地下工程施工扰动带土体剪切特性试验研究及对地面变形的影响

项目名称： 地下工程施工扰动带土体剪切特性试验研究及对地面变形的影响

项目编号： No.50809002

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 许成顺

作者单位： 北京工业大学

项目金额： 20万元

中文摘要： 地下工程在开挖等施工过程中不可避免地对周围土体及邻近建筑物产生扰动影响。长期以来，由于人们对地下基坑工程施工扰动引起的周围土体性质的改变和施工中结构与土体介质的变形、失稳、破坏的发展过程认识不足，导致城市基础设施在建设过程中产生基坑边坡失稳及坍塌等，并造成了人员伤亡等屡见不鲜的事故。 为了研究地下工程施工过程中不同位置处受扰动土体实际的应力和变形状态，探讨不同应力路径条件下土体的变形和破坏特性，本项目针对福建标准砂、粉土和原状粘土进行了试验研究，包括常规三轴压缩试验、等P压缩试验、等压固结减压压缩试验和偏压固结减压压缩试验，用不同剪切方式模拟了地下工程开挖过程中不同位置处的土体应力状态。 试验结果表明剪切路径对其强度的影响非常显著，当以偏差应力比归一化时，在相同剪切方式下，土体的强度具有很好的归一化特性；不同固结围压、相同剪切路径下，试样达到极限状态时在相同的应力比下趋于稳定，而且相同剪切方式下不同初始固结比对极限状态下的稳定应力比几乎没有影响；与此相反，不同剪切方式对内摩擦角具有显著差异，对于粉土和原状粘土，减压压缩条件下发挥的内摩擦角最大，常规压缩条件下发挥的内摩擦角最小。

中文关键词： 应力；内摩擦角；变形

英文摘要： There exists inevitable disturbing influence to the nearby architectures during the underground engineering excavation. For a long time, characteristic alterations of nearby soil caused by construction perturbation， and deformation,unstability and failure of structures of soil during the construction have not been clearly apprehended, a series of collapse and destruction of foundation pit and side slope occurred during the infrastructure construction in city, and casualties remains common occurrence. To study the actual stress and strain state of underground perturbed soil in different places under construction, investigate the deformation and failure characteristic of soil under different stress paths,the experimental tests of Fujian standard sand,silt and undisturbed clay are perrormed in this project,including conventional triaxial compressed tests, equal P compressed tests, equipressure consolidation decompressed tests and anisotropic consolidation decompressed tests.The stress state of soil in different places during the underground engineering excavation aer simulated by different paths. Results indicate that the shearing paths make obvious effects on soil strength.When normalized by deviatoric stress,strength of the soil gets appropriate normalizing characteristic under the same shearing path.Under the different confining pressure but the same shear path condition, when samples get to limit state, they tend to be constant at the same stress ratio. Moreover, different consolidation stress ratio barely affects the stable stress ratio under the same shear paths.On the contrary,different shearing paths make obvious effects on the internal friction.The internal friction angle under decompressed test is the highest, conventional triaxial compressed test the lowest to silt and undisturbed clay.

英文关键词： stres；internal friction angle；deformation