基于旁压试验的软土卸荷回弹变形研究

Research on Unloading Resilient Deformation of Soft Soil Based on Pressuremeter Test

软土地区地下空间开发过程中诸如深基坑开挖、盾构隧道掘进等均涉及土体卸荷回弹问题,该问题的研究对控制地下空间开发中的地质安全风险具有积极的意义。通过对上海地区不同深度土体进行原位旁压加卸载试验,结合室内K_(0)试验对土体的卸荷回弹特性进行研究。从卸载等级(UL)和卸载前最大载荷(UP)两个维度来研究软土卸载与回弹之间的变化关系。结果表明:相同加卸载条件下通过旁压试验推求的回弹模量大于室内试验结果,且随着卸载等级(UL)和卸载前最大载荷(UP)的增大,软土回弹模量逐渐减小;对于旁压卸载,土体卸载比与回弹模量对数曲线(R-lgE_(ur))呈线性关系,且对于同一层土,归一化的R-A·lgE_(ur)关系曲线斜率近似一致,卸载等级(UL)决定了该曲线斜率的大小。

In the process of underground space development in soft soil area,engineering constructions such as deep foundation pit excavation and tunnel excavation,both involve the issue of soil unloading resilient deformation,and the research on this problem has positive significance to control the geological safety risk in underground space development.The unloading resilient deformation properties of soft soil were studied based on the pressuremeter tests,combining with laboratory K_(0)tests for different depths at Shanghai area.The relationship between unloading and resilient deformation were discussed from the aspect of unloading level(UL)and maximal unloading pressure(UP).The results shows that:the unloading modulus obtained by in-situ test is larger than that of laboratory test ones under the same conditions,and both UL and UP are negatively correlated with the unloaded modulus.A linear relationship of R-lgE_(ur)can be concluded for unloading pressuremeter tests,and for the same type of soil,UL determined the the slope of the curve.of R-A·lgE_(ur).