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Editor Work2010 Vol. 18, No. 6
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2010, 18(6): 805-817.
Abstract
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The occurrence of rock avalanche always brings disastrous catastrophes because of its high speed and unexpected long runout. So,its kinematics or moving mechanism has been the focus of engineering geologists around the world since late 19th century. At present,there are four viewpoints abroad: air-lubrication model,grain flow model,momentum-transfer model and self-undrained loading model. Howver,they have not been widely accepted possibly because of complication. China is a country where frequent rock avalances occur. The research on this field is just at the beginning and most of the research results are qualitative. Based on a review of a plenty of literatures,this paper expounds the development status of study on the transport mechanism of rock avalanches in two aspects of theories and research techniques. It summarizes the existing numerous models,comments on the research difficulties at present. Finally,it puts forward the research directions in the future according to the present bottlenecks. This paper systematically sums up the relevant research status and can be helpful to the future research.
The occurrence of rock avalanche always brings disastrous catastrophes because of its high speed and unexpected long runout. So,its kinematics or moving mechanism has been the focus of engineering geologists around the world since late 19th century. At present,there are four viewpoints abroad: air-lubrication model,grain flow model,momentum-transfer model and self-undrained loading model. Howver,they have not been widely accepted possibly because of complication. China is a country where frequent rock avalances occur. The research on this field is just at the beginning and most of the research results are qualitative. Based on a review of a plenty of literatures,this paper expounds the development status of study on the transport mechanism of rock avalanches in two aspects of theories and research techniques. It summarizes the existing numerous models,comments on the research difficulties at present. Finally,it puts forward the research directions in the future according to the present bottlenecks. This paper systematically sums up the relevant research status and can be helpful to the future research.
2010, 18(6): 818-826.
Due to its unusually strong seismic shaking,the5 12Wenchuan Earthquake in 2008 induced hundreds of large-scale landslides.This paper is based on the interpreted data about 112 landslides,each of which has a plane area greater than 50000m2. It also uses the field investigation of representative large-scale landslides. It further conducts a systematic analysis on the distribution regularities of these large-scale landslides. It is suggested that the large-scale landslides not only show the distribution rules similar to those associated with the general landslides induced by Wenchuan Earthquake,but also present unique features in the distribution as well as sliding and moving ways. The occurrences of the large-scale landslides are usually attributed to the direct seismic forces resulting from the horizontal displacements of seismic faults. The distribution rules of large-scale landslides induced by Wenchuan Earthquake can be summarized as follows: (1)distance effect: about 80% large-scale landslides are distributed within the range of 5km from the Yinxiu-Beichuan fault(i.e. ,seismic fault ruptures). The farther the distance is,the lower the number of landslides is. (2) Locked segment effect: the large-scale landslides are mainly distributed in the five concentration zones closely related with the crossing,staggering and transforming section as well as the end of NE section of the seismic fault. The most concentrated zone is Hongbai-Chaping segment,where many large-scale landslides and the two largest landslides were induced by Wenchuan Earthquake. The second concentrated zone is Nanba-Donghekou segment at the NE end of the seismic fault,where the well-known Donghekou Landslide and Woqian Landslide are located. (3)Hanging wall effect: a vast majority of large-scale landslides (70%) are located in the hanging wall of the seismic fault,showing a clearHanging wall effect. (4)Direction effect: in the valley slopes almost perpendicular to the seismic fault,the number of large scale landslides at the slopes opposing the direction of seismic source are obviously higher than those facing the direction of seismic source,showingback slope effect.Meanwhile,the sliding and moving directions of large-scale landslides have some relations with the staggering direction of the seismic fault in each section.In Qingchuan area where the main fault activity was horizontal twisting and staggering,a considerable number of large scale landslides show the features of sliding and moving along the NE direction that was the staggering direction of the seismic fault.
Due to its unusually strong seismic shaking,the5 12Wenchuan Earthquake in 2008 induced hundreds of large-scale landslides.This paper is based on the interpreted data about 112 landslides,each of which has a plane area greater than 50000m2. It also uses the field investigation of representative large-scale landslides. It further conducts a systematic analysis on the distribution regularities of these large-scale landslides. It is suggested that the large-scale landslides not only show the distribution rules similar to those associated with the general landslides induced by Wenchuan Earthquake,but also present unique features in the distribution as well as sliding and moving ways. The occurrences of the large-scale landslides are usually attributed to the direct seismic forces resulting from the horizontal displacements of seismic faults. The distribution rules of large-scale landslides induced by Wenchuan Earthquake can be summarized as follows: (1)distance effect: about 80% large-scale landslides are distributed within the range of 5km from the Yinxiu-Beichuan fault(i.e. ,seismic fault ruptures). The farther the distance is,the lower the number of landslides is. (2) Locked segment effect: the large-scale landslides are mainly distributed in the five concentration zones closely related with the crossing,staggering and transforming section as well as the end of NE section of the seismic fault. The most concentrated zone is Hongbai-Chaping segment,where many large-scale landslides and the two largest landslides were induced by Wenchuan Earthquake. The second concentrated zone is Nanba-Donghekou segment at the NE end of the seismic fault,where the well-known Donghekou Landslide and Woqian Landslide are located. (3)Hanging wall effect: a vast majority of large-scale landslides (70%) are located in the hanging wall of the seismic fault,showing a clearHanging wall effect. (4)Direction effect: in the valley slopes almost perpendicular to the seismic fault,the number of large scale landslides at the slopes opposing the direction of seismic source are obviously higher than those facing the direction of seismic source,showingback slope effect.Meanwhile,the sliding and moving directions of large-scale landslides have some relations with the staggering direction of the seismic fault in each section.In Qingchuan area where the main fault activity was horizontal twisting and staggering,a considerable number of large scale landslides show the features of sliding and moving along the NE direction that was the staggering direction of the seismic fault.
