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Editor Work2006 Vol. 14, No. 5
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2006, 14(5): 69-615.
Abstract
This paper analyzes the stability of rock slope with finite element method with strength reduction along weak planes.The paper uses line-graded layer mesh technique to mesh the model and uses different mechanical parameters to simulate the intact rock and joints.It further uses simplified wave pressure equation to simulate the wave pressure of the low-frequency wave loading and brings a rational model dimension and submerged loading computation scheme.
This paper analyzes the stability of rock slope with finite element method with strength reduction along weak planes.The paper uses line-graded layer mesh technique to mesh the model and uses different mechanical parameters to simulate the intact rock and joints.It further uses simplified wave pressure equation to simulate the wave pressure of the low-frequency wave loading and brings a rational model dimension and submerged loading computation scheme.
2006, 14(5): 577-581.
According to plenty of field observation and a large quantity of identification and analyzation on specimens,slices and chemical composition,the development characteristics and the spacial variations of the Badong formation in the Three Gorges reservoir region are illustrated detailedly.The thickness of Badong formation is approximately 820m at least and 1420m at most with a tendence of gradual incrassation from east to west.Red terrene and grey terrene are the main compositions of the Badong formation.The former(section 2 and 4) is mostly composed of clastic rock or arenaceous argillaceous rock and the latter(section 1,3 and 5) is mainly composed of carbonate rock.Consequently,the Badong formation is a typical stratum assemblage of easy landslide.
According to plenty of field observation and a large quantity of identification and analyzation on specimens,slices and chemical composition,the development characteristics and the spacial variations of the Badong formation in the Three Gorges reservoir region are illustrated detailedly.The thickness of Badong formation is approximately 820m at least and 1420m at most with a tendence of gradual incrassation from east to west.Red terrene and grey terrene are the main compositions of the Badong formation.The former(section 2 and 4) is mostly composed of clastic rock or arenaceous argillaceous rock and the latter(section 1,3 and 5) is mainly composed of carbonate rock.Consequently,the Badong formation is a typical stratum assemblage of easy landslide.
2006, 14(5): 582-587.
Slope instability is one of the most important geohazards to offshore structures.It can cause great damages to oil production platforms,pipelines and electric cables which are based on the seafloor.In this study,a typical sea area in Chengdao Oilfield in the subaqueous delta of the Yellow River is chosen as the study area.Geophysical prospecting and geotechnical drilling are processed to get the stratification and the mechanical characteristics of the soil within the upper 10 m depth.The stability of the slope in this area is calculated using GEO-SLOPE/W.It turns out that slope instability may occur in clayey silt in the surface of the seafloor.The potential failure modes are discussed.It is concluded that the large waves caused by storm tides are the dominating triggering sources.
Slope instability is one of the most important geohazards to offshore structures.It can cause great damages to oil production platforms,pipelines and electric cables which are based on the seafloor.In this study,a typical sea area in Chengdao Oilfield in the subaqueous delta of the Yellow River is chosen as the study area.Geophysical prospecting and geotechnical drilling are processed to get the stratification and the mechanical characteristics of the soil within the upper 10 m depth.The stability of the slope in this area is calculated using GEO-SLOPE/W.It turns out that slope instability may occur in clayey silt in the surface of the seafloor.The potential failure modes are discussed.It is concluded that the large waves caused by storm tides are the dominating triggering sources.
2006, 14(5): 588-5914.
The drilled grout holes are used to test ground water table and ground temperature by chance of curtain grouting at the No.2 valley of Kunlun mountain tunnel.By analyses of ground water table and ground temperature and grouting-amount variation in the drilled grout hole,some ideas on thawing area developed state are identified for treatment of water seepage from the tunnel that:(1) the thawed depth at the No.2 valley is far greater than permafrost table at this area,and ground temperature at slope facing south is greater than that at slope facing north,(2) a thawed area exists 7 m around the center of the tunnel at the No.2 valley,and the thawed depth is below 2 to 5 m under the bottom of the tunnel,(3) the porosity of slope to south is higher than that of slope to north,and there are more than one underground channel between bedrock and the surface at the No.2 valley,the channel under the valley better than of slopes,(4) there are more than one unfrozen channel 17 to 30 m underground along the valley at least.
