Online Submission
Manuscript Tracking
Peer Review
Editor Work2006 Vol. 14, No. 4
Previous Issue
2006, 14(4): 433-437.
Abstract
This paper analyzes the main influences of environmental conditions on the constructions of the Qinghai-Tibet railway.The conditions are the instincts of temperature,moisture,and environment of permafrost..Then the features of the interactions between tthe engineering environment and the permafrost conditions in the permafrost region are discussed.Finally it is concluded that the key problem to ensure the engineering safety reliability in permafrost region is to control the heat erosion from external environment to the system of permafrost engineering environment.
This paper analyzes the main influences of environmental conditions on the constructions of the Qinghai-Tibet railway.The conditions are the instincts of temperature,moisture,and environment of permafrost..Then the features of the interactions between tthe engineering environment and the permafrost conditions in the permafrost region are discussed.Finally it is concluded that the key problem to ensure the engineering safety reliability in permafrost region is to control the heat erosion from external environment to the system of permafrost engineering environment.
2006, 14(4): 438-442.
A landslide occurred near the discharge water tower of Jinpen reservoir in Xian.It was a residual body of the downstream boundary segment of old landslide 1~# on the right bank of the Jinpen reservoir.A shortterm strong precipitation induced deformation of the slope and its sliding motion.The landslide was drawn with bedding-plane slip.At different plane sections,extents of the deformation and breakdown were different.The motion is similar to the plane rotation of a slope.The landslide was controlled by four group structure planes.The softening schistosity surface has the dipping direction from 150 to 170 and the dip angle from 35 to 55.The second structure interface has the dipping direction from 230 to 290 and dip angle from 35 to 55.They formed the control surfaces of sliding motion.The causes of the landslide are the softening schistosity surface,the strong precipitation,the gentle inclined and defective ground cover,and the gunite covering layer at the bottom of the slope.
A landslide occurred near the discharge water tower of Jinpen reservoir in Xian.It was a residual body of the downstream boundary segment of old landslide 1~# on the right bank of the Jinpen reservoir.A shortterm strong precipitation induced deformation of the slope and its sliding motion.The landslide was drawn with bedding-plane slip.At different plane sections,extents of the deformation and breakdown were different.The motion is similar to the plane rotation of a slope.The landslide was controlled by four group structure planes.The softening schistosity surface has the dipping direction from 150 to 170 and the dip angle from 35 to 55.The second structure interface has the dipping direction from 230 to 290 and dip angle from 35 to 55.They formed the control surfaces of sliding motion.The causes of the landslide are the softening schistosity surface,the strong precipitation,the gentle inclined and defective ground cover,and the gunite covering layer at the bottom of the slope.
2006, 14(4): 443-448.
There may not be many reports available in the literature about the lens and its mechanical behavior in the broken fault zone.Lens bodies are usually well developed in the sheared faults.The intensity and the deformed or broken mechanism of the broken fault zones are normally under the control of the lens bodies.Their engineering geological mechanism should be emphasized and examined in detail.This paper presents a case study on the lens and its mechanical behavior in a broken fualt zone.The findings of the study can be summarzied as follows:(1) There are various types of the lens bodies;(2) the fault lines and the mud membranes are usually distributed along the periphery of the lens body;(3)There are systems of joint cracks in the lens bodies;(4) The periphery of a lens body can be regarded as the structural surface or weak structural surface;(5) The lens body itself can be seen as a compound structure.Many mechanical behaviors of the lens body of the fault mud in the experiments of the original-location cutting and the single-axle compression are also revealed in the experiment of the original-location mechanics:(1) the periphery of the lens body has the mechanical effect of the structural surface;(2) the lens body controls the intensity and the deformed or broken mechanism.
There may not be many reports available in the literature about the lens and its mechanical behavior in the broken fault zone.Lens bodies are usually well developed in the sheared faults.The intensity and the deformed or broken mechanism of the broken fault zones are normally under the control of the lens bodies.Their engineering geological mechanism should be emphasized and examined in detail.This paper presents a case study on the lens and its mechanical behavior in a broken fualt zone.The findings of the study can be summarzied as follows:(1) There are various types of the lens bodies;(2) the fault lines and the mud membranes are usually distributed along the periphery of the lens body;(3)There are systems of joint cracks in the lens bodies;(4) The periphery of a lens body can be regarded as the structural surface or weak structural surface;(5) The lens body itself can be seen as a compound structure.Many mechanical behaviors of the lens body of the fault mud in the experiments of the original-location cutting and the single-axle compression are also revealed in the experiment of the original-location mechanics:(1) the periphery of the lens body has the mechanical effect of the structural surface;(2) the lens body controls the intensity and the deformed or broken mechanism.