2010, 18(6): 827-836.
Many debris flow hazards were triggered recently in the epicenter area of the 2008 Wenchuan Earthquake. The severest debris flow is the debris flow in Wenjia Gully on Aug.13, 2010.Wenjia Gully was a simply and ordinary gully and had no debris flow at all before the Wenchuan Earthquake.The formation conditions of debris flows were totally changed by a giant landslide caused by the earthquake.The giant landslide formed a landslidedebris deposition in the gully.The debris deposition had a volume of more than 30million cubic meters.The sediments were easily eroded by flash flood and formed debris flows.In the three raining seasons after the earthquake, a total of five large scale and giant scale debris flow were triggered.The largest and most harmful debris flow occurred on Aug.13, 2010.The total rainfall during the debris flow was 227mm,and the duration of debris flow was 2.5 hours.The volume of debris flow was 3.1 million cubic meters.The debris flow resulted in 7 fatalities, 5 persons listed as missing, 39 persons injured, 479 houses buried,and a direct economic loss of RMB 430 million. About 16%sediments of the landslide-debris deposition flew down out of the gully during the five large scale debris flows.New debris flows will be triggered by rainfall in the gully in the future.It will be a long-term effort for prevention and mitigation of the debris flow hazards in the gully.
Many debris flow hazards were triggered recently in the epicenter area of the 2008 Wenchuan Earthquake. The severest debris flow is the debris flow in Wenjia Gully on Aug.13, 2010.Wenjia Gully was a simply and ordinary gully and had no debris flow at all before the Wenchuan Earthquake.The formation conditions of debris flows were totally changed by a giant landslide caused by the earthquake.The giant landslide formed a landslidedebris deposition in the gully.The debris deposition had a volume of more than 30million cubic meters.The sediments were easily eroded by flash flood and formed debris flows.In the three raining seasons after the earthquake, a total of five large scale and giant scale debris flow were triggered.The largest and most harmful debris flow occurred on Aug.13, 2010.The total rainfall during the debris flow was 227mm,and the duration of debris flow was 2.5 hours.The volume of debris flow was 3.1 million cubic meters.The debris flow resulted in 7 fatalities, 5 persons listed as missing, 39 persons injured, 479 houses buried,and a direct economic loss of RMB 430 million. About 16%sediments of the landslide-debris deposition flew down out of the gully during the five large scale debris flows.New debris flows will be triggered by rainfall in the gully in the future.It will be a long-term effort for prevention and mitigation of the debris flow hazards in the gully.
2010, 18(6): 837-843.
512 Wenchuan earthquake triggered thousands of rockcollapses,landslides,debris flows and other geological disasters. In order to study the response of the doublesides slope to the earthquake,we designed a total of 11 models according to the field investigation. We took four factors into consideration to study the seismic response of the slope. The four factors are the slopedegree,the top width of slope,structure combination and the shape of the doublesides slope. The tests manifested that (a)seismic inertia force is the main factor that results in slope failure; (b)the deformation and failure of the slope has a relation to the initial seismic direction; (c)the doublesides slope shows an conjugatedshear phenomenon; (d)different structure combinations of slopes result in different failure modes; e)the conjugatedshear phenomenon is more obvious on the laddershaped doublesides slope. The test findings are well in line with the results of field investigation．
512 Wenchuan earthquake triggered thousands of rockcollapses,landslides,debris flows and other geological disasters. In order to study the response of the doublesides slope to the earthquake,we designed a total of 11 models according to the field investigation. We took four factors into consideration to study the seismic response of the slope. The four factors are the slopedegree,the top width of slope,structure combination and the shape of the doublesides slope. The tests manifested that (a)seismic inertia force is the main factor that results in slope failure; (b)the deformation and failure of the slope has a relation to the initial seismic direction; (c)the doublesides slope shows an conjugatedshear phenomenon; (d)different structure combinations of slopes result in different failure modes; e)the conjugatedshear phenomenon is more obvious on the laddershaped doublesides slope. The test findings are well in line with the results of field investigation．
2010, 18(6): 844-850.
Investigation of the slopes in Wenchuan earthquake shows that tension failures mostly appear in the slope crests,and shear failure in slope toe. Beginning with the stress state of soil,using the finitedifference method,the failure process of slope is analyzed under the given conditions of static,horizontal and coupled earthquake by monitoring the changing of state,displacement,and shearstrain increment. The calculated results indicate that the slope crest is tensile damage and shear failure appears in slope toe. It is different from the traditional opinion of geological engineering that slope damage under earthquakes is mainly shear failure due to seismic inertia force. A new method of the relative displacement of key points is put out to judge the dynamic stability. Numerical simulation results have good consistency with existing research results and postseismic investigation findings．
Investigation of the slopes in Wenchuan earthquake shows that tension failures mostly appear in the slope crests,and shear failure in slope toe. Beginning with the stress state of soil,using the finitedifference method,the failure process of slope is analyzed under the given conditions of static,horizontal and coupled earthquake by monitoring the changing of state,displacement,and shearstrain increment. The calculated results indicate that the slope crest is tensile damage and shear failure appears in slope toe. It is different from the traditional opinion of geological engineering that slope damage under earthquakes is mainly shear failure due to seismic inertia force. A new method of the relative displacement of key points is put out to judge the dynamic stability. Numerical simulation results have good consistency with existing research results and postseismic investigation findings．
2010, 18(6): 851-856.
