浅埋地下结构浮力模型试验研究

Model Test Study of Buoyancy on Shallow Underground Structure

摘要:

针对浅埋地下结构浮力试验的特点，研制了一套直接测定静水中结构底板所受浮力的模型试验系统.根据纯水中扬压力等于静水压力，确定了主要系统参数.利用该系统，对不同埋深下纯水、饱和砾石、中砂、细砂、粉土和黏性土中模型室底板受到的浮力及孔隙水压力进行了测试.试验结果表明，该系统在纯水中浮力测试的最大误差小于1%.饱和砾石、中砂、细砂和粉土中模型室底板所受浮力比其在相同条件下的纯水中受到的浮力小约5%，而饱和黏性土中模型室底板所受浮力与其在相同条件下的纯水中受到的浮力相等.饱和粉土和黏性土在填筑过程中，底板所受浮力极大，并可能超过被其排开的饱和土的重量，且测压管水头在填筑过程中均超过填土面高度，埋置越深的测压管水头越高.长期稳定状态下，饱和无黏性土和黏性土中各测压管中水头高度均与填土表面齐平.

Abstract:

According to the features of the test of buoyancy on shallow underground structure,a model test system which directly determined the hydrostatic buoyancy on the bottom-board of the structure was developed.Main system parameters were determined based on the principle that the uplift pressure equalled the hydrostatic pressure in pure water.The buoyancy on the bottom-board of the model cellar at different embedded depths in pure water,saturated gravel,medium sand,fine sand,silt and clay were determined by the system,as well as the pore pressure.The test results show that the system’s maximum error rate of pure water buoyancy test is less than 1%.The buoyancy on the bottom-board in saturated gravel,medium sand,fine sand and silt are about 5% less than that in pure water,whereas the buoyancy in saturated clay is equal to that in pure water. During the filling of saturated silt and clay,the buoyancy is so great that it may exceed the weight of the displaced saturated soil.During the process of filling,the water heads of all piezometers are higher than the surface of the soil. Moreover,the deeper the piezometer is ebedded,the higher the piezometric head will be.At the long-term stable state,the water heads of all piezometers in clay and nonclays are exactly as high as the filling surface.