基于离心模型试验的基坑突涌模式及机制研究

在软土地区,由承压水诱发的突涌是影响深基坑工程安全和稳定性的最重要因素,也是设计和施工亟待解决的关键技术问题。借助土工离心模型试验,就不同隔水土层、不同坑内桩基类型及平面布置对基坑突涌稳定及破坏模式的影响进行系统的试验研究。试验结果表明:软土地区承压水基坑突涌模式主要有3种:接触面涌水涌砂破坏、整体顶升破坏和隔水层表面砂沸破坏,与实际工程案例比较吻合。通过理论分析,认为基坑发生突涌的内在机制分别为:接触面涌水涌砂破坏是由于隔水层土体与地下结构接触面发生水力劈裂引起的;整体顶升破坏为地下结构与土体接触面或附近发生剪切破坏所致;表面砂沸破坏为隔水层在下部承压水作用下发生复合的拉剪破坏和剪切破坏的结果。

MODE AND MECHANISM OF BURSTING IN FOUNDATION PIT BASED ON CENTRIFUGAL MODEL TEST

In the soft soil areas，bursting induced by confined water is the most important factor which affects the safety and stability of deep foundation pit，and is the key technological problem of design and construction which is urgently solved. The influence of different impermeable layer types，pile types and the layouts of piles on the bursting stability and failure modes of foundation pit are studied systematically by centrifugal model test. The test results show that the failure modes of foundation pits bursting in soft soil areas can be mainly divided into three kinds，i.e. water and sand inrushing in contact surface between soil and underground structures，overall heaving failure and sand boiling on impermeable layer surface. Based on theoretical analysis，the internal mechanisms of bursting in foundation pits are cleared respectively that the contact surface between impermeable-layer and underground structures occurs hydraulic fracturing，contact surface or nearby occurs shear failure and impermeable layer occurs complex tensile-shear failure and shear failure.