Entropy originated from thermodynamics is an effective method of multi-objective decision and a measurement of system uncertainty. It is still not applied widely in geology especially in analysing the slope stability. So a new method for evaluating the slope stability is presented in this paper. It is based on the interaction matrix and information entropy. The new method combines the sensitivity of interaction matrix to each influencing factor on slope stability and the quantization of information entropy to the irregularity of slope. It can provide the objective result of slope stability using factors in geology, environmental and engineering. It has been shown that the result calculated with entropy method is consistent well with the geology data. The result of the new method has been applied to the stability analysis of the left bank slope at Long-tan hydropower dam site. In a word,it is a new analysistechnique with promotional value.
Entropy originated from thermodynamics is an effective method of multi-objective decision and a measurement of system uncertainty. It is still not applied widely in geology especially in analysing the slope stability. So a new method for evaluating the slope stability is presented in this paper. It is based on the interaction matrix and information entropy. The new method combines the sensitivity of interaction matrix to each influencing factor on slope stability and the quantization of information entropy to the irregularity of slope. It can provide the objective result of slope stability using factors in geology, environmental and engineering. It has been shown that the result calculated with entropy method is consistent well with the geology data. The result of the new method has been applied to the stability analysis of the left bank slope at Long-tan hydropower dam site. In a word,it is a new analysistechnique with promotional value.
2010, 18(6): 857-861.
Debris flow is one of the common mountain hazards and seriously threatens human lives and belongings and affects society development. Therefore,it is necessary to study more about its happening and development. The approach of combining the dynamic model equations with the use of the numerical methods can lead to in-depth understanding of the development of debris flow. This is an effective approach to study and forecast the debris flow disasters. However,a majority of the present dynamic model equations focus on the dynamic process,and ignore the combination of the static and dynamic process. In fact,this neglect may result in some mis-leading results under some condition. In this paper,the characteristics of static and dynamic resistance of one-dimensional debris flow are studied. By modifying the friction resistance term of the kinetic equation,the model equation is obtained for the uniform characteristic of static and dynamic. Based on the approximate Riemann solver of Roe scheme,the numerical solution with higher precision and resolution is achieved by use of MUSCL linear reconstruction.The numerical validation of an actual example proves the rationality of the modification of friction resistance term and the stability and effectivity of the developed numerical calculation.
Debris flow is one of the common mountain hazards and seriously threatens human lives and belongings and affects society development. Therefore,it is necessary to study more about its happening and development. The approach of combining the dynamic model equations with the use of the numerical methods can lead to in-depth understanding of the development of debris flow. This is an effective approach to study and forecast the debris flow disasters. However,a majority of the present dynamic model equations focus on the dynamic process,and ignore the combination of the static and dynamic process. In fact,this neglect may result in some mis-leading results under some condition. In this paper,the characteristics of static and dynamic resistance of one-dimensional debris flow are studied. By modifying the friction resistance term of the kinetic equation,the model equation is obtained for the uniform characteristic of static and dynamic. Based on the approximate Riemann solver of Roe scheme,the numerical solution with higher precision and resolution is achieved by use of MUSCL linear reconstruction.The numerical validation of an actual example proves the rationality of the modification of friction resistance term and the stability and effectivity of the developed numerical calculation.
2010, 18(6): 862-866.
Based on the systematic investigation of cha-shu-shan landslide on Chuan-Zang highway, this paper analyzes the landslide rock and soil structures,boundary conditions,deformation characteristics,influence factors and formation mechanism,and makes a in-depth discussions combined with 3DEC numerical simulation. The comprehensive analysis shows that the landslide is located in an active fault. The back edge rock is poor,and the front loose accumulation is thick. Under seismic activity,rainfall and other factors eliciting,the failure mechanism of landslide can be divided into the following 3 stages: (1)stage of toppling and pull-splitting,the back edge landslides stabilty is controled by the topography and structure of rock mass, where formes a rather strong dumped rupture deformation belt. Then generates slippage.(2)stage of creep deformation,the front loose accumulation body occurs creep deformation in a powerful gravity thrust.(3)stage of failing,clavicle segment are cutted in the weight thrust and the continuing effects of fault activity. Then the backedge potential slide plane and front shear slip plane are linked the whole landslide fails.
Based on the systematic investigation of cha-shu-shan landslide on Chuan-Zang highway, this paper analyzes the landslide rock and soil structures,boundary conditions,deformation characteristics,influence factors and formation mechanism,and makes a in-depth discussions combined with 3DEC numerical simulation. The comprehensive analysis shows that the landslide is located in an active fault. The back edge rock is poor,and the front loose accumulation is thick. Under seismic activity,rainfall and other factors eliciting,the failure mechanism of landslide can be divided into the following 3 stages: (1)stage of toppling and pull-splitting,the back edge landslides stabilty is controled by the topography and structure of rock mass, where formes a rather strong dumped rupture deformation belt. Then generates slippage.(2)stage of creep deformation,the front loose accumulation body occurs creep deformation in a powerful gravity thrust.(3)stage of failing,clavicle segment are cutted in the weight thrust and the continuing effects of fault activity. Then the backedge potential slide plane and front shear slip plane are linked the whole landslide fails.
2010, 18(6): 867-872.
