According to technology development and relative facilitation in digging and underground structures, ways, highways, all types of tunnels, underground train network, and other underground settle, storage are number of...According to technology development and relative facilitation in digging and underground structures, ways, highways, all types of tunnels, underground train network, and other underground settle, storage are number of structure built and developed in advanced countries. In most situation, tunnel digging operations are done years after its construction or are not recorded in new structures regulations;therefore, this research investigates soil settlement and inserting force to tunnel coverage by limiting studies about effects of tunnel shapes on soil settlement using Plaxis, Seismo Signal, and Seismo Aspect. This study shows that rectangular tunnel has the most settlement in soil surface and circular tunnel has the least settlement but horseshoe tunnel has similar behavior to circular tunnel;however, earth subsidence level by digging this tunnel is more than circular tunnel. In addition, sectional shape has direct effect on inserting forces on tunnel coverage.展开更多
A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a...A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.展开更多
A new approach was proposed to describe settlement behavior of an unsaturated soil with subgrade filling for high-speed railway. Firstly, based on Terzaghi consolidation theory, equations considering the variation coe...A new approach was proposed to describe settlement behavior of an unsaturated soil with subgrade filling for high-speed railway. Firstly, based on Terzaghi consolidation theory, equations considering the variation coefficient of consolidation with void ratio and saturation for consolidation of an unsaturated soil under stage continuous loading were derived, and according to analytical solutions of equations, a formula for settlement computation under stage continuous loading was obtained. Then, combined with the width-to-height ratio of subgrade to compute ground reaction, and by means of in-situ plate loading curves, a correctional approach was presented for the analysis of nonlinear settlement of foundation. Also, the comparison between calculated and measured loadsettlement behavior for an unsaturated soil in Qingdao-Ji'nan high-speed railway was given to demonstrate the effectiveness and accuracy of the proposed approach. It can be noted that the presented solution can be used to predict the settlement of an unsaturated soil foundation under stage continuous loading in engineering design.展开更多
This paper presents the logic relationship between rural settlement reconstruction and soil conservation in the Upper Yangtze River. Firstly, by introducing the concepts of ＂flow＂ and ＂intercepted flow＂, we probe ...This paper presents the logic relationship between rural settlement reconstruction and soil conservation in the Upper Yangtze River. Firstly, by introducing the concepts of ＂flow＂ and ＂intercepted flow＂, we probe into the dynamic mechanism on interaction between ecological and environmental system, and then point out that the ＂intercepting sites＂ are physical conditions for establishment of human settlements in mountains. Secondly, by using ecological theories, ＂flow＂, ＂source＂, and ＂sink＂, material cycle and energy flow in mountains have been discussed. Thirdly, according to dissipative structure theory and thermodynamic laws, a hypothesis has been proposed that ＂entropy flow＂ is a dynamic force for settlement evolution. Finally, it is argued that a project for soil conservation is set to control and utilize flows so rural settlements can be supported and farmers＇ life improved.展开更多
This article deals with the assessment of the soil nailing technique with a vertical inclusion to improve the geotechnical parameters of cohesive soil. A series of unconfined compression tests and direct shear tests w...This article deals with the assessment of the soil nailing technique with a vertical inclusion to improve the geotechnical parameters of cohesive soil. A series of unconfined compression tests and direct shear tests were carried out to establish the stressestrain relationship and strength characteristics of the reinforced clay sample by vertical steel nails. The shear strength performance of the new composite material was tested by varying the number of vertical inclusions, the embedment depth and the alignment radius. The results confirmed that the vertical bars/inclusions shared the vertical applied load with clay. Increase in the number of vertical inclusions significantly increases the shear strength and the stiffness with a remarkable reduction in settlement. When the clay samples were reinforced with six inclusions along the perimeter, the shear strength was increased to 231% for the embedment depth ratio equal to 0.85. To obtain the optimum effect in eliminating shear failure, the vertical inclusions should be extended to a deeper zone with sufficient numbers. It has been found that the vertical inclusions significantly influence the shear strength, and the brittle or general shear failure of the unreinforced sample can be diverted to partial/plastic shear failure.展开更多
