砂岩地基上地下结构浮力特性研究%

Buoyancy Characteristics of Underground Structure on Sandstone Foundation

为了研究砂岩地基上地下结构抗浮设计折减问题,通过室内模型试验与现场监测试验,进行砂岩地基上地下结构浮力特性研究,分析地下水渗流规律。结果表明:砂岩为不透水材料,渗流条件、渗透压、渗流时间对基础所受浮力均有影响,三者贡献程度不同,渗流条件影响最大;渗流条件变化时,渗透压、渗流时间对浮力的影响程度随之变化;砂岩地基上的地下结构浮力可进行安全折减,折减系数视基底与地基接触关系而定,二者仅简单接触、接触四周做封闭处理但砂岩内部存在裂隙、接触四周做封闭处理且砂岩完整3种情况下水压力折减系数分别为0.82～0.91,0.63～0.73,0.31～0.50;基坑回填时宜在地下结构四周一定范围内采用不透水材料形成隔水层,改变渗流路径,增加折减效果,放宽抗浮设计要求。研究结果旨在为地下空间结构抗浮设计提供一些依据。

The buoyancy characteristics of underground structures on sandstone foundation are studied for anti-floating design and the seepage laws of groundwater are analyzed by indoor model tests and field monitoring tests.Results show that since sandstone is impervious,seepage condition,seepage pressure,and seepage time could all affect the buoyancy acting on sandstone structure,among which seepage condition has the largest impact.The influence of seepage pressure and seepage time on buoyancy changes with the variation of seepage condition.The buoyancy of underground structure on sandstone foundation can be reduced safely,and the reduction coefficient depends on the contact between basement and ground.The reduction coefficients in three contact conditions(simple contact,contact with sealing treatment in the peripheral and fractures inside the sandstone,and contact with sealing treatment in the peripheral and no fracture inside the sandstone)are 0.82-0.91,0.63-0.73,0.31-0.50,respectively.It is recommended to ease the anti-floating requirements and adopt impermeable materials surrounding underground to alter seepage path and enhance reduction effect during foundation backfill.