2006, 14(4): 449-453.
Niuchang ancient underground caverns near Shangfan Village,Longyou County are composed of two caverns.Through field investigation,a vertical tensile crack was found in the No.1 rock pillar of No.1 cavern,which resulted from the overloading of upper rock layers.This paper presents the back analysis of the rock mass long-term tensile strength according to tensile cracks in the No.1 pillar,which not only helps to protect ancient engineering sites but also benefits the theoretical research on the long-term strength of rock mass.
Niuchang ancient underground caverns near Shangfan Village,Longyou County are composed of two caverns.Through field investigation,a vertical tensile crack was found in the No.1 rock pillar of No.1 cavern,which resulted from the overloading of upper rock layers.This paper presents the back analysis of the rock mass long-term tensile strength according to tensile cracks in the No.1 pillar,which not only helps to protect ancient engineering sites but also benefits the theoretical research on the long-term strength of rock mass.
2006, 14(4): 454-461.
Significant progresses have been made in understanding the development of liquefaction of saturated sand under shear vibration loading.But few researchers paid attention to the sand liquefaction under vertical cyclic loading.Jiaoxin railway is a high seismic intensity area after the alignment DK39+000.From the alignment DK283+550 to the alignment DK283+770,there are seismic liquefaction sand layers.It is highly possible to induce sand liquefaction by the dynamic loading of moving trains.In order to study the subgrade settlement characteristics before and after the commencement of the railway,this paper examines the concepts of sand liquefaction and the criterion of liquefaction at first.The paper further analyzes in details the settlement features of the subgrades in the sand liquefaction area.The analyses include the vertical settlement behaviors of sand layers and lateral displacement behavior.Finally,based on the test results,a constitutive model for the behavior of the sand under the condition of cyclic loading is put forward.
Significant progresses have been made in understanding the development of liquefaction of saturated sand under shear vibration loading.But few researchers paid attention to the sand liquefaction under vertical cyclic loading.Jiaoxin railway is a high seismic intensity area after the alignment DK39+000.From the alignment DK283+550 to the alignment DK283+770,there are seismic liquefaction sand layers.It is highly possible to induce sand liquefaction by the dynamic loading of moving trains.In order to study the subgrade settlement characteristics before and after the commencement of the railway,this paper examines the concepts of sand liquefaction and the criterion of liquefaction at first.The paper further analyzes in details the settlement features of the subgrades in the sand liquefaction area.The analyses include the vertical settlement behaviors of sand layers and lateral displacement behavior.Finally,based on the test results,a constitutive model for the behavior of the sand under the condition of cyclic loading is put forward.
2006, 14(4): 462-469.
The risk assessment is the core of risk management for the tunnel and underground projects,an important joint between risk identification and risk management and also a foundation of decision analysis.This paper presents a review onthe basic concept of risk assessment on the tunnel and underground projects,the present situation and the development of risk assessment methods as well as the recently most commonly used methods.The paper further discusses the problems to be solved and the future development needs on the risk assessment methods.
The risk assessment is the core of risk management for the tunnel and underground projects,an important joint between risk identification and risk management and also a foundation of decision analysis.This paper presents a review onthe basic concept of risk assessment on the tunnel and underground projects,the present situation and the development of risk assessment methods as well as the recently most commonly used methods.The paper further discusses the problems to be solved and the future development needs on the risk assessment methods.
2006, 14(4): 470-475.
To study the influence of the crushed rock slope protection on the temperature field of the embankment in permafrost region,finite element analysis is conducted,in which phase changes are taken into consideration to simulate the embankment with crushed rock slope protection layer of different thickness and the observation data of the climate and geological conditions in Qinghai-Tibet railway testing section are used as the upper boundary condition.The calculation results show that the crushed rock slope protection can enhance the stability of the embankment in permafrost region.The influence the crushed rock creates to the temperature field is relatively great near the toe of the embankment,and the crushed rock slope protection can prevent the embankment from longitudinal cracks to some extent.In practice,the thickness of the crushed rock layer can not be too thick.
