angle. When the water content of the sample exceeds the plastic limit, the decline becomes more obvious. The NMR of the loess shows that with the increase of the times of dry-wet cycling, micropores smaller than 0.025 μm inside the sample gradually transits to small pore groups of 0.025~0.63 μm and new pores begin to occur.
2
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.
3
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.
4
2020, 28(6): 1279-1291.
Due to the complex structure of rock and soil mass and various failure mechanisms,landslide early warning has always been a global problem of very challenging. At 5:53 a.m. on 17 February 2019 in Longjing Village,Maling Town,Xingyi City,Guizhou Province,a landslide geological disaster occurred. About 960,000 cubic meters of mountain had a bedding sliding,which posed a serious threat to the road and residential area located at the foot of the front slope. In this paper,we discuss the characteristics and successful early warning process of this Xingyi landslide in Guizhou Province,and analyze the key factors of successful early warning. On the basis of geological investigations on the landslide site,this paper comprehensively use satellite remote sensing,UAV aerial photography,lidar,surface displacement monitoring and other technical means to reveal the historical deformation and pre-sliding deformation characteristics of the landslide. Finally,we analyze the mechanism of the landslide. After preliminary analysis,we conclude that Xingyi landslide belongs to a typical bedding rock landslide with weak intercalation. The slope in the source area of the landslide was an unstable slope formed after the first sliding in 2014. It had a combination of unfavorable slope structure and weak intercalation. Under the action of long-term gravity and groundwater,it eventually evolved into a landslide geological disaster. In the process of landslide evolution,the strength of the weak intercalation decreased after the interaction with groundwater,and its physical and mechanical properties also became poor,which was easy to produce extrusion deformation and led to compression and shear deformation of the sliding body towards the free direction,resulting in cracking of the rear edge and side boundary slope. Such cracks formed the main control structural plane. Before the landslide,the researchers installed two kinds of displacement monitoring sensors,the global navigation satellite system(GNSS) and the adaptive crack meter,to continuously monitor the deformation of the landslide. The on-site monitoring data is transmitted to the"geological disaster monitoring and early warning system" in real time,which was independently developed by researchers. The system automatically calculates the monitoring data and issues the early warning results through a variety of threshold comprehensive early warning models. According to the analysis of monitoring data,the landslide experienced the initial acceleration deformation stage,the intermediate acceleration deformation stage,the temporary sliding stage,and finally the disaster occurred. At each stage,the system released the early warning information in time according to the four-level early warning mechanism. Especially after the landslide entered the critical slide stage,the system sent out the red early warning 53 minutes in advance,which created the time condition for disaster emergency disposal and completely avoided the loss of personnel and economy. The successful early warning of the landslide reflected the applicability of the self-developed geological disaster monitoring and early warning system,early warning model and monitoring instrument,which can provide reference for research and application of similar landslide monitoring and early warning in the future.
Due to the complex structure of rock and soil mass and various failure mechanisms,landslide early warning has always been a global problem of very challenging. At 5:53 a.m. on 17 February 2019 in Longjing Village,Maling Town,Xingyi City,Guizhou Province,a landslide geological disaster occurred. About 960,000 cubic meters of mountain had a bedding sliding,which posed a serious threat to the road and residential area located at the foot of the front slope. In this paper,we discuss the characteristics and successful early warning process of this Xingyi landslide in Guizhou Province,and analyze the key factors of successful early warning. On the basis of geological investigations on the landslide site,this paper comprehensively use satellite remote sensing,UAV aerial photography,lidar,surface displacement monitoring and other technical means to reveal the historical deformation and pre-sliding deformation characteristics of the landslide. Finally,we analyze the mechanism of the landslide. After preliminary analysis,we conclude that Xingyi landslide belongs to a typical bedding rock landslide with weak intercalation. The slope in the source area of the landslide was an unstable slope formed after the first sliding in 2014. It had a combination of unfavorable slope structure and weak intercalation. Under the action of long-term gravity and groundwater,it eventually evolved into a landslide geological disaster. In the process of landslide evolution,the strength of the weak intercalation decreased after the interaction with groundwater,and its physical and mechanical properties also became poor,which was easy to produce extrusion deformation and led to compression and shear deformation of the sliding body towards the free direction,resulting in cracking of the rear edge and side boundary slope. Such cracks formed the main control structural plane. Before the landslide,the researchers installed two kinds of displacement monitoring sensors,the global navigation satellite system(GNSS) and the adaptive crack meter,to continuously monitor the deformation of the landslide. The on-site monitoring data is transmitted to the"geological disaster monitoring and early warning system" in real time,which was independently developed by researchers. The system automatically calculates the monitoring data and issues the early warning results through a variety of threshold comprehensive early warning models. According to the analysis of monitoring data,the landslide experienced the initial acceleration deformation stage,the intermediate acceleration deformation stage,the temporary sliding stage,and finally the disaster occurred. At each stage,the system released the early warning information in time according to the four-level early warning mechanism. Especially after the landslide entered the critical slide stage,the system sent out the red early warning 53 minutes in advance,which created the time condition for disaster emergency disposal and completely avoided the loss of personnel and economy. The successful early warning of the landslide reflected the applicability of the self-developed geological disaster monitoring and early warning system,early warning model and monitoring instrument,which can provide reference for research and application of similar landslide monitoring and early warning in the future.
