粉状和砾状煤系土的水敏感性及边坡稳定性分析

煤系土具有遇水软化的特点,强度随着含水率的增加而降低。以分布在广梧高速公路沿线的粉状和砾状煤系土为试样,通过常规直接剪切试验测定了不同含水状态下粉状和砾状煤系土的抗剪强度,对比分析了两者的水敏感性,并以此为基础采用强度折减法研究了含水率对粉状和砾状煤系土边坡稳定安全系数的影响。结果表明,起始含水率越大粉状和砾状煤系土的抗剪强度越小。随着含水率的增大,粉状煤系土黏聚力和内摩擦角分别呈指数函数以及线性函数关系形式减小;砾状煤系土黏聚力变化表现出明显的分段性:先小幅减小而后急剧减小,其内摩擦角则随着含水率的增加先小幅增加,后逐渐减小;粉状和砾状煤系土边坡的稳定安全系数都近似呈现直线型减小。粒组成分和风化作用的不同是粉状和砾状煤系土水敏感性不同的主要原因。研究结果为营运期广梧高速公路煤系土边坡的养护提供了建议。

Study on the water sensitivity of powered and rudaceous soil of coal measure strata and slope stability analysis

Soil of coal measure strata is weakened when encountering water and its strength is sharply dropped with increasing water content. The shear strengths of powered and rudaceous soil of coal measure strata taken from Guang-Wu Expressway were measured by direct shear test, and the influences of water contents on shear strengths of the powered and rudaceous soil of coal measure strata were analyzed. The strength reduction method was employed to analyse the safety factor of the powered and rudaceous soil of coal measure strata slope. The results indicate that there are negative relationships between the shear strengths and initial water contents of the powered and rudaceous soil of coal measure strata. With increase of water content, the cohesion of powered soil of coal measure strata and its water content decreases in the form of exponential function, while its internal friction angle decreases in the form of linear function. With increase of water content, the cohesion of rudaceous soil of coal measure strata decreases in segments. It firstly decreases by small margin and then sharply declines. The internal friction of rudaceous soil of coal measure strata firstly increases by small margin and then gradually decreases with water content increasing. The safety factor of the powered and rudaceous soil of coal measure strata slope decreases approximately linear with water content increasing. Powered and rudaceous soil of coal measure strata have different water sensitivity mainly because of the difference of their gain size composition and weathering. The research results provide suggestions for maintenance of the coal soil slope of Guang-Wu Expressway under operating period.