试验条件对粉煤灰改良膨胀土抗剪指标影响研究

TEST CONDITIONS FOR FLY ASH TO IMPROVE EXPANSIVE SOILS SHEAR STRENGTH INDICATORS

以宜昌市某路段膨胀土为研究对象,将不同质量的粉煤灰掺入其中,通过改变剪切速率和上覆荷载条件,分析非标准剪切速率0.8 mm/min和2.4 mm/min和非标准垂直压力12.5~50 k Pa、62.5~100 k Pa、100~400 k Pa下粉煤灰改良膨胀土的抗剪强度。试验结果表明:(1)不同剪切速率和垂直压力下,改良膨胀土的内摩擦角和粘聚力都先增大后减小;(2)在同一上覆荷载条件下,剪切速率越大,改良膨胀土的内摩擦角越小,粘聚力越大,抗剪强度越高;(3)在同一剪切速率下,上覆荷载越大,内摩擦角越大,粘聚力越小,抗剪强度越大;(4)在不同剪切速率和上覆荷载条件下,在0.8 mm/min的剪切速率下,掺入14%左右的粉煤灰改良效果是最佳的,在2.4 mm/min的剪切速率下,掺入16%左右的粉煤灰改良效果是最佳的。这为确保公路路基边坡稳定性提供了相关理论数据。

Taking the expansive soil in a certain section of Yichang City as the research object,fly ash with different qualities was incorporated into it. By changing the shear rate and the overlying load conditions,analysis of non standard shear rate of 0. 8 mm/min and 2. 4 mm/min and non standard vertical pressure 12. 5 ～ 50 k Pa,62. 5 ～ 100 k Pa,100 ～ 400 k Pa of fly ash modified expansive soil on its influence shear strength index. The test results show that：（1） under the different shear rate and vertical pressure,the internal friction angle and cohesive force of the improved expansive soil first increased and then decreased;（ 2） under the same overloading condition,the greater the shear rate,the smaller the internal friction angle,the greater the cohesive force and the higher the shear strength of the improved expansive soil;（ 3） under the same shear rate,the greater the overburden load,the greater the internal friction angle,the smaller the cohesive force and the greater the shear strength;（4） under different shear rate and overlying load,the shear rate of 0. 8 mm/min under mixed with 14% fly ash improved effect is the best,in the 2. 4 mm/min under the shear rate of mixed with 16% fly ash improved effect is the best,which provide the theoretical data to ensure the stability of highway subgrade slope.