摘要
落球检测技术多用于测定填土路基的力学性质,但其可靠性缺乏深入的理论分析和对比验证。采用移动网格对落球检测的全过程进行三维物质点法模拟,通过改变被测土体的本构模型、弹性模量和强度参数(黏聚力、内摩擦角),分析土体的变形破坏特征,利用球体的加速度、接触时间和位移特征反推土体的变形模量和强度参数。模拟分析表明:当假定被测土体处于线弹性状态时,基于Hertz接触理论估算的弹性模量与模型设定值吻合较好;当被测土体发生较大塑性变形时,基于Hertz理论估算的变形模量以塑性变形为主,且在同一强度参数下趋于一致,基于修正Vesic空腔扩张理论估算的强度参数与设定值相差较大。在测试过程中,当土体以弹性变形为主时,估算的变形模量和强度参数具有一定的参考价值;当土体强度较低且以塑性变形为主时,估算的变形模量与平板载荷试验结果相差较大,其准确性存在一定问题。相关结论为评估落球检测结果的有效性、促进该技术的推广应用,提供了一定的参考依据。
Falling ball test is widely used for determining mechanical properties of fill subgrade in the field,but its reliability has not been adequately evaluated using theoretical analysis and verifications.The whole process of the falling ball test is simulated by 3D material point method(MPM)with moving meshes.By changing the constitutive model,elastic modulus and strength parameters of the test soil,the deformation and failure characteristics of the soil are analyzed,and the deformation modulus and strength parameters of soil are deduced from the acceleration,contact time and displacement of the sphere.The numerical simulations indicate that the elastic modulus estimated based on Hertzian contact theory is in good agreement with the real one when the test soil is in linear elastic state;when the soil has large plastic deformation,the deformation modulus calculated based on Hertzian theory mainly includes plastic deformation,and tends to be consistent under the same strength parameters.The strength parameters estimated based on modified Vesic cavity expansion theory are quite different from the real ones.When the soil is mainly subjected to elastic deformation during the test,the estimated deformation modulus and strength parameters have certain reference value.When the soil is mainly subjected to plastic deformation,the deformation modulus estimated by falling ball test is quite different from those of plate load test,so there are some problems in its accuracy.The conclusions drawn in this paper provide useful reference for evaluating the effectiveness of the falling ball test results and promoting its wide application in engineering practices.
作者
张春新
朱鸿鹄
周谷宇
张巍
周公旦
ZHANG Chunxin;ZHU Honghu;ZHOU Guyu;ZHANG Wei;ZHOU Gongdan(School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;Key Laboratory of Mountain Hazards and Earth Surface Processes,Chinese Academy of Sciences,Chengdu 610041,China)
出处
《防灾减灾工程学报》
CSCD
北大核心
2021年第2期311-320,共10页
Journal of Disaster Prevention and Mitigation Engineering
基金
国家自然科学基金项目(41722209,41672277)
中国科学院山地灾害与地表过程重点实验室开放基金项目(2018)资助
关键词
物质点法
移动网格
落球检测技术
岩土参数
material point method(MPM)
moving mesh
falling ball test
geotechnical parameter
作者简介
张春新(1997—),男,硕士研究生。主要从事地质工程大变形数值模拟研究。E-mail:cxzhang@smail.nju.edu.cn;通讯作者:朱鸿鹄(1979—),男,教授,博导。主要从事地质工程、岩土力学方面的研究。E-mail:zhh@nju.edu.cn