The drilled grout holes are used to test ground water table and ground temperature by chance of curtain grouting at the No.2 valley of Kunlun mountain tunnel.By analyses of ground water table and ground temperature and grouting-amount variation in the drilled grout hole,some ideas on thawing area developed state are identified for treatment of water seepage from the tunnel that:(1) the thawed depth at the No.2 valley is far greater than permafrost table at this area,and ground temperature at slope facing south is greater than that at slope facing north,(2) a thawed area exists 7 m around the center of the tunnel at the No.2 valley,and the thawed depth is below 2 to 5 m under the bottom of the tunnel,(3) the porosity of slope to south is higher than that of slope to north,and there are more than one underground channel between bedrock and the surface at the No.2 valley,the channel under the valley better than of slopes,(4) there are more than one unfrozen channel 17 to 30 m underground along the valley at least.
2006, 14(5): 592-596.
A sort of silty clay which has both high hydrophilic clay mineral contents and high liquid and plastic limits exists in the swampy and lacustrine plain in Yangcheng Lake area of Suzhou..Although it has certain swelling and shrinkage properties in the natural state,it doesnt belong to classical expansive soils.But while this soil is disturbed and compacted,with the dry density increasing and water content decreasing,its swelling and shringkage properties become very apparent.Hence the remolded clay can be called man-made expansive soil.Through analyzing the outcome of the experiments on the soil samples taken from the three earth-fetching areas on the northeast of Yangcheng Lake,from which the earth for the road base is collected,this paper discusses the special properties of the silty clay in this area and provides the scientific guidance for the future construction.
A sort of silty clay which has both high hydrophilic clay mineral contents and high liquid and plastic limits exists in the swampy and lacustrine plain in Yangcheng Lake area of Suzhou..Although it has certain swelling and shrinkage properties in the natural state,it doesnt belong to classical expansive soils.But while this soil is disturbed and compacted,with the dry density increasing and water content decreasing,its swelling and shringkage properties become very apparent.Hence the remolded clay can be called man-made expansive soil.Through analyzing the outcome of the experiments on the soil samples taken from the three earth-fetching areas on the northeast of Yangcheng Lake,from which the earth for the road base is collected,this paper discusses the special properties of the silty clay in this area and provides the scientific guidance for the future construction.
2006, 14(5): 597-602.
Primary state soil sampling is an important tache in engineering exploration,different sampling method has different affection to the quality of soil sample.Generally speaking,the big primary soil sample collected in shaft is the true primary state soil sample,the sample collected by soil collected equipment in drilling is of different degree disturbance.The disturbing degree is different with different sampling method in drilling hole.Through comparative analysis to the test data of tow sampling methods in drilling hole and sampling method in shaft,it was found out by the author that the drilling sampling method has obvious disturbance and depression to the soil sample,which caused the soil samples dry density to be increased,porosity ratio to be decreased,filtration coefficient to be decreased,and modulus of compression to be increased.Meanwhile,it was found out that the sample quality collected with fast irruptive is slightly better than samples quality collected by upper irruptive.In order to ensure the safety of engineering,it should be careful to use the test result of normal drilling sampling,the pitting sampling,shaft sampling,or double-tubles and thin-wall soil collecting methods should be used.
Primary state soil sampling is an important tache in engineering exploration,different sampling method has different affection to the quality of soil sample.Generally speaking,the big primary soil sample collected in shaft is the true primary state soil sample,the sample collected by soil collected equipment in drilling is of different degree disturbance.The disturbing degree is different with different sampling method in drilling hole.Through comparative analysis to the test data of tow sampling methods in drilling hole and sampling method in shaft,it was found out by the author that the drilling sampling method has obvious disturbance and depression to the soil sample,which caused the soil samples dry density to be increased,porosity ratio to be decreased,filtration coefficient to be decreased,and modulus of compression to be increased.Meanwhile,it was found out that the sample quality collected with fast irruptive is slightly better than samples quality collected by upper irruptive.In order to ensure the safety of engineering,it should be careful to use the test result of normal drilling sampling,the pitting sampling,shaft sampling,or double-tubles and thin-wall soil collecting methods should be used.
2006, 14(5): 603-608.
