优先流对粉砂土抗剪性能影响试验研究

Experimental Study on Influence of Preferential Flow on Anti-shear Performance of Silty Sand

优先流会引起含水率增加,从而影响土的抗剪强度.为此,运用染色示踪技术,在室外进行优先流渗流试验;每10 cm一层,对样地竖直剖切;采用图像处理软件对优先流渗流特征进行分析评价.根据测定的土样含水率制作试块,进行冻融及直剪试验.结果表明:优先流染色面积比变化幅度大,浮动区间为39.76%~52.84%;基质流深度较深,平均为13.4 cm;优先流比平均为23.94%,优先流现象明显;随着冻融次数的增加,含水率变化导致内摩擦角呈减小的趋势;在-5、-10和-15℃时,粉砂土11次冻融后内摩擦角与0次冻融相比,最佳含水率分别降低了0.86%、1.60%、2.92%,优先流含水率分别降低了3.02%、4.69%、6.00%;优先流含水率下粉砂土黏聚力降幅比高于最佳含水率1.27%.因此,优先流含水率对土体抗剪强度有较大影响.

The preferential flow will cause an increase of moisture content,which will affect the shear strength of the soil.For this purpose,dyeing and tracing techniques were used to conduct the preferential flow test outdoors.The sample was cut vertically every 10 cm as a layer.The image processing software was used to analyze and evaluate the characteristics of preferential flow.The test pieces were prepared according to the measured moisture content of the soil sample,then the freeze-thaw tests and the direct shear tests were carried out.The results show that the dyeing area ratio of preferential flow varies greatly,and the range is 39.76%~52.84%.The depth of the matrix flow is deep,and the average is 13.4 cm.The average preferential flow ratio is 23.94%,and the preferential flow phenomenon is obvious.With the increase of freezing-thawing cycles,the variation of water content leads to the decrease of internal friction angle.At-5,-10 and-15℃,after 11 times of freezing-thawing,the internal friction angles at the optimum moisture content decrease by 0.86%,1.60%and 2.92%,respectively,and those at the preferential flow moisture content decrease by 3.02%,4.69%,and 6.00%,compared with those of 0 times of freezing-thawing.Also the reduced cohesion ratio of silty soils under priority flow moisture content is 1.27%higher than that of optimum moisture content.Therefore,the preferential flow moisture content has a great impact on the soil shear strength.