桩基施工对邻近顶管隧道的扰动影响

长江漫滩沉积软土为第四系以来新近河流漫滩相沉积物，成分以粉质黏土、粉细砂、细砂为主，表现为高压缩性、低强度、易触变，在长江漫滩相软土地基上兴建高速公路、高速铁路等基础设施，需要对软土地基进行加固处理。地基处理施工引起长江漫滩相软土产生类似于液化的“触变”现象，导致软土地基产生灾变破坏。本文依托南沿江高速铁路软土地基处理工程，对水泥搅拌桩施工引起的长江漫滩相软土地基灾变现象进行总结，软土地基灾变现象主要为搅拌桩顶下沉、搅拌桩钻芯孔内喷水冒浆、地基开裂破坏和地基沉降大且速度快，沉降不收敛。针对长江漫滩相软土地基处理的水泥搅拌桩施工，通过现场监测软土的土压力、超孔隙水压力和深层水平位移，评价搅拌桩施工对软土的影响程度，提出长江漫滩相软土地基灾变的判据，分析软土物理力学性质的变异特性。

The disturbance influence of pile foundation construction on adjacent pipe jacking tunnel

The sedimentary soft soil in Yangtze River floodplain is the fluvial facies sediment since the quaternary period, and mainly composed of silty clay, silty fine sand and fine sand, and is characterized by high compressibility, low strength and easy liquefaction. Therefore, the soft soil foundation needs to be improved during the construction of expressway, high-speed railway and other infrastructure. Thixotropic phenomenon, similar to liquefaction, is caused by improvement construction of soft soil foundation in the Yangtze River floodplain, and leads to the disaster of the soft soil foundation. The foundation treatment construction causes the soft soil to produce a damage phenomenon similar to liquefaction, resulting in catastrophic disaster to the soft soil foundation. The disaster phenomenon of the soft soil foundation is summarized and caused by the construction of deep cement mixing(DCM)column of high-speed railway in the South Yangtze River. The disaster phenomenon of the soft soil foundation mainly includes the sinkhole at the top of deep cement mixing column, the water and slurry spraying during the coring of deep cement mixing column, the cracks in soft soil foundation, the large amount and fast speed of settlement. In-site monitoring of earth pressure, pore water pressure and soil horizontal displacement of soft soil are carried in the construction of deep cement mixing column in the soft soil foundation. The disturbance of the soft soil is evaluated and the disaster criterion of the soft soil foundation is put forward during the construction of deep cement mixing columns. The property variation of soft soils Yangtze River floodplain is also analyzed.