A series of tests were conducted to analyze temperature field distribution and thawing settlement of a thawing soil under static and dynamic loading at various cooling and thawing temperatures. The results demonstrate...A series of tests were conducted to analyze temperature field distribution and thawing settlement of a thawing soil under static and dynamic loading at various cooling and thawing temperatures. The results demonstrate： （1） the temperature field distribution of the thawing soil was not significantly influenced by the loading form under the tested loading conditions; similar results were obtained for samples at different dynamic loading frequencies and different dynamic loading ampli- tudes, which verified the independence of loading form and temperature field; （2） changed temperature field distributions were found in thawing soil with different cooling and thawing temperatures, and the cooling and thawing temperature of the samples were the main factors affecting their temperature distributions; （3） under the tested conditions, thawing set- tlements were little influenced by the thawing temperature and the dynamic loading frequency; and （4） a linear relation- ship existed between the thawing settlement and the cooling temperature, and a logarithmic function could be used to describe the relationship between the thawing settlement and the loading amplitude.展开更多
Transportation agencies spend millions of dollars annually to repair civil transportation infrastructure including pavements,earth structures and approach slabs distressed by soft compressible soils and expansive soil...Transportation agencies spend millions of dollars annually to repair civil transportation infrastructure including pavements,earth structures and approach slabs distressed by soft compressible soils and expansive soils.Several research studies performed at the University of Texas at Arlington(UTA) focused on stabilizing these problematic soils so that they will provide better and more stable support to the transportation infrastructure.This paper focuses on a summary of two major distresses and mechanisms,and remedial measures for addressing these distress problems.A combined lime-cement stabilization method is fully evaluated in providing better support of pavement infrastructure,and these results are described here.Another major transportation infrastructure problem involving bridge approach slabs requires different treatment methods,and these results are briefly described.As a part of the recently completed research study assessments,both shallow and deep soil treatment methods for stabilizing soils are fully evaluated for their effectiveness in arresting the distress posed to the pavements and bridge approach slabs.These results along with a few future research needs are presented in this paper.展开更多
Lagoon berms in western Alaska are difficult to design and build due to limited resources, high cost of construction and materials, and warm permafrost conditions. This paper explores methods to treat locally availabl...Lagoon berms in western Alaska are difficult to design and build due to limited resources, high cost of construction and materials, and warm permafrost conditions. This paper explores methods to treat locally available frozen materials and use them for berm construction. The goal is to find an optimized mix ratio for cement and additives that can be effective in increasing the strength and decreasing the thaw settlement of an ice-rich frozen silty soil. Soil of similar type and ice content to the permafrost found at a project site in Eek, Alaska is prepared in a cold room. The frozen soil is pulverized and cement, additives and fibers are added to the samples for enhancing shear strength and controlling thaw settlement. Thaw settlement and direct shear tests are performed to assess strength and settlement characteristics. This paper presents a sample preparation method, data from thaw settlement and direct shear tests, and analyses of the test results and preliminary conclusions.展开更多