Under the background of global sea-level rise,the range of coastal erosion has become larger,and erosion degree has become more and more serious in recent years.Coastal erosion disasters have threatened the survival and living environments of coastal zones,and have gradually brought a great economic loss.Until now,occurrence mechanism and stability evaluation of coastal erosion disasters have not been fully understood yet.A majority of researchers at present are focused on the impact of wave,storm surge and other objective factors on coastal erosion.The geological factors including lithologic conditions,rock and soil mechanical properties and bank structures are seldom studied.Therefore,this paper points out that further investigations on coastal erosion disasters shall be strengthened on the following five issues: (1)correlation between coastal erosions and geological environmental conditions; (2)regional characteristics and law of development and distribution of coastal erosions; (3)deformation and failure modes of erosion banks; (4)mechanical properties of rocks and soils under different erosion factors; (5)evaluation mechanism of coastal stability.
Under the background of global sea-level rise,the range of coastal erosion has become larger,and erosion degree has become more and more serious in recent years.Coastal erosion disasters have threatened the survival and living environments of coastal zones,and have gradually brought a great economic loss.Until now,occurrence mechanism and stability evaluation of coastal erosion disasters have not been fully understood yet.A majority of researchers at present are focused on the impact of wave,storm surge and other objective factors on coastal erosion.The geological factors including lithologic conditions,rock and soil mechanical properties and bank structures are seldom studied.Therefore,this paper points out that further investigations on coastal erosion disasters shall be strengthened on the following five issues: (1)correlation between coastal erosions and geological environmental conditions; (2)regional characteristics and law of development and distribution of coastal erosions; (3)deformation and failure modes of erosion banks; (4)mechanical properties of rocks and soils under different erosion factors; (5)evaluation mechanism of coastal stability.
2010, 18(6): 873-879.
To study the phenomena of the large-scale landslides in the event of time occurrence,this paper conducts some statistics on the time of distribution and induction factors about the large-scale landslide,which occurred in recent years in China. Observed from the statistics about the time distribution and the induction factor of large-scale landslides,the natural slopes often had the destruction under certain induction factors.However,the large-scale landslide occurrence in the time distribution is easy to be found around plenilune or meniscus.The specific time which occurs in one day presents the characteristic of normal distribution.Therefore,according to the earth tide theory,as well as the time corresponding relations between the tide-producing force and the landslide occurrence during one day,this paper suggests the earth tide is one of the factors which induce instability of large scale landslide.Because simultaneously the creep characteristic of different materials which compose landslide is different,which caused the large-scale landslide occurrence often to have in advance or the hysteresis.The above result has provided certain theory support for the landslide forecast or prevention.
To study the phenomena of the large-scale landslides in the event of time occurrence,this paper conducts some statistics on the time of distribution and induction factors about the large-scale landslide,which occurred in recent years in China. Observed from the statistics about the time distribution and the induction factor of large-scale landslides,the natural slopes often had the destruction under certain induction factors.However,the large-scale landslide occurrence in the time distribution is easy to be found around plenilune or meniscus.The specific time which occurs in one day presents the characteristic of normal distribution.Therefore,according to the earth tide theory,as well as the time corresponding relations between the tide-producing force and the landslide occurrence during one day,this paper suggests the earth tide is one of the factors which induce instability of large scale landslide.Because simultaneously the creep characteristic of different materials which compose landslide is different,which caused the large-scale landslide occurrence often to have in advance or the hysteresis.The above result has provided certain theory support for the landslide forecast or prevention.
2010, 18(6): 880-886.
Based on the extensively literature review,this paper summarizes the main issues in the research work of physical sub-ground erosion. The ppaer points out that the engineering geological problems related to the physical sub-ground erosion become more and more serious with the development of various construction projects. However,resulting from the multiplicity,complexity and randomness of the physical sub-ground erosion process,some concepts related to the physical sub-ground erosion are still confusing because of the wrongly or inaccuracy definations,which makes it difficult to academic exchanges.By analyzing of the mechanism,the precise conceptual models ofpiping,seepage compression,contact piping,soil flowing,soil bursting,contact soil flowing,flowing sandandflow solidsare established in this paper,which forms an essential bases of the further research work on the sub-ground erosion.
Based on the extensively literature review,this paper summarizes the main issues in the research work of physical sub-ground erosion. The ppaer points out that the engineering geological problems related to the physical sub-ground erosion become more and more serious with the development of various construction projects. However,resulting from the multiplicity,complexity and randomness of the physical sub-ground erosion process,some concepts related to the physical sub-ground erosion are still confusing because of the wrongly or inaccuracy definations,which makes it difficult to academic exchanges.By analyzing of the mechanism,the precise conceptual models ofpiping,seepage compression,contact piping,soil flowing,soil bursting,contact soil flowing,flowing sandandflow solidsare established in this paper,which forms an essential bases of the further research work on the sub-ground erosion.
2010, 18(6): 887-893.
By taking the loess of Yangling area in Shaanxi province as the research object,a direct shear test is conducted with different water contents,dry densities and times of freezing-thawing cycles. The tests are to explore the way and the criterion of long-term freezing-thawing cycles.Then the characteristic of loess deterioration with long-term freezing-thawing cycles is studied in a closed system.The test result show that: (1)in the condition of long-term freezing-thawing cycles,the surface of loess is destroyed greatly; (2)the cohesion of loess decreases firstly and increases later according to the suggestion.The freezing-thawing cycles and the minimum value are normally appeared in ten freezing-thawing cycles.The internal friction angle of loess keeps invariable basically. The strength of loess is affected greatly in three-five freezing-thawing cycles,which can lead to strength deterioration of loess.But with the time going,the influence of freezing-thawing cycles is reflected on the transmutation of loess surface.
