平面应变加–卸载试验中砂土的黏性特征及本构模型化  

VISCOUS BEHAVIORS AND CONSTITUTIVE MODELING OF SAND UNDER PLANE STRAIN LOADING-UNLOADING TESTS

作　　者：彭芳乐[1,2] 谭轲[1,2] 龙冈文夫[3] 

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]同济大学岩土及地下工程教育部重点实验室,上海200092 [3]东京理科大学土木工程系

出　　处：《岩石力学与工程学报》2011年第1期184-192,共9页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(40972176);教育部新世纪优秀人才支持计划基金(NCET–06–0378);上海市重点学科建设项目(B308)

摘　　要：通过丰浦砂的平面应变循环加载试验,分析砂土在加–卸载条件下相应的黏性特征。试验比较不同加载应变速率下2组砂土的应力–应变响应,进行蠕变加载,着重研究卸载过程中砂土的黏性特征。试验表明砂土的黏性特征与加载速率以及应力水平密切相关,且加载速率变化所引起的砂土黏性会随着加载的继续和应变的增大而逐渐衰减。卸载开始后,砂土垂直应变并未立即降低,而在一段时间范围内仍旧保持增大趋势。卸载过程中的蠕变试验还表明砂土具有"蠕变恢复"的特性。针对砂土的以上黏性特征,基于三要素模型的基本框架,提出瞬时黏性效应(TESRA)模型用以模拟加载和卸载阶段砂土黏性特征。根据试验所得到的砂土应力–应变关系,对第一次加载循环(初始加载–卸载)的砂土应力–应变响应和时程响应进行模拟,并证明瞬时黏性效应(TESRA)模型能够比较精确地模拟砂土在加–卸载循环中的黏性特征。Based on a series of plane strain cyclic tests on air-dried Toyoura sand,the viscous properties of sand under loading-unloading conditions are presented.Comparisons are made on the stress-strain relationships of two sets of tests using different strain loading rates.Creep stages are also performed during the tests.Special attentions are paid to the viscous behavior of sand during unloading.The tests reveal that the viscous behaviors of sand are deeply related to the strain loading rate as well as the stress level.The viscous behaviors of sand caused by the viscosity of loading will be weakened with the increased of load and strain.Furthermore it is found during the unloading test,the vertical strain of sand continues to grow for a certain period of time even when the unloading has already begun.The behavior of creep recovery is also observed during unloading.Based on the general framework of the three-component model,the temporary effects of strain rate and acceleration（TESRA） model is put forward and modified for the simulation of viscous behaviors of sand during loading-unloading.The detailed formulation and controlling parameter are presented,enabling the implementation of a reasonable numerical simulation.Applying this model,simulation is conducted on the primary loading-unloading stage of sand in the plane strain tests.The stress-strain relations as well as the time history of strain are obtained.Through comparisons between the results from test measurement and numerical simulation outputs,the TESRA model is proved both effective and precise for simulating the viscous behaviors of sand during loading-unloading.

关 键 词：土力学 砂土 黏性 循环加载 加–卸载 应力–应变关系 加载速率 蠕变恢复 

分 类 号：TU432[建筑科学—岩土工程]