深厚填土区碎石土抗剪性能及桩基力学特性分析

Shear Resistance of Gravel Soil and the Mechanical Properties of Pile Foundation in Deep Filling Area

碎石土作为工程中常见的填土材料,其抗剪性能受含水率和含石量的影响较大。道路建设中以碎石土填料为承载基础的桥梁桩基在荷载作用下的力学特性也受多因素影响。以渝黔高速公路綦江北互通段公路桥梁建设项目为依托,选取施工现场的碎石土材料进行不同含水率和含石量的抗剪性能试验;基于MIDAS/GTS有限元软件建立深厚填土区以碎石土作为填土材料的桩基计算模型。研究结果表明:碎石土体黏聚力随着含水量增加而平缓减小,当含水率超过一定值时,其黏聚力减小较快,内摩擦角也随着含水率的增加而减小;黏聚力随着含石量的增大逐渐减小,内摩擦角则随着含石量增加而增大;先施加堆载造成的桩顶沉降变化幅度小于先施加桩载再施加堆载的变化情况,产生沉降较小的是先施加桩载再堆载最后桩载;桩侧摩阻力的变化规律与加载大小及顺序有关,取决于桩土之间的相对位移。

As a common filling material in engineering,the shear properties of gravel soil were greatly affected by water content and stone content.In highway and railway construction,the mechanical properties of bridge pile foundations filling with gravel soil as the bearing foundation were also affected by multiple factors under the action of load.Based on the highway bridge construction project in Qijiangbei interchange section of Chongqing-Guizhou Expressway,the gravelly soil material was taken from the construction site for shear performance tests with different moisture content and stone content.Based on MIDAS/GTS finite element analysis software,the calculation model of pile foundation with gravel soil as filling material in deep filling area was established.The results show that the cohesion of gravel soil firstly decreases gently with the increase of water content,but when the water content exceeds a certain value,the cohesion decreases rapidly,and the angle of internal friction decreases with the increase of water content.The cohesion decreases with the increase of stone content and the angle of internal friction increases with the increase of stone content.The variation range of pile top settlement caused by heap load first is less than that caused by pile load first and then heap load,and the final settlement of pile caused by pile load first and then heap load and last pile load is relatively small.The variation law of pile side friction resistance is related to the loading size and order and depends on the relative displacement between pile and soil.