To study the influence of the crushed rock slope protection on the temperature field of the embankment in permafrost region,finite element analysis is conducted,in which phase changes are taken into consideration to simulate the embankment with crushed rock slope protection layer of different thickness and the observation data of the climate and geological conditions in Qinghai-Tibet railway testing section are used as the upper boundary condition.The calculation results show that the crushed rock slope protection can enhance the stability of the embankment in permafrost region.The influence the crushed rock creates to the temperature field is relatively great near the toe of the embankment,and the crushed rock slope protection can prevent the embankment from longitudinal cracks to some extent.In practice,the thickness of the crushed rock layer can not be too thick.
2006, 14(4): 476-480.
Because of the complex geology conditions,there are many special accumulations along the up-reach of Minjiang river,southwest,China. In particular,there one or several seams of sand along the upriver of Minjiang river,southwest,China.Many practices have proved that the excavation will lead the sand seams to emerge big deformation,and then lead the accumulation to fail.This paper presents a FEM analysis on the failure mechanism.It examines how the sand seams affect the stability of the accumulations under the condition of excavation.
Because of the complex geology conditions,there are many special accumulations along the up-reach of Minjiang river,southwest,China. In particular,there one or several seams of sand along the upriver of Minjiang river,southwest,China.Many practices have proved that the excavation will lead the sand seams to emerge big deformation,and then lead the accumulation to fail.This paper presents a FEM analysis on the failure mechanism.It examines how the sand seams affect the stability of the accumulations under the condition of excavation.
2006, 14(4): 481-487.
Based on the elasto-plastic model and Mohr-Coulomb yielding criterion,a 2D finite element method(FEM) is applied to conduct numerical simulation of excavated sliding cut slope on the navigation route 1+016～1+080 of Longtan Hydropower Station.The calculated result are presented for the stress field,displacement field and plastic yielding area before the slope slid.The results show that there was an apparent plastic area at sliding cut slope which was in a state of critical instability.There was continuous deformation in the slope during excavation.Especially the deformation suddenly expanded when lower part of the slope was being excavated.The supporting system in the plastic area ahead of the landslide had reached its limit bearing capacity.The cut slope was ready to fail suddenly and quickly.
Based on the elasto-plastic model and Mohr-Coulomb yielding criterion,a 2D finite element method(FEM) is applied to conduct numerical simulation of excavated sliding cut slope on the navigation route 1+016～1+080 of Longtan Hydropower Station.The calculated result are presented for the stress field,displacement field and plastic yielding area before the slope slid.The results show that there was an apparent plastic area at sliding cut slope which was in a state of critical instability.There was continuous deformation in the slope during excavation.Especially the deformation suddenly expanded when lower part of the slope was being excavated.The supporting system in the plastic area ahead of the landslide had reached its limit bearing capacity.The cut slope was ready to fail suddenly and quickly.
2006, 14(4): 488-495.
It is a rather well-known fact that bank-slope deformation and failure result from the coupling of Earths endogenic and exogenic geological processes,in which different dynamic-force factor has a different correlation to the evolution of bank-slope.In Tiger Leaping-gorge region,endogenic and exogenic geological processes are very prominent,and in different reaches the deformed and failured masses develop dissimilarly.The correlated degree of the density of deformed and failured masses and correlative dynamic force factors in Tiger-Leaping Gorge Reach are analyzed by effect measure analysis method which combines qualitative and quantitative analysis,and the key dynamic factors of bank-slope stability are established,which can provided the scientific information for origin division,evaluation,prevention of geological hazards and project planning.
It is a rather well-known fact that bank-slope deformation and failure result from the coupling of Earths endogenic and exogenic geological processes,in which different dynamic-force factor has a different correlation to the evolution of bank-slope.In Tiger Leaping-gorge region,endogenic and exogenic geological processes are very prominent,and in different reaches the deformed and failured masses develop dissimilarly.The correlated degree of the density of deformed and failured masses and correlative dynamic force factors in Tiger-Leaping Gorge Reach are analyzed by effect measure analysis method which combines qualitative and quantitative analysis,and the key dynamic factors of bank-slope stability are established,which can provided the scientific information for origin division,evaluation,prevention of geological hazards and project planning.
2006, 14(4): 496-501.