5
2020, 28(6): 1233-1245.
The 2008 "5.12" Wenchuan earthquake greatly changed the characteristics of debris flows in the earthquake zone. The earthquake not only enhanced the activity of debris flows,but also made the earthquake area under the threat of debris flows for a long time. During the past 10 years after the earthquake,debris flows occurred frequently. It is of great significance to study the characteristics and development trend of debris flows in Wenchuan County. We analyze the longitudinal gradient,gully density and slope gradient in Wenchuan County by means of remote sensing interpretation and field investigation. We further analyze the rainfall spatial and temporal trends and critical rainfall characteristics of debris flows in Wenchuan County by collecting rainfall data and previous research. According to the study,the average annual rainfall in Wenchuan County increased by 5.17% after the earthquake. The rainfall was mainly in July and September,the amount of rainfall decreased gradually from north to south. The gully density of debris flow gully is between 0.2 and 4,which belongs to the soil erosion area of the micro-degree. The longitudinal gradient of debris flow is large,which is conducive to the occurrence of debris flow. The slope gradient of debris flows is 30°~40°,which is conducive to the occurrence of disasters. The rainfall threshold of the post-earthquake debris flow shows a slow increased in 2008-2013, but declined in 2019. It is expected that it can take a long time to return to the pre-earthquake levels. The provenance of debris flows in Wenchuan County is abundant,and the amount of provenance in the earthquake is decreased in a fluctuating tendency.
The 2008 "5.12" Wenchuan earthquake greatly changed the characteristics of debris flows in the earthquake zone. The earthquake not only enhanced the activity of debris flows,but also made the earthquake area under the threat of debris flows for a long time. During the past 10 years after the earthquake,debris flows occurred frequently. It is of great significance to study the characteristics and development trend of debris flows in Wenchuan County. We analyze the longitudinal gradient,gully density and slope gradient in Wenchuan County by means of remote sensing interpretation and field investigation. We further analyze the rainfall spatial and temporal trends and critical rainfall characteristics of debris flows in Wenchuan County by collecting rainfall data and previous research. According to the study,the average annual rainfall in Wenchuan County increased by 5.17% after the earthquake. The rainfall was mainly in July and September,the amount of rainfall decreased gradually from north to south. The gully density of debris flow gully is between 0.2 and 4,which belongs to the soil erosion area of the micro-degree. The longitudinal gradient of debris flow is large,which is conducive to the occurrence of debris flow. The slope gradient of debris flows is 30°~40°,which is conducive to the occurrence of disasters. The rainfall threshold of the post-earthquake debris flow shows a slow increased in 2008-2013, but declined in 2019. It is expected that it can take a long time to return to the pre-earthquake levels. The provenance of debris flows in Wenchuan County is abundant,and the amount of provenance in the earthquake is decreased in a fluctuating tendency.
- First
- Prev
- 1
- 2
- 3
- 4
- 5
- Next
- Last
- Total:8
- To
- Go
微信 | 公众平台 