The mositure content is an important controlling factor of the mechanical property of unsaturated soil.The main kind of soil mass surrounding Beijing Suzhoujie Subway tunnel is unsaturated cohesive soil.By using the method of drill sampling the samples of the soil mass system around the tunnel area were obtained.The relationship between the deformation and strength and the moisture content of the unsaturated cohesive soil mass were established through triaxial tests.And furthermore the relationship between the main parameters and the moisture content of the unsaturated cohesive soil mass were established. Based on that,the mechanical parameters of the soils in different areas of the construction site were determined.Through the analytical method of finite element numerical modeling,the stability of the soil mass and the ground settlement during the construction were studied.And the stability of the soil mass during the construction of tunnel with the consideration of the moisture content variation were made clear.
The mositure content is an important controlling factor of the mechanical property of unsaturated soil.The main kind of soil mass surrounding Beijing Suzhoujie Subway tunnel is unsaturated cohesive soil.By using the method of drill sampling the samples of the soil mass system around the tunnel area were obtained.The relationship between the deformation and strength and the moisture content of the unsaturated cohesive soil mass were established through triaxial tests.And furthermore the relationship between the main parameters and the moisture content of the unsaturated cohesive soil mass were established. Based on that,the mechanical parameters of the soils in different areas of the construction site were determined.Through the analytical method of finite element numerical modeling,the stability of the soil mass and the ground settlement during the construction were studied.And the stability of the soil mass during the construction of tunnel with the consideration of the moisture content variation were made clear.
2006, 14(5): 616-619.
Developments in theories and techniques for blasting are important to blasting industriesand construction of civil infrastructures.The basic concept of blasting in rock mass is defined and examined based on the theoretical developments and engineering applications of blasting over the last few decades.The explosive features,rock mass characteristics and their interactions are discussed in details.It is found that a well understanding of the in-situ geological conditions is essential to successful blasting.The explosive energy feature has to be allocated according to the rock mass characteristics so that the interaction of explosive and rock mass can be optimized for effectiveness.In terms of rock mass and the associated blasting features,the in-situ rock mass can be classified into two categories:(a) pseudo homogeneous and continuous rock mass,(b) discontinuous rock mass.Both test and practice have shown that blasting results in the pseudo homogeneous rock mass are controlled by local topographic minimum resistant line and they are by rock mass discontinuities in the discontinuous rock mass.The theory of blasting control in engineering geology includes developed the two categories of rock mass and their corresponding blasting features.
Developments in theories and techniques for blasting are important to blasting industriesand construction of civil infrastructures.The basic concept of blasting in rock mass is defined and examined based on the theoretical developments and engineering applications of blasting over the last few decades.The explosive features,rock mass characteristics and their interactions are discussed in details.It is found that a well understanding of the in-situ geological conditions is essential to successful blasting.The explosive energy feature has to be allocated according to the rock mass characteristics so that the interaction of explosive and rock mass can be optimized for effectiveness.In terms of rock mass and the associated blasting features,the in-situ rock mass can be classified into two categories:(a) pseudo homogeneous and continuous rock mass,(b) discontinuous rock mass.Both test and practice have shown that blasting results in the pseudo homogeneous rock mass are controlled by local topographic minimum resistant line and they are by rock mass discontinuities in the discontinuous rock mass.The theory of blasting control in engineering geology includes developed the two categories of rock mass and their corresponding blasting features.
2006, 14(5): 620-626.
It is an important and complex task to construct soil constitutive model.Up to now,there are hundreds of soil constitutive models which have been provided by scholars in China and abroad.These models have been reviewed and documented in many literatures.However,because they were constructed and developed mainly on the basis of disturbed soils or sandy soils,these models are not able to describe the various nonlinear behavior induced by structural property of soil.Subsequently,the calculated results can greatly different with the results of tests performed in situ.Generally,natural soils have structural property.So it is necessary to construct soil constitutive models which can take account of the soil structural property.Some scholars have proposed soil constitutive models that can take account of structural property on the basis of all kinds of theories and methods,and have achieved satisfactory results.But up to now,there are few literatures to give a state of the art review on soil structural constitutive models.Therefore,the paper presents a review on thethe current situation of soil structural constitutive models,points out some issues in use of the soil structural constitutive models
It is an important and complex task to construct soil constitutive model.Up to now,there are hundreds of soil constitutive models which have been provided by scholars in China and abroad.These models have been reviewed and documented in many literatures.However,because they were constructed and developed mainly on the basis of disturbed soils or sandy soils,these models are not able to describe the various nonlinear behavior induced by structural property of soil.Subsequently,the calculated results can greatly different with the results of tests performed in situ.Generally,natural soils have structural property.So it is necessary to construct soil constitutive models which can take account of the soil structural property.Some scholars have proposed soil constitutive models that can take account of structural property on the basis of all kinds of theories and methods,and have achieved satisfactory results.But up to now,there are few literatures to give a state of the art review on soil structural constitutive models.Therefore,the paper presents a review on thethe current situation of soil structural constitutive models,points out some issues in use of the soil structural constitutive models
2006, 14(5): 627-631.