By taking the loess of Yangling area in Shaanxi province as the research object,a direct shear test is conducted with different water contents,dry densities and times of freezing-thawing cycles. The tests are to explore the way and the criterion of long-term freezing-thawing cycles.Then the characteristic of loess deterioration with long-term freezing-thawing cycles is studied in a closed system.The test result show that: (1)in the condition of long-term freezing-thawing cycles,the surface of loess is destroyed greatly; (2)the cohesion of loess decreases firstly and increases later according to the suggestion.The freezing-thawing cycles and the minimum value are normally appeared in ten freezing-thawing cycles.The internal friction angle of loess keeps invariable basically. The strength of loess is affected greatly in three-five freezing-thawing cycles,which can lead to strength deterioration of loess.But with the time going,the influence of freezing-thawing cycles is reflected on the transmutation of loess surface.
2010, 18(6): 894-899.
The physicochemical characteristics as well as the mechanical characteristics of aeolian sand are studied through tests in this paper. The result shows that the standard compaction curve of aeolian sand in the Mu Us desert different from that of silt and mud soil. The split-blip character of the standard compaction curve suggests that the higher dry density of aeolian sand can be obtained when the sand is dry or with the optimum moisture content. The aeolian sand has a low-compression ability and the compressibility is related with the initial dry density,water content and the load. The triaxial shear test shows that both of the density and the water content contribute to the shearing stregnth of the sand,between which the density contributes more and the water content only contributes a little. The work in this paper can offer some basic data for the resolution of the engineering geological problems in the Mu Us desert.
The physicochemical characteristics as well as the mechanical characteristics of aeolian sand are studied through tests in this paper. The result shows that the standard compaction curve of aeolian sand in the Mu Us desert different from that of silt and mud soil. The split-blip character of the standard compaction curve suggests that the higher dry density of aeolian sand can be obtained when the sand is dry or with the optimum moisture content. The aeolian sand has a low-compression ability and the compressibility is related with the initial dry density,water content and the load. The triaxial shear test shows that both of the density and the water content contribute to the shearing stregnth of the sand,between which the density contributes more and the water content only contributes a little. The work in this paper can offer some basic data for the resolution of the engineering geological problems in the Mu Us desert.
2010, 18(6): 900-905.
In this paper,the stress-strain relationship of soil established from shear tests is distinguished into two kinds-strain hardening type and strain softening type. A new stress-strain model which can not only describes strain hardening stress-strain curve but also strain softening stress-strain curve is presented. The equation of tangent modulus is deduced. The paper presents the simplified form of the expression when it was employed to describe strain hardening stress-strain curve. The method of fixing the parameter and the relationship between the parameters and the confining pressure was studied. Comparing this new model with Duncan-Chang model and the strain softening model, it is found that this new model can better meet test results. The simplified form of new model is more accurately to describe strain hardening stress-strain curve and can describe more kinds of curve comparison with Duncan-Chang mode1. It is able to display variety of the stress-strain curve of soils using a changeable parameter. The unified expression provides a base to develop a general nonlinear mechanics model of soils.
In this paper,the stress-strain relationship of soil established from shear tests is distinguished into two kinds-strain hardening type and strain softening type. A new stress-strain model which can not only describes strain hardening stress-strain curve but also strain softening stress-strain curve is presented. The equation of tangent modulus is deduced. The paper presents the simplified form of the expression when it was employed to describe strain hardening stress-strain curve. The method of fixing the parameter and the relationship between the parameters and the confining pressure was studied. Comparing this new model with Duncan-Chang model and the strain softening model, it is found that this new model can better meet test results. The simplified form of new model is more accurately to describe strain hardening stress-strain curve and can describe more kinds of curve comparison with Duncan-Chang mode1. It is able to display variety of the stress-strain curve of soils using a changeable parameter. The unified expression provides a base to develop a general nonlinear mechanics model of soils.
2010, 18(6): 906-912.
This paper studies the reinforcement of soft clay by dynamic consolidation with drainage.It develops a large-scale indoor simulation equipment and conducts some tests.It is focused on the monitoring and analyzing for settlement of tamping points as well as instantaneous and long-term variations of pore water pressure.The findings are that the wave generated by tamping spreads inward the soil and it can form stretcher fissures.The fissures become the first drainage channel.The variation of pore water pressure has fluctuations.At the tamping time it appears negative growth. Then it accumulates upward.The increasing range of pore water pressure is relevant with depth.The sand bedding can be used for drainage as well as static load for consolidation.
This paper studies the reinforcement of soft clay by dynamic consolidation with drainage.It develops a large-scale indoor simulation equipment and conducts some tests.It is focused on the monitoring and analyzing for settlement of tamping points as well as instantaneous and long-term variations of pore water pressure.The findings are that the wave generated by tamping spreads inward the soil and it can form stretcher fissures.The fissures become the first drainage channel.The variation of pore water pressure has fluctuations.At the tamping time it appears negative growth. Then it accumulates upward.The increasing range of pore water pressure is relevant with depth.The sand bedding can be used for drainage as well as static load for consolidation.
2010, 18(6): 913-919.