The fractal characteristics of particle size distribution of soil-rock mixtures in the right bank of Long-pan in Tiger-Leaping Gorge area are studied by using fractal geometry theory.The quantitative equations reflecting the relationship between particle size average and fractal dimensions are established.It is found that the statistical self-similarity of particle size distribution exists in the soil-rock mixtures.For the soil-rock mixtures is poorly graded,the fractal curve shows special double fractal dimensions,which has relations with the origin and formation of the soil-rock mixtures.
The fractal characteristics of particle size distribution of soil-rock mixtures in the right bank of Long-pan in Tiger-Leaping Gorge area are studied by using fractal geometry theory.The quantitative equations reflecting the relationship between particle size average and fractal dimensions are established.It is found that the statistical self-similarity of particle size distribution exists in the soil-rock mixtures.For the soil-rock mixtures is poorly graded,the fractal curve shows special double fractal dimensions,which has relations with the origin and formation of the soil-rock mixtures.
2006, 14(4): 502-507.
Shear strength of rock joints is an important parameter for both comparison of engineering geological conditions and stability analysis of the rock mass surrounding the pre-selected area of geological disposal repository.Based on grouping of the tonalite joints in Jiujing area,the directive statistical evaluation method was used to estimate the joint roughness coefficient(JRC).Effective length for empirical estimation of joint shear strength values was determined through the evaluation of scale dependence of JRC.Shear strength parameters along four directions of each joint group were calculated by using the JRC-JCS model.Finally,anisotropic characteristic of the rock joint shear strength was evaluated.
Shear strength of rock joints is an important parameter for both comparison of engineering geological conditions and stability analysis of the rock mass surrounding the pre-selected area of geological disposal repository.Based on grouping of the tonalite joints in Jiujing area,the directive statistical evaluation method was used to estimate the joint roughness coefficient(JRC).Effective length for empirical estimation of joint shear strength values was determined through the evaluation of scale dependence of JRC.Shear strength parameters along four directions of each joint group were calculated by using the JRC-JCS model.Finally,anisotropic characteristic of the rock joint shear strength was evaluated.
2006, 14(4): 508-512.
Based on the disturbance and damage analysis of tunnels surrounding rock due to excavation,the mechanism of instability of deep-buried hardrock tunnels is examined with catastrophe theory.Based on the potential energy principle,the cusp catastrophe model of instability of deep-buried hardrock tunnels is established.The mechanical criterions of instability are educed.Results show that the instability of deep-buried hardrock tunnels is not only influenced by rock mass characters and loads,but also related with the ratio of the stiffness of elastic regions over the stiffness of plastic regions.During excavation,the more serious the degree of disturbance and damage of surrounding rock,the less the integrity factor of rock mass,the higher the degree of softening of mechanical index,the larger the range of plastic regions,and the less the stiffness ratio,the more possible the instability of surrounding rock system.The analysis of an actual case shows that the analytical results are accordance to the practical experience.The present results can offer references for preventing instability and damage of tunnels,taking reasonable construction technique and supporting measurements.
Based on the disturbance and damage analysis of tunnels surrounding rock due to excavation,the mechanism of instability of deep-buried hardrock tunnels is examined with catastrophe theory.Based on the potential energy principle,the cusp catastrophe model of instability of deep-buried hardrock tunnels is established.The mechanical criterions of instability are educed.Results show that the instability of deep-buried hardrock tunnels is not only influenced by rock mass characters and loads,but also related with the ratio of the stiffness of elastic regions over the stiffness of plastic regions.During excavation,the more serious the degree of disturbance and damage of surrounding rock,the less the integrity factor of rock mass,the higher the degree of softening of mechanical index,the larger the range of plastic regions,and the less the stiffness ratio,the more possible the instability of surrounding rock system.The analysis of an actual case shows that the analytical results are accordance to the practical experience.The present results can offer references for preventing instability and damage of tunnels,taking reasonable construction technique and supporting measurements.
2006, 14(4): 513-517.
Considering the characteristics of Hujiaba double-arch highway tunnel constructed with three pilot tunnels excavated in advance and its large excavation width and shallow buried depth,safety construction measures were put forward such as the grouting from the ground surface,excavating by manpower in the upper bench and blasting in lower bench,blasting with small detonation dose,timely installation of the inverts,and so on.The field monitoring works focused on the following three items:(1) the displacement of surrounding rock;such as crown settlement,displacement of the ground,displacement of inner surrounding rock;(2) the stress and stain of support structure;(3) the internal force in the mid-partition wall.During construction,monitoring data was analyzed in time.Structural material parameters were analyzed backward and modified in response to the monitoring data in order to guarantee safety construction.The engineering practice has proved the applicability and feasibility of the safety monitoring and informationization construction methods.