In this paper two methods of calculating the variance of the samples spatial means are used to study the influence of the self-correlation distance on the variation of the coefficient of consolidation.The analysis results indicate that the variability of the coefficient of consolidation increases with the self-correlation distance increasing.For different variabilities of the coefficient of consolidation of different soils,the influences on the average degree of one-dimensional consolidation are different.
In this paper two methods of calculating the variance of the samples spatial means are used to study the influence of the self-correlation distance on the variation of the coefficient of consolidation.The analysis results indicate that the variability of the coefficient of consolidation increases with the self-correlation distance increasing.For different variabilities of the coefficient of consolidation of different soils,the influences on the average degree of one-dimensional consolidation are different.
2006, 14(5): 632-636.
As an in-situ test technique originated in 1980s,the piezocone penetration test(CPTU) has been attracting wide attention and widely used in the western country because of its advantages.Due to the differences in equipment design,technique code and operation method,there are lots of general factors affecting interpretation for the CPTU data.On the basis of the past investigation,the general factors affecting interpretation for the CPTU data are analyzed and summarized for the sake of attracting attention in use of the CPTU data.The corrections on various factors that influence primary measured data are described in brief.
As an in-situ test technique originated in 1980s,the piezocone penetration test(CPTU) has been attracting wide attention and widely used in the western country because of its advantages.Due to the differences in equipment design,technique code and operation method,there are lots of general factors affecting interpretation for the CPTU data.On the basis of the past investigation,the general factors affecting interpretation for the CPTU data are analyzed and summarized for the sake of attracting attention in use of the CPTU data.The corrections on various factors that influence primary measured data are described in brief.
2006, 14(5): 637-643.
Studies have shown that the electrical resistivity of soil can well represent its geotechnical properties,such as characteristics of soil contamination and ground liquefaction potential.This paper reviews the theory of soil electrical resistivity and measurement of soil electrical resistivity both in the lab and in the field.With summarizing literature works,the application of soil resistivity method for the ground improvement engineering is introduced,particularly in the evaluation of cement-treated soil column,ground improvement effect,potential of ground liquefaction,properties of compacted soil and ground contamination.Finally,the problems and the application prospects of the electrical resistivity study are discussed.
Studies have shown that the electrical resistivity of soil can well represent its geotechnical properties,such as characteristics of soil contamination and ground liquefaction potential.This paper reviews the theory of soil electrical resistivity and measurement of soil electrical resistivity both in the lab and in the field.With summarizing literature works,the application of soil resistivity method for the ground improvement engineering is introduced,particularly in the evaluation of cement-treated soil column,ground improvement effect,potential of ground liquefaction,properties of compacted soil and ground contamination.Finally,the problems and the application prospects of the electrical resistivity study are discussed.
2006, 14(5): 644-648.
By using the numerical model analysis software ADINA developed for large-scale geotechnical engineering problems,the improvements to the compression strength,elastic modulus c and values of the separate rock blocks after systematic bolts reinforcement are discussed,and the influence degree of systematic bolts on the rock mass of different strength is analysed.The anisotropy of the reinforced rock mass is also preliminarily studied,and it is found that bolts of vertical arrangement have major effect on the elastic modulus of the rock mass,but have minor effect on its compression strength.
By using the numerical model analysis software ADINA developed for large-scale geotechnical engineering problems,the improvements to the compression strength,elastic modulus c and values of the separate rock blocks after systematic bolts reinforcement are discussed,and the influence degree of systematic bolts on the rock mass of different strength is analysed.The anisotropy of the reinforced rock mass is also preliminarily studied,and it is found that bolts of vertical arrangement have major effect on the elastic modulus of the rock mass,but have minor effect on its compression strength.
2006, 14(5): 649-653.