A physical model experimental system is developed in order to investigate the temperature variation with time in soil depth profile.The thermal conduction characteristics in soil profile with different surface covers but under the same heat source are compared and analyzed.The obtained results show that (a)the soil temperature increases quickly at the beginning stage and then tends to a relative stable value; (b)with increasing depth,the initial temperature increase rate of soil decreases exponentially; and (c)the final equilibrium temperature of soil also decreases with increasing depth.It is observed that the damping and retarding effects of soil temperature with depth are obvious.By comparing with bare soil,the initial temperature increase rate and final equilibrium temperature of soil with surface concrete plate cover are higher.The thermal flux in soil profile,which is measured by thermal flux plate,reflects the thermal conduction characteristics in time,and directly depends on the variation of temperature gradient between soil layers.
A physical model experimental system is developed in order to investigate the temperature variation with time in soil depth profile.The thermal conduction characteristics in soil profile with different surface covers but under the same heat source are compared and analyzed.The obtained results show that (a)the soil temperature increases quickly at the beginning stage and then tends to a relative stable value; (b)with increasing depth,the initial temperature increase rate of soil decreases exponentially; and (c)the final equilibrium temperature of soil also decreases with increasing depth.It is observed that the damping and retarding effects of soil temperature with depth are obvious.By comparing with bare soil,the initial temperature increase rate and final equilibrium temperature of soil with surface concrete plate cover are higher.The thermal flux in soil profile,which is measured by thermal flux plate,reflects the thermal conduction characteristics in time,and directly depends on the variation of temperature gradient between soil layers.
2010, 18(6): 920-925.
This paper simulates the variation law of mechanical and hydraulic behavior unsaturated soils in the process of repetitively raining or evaporation. It establishes a hysteresis model on the basis of the basic principle of traditional domain model. The model is simple and can be easily adapted to programming. It is compared to some experimental data and other hysteresis models. The reliability of the proposed model is validated. The result demonstrates its good applicability in practice. Meanwhile, this model can be used as a basis in the research of the permeability and strength characteristic, together with the constitutive theories for unsaturated soils.
This paper simulates the variation law of mechanical and hydraulic behavior unsaturated soils in the process of repetitively raining or evaporation. It establishes a hysteresis model on the basis of the basic principle of traditional domain model. The model is simple and can be easily adapted to programming. It is compared to some experimental data and other hysteresis models. The reliability of the proposed model is validated. The result demonstrates its good applicability in practice. Meanwhile, this model can be used as a basis in the research of the permeability and strength characteristic, together with the constitutive theories for unsaturated soils.
2010, 18(6): 926-932.
Grouting is a common measure for leakage control in dam rock mass. , Currently the physical grouting test is used to determine the parameters such as grouting ratio and pitch. It must spend a lot of time and effort. This paper develops a 3-dimesional numerical simulation test of grouting seepage for rapid determining grouting schemes. It uses a dam site with known geological conditions and analysis of rock leakage. It simulates the migration regularity of groundwater water before store water in the reservoir. The simulated results are compared with actual drilling data and ground water migration patterns in flat adit. The assumption of groundwater migration rule is also compared. It then simulates the groundwater reservoir migration regularity of groundwater, simulates and understands migration regularity of groundwater, and the direction of migration. The preliminary judgment is done according to the actual situation of groundwater migration direction. Finally, numerical simulation determines the certain proportion of slurry grouting for grouting quantity and the situation of the actual grouting test results. The results show that the numerical simulation test can establish the relationship between mix design of slurry grouting and the effect of grounting. This relationship can be used for quick selection of the mix design in similar proportions.
Grouting is a common measure for leakage control in dam rock mass. , Currently the physical grouting test is used to determine the parameters such as grouting ratio and pitch. It must spend a lot of time and effort. This paper develops a 3-dimesional numerical simulation test of grouting seepage for rapid determining grouting schemes. It uses a dam site with known geological conditions and analysis of rock leakage. It simulates the migration regularity of groundwater water before store water in the reservoir. The simulated results are compared with actual drilling data and ground water migration patterns in flat adit. The assumption of groundwater migration rule is also compared. It then simulates the groundwater reservoir migration regularity of groundwater, simulates and understands migration regularity of groundwater, and the direction of migration. The preliminary judgment is done according to the actual situation of groundwater migration direction. Finally, numerical simulation determines the certain proportion of slurry grouting for grouting quantity and the situation of the actual grouting test results. The results show that the numerical simulation test can establish the relationship between mix design of slurry grouting and the effect of grounting. This relationship can be used for quick selection of the mix design in similar proportions.
2010, 18(6): 933-939.
The adverse geologic elements within the dam foundation below left pedestal of the jinping I project cause not only the disruption of rock mass in integrity,but also the nonhomogeneous deformation of foundation interface,which can endanger the safety of the arc dam. Based upon their environments of rock masses qualities,the geologic defects are classified into three major classes: the anaclinal and bed-paralleled structural zone,the steep dipping and cross-bedding structural zone and the Karst fracture zone.Furthermore,the control action of the various geologic defects on the dam foundation in integrity,homogeneity,and deformation is discussed.The wave velocity and attenuation characteristic of their typical speed curves of sonic wave are also analyzed.Thereby,the qualitative evaluation of the influence degree of geologic defect to rock masses in dam foundation is made by zoning in order ofslightly,moderatelyandhighlyrates.And the conclusions emphasize that the anaclinal and bed-paralleled structural zones are large scale,and have small spacing and low wave velocity value(2500～3500m s-1) near the fault f2. The zones not only control over the shearing properties of rock masses,but also have a highly-degree influence on the differential deformation and the stress distribution of the dam foundation,which should be deal with separately.
