竖向卸荷下砂土和粉质黏土力学特性试验研究  

Experimental study on mechanical behavior of sand and silty clay under vertical unloading

作　　者：吴楷 陈仁朋[1,2,3] 孟凡衍 胡博 WU Kai;CHEN Renpeng;MENG Fanyan;HU Bo(Research Center for Advanced Underground Space Technologies of Hunan University,Changsha 410082,China;College of Civil Engineering,Hunan University,Changsha 410082,China;Key Laboratory of Building Safety and Energy Efficiency of Ministry of Education,Hunan University,Changsha 410082,China)

机构地区：[1]湖南大学地下空间先进技术研究中心,湖南长沙410082 [2]湖南大学土木工程学院,湖南长沙410082 [3]湖南大学建筑安全与节能教育部重点实验室,湖南长沙410082

出　　处：《岩土工程学报》2024年第10期2174-2182,共9页Chinese Journal of Geotechnical Engineering

摘　　要：土体极限卸荷比和临界卸荷比是确定基坑底扰动区深度的重要指标。基于福建标准砂和福州粉质黏土开展了多组竖向卸荷试验,根据归一化回弹变形确定了土体卸荷比特征值。试验结果表明:竖向卸荷下土体表现出三阶段回弹变形规律;小于临界卸荷比时,土体回弹变形可忽略不计;而大于极限卸荷比时,土体回弹变形、侧压力系数快速增加,回弹模量和剪切模量显著弱化,水平残余应力比出现拐点且开始下降。此外,针对既有卸荷试验研究,总结了试验手段和卸荷比特征值的判断依据,并给出黏性土、粉土和砂土等土体的卸荷比特征值统计均值。The ultimate unloading ratio and the critical unloading ratio are the crucial parameters for determining the depth of disturbance below excavation base.The vertical unloading tests are performed on the Fujian sand and Fuzhou silty clay,with characteristic unloading ratios determined based on the normalized resilience value.The results indicate that the unloading response of soils changes in three phases.When the loading ratio is less than the critical unloading ratio,the response of soils can be ignored.Meanwhile,as the loading ratio exceeds the ultimate unloading ratio,the normalized resilience value and lateral pressure coefficient of soils increase rapidly,and the resilience modulus and shear modulus decrease significantly.Additionally,at this point,the horizontal residual stress ratio displays an inflection point and begins to decline.Furthermore,the test methods and the judgment criteria of characteristic unloading ratios are analyzed.The statistical mean values of the characteristic unloading ratios of clay,silt and sand in the unloading tests are calculated.

关 键 词：开挖卸荷 扰动 卸荷比 剪切波速 侧压力系数 

分 类 号：TU43[建筑科学—岩土工程]