地基处理施工扰动引起软土灾变的识别方法

Identification Method of Soft Soil Disaster Due to Ground Improvement Construction

沿长江两岸沉积了第四系漫滩相软土,新近河流漫滩相沉积物以粉质黏土、粉细砂、细砂为主,表现为高压缩性、低强度、易触变液化,地基处理施工扰动引起漫滩相软土产生灾变破坏。对地基处理施工扰动引起的长江漫滩相软土灾变现象进行总结,通过在地基处理现场监测软土的土压力、孔隙水压力和土体水平位移,提出地基处理施工扰动引起漫滩相软土灾变的判据,建立施工扰动引起长江漫滩相软土灾变的判别方法。水泥搅拌桩施工扰动引起软土灾变表现为搅拌桩桩顶下沉,形成充满水的空洞,搅拌桩顶下沉量最大达到70 cm,并伴有大量细砂翻涌;在水泥搅拌桩钻芯取样过程中,相邻水泥搅拌桩位置出现喷水冒浆现象,搅拌桩的取芯率不足60%,水泥搅拌桩成桩质量很差;软土灾变位置处测得的超孔隙水压力大于土压力。

The Yangtze River floodplain sedimentary soft soil is the fluvial facies sediment since the quaternary period,and it is mainly composed of silty clay,silty fine sand and fine sand,which is characterized by high compressibility,low strength and easy liquefaction.Thixotropic phenomenon is caused by the improvement construction of soft soil foundation in the Yangtze River floodplain,and leads to the disaster of the soft soil foundation.The disaster phenomenon of the Yangtze River floodplain soft soil foundation is summarized as caused by the ground improvement construction.In-site monitoring of earth pressure,pore water pressure and horizontal soil displacement of soft soil are monitored in the construction of ground improvement in Yangtze River floodplain soft soil foundation.The disturbance of Yangtze River floodplain soft soil is evaluated and the disaster criterion of Yangtze River floodplain soft soil foundation is put forward during the construction of ground improvement.The soft soil disaster caused by the construction disturbance of cement deep mixing column is characterized by the sinking of the column top.The maximum sinking amount of the column top reaches 70cm,accompanied by a large amount of fine sand pouring out.In the process of drilling core sampling of cement deep mixing column,water spray and slurry appear in the position of adjacent cement deep mixing column,the core extraction rate of cement mixing column is less than 60%,and the quality of deep mixing column is poor.The excess pore water pressure measured at the disaster position of soft soil is greater than the soil pressure.