In this paper, numerical simulation with soil-water coupling finite element-finite difference（FE-FD） analysis is conducted to investigate the settlement and the excess pore water pressure（EPWP） of a piled-raft fou...In this paper, numerical simulation with soil-water coupling finite element-finite difference（FE-FD） analysis is conducted to investigate the settlement and the excess pore water pressure（EPWP） of a piled-raft foundation due to cyclic high-speed（speed： 300km/h） train loading. To demonstrate the performance of this numerical simulation, the settlement and EPWP in the ground under the train loading within one month was calculated and confirmed by monitoring data, which shows that the change of the settlement and EPWP can be simulated well on the whole. In order to ensure the safety of train operation, countermeasure by the fracturing grouting is proposed. Two cases are analyzed, namely, grouting in No-4 softest layer and No-9 pile bearing layer respectively. It is found that fracturing grouting in the pile bearing layer（No-9 layer） has better effect on reducing the settlement.展开更多
This paper presents an analytical solution of the one-dimensional consolidation in unsaturated soil with a finite thickness under vertical loading and confinements in the lateral directions. The boundary contains the ...This paper presents an analytical solution of the one-dimensional consolidation in unsaturated soil with a finite thickness under vertical loading and confinements in the lateral directions. The boundary contains the top surface permeable to water and air and the bottom impermeable to water and air. The analytical solution is for Fredlund＇s one-dimensional consolidation equation in unsaturated soils. The transfer relationship between the state vectors at top surface and any depth is obtained by using the Laplace transform and Cayley-Hamilton mathematical methods to the governing equations of water and air, Darcy＇s law and Fick＇s law. Excess pore-air pressure, excess pore-water pressure and settlement in the Laplace-transformed domain are obtained by using the Laplace transform with the initial conditions and boundary conditions. By performing inverse Laplace transforms, the analytical solutions are obtained in the time domain. A typical example illustrates the consolidation characteristics of unsaturated soil from an- alytical results. Finally, comparisons between the analytical solutions and results of the finite difference method indicate that the analytical solution is correct.展开更多
This paper describes the engineeringapplication of soil improvement in manylarge coal-fired power plants designed byEast China Electric Power Design Institute.Soil improvement technology is especiallysuitable for stre...This paper describes the engineeringapplication of soil improvement in manylarge coal-fired power plants designed byEast China Electric Power Design Institute.Soil improvement technology is especiallysuitable for strengthening soft soil. Exceptfor increasing soil bearing capacity andcontrolling soil deformation, it can also beused to eliminate loose sand liquefactionunder seismic loading, or to strengthen slopestability. The applications introduced in thispaper include dynamic consolidation,drained consolidation, stone pile, soil-cement mixed pile, jet grouting andcompacting grouting, reinforced earth, etc.The kinds of soil layer to be improvedinclude typical Shanghai soft soil, loose siltand silt sand, miscellaneous fill andhydraulic filled soil. As a result of thetreatments described in this paper, nobuilding fissures caused by soil differentialsettlement had ever occurred in the powerplants engineered by ECEPDI andconstructed in 1990s.展开更多
Problematic soils usually cause considerable problems to engineering projects. As an example, soil structure collapse caused by moisture increment or rising underground water level results in huge settlements. This ty...Problematic soils usually cause considerable problems to engineering projects. As an example, soil structure collapse caused by moisture increment or rising underground water level results in huge settlements. This type of problematic soil, named collapsible soil, can cause dramatic problems and should be amended where exists. Today, the use of different techniques for soil reinforcement and soil improvement is widely used to treat soil properties. One of these methods is Deep Soil Mixing (DSM) method. This method becomes more important in the cases of studying and examining collapsible soils. In this research, the settlement of amended collapsible soils, applying deep soil mixing method, is examined. The experiments show that soil amendment using this method, well prevents the settlement of collapsible soils giving rise to bearing capacity.展开更多
The prediction of embankment settlement is a critically important issue for the serviceability of subgrade projects,especially the post-construction settlement.A number of methods have been proposed to predict embankm...The prediction of embankment settlement is a critically important issue for the serviceability of subgrade projects,especially the post-construction settlement.A number of methods have been proposed to predict embankment settlement;however,all of these methods are based on a parameter,i.e.the initial time point.The difference of the initial time point determined by different designers can de?nitely induce errors in prediction of embankment settlement.This paper proposed a concept named"potential settlement"and a simpli?ed method based on the in situ data.The key parameter"b"in the proposed method was veri?ed using theoretical method and?eld data.Finally,an example was used to demonstrate the advantages of the proposed method by comparing with other methods and the observation data.展开更多