This paper presents an application case of fiber optic sensor in the Structural Health Monitoring of tunnels.In the No.3 Tunnel of Bainijing in Yunnan Province,BOTDR was applied to monitor the arch rings.According to the geological condition of the tunnel,ten arch rings were selected at the end of the tunnel and fiber optic sensors were installed in them.In the following whole year,the strain distribution of these cross sections was recorded.The monitoring results showed that these ten arch rings retained stable in the monitoring period except the arch ring at the alignment of K84+508.2,where the surface of lining expanded in rainy season.It was believed that the rain infiltrated into the soil and increased the pressure of the adjacent rock mass,and then the arch ring was crushed to deform.
This paper presents an application case of fiber optic sensor in the Structural Health Monitoring of tunnels.In the No.3 Tunnel of Bainijing in Yunnan Province,BOTDR was applied to monitor the arch rings.According to the geological condition of the tunnel,ten arch rings were selected at the end of the tunnel and fiber optic sensors were installed in them.In the following whole year,the strain distribution of these cross sections was recorded.The monitoring results showed that these ten arch rings retained stable in the monitoring period except the arch ring at the alignment of K84+508.2,where the surface of lining expanded in rainy season.It was believed that the rain infiltrated into the soil and increased the pressure of the adjacent rock mass,and then the arch ring was crushed to deform.
2006, 14(5): 654-660.
Project option assessment has been well solved by using fuzzy decision method.Fuzzy decision model considering economic benefit and stability was established aiming to solve the question about stability of open pit slope and underground stope during the transition period from open pit to underground mining,in which fuzzy mathematics was used and stress and strain of the slope and underground stope caused by digging the first section combined with economic indices of ore block stripping ratio and recovery rate were comprehensively considered.By means of scientifically determining the membership function of each factor and establishing the weight of each factor by constructing the judging matrix through binary taxis,the optimal one was selected from nine schemes made up of different combination of room structural parameters,which could ensure not only safety production but also better economic profit.
Project option assessment has been well solved by using fuzzy decision method.Fuzzy decision model considering economic benefit and stability was established aiming to solve the question about stability of open pit slope and underground stope during the transition period from open pit to underground mining,in which fuzzy mathematics was used and stress and strain of the slope and underground stope caused by digging the first section combined with economic indices of ore block stripping ratio and recovery rate were comprehensively considered.By means of scientifically determining the membership function of each factor and establishing the weight of each factor by constructing the judging matrix through binary taxis,the optimal one was selected from nine schemes made up of different combination of room structural parameters,which could ensure not only safety production but also better economic profit.
2006, 14(5): 661-664.
The cultural relic investigation has its special characteristics in the field of engineering geological investigation.Based on partial exhumation in prophase,archeologists inferred that the ancient moat is buried around the rampart of Liye Qin Dynasty Ancient City and that some rare cultural relic might be imbedded at the bottom of the moat.It is of great significance to identify the location of the moat precisely to protect,exhume and utilize the site further.Various disturbances lead to very knotty exploration for the precise location of the moat because of sediment on surface,latter-day ponds superposed withpartial moat,breakage to cultural relic by conventional investigation method,and serious electromagnetism disturbances.The integrative scheme with high density electrical method and improved sampling cone penetration test is used to solve these difficulties.Practical application shows that the new feasible method has many unmatchable advantages in survey for cultural relic site.
The cultural relic investigation has its special characteristics in the field of engineering geological investigation.Based on partial exhumation in prophase,archeologists inferred that the ancient moat is buried around the rampart of Liye Qin Dynasty Ancient City and that some rare cultural relic might be imbedded at the bottom of the moat.It is of great significance to identify the location of the moat precisely to protect,exhume and utilize the site further.Various disturbances lead to very knotty exploration for the precise location of the moat because of sediment on surface,latter-day ponds superposed withpartial moat,breakage to cultural relic by conventional investigation method,and serious electromagnetism disturbances.The integrative scheme with high density electrical method and improved sampling cone penetration test is used to solve these difficulties.Practical application shows that the new feasible method has many unmatchable advantages in survey for cultural relic site.
2006, 14(5): 665-669.