The adverse geologic elements within the dam foundation below left pedestal of the jinping I project cause not only the disruption of rock mass in integrity,but also the nonhomogeneous deformation of foundation interface,which can endanger the safety of the arc dam. Based upon their environments of rock masses qualities,the geologic defects are classified into three major classes: the anaclinal and bed-paralleled structural zone,the steep dipping and cross-bedding structural zone and the Karst fracture zone.Furthermore,the control action of the various geologic defects on the dam foundation in integrity,homogeneity,and deformation is discussed.The wave velocity and attenuation characteristic of their typical speed curves of sonic wave are also analyzed.Thereby,the qualitative evaluation of the influence degree of geologic defect to rock masses in dam foundation is made by zoning in order ofslightly,moderatelyandhighlyrates.And the conclusions emphasize that the anaclinal and bed-paralleled structural zones are large scale,and have small spacing and low wave velocity value(2500～3500m s-1) near the fault f2. The zones not only control over the shearing properties of rock masses,but also have a highly-degree influence on the differential deformation and the stress distribution of the dam foundation,which should be deal with separately.
2010, 18(6): 940-949.
The activity of a main fault in the near field of Bala hydropower station in Maerkang is very important to engineering design and dam site selection.With the integrative analysis of investigation,ESR dating,quartz shape scanning in the fault gouge and seismic activity,we find that all faults in the near field region of Bala power station except Songgang fault has no perceptible activities in the earth surface since the Late Pleistocene.So they have no side influence to the engineering construction.In the middle section of Songgang fault,small earthquakes occurred frequently in the past several decades.But hardly any evidence can be found to indicate the fault is a active fault.The south section was still active in Late Pleistocene,because the second level river terrace was cut by 0.3m.The north section has been inactive since the Late Pleistocene.The Ribu fault is not active.It has been as same as the middle section of Songgang fault since the Late Pleistocene.But the seismic activity is distinct in the deep part of subsurface.Engineering must keep away from the faults such as Ribu fault and the middle and sourth sections of Songgang fault.It may induce large surface deformation and fracture.The seismic risk evaluation of the Songgang fault has indicated that the maximal magnitude of earthquake possibly induced by Songgang fault might be Ms=6.95. Considering the factors of inadequate safe distance between Songgang fault and upper site,poor petro-physical properties in upper site and small height of water in lower site,its better to choose the middle site for the hyderpower dam.
The activity of a main fault in the near field of Bala hydropower station in Maerkang is very important to engineering design and dam site selection.With the integrative analysis of investigation,ESR dating,quartz shape scanning in the fault gouge and seismic activity,we find that all faults in the near field region of Bala power station except Songgang fault has no perceptible activities in the earth surface since the Late Pleistocene.So they have no side influence to the engineering construction.In the middle section of Songgang fault,small earthquakes occurred frequently in the past several decades.But hardly any evidence can be found to indicate the fault is a active fault.The south section was still active in Late Pleistocene,because the second level river terrace was cut by 0.3m.The north section has been inactive since the Late Pleistocene.The Ribu fault is not active.It has been as same as the middle section of Songgang fault since the Late Pleistocene.But the seismic activity is distinct in the deep part of subsurface.Engineering must keep away from the faults such as Ribu fault and the middle and sourth sections of Songgang fault.It may induce large surface deformation and fracture.The seismic risk evaluation of the Songgang fault has indicated that the maximal magnitude of earthquake possibly induced by Songgang fault might be Ms=6.95. Considering the factors of inadequate safe distance between Songgang fault and upper site,poor petro-physical properties in upper site and small height of water in lower site,its better to choose the middle site for the hyderpower dam.
2010, 18(6): 950-955.
As petroleum strategic storages,unlined caverns for storage of oil need suitable hydrogeologic and engineering geological conditions.However,there are many bad geological bodies in the storage regions. They directly influence the hydrogeologic and engineering geological conditions in storage regions.In the paper,Jinzhou underground oil storages is considered as an example to analyze the altered rocks with expansibility in underground oil storages.There are many altered rocks in the region,and they belong to hydrothermal alteration by intrusion of basic dykes.The altered rocks have weak expansibility.It is found by disintegration test that the altered rocks can disintegrate.Through identification of minerals and rocks and X-ray diffraction analysis,it is found that clay mineral of the altered rocks is smectite.According to properties of the altered rocks with expansibility,the paper present control measures in the altered rock section during the construction of underground caverns for storage of oil.
As petroleum strategic storages,unlined caverns for storage of oil need suitable hydrogeologic and engineering geological conditions.However,there are many bad geological bodies in the storage regions. They directly influence the hydrogeologic and engineering geological conditions in storage regions.In the paper,Jinzhou underground oil storages is considered as an example to analyze the altered rocks with expansibility in underground oil storages.There are many altered rocks in the region,and they belong to hydrothermal alteration by intrusion of basic dykes.The altered rocks have weak expansibility.It is found by disintegration test that the altered rocks can disintegrate.Through identification of minerals and rocks and X-ray diffraction analysis,it is found that clay mineral of the altered rocks is smectite.According to properties of the altered rocks with expansibility,the paper present control measures in the altered rock section during the construction of underground caverns for storage of oil.
2010, 18(6): 956-962.
The study on rock mass parameters after the excavation is always the focus of the engineering.It is the basic work of the rock stability evaluation.This paper is based on the engineering of JinPing Underground Caverns.It classifies the engineering geological rock group about different stake Nos,re-classify the rock mass and evaluation of its quality. It uses the Geological Strength Index(GIS)method and introduces the the number of joint per cubic meter. It can make the evaluation system reasonable. At last the rock mass parameters can be found by regression method. It is found that the calculated values of the cohesion and Internal friction angle are similar to the recommended values.This method is relatively easy. It can provide reference for the selection of mechanical parameters of other underground excavation engineering with similar geological conditions.