Considering the characteristics of Hujiaba double-arch highway tunnel constructed with three pilot tunnels excavated in advance and its large excavation width and shallow buried depth,safety construction measures were put forward such as the grouting from the ground surface,excavating by manpower in the upper bench and blasting in lower bench,blasting with small detonation dose,timely installation of the inverts,and so on.The field monitoring works focused on the following three items:(1) the displacement of surrounding rock;such as crown settlement,displacement of the ground,displacement of inner surrounding rock;(2) the stress and stain of support structure;(3) the internal force in the mid-partition wall.During construction,monitoring data was analyzed in time.Structural material parameters were analyzed backward and modified in response to the monitoring data in order to guarantee safety construction.The engineering practice has proved the applicability and feasibility of the safety monitoring and informationization construction methods.
2006, 14(4): 518-521.
Three-dimensional(3D) display and real-time browsing to the topography of typical segments in Sichuan-Tibet highway are realized by the means of the digitalization to topographical map and regional geological map.The 3D topographical map can provide vectorial base map for the overlay analysis of stratum,lithology,tectonics,and the distribution of geological hazards when utilizing Geographical Information System to further study the geological hazards along the highway.The visualization of 3D topographies for typical segments along Sichuan-Tibet highway would have definite values to the road layout,the bypassing of the geological hazards and the location selection of excavating railway tunnels in Sichuan-Tibet railway design.
Three-dimensional(3D) display and real-time browsing to the topography of typical segments in Sichuan-Tibet highway are realized by the means of the digitalization to topographical map and regional geological map.The 3D topographical map can provide vectorial base map for the overlay analysis of stratum,lithology,tectonics,and the distribution of geological hazards when utilizing Geographical Information System to further study the geological hazards along the highway.The visualization of 3D topographies for typical segments along Sichuan-Tibet highway would have definite values to the road layout,the bypassing of the geological hazards and the location selection of excavating railway tunnels in Sichuan-Tibet railway design.
2006, 14(4): 522-525.
Based on the fundamental theories of fuzzy mathematics, the factors which influence silts liquefaction are analyzed.The average particle diameter,relative density,SPT blow counts of the silt and the effective overloading are selected as the evaluation index to construct the model of fuzzy pattern recognition for the silt liquefaction discrimination.The verification and application of the model indicate that this methodology is a effective tool in objectively evaluating and predicting the liquefaction potential of silt.
Based on the fundamental theories of fuzzy mathematics, the factors which influence silts liquefaction are analyzed.The average particle diameter,relative density,SPT blow counts of the silt and the effective overloading are selected as the evaluation index to construct the model of fuzzy pattern recognition for the silt liquefaction discrimination.The verification and application of the model indicate that this methodology is a effective tool in objectively evaluating and predicting the liquefaction potential of silt.
2006, 14(4): 526-530.
The checking computation of pile structural strength of statically jacked pile during its installation is not explicitly established in the codes of pile foundation design.In this paper the following issues are discussed:(1) the relationship between the sinking-pile resistance and the pile tip depth in the bearing layer;(2) the estimation of sinking-pile resistance from the specific penetration resistance of static penetration test;(3) the checking computation of pile structural strength of static-press pile in the process of installation.
The checking computation of pile structural strength of statically jacked pile during its installation is not explicitly established in the codes of pile foundation design.In this paper the following issues are discussed:(1) the relationship between the sinking-pile resistance and the pile tip depth in the bearing layer;(2) the estimation of sinking-pile resistance from the specific penetration resistance of static penetration test;(3) the checking computation of pile structural strength of static-press pile in the process of installation.
2006, 14(4): 531-536.
Pile bearing capacity is an important parameter in foundation design.One of the key means to determine the pile bearing capacity is the conventional static load test at construction site.A pile testing project at Luohe Bridge along Huangling-Yanan Highway employs the piles of the bridge as the anchor piles.The anchor piles are stressed to form an anchor-pulling system.The test pile stress,the anchor pile stress and the displacement on top of the pile measured during the loading test show that it is feasible for the anchor-pulling system to use pre-stress technique and to take the piles of bridge as anchor piles for the static pile load test.At the same time,the equation is developed to determine the value of prestressing force applied to the anchor piles.Essential measures to make sure that those piles still have sufficient bearing capacity for the bridge after being used as anchor piles are also put forward.The results of this paper are of significance to shorten the construction period,reduce the test cost and broaden the application scope of prestressing techniques.