The stability assessment of Beimengou slope is achieved on the basis of the safety factor calculated by the strength reduction FEM.Through the reduction of values,the FEM computation will not converge when the model reaches instability state,and the safety factor is just the reduction coefficient at this state.According to the calculation,the failure mode and failure propagation tendency of the slope can be obtained,which helps to understand the failure mechanism of the slope.The calculation results show that the safety factor calculated by the strength reduction FEM is fairly close to the that calculated by the traditional limit equilibrium method.Therefore,strength reduction FEM provides a new way to evaluate slope stability.
The stability assessment of Beimengou slope is achieved on the basis of the safety factor calculated by the strength reduction FEM.Through the reduction of values,the FEM computation will not converge when the model reaches instability state,and the safety factor is just the reduction coefficient at this state.According to the calculation,the failure mode and failure propagation tendency of the slope can be obtained,which helps to understand the failure mechanism of the slope.The calculation results show that the safety factor calculated by the strength reduction FEM is fairly close to the that calculated by the traditional limit equilibrium method.Therefore,strength reduction FEM provides a new way to evaluate slope stability.
2006, 14(5): 670-676.
The prevention of landslip is a comprehensive project,and the safety of prevention engineering depends on slope investigation、designing and construction quality.In this paper,the problems existing in every stage of landslip prevention engineering are illustrated with real cases,and several points that should be paid attention to are discussed.The previous engineering experience is summarized and slope monitoring in the prevention engineering is emphasized,which can be used as reference in future landslip prevention engineering.
The prevention of landslip is a comprehensive project,and the safety of prevention engineering depends on slope investigation、designing and construction quality.In this paper,the problems existing in every stage of landslip prevention engineering are illustrated with real cases,and several points that should be paid attention to are discussed.The previous engineering experience is summarized and slope monitoring in the prevention engineering is emphasized,which can be used as reference in future landslip prevention engineering.
2006, 14(5): 677-682.
To study the deformation characteristics of the thaw slumping body at the alignment of K3035 in permafrost area of Qinghai-Tibet Platean,two deformation monitoring boreholes were instrumented with Geokon-603 clinometers,and one borehole lay in the non-sliding soil body while the other lay in the front part of the slumping soil body.Monitoring results of nearly one year show that the thaw slumping body developed in the slope of small dip angle has obvious deformation and its displacement mainly occurs in shallow soil area and decreases with depth.The monitoring results were verified by numerical simulations.The monitoring data comparisons between the thaw slumping body at the alignment of K3035(southern slope) and that at the alignment of K3057(northern slope) were carried out.With reference to both the leading edge and the rear edge of the thaw slumping body,the deformation of the former thaw slumping body is always greater than that of the latter.While in the slope with no thaw slumping(at the alignment of DK1139 of Qinghai-Tibet railway) the deformation is very limited.The difference indicates that on the one hand excavation is the direct factor causing thaw slumping,and on the other hand,because of thaw slumping,the soil body at the rear edge of the slope which is relatively stable originally will experience relatively large creep.
To study the deformation characteristics of the thaw slumping body at the alignment of K3035 in permafrost area of Qinghai-Tibet Platean,two deformation monitoring boreholes were instrumented with Geokon-603 clinometers,and one borehole lay in the non-sliding soil body while the other lay in the front part of the slumping soil body.Monitoring results of nearly one year show that the thaw slumping body developed in the slope of small dip angle has obvious deformation and its displacement mainly occurs in shallow soil area and decreases with depth.The monitoring results were verified by numerical simulations.The monitoring data comparisons between the thaw slumping body at the alignment of K3035(southern slope) and that at the alignment of K3057(northern slope) were carried out.With reference to both the leading edge and the rear edge of the thaw slumping body,the deformation of the former thaw slumping body is always greater than that of the latter.While in the slope with no thaw slumping(at the alignment of DK1139 of Qinghai-Tibet railway) the deformation is very limited.The difference indicates that on the one hand excavation is the direct factor causing thaw slumping,and on the other hand,because of thaw slumping,the soil body at the rear edge of the slope which is relatively stable originally will experience relatively large creep.
2006, 14(5): 683-688.
Compaction degree is the key index to control construction of embankment.In this paper the settlement of embankment is simulated by centrifugal test and FEM analysis under different compact degrees,and the relationships between cohesion,friction angle and compact degree and characteristics of embankment settlement under different compact degrees are obtained,which provides important basis for construction of embankment.
Compaction degree is the key index to control construction of embankment.In this paper the settlement of embankment is simulated by centrifugal test and FEM analysis under different compact degrees,and the relationships between cohesion,friction angle and compact degree and characteristics of embankment settlement under different compact degrees are obtained,which provides important basis for construction of embankment.