An experimental program is conducted on model piled rafts in sand soil.The experimental program is aimed to investigate the behavior of raft on settlement reducing piles.The testing program includes tests on models of...An experimental program is conducted on model piled rafts in sand soil.The experimental program is aimed to investigate the behavior of raft on settlement reducing piles.The testing program includes tests on models of single pile,unpiled rafts and rafts on 1,4,9,or 16 piles.The model piles beneath the rafts are closed ended displacement piles installed by driving.Three lengths of piles are used in the experiments to represent slenderness ratio,L/D,of 20,30 and 50,respectively.The dimensions of the model rafts are 30 cm×30 cm with different thickness of 0.5 cm,1.0 cm or 1.5 cm.The raft-soil stiffness ratios of the model rafts ranging from 0.39 to 10.56 cover flexible to very stiff rafts.The improvement in the ultimate bearing capacity is represented by the load improvement ratio,LIR,and the reductions in average settlement and differential settlement are represented by the settlement ratio,SR,and the differential settlement ratio,DSR,respectively.The effects of the number of settlement reducing piles,raft relative stiffness,and the slenderness ratio of piles on the load improvement ratio,settlement ratio and differential settlement ratio are presented and discussed.The results of the tests show the effectiveness of using piles as settlement reduction measure with the rafts.As the number of settlement reducing piles increases,the load improvement ratio increases and the differential settlement ratio decreases.展开更多
It is nowadays well reported that collapsible soils spread in many countries, including United States, Russia, China, South America (e.g. Brazil), South and North Africa (e.g. Egypt, Algeria), Middle East (e.g. Saudi ...It is nowadays well reported that collapsible soils spread in many countries, including United States, Russia, China, South America (e.g. Brazil), South and North Africa (e.g. Egypt, Algeria), Middle East (e.g. Saudi Arabia) and many countries in Eastern Europe. In general, collapsible soils are located in arid and semi-arid regions around the world. This special type of soil is characterized by abrupt reduction in strength, excessive and sudden settlement when it becomes wet leading to failure of the structure. Construction on such a kind of soil is one of the prominent problems in geotechnical engineering. The main objectives of this study are reporting geological and geotechnical zonation maps for potentially collapsible soils in inhabited areas in Egypt. Furthermore, a design technique for foundations built on a shallow depth of Egyptian macro-porous collapsible soils (less than 4 m) is developed. The design method includes a design chart for soil collapse field classification in terms of the most governing parameters, a method for foundation settlement estimation based on a correlation between the wetting-induced collapse strain and the applied pressure, and a design practice to guide practicing engineers to select the appropriate foundation system to construct on such soil with a great degree of confidence and safety.展开更多
文摘According to technology development and relative facilitation in digging and underground structures, ways, highways, all types of tunnels, underground train network, and other underground settle, storage are number of structure built and developed in advanced countries. In most situation, tunnel digging operations are done years after its construction or are not recorded in new structures regulations;therefore, this research investigates soil settlement and inserting force to tunnel coverage by limiting studies about effects of tunnel shapes on soil settlement using Plaxis, Seismo Signal, and Seismo Aspect. This study shows that rectangular tunnel has the most settlement in soil surface and circular tunnel has the least settlement but horseshoe tunnel has similar behavior to circular tunnel;however, earth subsidence level by digging this tunnel is more than circular tunnel. In addition, sectional shape has direct effect on inserting forces on tunnel coverage.
基金Project(SWJT11ZT04)supported by the Central College Foundation of ChinaProject(2008g032-A)supported by the Major Projects S&T Foundation of China’s Ministry of Railways,China
文摘A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.
