Considering the influence of strain softening, the solutions of stress, displacement, plastic softening region radius and plastic residual region radius were derived for circular openings in nonlinear rock masses subj...Considering the influence of strain softening, the solutions of stress, displacement, plastic softening region radius and plastic residual region radius were derived for circular openings in nonlinear rock masses subjected to seepage. The radial stress distribution curve, ground reaction curve, and relation curve between plastic softening region radius and supporting force in three different conditions were drawn respectively. From the comparisons among these results for different conditions, it is found that when the supporting force is the same, the displacement of tunnel wall considering both seepage and strain softening is 85.71% greater than that only considering seepage. The increase values of radial displacement at 0.95 m and plastic softening region radius at 6.6 m show that the seepage and strain softening have the most unfavorable effects on circular opening stability in strain softening rock masses.展开更多
城市地面沉降的主要原因之一是地下水渗流,有限元方法难以揭示地面沉降的细观机制,而能够揭示细观机制的离散元方法(discrete element method,DEM)却难以建立具有复杂形状的流场模型.基于DEM和计算流体动力学(computational fluid dynam...城市地面沉降的主要原因之一是地下水渗流,有限元方法难以揭示地面沉降的细观机制,而能够揭示细观机制的离散元方法(discrete element method,DEM)却难以建立具有复杂形状的流场模型.基于DEM和计算流体动力学(computational fluid dynamics,CFD)耦合原理,借助DEM程序PFC3D与CFD程序Fluent,实现了基于颗粒细观的流固耦合计算.通过建立单颗粒沉降、基坑临空面渗漏、河道边坡渗流3个算例验证了CFD-DEM方法的正确性与可行性.模拟结果表明,这种CFD-DEM方法可从细观角度展现渗流引起地面沉降的整个动态过程,也可实现对各种复杂形状流场的模拟求解计算.在渗流作用下土体稳定性发生变化,土颗粒运动造成土体流失,最终形成地面沉降.此外,水力梯度越大,地表沉降值越大,从土体细观角度展现了渗流作用下地面沉降的整个动态过程,可对相应城市地质病害防治进行机理研究.展开更多
The functioning mechanism of groundwater and its make-up water in the process of ground subsidence was studied from such three aspects as osmotic corrasion, osmotic pressure effect and concretion effect, As to osmotic...The functioning mechanism of groundwater and its make-up water in the process of ground subsidence was studied from such three aspects as osmotic corrasion, osmotic pressure effect and concretion effect, As to osmotic corrasion, its forming conditions, mechanical mechanism and process were analyzed, As to osmotic pressure effect, it was mainly studied from hydrostatic pressurizing effect, sop softening effect and negative pressure sealing effect. Through concretion and saturation of soil, the factors of concretion settlement were analyzed. The results showed that both groundwater and its make-up water are important triggering factors to ground subsidence.展开更多
The Kenya Rift Valley is relatively prone to underground erosion ground fissures and associated disasters,which gravely hinder local engineering construction and economic development.In this research,we performed fiel...The Kenya Rift Valley is relatively prone to underground erosion ground fissures and associated disasters,which gravely hinder local engineering construction and economic development.In this research,we performed field and experimental studies on ground fissures in the Kenya Rift Valley area,and determined the structural characteristics of underground erosion fissures.Based on a geological survey of the area,we generalized a geological model for typical ground fissures and reproduced the intermediate process of ground fissure propagation using a large-scale physical model test.Further,the development process of underground erosion fissures were categorized into four stages:uniform infiltration,preferential infiltration,cavity expansion,and collapse formation stages.During the development of underground erosion fissures,water content was distributed symmetrically along the fissures,and these fissures acted as the primary infiltration paths of water.When the ground collapsed,the increase in negative pore water pressure was greater,whereas the increase in positive pore water pressure was less in the shallow soil;moreover,in the deep soil,the increase in positive pore water pressure was greater than that of negative pore water pressure.Additionally,the earth pressure increment initially increased and then decreased with the development of erosion.During underground erosion collapse,the water content and pore water pressure appeared to increase and decrease rapidly.These results can be employed to predict the occurrence of underground erosion ground fissures and the resulting soil collapse.展开更多
基金Project(09JJ1008) supported by Hunan Provincial Science Foundation of ChinaProject(200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China
文摘Considering the influence of strain softening, the solutions of stress, displacement, plastic softening region radius and plastic residual region radius were derived for circular openings in nonlinear rock masses subjected to seepage. The radial stress distribution curve, ground reaction curve, and relation curve between plastic softening region radius and supporting force in three different conditions were drawn respectively. From the comparisons among these results for different conditions, it is found that when the supporting force is the same, the displacement of tunnel wall considering both seepage and strain softening is 85.71% greater than that only considering seepage. The increase values of radial displacement at 0.95 m and plastic softening region radius at 6.6 m show that the seepage and strain softening have the most unfavorable effects on circular opening stability in strain softening rock masses.