Pile bearing capacity is an important parameter in foundation design.One of the key means to determine the pile bearing capacity is the conventional static load test at construction site.A pile testing project at Luohe Bridge along Huangling-Yanan Highway employs the piles of the bridge as the anchor piles.The anchor piles are stressed to form an anchor-pulling system.The test pile stress,the anchor pile stress and the displacement on top of the pile measured during the loading test show that it is feasible for the anchor-pulling system to use pre-stress technique and to take the piles of bridge as anchor piles for the static pile load test.At the same time,the equation is developed to determine the value of prestressing force applied to the anchor piles.Essential measures to make sure that those piles still have sufficient bearing capacity for the bridge after being used as anchor piles are also put forward.The results of this paper are of significance to shorten the construction period,reduce the test cost and broaden the application scope of prestressing techniques.
2006, 14(4): 537-841.
Composite foundation theories,based on an equal-strain concept between soil and columns in the reinforced area,is commonly used in China to design deep mixed column(DMC) foundations.However,many case studies show that differential deformations between soil and columns in the reinforced area are obvious under the loading of highway embankments.The strength of DMCs can not be fully mobilized.The composite modulus of the reinforced area should be modified for the calculation of differential deformations.Finite element method(FEM) is used in this study to investigate the behavior of DMC foundations under the embankment loading,and a reasonable strength range of DMCs is put forward.Finally a method is proposed to reasonably estimate the modified composite modulus of the reinforced area by considering the degree of mobilization of DMCs.
Composite foundation theories,based on an equal-strain concept between soil and columns in the reinforced area,is commonly used in China to design deep mixed column(DMC) foundations.However,many case studies show that differential deformations between soil and columns in the reinforced area are obvious under the loading of highway embankments.The strength of DMCs can not be fully mobilized.The composite modulus of the reinforced area should be modified for the calculation of differential deformations.Finite element method(FEM) is used in this study to investigate the behavior of DMC foundations under the embankment loading,and a reasonable strength range of DMCs is put forward.Finally a method is proposed to reasonably estimate the modified composite modulus of the reinforced area by considering the degree of mobilization of DMCs.
2006, 14(4): 542-546.
With the field testing to single piles and pile groups,the effect of prefabricated vertical drains(PVD) installed in advance surrounding the dry jet mixed(DJM) piles on the pile quality of DJM is presented in this paper.The testing results indicate that the standard penetration test blow counts and the unconfined compression strength of DJM columns with PVD are higher than those of DJM without PVD,especially in deeper layers.The fracturing caused by excess pore pressure during the DJM installation and the drainage provided by the PVC drains increase the permeability of surrounding clay,and thus make the installation of soil-cement columns easier and more uniform,especially in deeper layers.
With the field testing to single piles and pile groups,the effect of prefabricated vertical drains(PVD) installed in advance surrounding the dry jet mixed(DJM) piles on the pile quality of DJM is presented in this paper.The testing results indicate that the standard penetration test blow counts and the unconfined compression strength of DJM columns with PVD are higher than those of DJM without PVD,especially in deeper layers.The fracturing caused by excess pore pressure during the DJM installation and the drainage provided by the PVC drains increase the permeability of surrounding clay,and thus make the installation of soil-cement columns easier and more uniform,especially in deeper layers.
2006, 14(4): 547-552.
There are many factors affecting settlement and deformation of CFG pile composite foundation.In this paper,with the use of the finite difference analysis package FLAC-3D,these factors are analyzed systematically,including the cushioning layer,load,length of pile,modulus ratio of pile and soil,replacement ratio,modulus ratio of the soil around the pile and the soil under the pile tip,pile group and so on.The relationship between settlement and those factors are discussed,and the methods or measurements of reducing settlement are suggested.It is a useful reference for the practical engineering optimization design.
There are many factors affecting settlement and deformation of CFG pile composite foundation.In this paper,with the use of the finite difference analysis package FLAC-3D,these factors are analyzed systematically,including the cushioning layer,load,length of pile,modulus ratio of pile and soil,replacement ratio,modulus ratio of the soil around the pile and the soil under the pile tip,pile group and so on.The relationship between settlement and those factors are discussed,and the methods or measurements of reducing settlement are suggested.It is a useful reference for the practical engineering optimization design.
