地下水位对砾性土层剪切波速的影响研究

Influence of underground water tables on shear wave velocity of gravelly soils

通过地下水位修正来间接反应有效应力对土层剪切波速的影响的方法被应用于我国剪切波速法砂土液化判别,但现行方法不适用于砾性土层。利用GDS大粒径三轴-剪切波速系统测试不同含砾量,不同相对密度的砾性土在不同应力条件下的剪切波速,研究有效应力对砾性土剪切波速的影响。结果表明:砾性土的剪切波速与有效应力满足幂函数关系,其指数参数稳定,不受土性影响;结合对汶川地震震后调查的砾性土的上覆土层分析,推导出适合砾性土层剪切波速判别法的水位修正公式,给出了简化的线性表达;并分析了地下水位变化对剪切波速测试结果的影响。

The method assessing the influence of varying effective stresses induced by underground water tables change on shear wave velocity （v） has been used in vs - based liquefaction evaluation, yet the method is unappli- cable for gravelly soils. A grand triaxial apparatus and vstest apparatus are used to measure vs of different effectively - stressed gravelly soils with different gravel contents and relative densities to investigate the influence of effective stress on vs of gravelly soils. The test results indicate ： the vs of gravelly soils keep an exponential relation with re- spect to effective stresses, and that the exponential index is stable and independent of soil properties ; analyzing the overburden soil layer data of the gravel sites investigated in the Wenchuan earthquake, a linear expression of the corrected formula of vs - based liquefaction evaluation by underground water tables is deduced and proposed ; the in- fluence of underground water tables change on vs testing is analyzed.