文摘城市地面沉降的主要原因之一是地下水渗流,有限元方法难以揭示地面沉降的细观机制,而能够揭示细观机制的离散元方法(discrete element method,DEM)却难以建立具有复杂形状的流场模型.基于DEM和计算流体动力学(computational fluid dynamics,CFD)耦合原理,借助DEM程序PFC3D与CFD程序Fluent,实现了基于颗粒细观的流固耦合计算.通过建立单颗粒沉降、基坑临空面渗漏、河道边坡渗流3个算例验证了CFD-DEM方法的正确性与可行性.模拟结果表明,这种CFD-DEM方法可从细观角度展现渗流引起地面沉降的整个动态过程,也可实现对各种复杂形状流场的模拟求解计算.在渗流作用下土体稳定性发生变化,土颗粒运动造成土体流失,最终形成地面沉降.此外,水力梯度越大,地表沉降值越大,从土体细观角度展现了渗流作用下地面沉降的整个动态过程,可对相应城市地质病害防治进行机理研究.
基金financially supported by the National Nature Science Foundation of China (No.50490271)the National Key Technologies R & D Program of China (No.2004BA615A-18).
文摘The functioning mechanism of groundwater and its make-up water in the process of ground subsidence was studied from such three aspects as osmotic corrasion, osmotic pressure effect and concretion effect, As to osmotic corrasion, its forming conditions, mechanical mechanism and process were analyzed, As to osmotic pressure effect, it was mainly studied from hydrostatic pressurizing effect, sop softening effect and negative pressure sealing effect. Through concretion and saturation of soil, the factors of concretion settlement were analyzed. The results showed that both groundwater and its make-up water are important triggering factors to ground subsidence.
基金supported by the National Science Foundation of China(No.41920104010,41877250,and 41807243)。
文摘The Kenya Rift Valley is relatively prone to underground erosion ground fissures and associated disasters,which gravely hinder local engineering construction and economic development.In this research,we performed field and experimental studies on ground fissures in the Kenya Rift Valley area,and determined the structural characteristics of underground erosion fissures.Based on a geological survey of the area,we generalized a geological model for typical ground fissures and reproduced the intermediate process of ground fissure propagation using a large-scale physical model test.Further,the development process of underground erosion fissures were categorized into four stages:uniform infiltration,preferential infiltration,cavity expansion,and collapse formation stages.During the development of underground erosion fissures,water content was distributed symmetrically along the fissures,and these fissures acted as the primary infiltration paths of water.When the ground collapsed,the increase in negative pore water pressure was greater,whereas the increase in positive pore water pressure was less in the shallow soil;moreover,in the deep soil,the increase in positive pore water pressure was greater than that of negative pore water pressure.Additionally,the earth pressure increment initially increased and then decreased with the development of erosion.During underground erosion collapse,the water content and pore water pressure appeared to increase and decrease rapidly.These results can be employed to predict the occurrence of underground erosion ground fissures and the resulting soil collapse.
