考虑密度影响的砂土静止土压力系数研究  

Coefficient of earth pressure at rest of sand considering density effect

作　　者：蔡正银[1] 朱洵 代志宇 CAI Zhengyin;ZHU Xun;DAI Zhiyu(Department of Geotechnical Engineering,Nanjing Hydraulic Research Institute,Nanjing,Jiangsu 210024,China)

机构地区：[1]南京水利科学研究院岩土工程研究所,江苏南京210024

出　　处：《岩石力学与工程学报》2021年第8期1664-1671,共8页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(51879167);中央级公益性科研院所基本科研业务费专项资金(Y317011,Y319006)。

摘　　要：静止土压力系数是支挡结构设计与分析中非常重要的参数,其值决定了作用于结构上初始水平土压力的大小。以福建标准砂为研究对象,开展均质砂土地基离心模型试验,研究砂土静止土压力系数随初始相对密度的变化规律;进行砂土在不同初始相对密度下的三轴固结排水试验,获得砂土峰值强度随初始相对密度的变化规律;综合离心模型试验和三轴试验结果提出可反应砂土静止土压力系数-峰值摩擦角关系的“南水公式”,即K_(0)=sinφ′-0.16 。为了验证南水公式的正确性,提出可描述砂土细观受力特征的颗粒微结构概化模型,通过推导得到砂土静止土压力系数与其微结构颗粒接触角及摩擦偏移角之间的关系,初步探讨初始相对密度对砂土内部传力机制的影响,指出随着砂土相对密度的增加颗粒微结构存在由高阶环状单元结构向低阶稳定单元结构转化的可能,而低阶稳定单元结构的双重支撑作用将促进颗粒竖向应力向侧向的传递。研究成果对完善砂土土压力理论具有一定的参考价值。The coefficient of earth pressure at rest is one of the important parameters in the design and analysis of bracing structures,and its value determines the magnitude of the initial horizontal earth pressure acting on the structures.Taking the Fujian standard sand as the object,the centrifugal model tests and the triaxial consolidated drained tests are performed to investigate the variation rules of both the coefficient of earth pressure at rest and the peak strength of the sand with the initial relative density.Based on the above test results,a NHRI equation,which can truly reflect the relationship between the earth pressure at rest and the peak friction angle of sand,is proposed.To validate the correctness of the NHRI equation,a conceptualized model for microstructure of particles to depict the mesoscopic stress characteristics is put forward.The relationships between the coefficient of earth pressure at rest of sand with the contact angle and the deviation angle of particles are obtained through derivation of the NHRI equation.The effect of the initial relative density on the internal stress transfer mechanism of sand is preliminarily discussed.It is pointed out that with increasing the relative density of sand,there exists the possibility for the microstructure of particles to transform from the high-order circular unit structure to the low-order steady unit structure,while that the dual-bracing action of the low-order steady unit structure will promote the vertical stress of particles to laterally transfer.The research results are of a certain reference value to improve the earth pressure theories of sand.

关 键 词：土力学 砂土 相对密度 静止土压力 离心模型试验 南水公式 

分 类 号：TU43[建筑科学—岩土工程]