基金Project(2010G003-F)supported by the Research and Development Program for Technology of the Chinese Ministry of Railway
文摘A new approach was proposed to describe settlement behavior of an unsaturated soil with subgrade filling for high-speed railway. Firstly, based on Terzaghi consolidation theory, equations considering the variation coefficient of consolidation with void ratio and saturation for consolidation of an unsaturated soil under stage continuous loading were derived, and according to analytical solutions of equations, a formula for settlement computation under stage continuous loading was obtained. Then, combined with the width-to-height ratio of subgrade to compute ground reaction, and by means of in-situ plate loading curves, a correctional approach was presented for the analysis of nonlinear settlement of foundation. Also, the comparison between calculated and measured loadsettlement behavior for an unsaturated soil in Qingdao-Ji'nan high-speed railway was given to demonstrate the effectiveness and accuracy of the proposed approach. It can be noted that the presented solution can be used to predict the settlement of an unsaturated soil foundation under stage continuous loading in engineering design.
基金the Key Social Research Project of Education Ministry (04JZD0010)
文摘This paper presents the logic relationship between rural settlement reconstruction and soil conservation in the Upper Yangtze River. Firstly, by introducing the concepts of ＂flow＂ and ＂intercepted flow＂, we probe into the dynamic mechanism on interaction between ecological and environmental system, and then point out that the ＂intercepting sites＂ are physical conditions for establishment of human settlements in mountains. Secondly, by using ecological theories, ＂flow＂, ＂source＂, and ＂sink＂, material cycle and energy flow in mountains have been discussed. Thirdly, according to dissipative structure theory and thermodynamic laws, a hypothesis has been proposed that ＂entropy flow＂ is a dynamic force for settlement evolution. Finally, it is argued that a project for soil conservation is set to control and utilize flows so rural settlements can be supported and farmers＇ life improved.
文摘This article deals with the assessment of the soil nailing technique with a vertical inclusion to improve the geotechnical parameters of cohesive soil. A series of unconfined compression tests and direct shear tests were carried out to establish the stressestrain relationship and strength characteristics of the reinforced clay sample by vertical steel nails. The shear strength performance of the new composite material was tested by varying the number of vertical inclusions, the embedment depth and the alignment radius. The results confirmed that the vertical bars/inclusions shared the vertical applied load with clay. Increase in the number of vertical inclusions significantly increases the shear strength and the stiffness with a remarkable reduction in settlement. When the clay samples were reinforced with six inclusions along the perimeter, the shear strength was increased to 231% for the embedment depth ratio equal to 0.85. To obtain the optimum effect in eliminating shear failure, the vertical inclusions should be extended to a deeper zone with sufficient numbers. It has been found that the vertical inclusions significantly influence the shear strength, and the brittle or general shear failure of the unreinforced sample can be diverted to partial/plastic shear failure.
基金provided by National Natural Science Foundation of China (NSFC) under Grant Nos.41001036 and 41171064
文摘A series of tests were conducted to analyze temperature field distribution and thawing settlement of a thawing soil under static and dynamic loading at various cooling and thawing temperatures. The results demonstrate： （1） the temperature field distribution of the thawing soil was not significantly influenced by the loading form under the tested loading conditions; similar results were obtained for samples at different dynamic loading frequencies and different dynamic loading ampli- tudes, which verified the independence of loading form and temperature field; （2） changed temperature field distributions were found in thawing soil with different cooling and thawing temperatures, and the cooling and thawing temperature of the samples were the main factors affecting their temperature distributions; （3） under the tested conditions, thawing set- tlements were little influenced by the thawing temperature and the dynamic loading frequency; and （4） a linear relation- ship existed between the thawing settlement and the cooling temperature, and a logarithmic function could be used to describe the relationship between the thawing settlement and the loading amplitude.
