不同剪切速率对改良膨胀土抗剪强度影响研究

为了研究不同方法改良的膨胀土在不同剪切速率下抗剪强度指标的变化规律,分别在2.4mm/min和0.8 mm/min剪切速率下对风化砂、石灰、水泥以及粉煤灰改良的膨胀土样进行了室内直接剪切试验,得到了不同剪切速率下改良膨胀土的抗剪强度指标值。试验结果表明:(1)剪切速率对同一材料改良膨胀土的内摩擦角和粘聚力均有影响,并且对粘聚力的影响要大于对内摩擦角。(2)风化砂改良膨胀土的内摩擦角和粘聚力均随剪切速率的增大而增大。(3)同一剪切速率下,掺砂改良膨胀土的内摩擦角随掺砂比例的增大先增大后减小,粘聚力随掺砂比例的增大而减小。(4)同一剪切速率下,掺水泥改良膨胀土的抗剪强度指标最大。从效果上看,掺风化砂、石灰、水泥和粉煤灰均能提高膨胀土的抗剪强度。

Study on influences of different shear rates on shear strengths of improved expansive soils

In order to study the changing law of the shear strength indexes under different shear rates of the expansive soils improved by different methods，the indoor direct shear tests on the samples of the expansive soils improved by weathered sand，lime，cement and fly-ash are made under the shear rates of 2.4 mm/min and 0.8 mm/min respectively，and then the values of the shear strength indexes of the expansive soils under different shear rates are obtained. The results show that：（1）the shear rate has the impact on both the internal friction angle and the cohesion of the expansive soils improved with the same material，while the impact on the cohesion is larger than that of the internal friction angle；（2）both the internal friction angle and the cohesion of the expansive soil improved with weathered sand are to be increased along with the increment of the shear rate；（3）under the same shear rate，the internal friction of the expansive soil improved with sand is to be increased at first and then decreased along with the increment of the mixing ratio of sand，while the cohesion is to be decreased along with the increment of the mixing ratio of sand；（4）under the same shear rate，the index of the shear strength of the expansive soil improved with cement is the largest. In the aspect of the effect，no matter whether mixed with weathered sand，lime，cement or fly-ash，the shear strengths of all the improved expansive soils can be increased.