考虑应力修正的麦秆土直剪试验抗剪强度指标研究

为了分析麦秆含量对土壤抗剪强度指标的影响,获取更可靠的抗剪强度指标,推广能源节约型农业耕作生产,用TMS-PRO计算机控制质构仪做麦秆剪切试验。用应变控制式直剪试验研究原状与重塑麦秆土抗剪强度指标,分析麦秆含量对土壤抗剪强度指标的影响。应用应力修正法对直剪试验的正应力与剪应力进行修正,研究修正前、后麦秆土抗剪强度指标的变化量及随麦秆含量的变化规律,并对原状与重塑麦秆土修正前、后的黏聚力、内摩擦角拟合线分别进行叠加。试验结果表明:麦秆抗剪强度随含水量的增加而增大,麦秆土抗剪强度指标随麦秆含量的增加而增大,黏聚力符合线性拟合的规律、内摩擦角符合二次函数拟合的规律。考虑应力修正后原状与重塑麦秆土黏聚力较修正前提高了24%、内摩擦角较修正前提高了18%;未经修正的原状与重塑麦秆土在麦秆含量为0.58%时具有相同的黏聚力,在麦秆含量为0.37%时具有相同的内摩擦角;考虑应力修正后的原状与重塑麦秆土在麦秆含量为0.65%时具有相同的黏聚力,在麦秆含量为0.40%时具有相同的内摩擦角;在交汇点之后麦秆土抗剪强度指标增速表现为原状大于重塑。

Experimental research on shear strength index of wheat straw-soil by direct shear test considering stress correction

In order to analyze the effects of wheat straw content on soil shear strength index, obtain more reliable shear strength index, promotion of energy saving agriculture production, the wheat straw shear strength was measured by TMS-PRO texture analyzer with shear box, the shear strength index of undisturbed and remolded wheat straw-soil was measured by strain controlled direct shear test, the effect of wheat straw content on soil shear strength index was analyzed. The normal stress and shear stress of direct shear test were modified by stress correction method, the variation and law as wheat straw content which shear strength index of wheat straw-soil before and after correction, overlapping cohesion fitting lines and internal friction angle fitting curves before and after correction, respectively. Results showed that shear strength of wheat straw increased with moisture content, wheat straw-soil shear strength index with wheat straw content increasing, cohesion showed a linear trend, internal friction angle showed a quadratic trend. The cohesion was increased by 24% and the internal friction angle was increased by 18% compared with that before correction for the undisturbed and remolded wheat straw-soil. The undisturbed and remolded wheat straw-soil had the same cohesion and internal friction angle before correction when the wheat straw content was 0.58% and 0.37%, respectively. Similar results were obtained when stress correction considered, the resultant point of cohesion and internal friction angle intersection was observed at a wheat straw density of 0.65% and 0.40% for undisturbed and remolded wheat straw-soil, respectively. After the intersection, as wheat straw density was increased, the shear strength index of undisturbed wheat straw-soil increased more than did the remolded wheat straw-soil.