The study on rock mass parameters after the excavation is always the focus of the engineering.It is the basic work of the rock stability evaluation.This paper is based on the engineering of JinPing Underground Caverns.It classifies the engineering geological rock group about different stake Nos,re-classify the rock mass and evaluation of its quality. It uses the Geological Strength Index(GIS)method and introduces the the number of joint per cubic meter. It can make the evaluation system reasonable. At last the rock mass parameters can be found by regression method. It is found that the calculated values of the cohesion and Internal friction angle are similar to the recommended values.This method is relatively easy. It can provide reference for the selection of mechanical parameters of other underground excavation engineering with similar geological conditions.
2010, 18(6): 963-970.
The soundness diagnosis testing was carried out on the quality state of a tunnel at Fenghuo Mountain tunnel.This tunnel is one of the permafrost tunnels in frost soil area along the Qinghai-Tibet Railway line.The testing was done some years later after the railway was used. The tunnel is in alpine permafrost zone.The tunnel body is in the frozen rocks.At both ends of the tunnel,the dominant rocks are sandstone and shale,where the frozen soils are ice-rich.Due to the seasonal effects of freezing and thawing,defects were appear in the tunnel more and more. The defects are manifested mainly as lining cracks,leaking and gushing water,lining crisp peeling.In order to accurately understand the quality state of the tunnel lining,the geological penetrating radar technique was used to defect and quantify the defects in the tunnel field.The technique was applied to the tunnel lining structure quality inspection.The technique changed the traditional destructive testing method.The technique is fast,simple,non-destructive,and accurate.Through the in-situ data processing and analysis,the technique can accurately detect lining thickness,find out of lining and filling the empty space behind the non-dense area.The test results show the following.The tunnel in the frozen atrocious weather environment,the lining appearance was not damaged.Seepage was found in the openings of two ends.The lining with empty is the most serious defect level and had a measured length of 20m.The line with the secondary serious defect level had a length of 98m.The lining backfill behind the non-compact class is the third serious defect level and has a measured length of 41m.The most serious level has a line length of 33m.Test results are basically consistent with the actual defect situation. The results can provide a scientific basis for normal operation of the tunnel and reliable foundation for defect treatment in the future.Practical evidence proved the use of geological penetrating radar to make health diagnostic tests for the tunnel is feasible.
The soundness diagnosis testing was carried out on the quality state of a tunnel at Fenghuo Mountain tunnel.This tunnel is one of the permafrost tunnels in frost soil area along the Qinghai-Tibet Railway line.The testing was done some years later after the railway was used. The tunnel is in alpine permafrost zone.The tunnel body is in the frozen rocks.At both ends of the tunnel,the dominant rocks are sandstone and shale,where the frozen soils are ice-rich.Due to the seasonal effects of freezing and thawing,defects were appear in the tunnel more and more. The defects are manifested mainly as lining cracks,leaking and gushing water,lining crisp peeling.In order to accurately understand the quality state of the tunnel lining,the geological penetrating radar technique was used to defect and quantify the defects in the tunnel field.The technique was applied to the tunnel lining structure quality inspection.The technique changed the traditional destructive testing method.The technique is fast,simple,non-destructive,and accurate.Through the in-situ data processing and analysis,the technique can accurately detect lining thickness,find out of lining and filling the empty space behind the non-dense area.The test results show the following.The tunnel in the frozen atrocious weather environment,the lining appearance was not damaged.Seepage was found in the openings of two ends.The lining with empty is the most serious defect level and had a measured length of 20m.The line with the secondary serious defect level had a length of 98m.The lining backfill behind the non-compact class is the third serious defect level and has a measured length of 41m.The most serious level has a line length of 33m.Test results are basically consistent with the actual defect situation. The results can provide a scientific basis for normal operation of the tunnel and reliable foundation for defect treatment in the future.Practical evidence proved the use of geological penetrating radar to make health diagnostic tests for the tunnel is feasible.
2010, 18(6): 971-975.
Because of the complexity of geological conditions of tunnel surrounding rock and the limitation of site investigation before tunnel construction,the geological prospecting results usually do not agree with the real conditions. Consequently,advanced detection methods must be adopted in tunnel engineering in order to insure the construction safety. The paper presents the use of the ground penetration radar SIR-3000 system in Mangtouling tunnel along the Chenzhou-Ningyuan express highway. The data was processed with the spatial filter and Hilbert transform. Karst cave and the cranny were forecasted in the front of tunnel face by GPR results. The excavation result testified the validity of the forecasted results. A better forecast effect was obtained. The result illuminates the serviceability of spatial filtering and Hilbert transform for GPR data processing.
Because of the complexity of geological conditions of tunnel surrounding rock and the limitation of site investigation before tunnel construction,the geological prospecting results usually do not agree with the real conditions. Consequently,advanced detection methods must be adopted in tunnel engineering in order to insure the construction safety. The paper presents the use of the ground penetration radar SIR-3000 system in Mangtouling tunnel along the Chenzhou-Ningyuan express highway. The data was processed with the spatial filter and Hilbert transform. Karst cave and the cranny were forecasted in the front of tunnel face by GPR results. The excavation result testified the validity of the forecasted results. A better forecast effect was obtained. The result illuminates the serviceability of spatial filtering and Hilbert transform for GPR data processing.
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