2006, 14(5): 689-693.
On the upper part of foundation in the ancient city,there is a large number of miscellaneous fill which is mainly composed of stove ashes and is variable in thickness.With the rapid development of urbanization,to utilize underground space of high buildings is becoming more and more necessary in renovating of the ancient town.Especially,it is serious and crucial to choose a reasonable and economical supporting procedure in excavating deep pit under vulnerable environmental condition such as this miscellaneous foundation.Since any supporting procedure has its limitation,geotechnical engineers should take site engineering geological conditions and feature of foundation pit into account,and choose composite supporting procedures to get better retaining effect.Taking one deep foundation pit of miscellaneous fill for instance,this paper describes its engineering geologic properties,and parameter,design calculation for the anchor rod sheet piling wall and soil nailing wall.This work can provide reference and guideline for the similar engineering to determine its retaining procedure and design of deep foundation pit.
On the upper part of foundation in the ancient city,there is a large number of miscellaneous fill which is mainly composed of stove ashes and is variable in thickness.With the rapid development of urbanization,to utilize underground space of high buildings is becoming more and more necessary in renovating of the ancient town.Especially,it is serious and crucial to choose a reasonable and economical supporting procedure in excavating deep pit under vulnerable environmental condition such as this miscellaneous foundation.Since any supporting procedure has its limitation,geotechnical engineers should take site engineering geological conditions and feature of foundation pit into account,and choose composite supporting procedures to get better retaining effect.Taking one deep foundation pit of miscellaneous fill for instance,this paper describes its engineering geologic properties,and parameter,design calculation for the anchor rod sheet piling wall and soil nailing wall.This work can provide reference and guideline for the similar engineering to determine its retaining procedure and design of deep foundation pit.
2006, 14(5): 694-698.
Based on the characteristics of soil dynamic consolidation(DC),nonlinear FEM with momentary display function is applied to simulate the collision process of dynamic consolidation.This study simulated the dynamic consolidation of loess numerically to generate an elastic-plastic finite element representation of soils.In this study,material nonlinearity,geometric nonlinearity,contact nonlinearity,movement nonlinearity and coupling characteristics of them were taken into account.The histories of soil stress,collision force of hammer were obtained;at the same time,the deformation of soil and soil density were acquired at different depth,and comparisons were made of the displacement and the stress of soil.The consolidation mechanism of dynamic compaction is investigated and some useful conclusions are gained.
Based on the characteristics of soil dynamic consolidation(DC),nonlinear FEM with momentary display function is applied to simulate the collision process of dynamic consolidation.This study simulated the dynamic consolidation of loess numerically to generate an elastic-plastic finite element representation of soils.In this study,material nonlinearity,geometric nonlinearity,contact nonlinearity,movement nonlinearity and coupling characteristics of them were taken into account.The histories of soil stress,collision force of hammer were obtained;at the same time,the deformation of soil and soil density were acquired at different depth,and comparisons were made of the displacement and the stress of soil.The consolidation mechanism of dynamic compaction is investigated and some useful conclusions are gained.
2006, 14(5): 699-702.
Based on the attenuation information(waveform and spectrum) in the seismogram,the seismic quality factor Q can be calculated for the rock mass.This paper presents some typical methods to compute the Q value to evaluate the rock mass quality.The methods include amplitude,rise-time, spectral ratio,and centroid frequency shift.The paper gives the principles of these methods,and discusses their stability and applicability.
Based on the attenuation information(waveform and spectrum) in the seismogram,the seismic quality factor Q can be calculated for the rock mass.This paper presents some typical methods to compute the Q value to evaluate the rock mass quality.The methods include amplitude,rise-time, spectral ratio,and centroid frequency shift.The paper gives the principles of these methods,and discusses their stability and applicability.
2006, 14(5): 703-708.