文摘Transportation agencies spend millions of dollars annually to repair civil transportation infrastructure including pavements,earth structures and approach slabs distressed by soft compressible soils and expansive soils.Several research studies performed at the University of Texas at Arlington(UTA) focused on stabilizing these problematic soils so that they will provide better and more stable support to the transportation infrastructure.This paper focuses on a summary of two major distresses and mechanisms,and remedial measures for addressing these distress problems.A combined lime-cement stabilization method is fully evaluated in providing better support of pavement infrastructure,and these results are described here.Another major transportation infrastructure problem involving bridge approach slabs requires different treatment methods,and these results are briefly described.As a part of the recently completed research study assessments,both shallow and deep soil treatment methods for stabilizing soils are fully evaluated for their effectiveness in arresting the distress posed to the pavements and bridge approach slabs.These results along with a few future research needs are presented in this paper.
文摘Lagoon berms in western Alaska are difficult to design and build due to limited resources, high cost of construction and materials, and warm permafrost conditions. This paper explores methods to treat locally available frozen materials and use them for berm construction. The goal is to find an optimized mix ratio for cement and additives that can be effective in increasing the strength and decreasing the thaw settlement of an ice-rich frozen silty soil. Soil of similar type and ice content to the permafrost found at a project site in Eek, Alaska is prepared in a cold room. The frozen soil is pulverized and cement, additives and fibers are added to the samples for enhancing shear strength and controlling thaw settlement. Thaw settlement and direct shear tests are performed to assess strength and settlement characteristics. This paper presents a sample preparation method, data from thaw settlement and direct shear tests, and analyses of the test results and preliminary conclusions.
基金National Natural Science Foundation of China under Grant Nos.41627801 and 41372284The Special Project Fund of Taishan Scholars of Shandong Province under Grant No.2015-212China Postdoctoral Science Foundation under Grant No.2017M612227
文摘In this paper, numerical simulation with soil-water coupling finite element-finite difference（FE-FD） analysis is conducted to investigate the settlement and the excess pore water pressure（EPWP） of a piled-raft foundation due to cyclic high-speed（speed： 300km/h） train loading. To demonstrate the performance of this numerical simulation, the settlement and EPWP in the ground under the train loading within one month was calculated and confirmed by monitoring data, which shows that the change of the settlement and EPWP can be simulated well on the whole. In order to ensure the safety of train operation, countermeasure by the fracturing grouting is proposed. Two cases are analyzed, namely, grouting in No-4 softest layer and No-9 pile bearing layer respectively. It is found that fracturing grouting in the pile bearing layer（No-9 layer） has better effect on reducing the settlement.
文摘This paper presents an analytical solution of the one-dimensional consolidation in unsaturated soil with a finite thickness under vertical loading and confinements in the lateral directions. The boundary contains the top surface permeable to water and air and the bottom impermeable to water and air. The analytical solution is for Fredlund＇s one-dimensional consolidation equation in unsaturated soils. The transfer relationship between the state vectors at top surface and any depth is obtained by using the Laplace transform and Cayley-Hamilton mathematical methods to the governing equations of water and air, Darcy＇s law and Fick＇s law. Excess pore-air pressure, excess pore-water pressure and settlement in the Laplace-transformed domain are obtained by using the Laplace transform with the initial conditions and boundary conditions. By performing inverse Laplace transforms, the analytical solutions are obtained in the time domain. A typical example illustrates the consolidation characteristics of unsaturated soil from an- alytical results. Finally, comparisons between the analytical solutions and results of the finite difference method indicate that the analytical solution is correct.
文摘This paper describes the engineeringapplication of soil improvement in manylarge coal-fired power plants designed byEast China Electric Power Design Institute.Soil improvement technology is especiallysuitable for strengthening soft soil. Exceptfor increasing soil bearing capacity andcontrolling soil deformation, it can also beused to eliminate loose sand liquefactionunder seismic loading, or to strengthen slopestability. The applications introduced in thispaper include dynamic consolidation,drained consolidation, stone pile, soil-cement mixed pile, jet grouting andcompacting grouting, reinforced earth, etc.The kinds of soil layer to be improvedinclude typical Shanghai soft soil, loose siltand silt sand, miscellaneous fill andhydraulic filled soil. As a result of thetreatments described in this paper, nobuilding fissures caused by soil differentialsettlement had ever occurred in the powerplants engineered by ECEPDI andconstructed in 1990s.