2006, 14(4): 553-556.
With several years experiences in this industry,the author introduces common problems and the corresponding solutions for hand dug piles in Guangxis Karst region,especially regions with highly developed Karst erosion,rich groundwater and high water level.Project examples are also presented in this paper,which are useful references for similar projects in Karst Region.
With several years experiences in this industry,the author introduces common problems and the corresponding solutions for hand dug piles in Guangxis Karst region,especially regions with highly developed Karst erosion,rich groundwater and high water level.Project examples are also presented in this paper,which are useful references for similar projects in Karst Region.
2006, 14(4): 557-563.
Although currently nonlinear properties have been considered in some designs of the piled raft foundations,the superstructures are still not taken into account.It is meaningful to study the mechanism of the nonlinear interaction of the piled raft foundation and the superstructure and to optimize the design of piled raft foundations.In this paper,the sub-structure method is used to agglomerate the rigidity and load of the superstructure.The rafts is simulated by the plane-shell element,and the nonlinear performance of the piles is analyzed using the generalized shear displacement method,and the elastic interaction between the pile and the surrounding soils is determined by finite layer method.A new theoretical method and the corresponding computing program for the nonlinear analysis of the piled raft foundations with the consideration of their interactions with the superstructures are established.By the analysis to a real case,the nonlinear interaction mechanism and the reasonable layout of piles are further discussed.And finally the possible ways to optimize the design of the piles raft foundations are put forward in which the optimization object is the differential settlement.
Although currently nonlinear properties have been considered in some designs of the piled raft foundations,the superstructures are still not taken into account.It is meaningful to study the mechanism of the nonlinear interaction of the piled raft foundation and the superstructure and to optimize the design of piled raft foundations.In this paper,the sub-structure method is used to agglomerate the rigidity and load of the superstructure.The rafts is simulated by the plane-shell element,and the nonlinear performance of the piles is analyzed using the generalized shear displacement method,and the elastic interaction between the pile and the surrounding soils is determined by finite layer method.A new theoretical method and the corresponding computing program for the nonlinear analysis of the piled raft foundations with the consideration of their interactions with the superstructures are established.By the analysis to a real case,the nonlinear interaction mechanism and the reasonable layout of piles are further discussed.And finally the possible ways to optimize the design of the piles raft foundations are put forward in which the optimization object is the differential settlement.
2006, 14(4): 564-569.
The 13th,14th and 15th tunnels on general main canal of the First-phase Engineering of Gansu Yintao Water Supply Project go through saturated loess stratum in al-lQ2.Underground water level is about 4 to 37 meters higher than the tunnel crest.The saturated degree of loess is generally 98～100℅.The saturated loess stability is poor.Choosing the method of the construction in the tunnel is very important.its the engineering characteristics are examined using engineering geology methods.The Drucker-Prager elastic-plastic model and associated flow rule are adopted.The stability of the traditional drilling and blasting method is assessed for the tunnel.It is found that the drilling and blasting method,can cause the large lower stress area in the tunnel surroundings.The displacement of the tunnel is quickly developed and very large.Consequently,the tunnel crest can fall and collapse.It can results in sinking in the ground.The paper further analyzes the adaptability of the shield tunneling method.This construction method has lower risk.It quickly closes to round the rock using the shield in the construction process.Therefore, it is suggested that this tunnel choose the shield tunneling method.
The 13th,14th and 15th tunnels on general main canal of the First-phase Engineering of Gansu Yintao Water Supply Project go through saturated loess stratum in al-lQ2.Underground water level is about 4 to 37 meters higher than the tunnel crest.The saturated degree of loess is generally 98～100℅.The saturated loess stability is poor.Choosing the method of the construction in the tunnel is very important.its the engineering characteristics are examined using engineering geology methods.The Drucker-Prager elastic-plastic model and associated flow rule are adopted.The stability of the traditional drilling and blasting method is assessed for the tunnel.It is found that the drilling and blasting method,can cause the large lower stress area in the tunnel surroundings.The displacement of the tunnel is quickly developed and very large.Consequently,the tunnel crest can fall and collapse.It can results in sinking in the ground.The paper further analyzes the adaptability of the shield tunneling method.This construction method has lower risk.It quickly closes to round the rock using the shield in the construction process.Therefore, it is suggested that this tunnel choose the shield tunneling method.
微信 | 公众平台 