Finite element analysis model of the T-shaped short-leg shear wall is constructed by using the 3D solid elements package SOLID65 of the general FEA program ANSYS.The simulation covers the whole loading process from the elastic deformation stage to the crack and failure of the concrete.Several factors which may influence the bearing capacity,deformation capacity and ductility of the short-leg shear wall are discussed,such as concrete strength grade, reinforcement ratio,ratio of axial compressive force to axial compressive ultimate capacity of section and ratio of height to sectional thickness of the wallcolumn.The failure process and its cause are analyzed and the response of the short-leg shear wall under the combination loading of the axial compressive force and progressive lateral forces.The simulation results indicate that raising the concrete strength grade and ratio of axial compressive force to axial compressive ultimate capacity of section can increase the loads of crack and yielding as well as the ultimate bearing capacity of the specimen while the deformation capacity and ductility should also be considered.Bearing capacity,deformation capacity and ductility of the shear wall are relatively good when reinforcement ratio is between 1.4% and 1.6%.ratio of height to sectional thickness of the wall-column is an unsteady factor,but deformation capacity and ductility are relatively good when this ratio is between 6.5 and 7.1.
Finite element analysis model of the T-shaped short-leg shear wall is constructed by using the 3D solid elements package SOLID65 of the general FEA program ANSYS.The simulation covers the whole loading process from the elastic deformation stage to the crack and failure of the concrete.Several factors which may influence the bearing capacity,deformation capacity and ductility of the short-leg shear wall are discussed,such as concrete strength grade, reinforcement ratio,ratio of axial compressive force to axial compressive ultimate capacity of section and ratio of height to sectional thickness of the wallcolumn.The failure process and its cause are analyzed and the response of the short-leg shear wall under the combination loading of the axial compressive force and progressive lateral forces.The simulation results indicate that raising the concrete strength grade and ratio of axial compressive force to axial compressive ultimate capacity of section can increase the loads of crack and yielding as well as the ultimate bearing capacity of the specimen while the deformation capacity and ductility should also be considered.Bearing capacity,deformation capacity and ductility of the shear wall are relatively good when reinforcement ratio is between 1.4% and 1.6%.ratio of height to sectional thickness of the wall-column is an unsteady factor,but deformation capacity and ductility are relatively good when this ratio is between 6.5 and 7.1.
2006, 14(5): 709-714.
The authors introduce the related theories on silt reinforced with slag powder first.The improvement of silt by adding slag power is attributed to the micro-aggregate filling effect and pozzolana binding effect,and the latter effect consists of hydration,inspiration and ion exchanging.It is suggested that the micro-aggregate filling effect is highly correlated with the fineness of slag powder and the two effects are summed up with framed chart.On the other hand,the tests of unconfined saturated compression,water stability,freezing stability,temperature shrinkage and dry shrinkage of silt consolidated by slag powder and silt consolidated by lime power were conducted and the test results were compared.The results indicate that road performance of silt consolidated by slag powder is better than those of silt consolidated by lime powder,which provides experimental evidence to its engineering application.
The authors introduce the related theories on silt reinforced with slag powder first.The improvement of silt by adding slag power is attributed to the micro-aggregate filling effect and pozzolana binding effect,and the latter effect consists of hydration,inspiration and ion exchanging.It is suggested that the micro-aggregate filling effect is highly correlated with the fineness of slag powder and the two effects are summed up with framed chart.On the other hand,the tests of unconfined saturated compression,water stability,freezing stability,temperature shrinkage and dry shrinkage of silt consolidated by slag powder and silt consolidated by lime power were conducted and the test results were compared.The results indicate that road performance of silt consolidated by slag powder is better than those of silt consolidated by lime powder,which provides experimental evidence to its engineering application.
2006, 14(5): 715-720.
The three-dimensional visualization technology is widely used for its vivid regeneration of the real ground configuration from the investigated ground information and its proper description of the spatial relationships of structural elements.In this paper a 3D geo-body visualization method with the basic body elements of triangular prisms is introduced.The model is constructed with virtual drilling information through the self-decomposition of triangles and sufficiently considering the geological structures like faults in the geological body.The internal information of the geological body is displayed through the technique of self-decomposition.Finally,real drilling data is input to verify the model and the result indicates it is feasible.
The three-dimensional visualization technology is widely used for its vivid regeneration of the real ground configuration from the investigated ground information and its proper description of the spatial relationships of structural elements.In this paper a 3D geo-body visualization method with the basic body elements of triangular prisms is introduced.The model is constructed with virtual drilling information through the self-decomposition of triangles and sufficiently considering the geological structures like faults in the geological body.The internal information of the geological body is displayed through the technique of self-decomposition.Finally,real drilling data is input to verify the model and the result indicates it is feasible.
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