文摘Problematic soils usually cause considerable problems to engineering projects. As an example, soil structure collapse caused by moisture increment or rising underground water level results in huge settlements. This type of problematic soil, named collapsible soil, can cause dramatic problems and should be amended where exists. Today, the use of different techniques for soil reinforcement and soil improvement is widely used to treat soil properties. One of these methods is Deep Soil Mixing (DSM) method. This method becomes more important in the cases of studying and examining collapsible soils. In this research, the settlement of amended collapsible soils, applying deep soil mixing method, is examined. The experiments show that soil amendment using this method, well prevents the settlement of collapsible soils giving rise to bearing capacity.
基金a part of the project "Universities Natural Science Research Project in Anhui Province" (KJ2011Z375)supported by Department of Education of Anhui Province
文摘The prediction of embankment settlement is a critically important issue for the serviceability of subgrade projects,especially the post-construction settlement.A number of methods have been proposed to predict embankment settlement;however,all of these methods are based on a parameter,i.e.the initial time point.The difference of the initial time point determined by different designers can de?nitely induce errors in prediction of embankment settlement.This paper proposed a concept named"potential settlement"and a simpli?ed method based on the in situ data.The key parameter"b"in the proposed method was veri?ed using theoretical method and?eld data.Finally,an example was used to demonstrate the advantages of the proposed method by comparing with other methods and the observation data.
文摘An experimental program is conducted on model piled rafts in sand soil.The experimental program is aimed to investigate the behavior of raft on settlement reducing piles.The testing program includes tests on models of single pile,unpiled rafts and rafts on 1,4,9,or 16 piles.The model piles beneath the rafts are closed ended displacement piles installed by driving.Three lengths of piles are used in the experiments to represent slenderness ratio,L/D,of 20,30 and 50,respectively.The dimensions of the model rafts are 30 cm×30 cm with different thickness of 0.5 cm,1.0 cm or 1.5 cm.The raft-soil stiffness ratios of the model rafts ranging from 0.39 to 10.56 cover flexible to very stiff rafts.The improvement in the ultimate bearing capacity is represented by the load improvement ratio,LIR,and the reductions in average settlement and differential settlement are represented by the settlement ratio,SR,and the differential settlement ratio,DSR,respectively.The effects of the number of settlement reducing piles,raft relative stiffness,and the slenderness ratio of piles on the load improvement ratio,settlement ratio and differential settlement ratio are presented and discussed.The results of the tests show the effectiveness of using piles as settlement reduction measure with the rafts.As the number of settlement reducing piles increases,the load improvement ratio increases and the differential settlement ratio decreases.
文摘It is nowadays well reported that collapsible soils spread in many countries, including United States, Russia, China, South America (e.g. Brazil), South and North Africa (e.g. Egypt, Algeria), Middle East (e.g. Saudi Arabia) and many countries in Eastern Europe. In general, collapsible soils are located in arid and semi-arid regions around the world. This special type of soil is characterized by abrupt reduction in strength, excessive and sudden settlement when it becomes wet leading to failure of the structure. Construction on such a kind of soil is one of the prominent problems in geotechnical engineering. The main objectives of this study are reporting geological and geotechnical zonation maps for potentially collapsible soils in inhabited areas in Egypt. Furthermore, a design technique for foundations built on a shallow depth of Egyptian macro-porous collapsible soils (less than 4 m) is developed. The design method includes a design chart for soil collapse field classification in terms of the most governing parameters, a method for foundation settlement estimation based on a correlation between the wetting-induced collapse strain and the applied pressure, and a design practice to guide practicing engineers to select the appropriate foundation system to construct on such soil with a great degree of confidence and safety.
