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为了便捷、有效且减少地表破坏面积地原位测定根—土复合体抗剪强度,采用改制后的十字剪切仪在青海大学校内原生植被生长的试验区,分别进行了三种植被覆盖度和三种含水量条件下根—土复合体原位十字剪切试验和室内直接剪切试验。试验结果显示:当土体含水量相同时,室内直剪试验测得的根—土复合体平均粘聚力为20.39~36.49kPa,原位十字剪切试验测得的根—土复合体抗剪强度为35.92~102.36kPa;当植被覆盖度相同时,室内直剪试验测得的根—土复合体平均粘聚力为32.46~23.32kPa,原位十字剪切试验测得的根—土复合体抗剪强度为109.7~68.12kPa。两种试验结果均表现为:根—土复合体的抗剪强度随植被覆盖度的增大而增大,随含水量的增大而减小。原位十字剪切试验测得的根—土复合体抗剪强度值大于直接剪切试验所测得的剪切强度值,平均增幅达到94.23%。两种试验结果产生差异的主要原因是由于剪切过程中剪切方式、破坏面积、受剪根系的数量及破坏程度不同而造成。其中,原位十字剪切试验是在原位不破坏土体结构和根系分布的基础上,将根—土复合体完全剪破,相对更能准确、直观地反映边坡滑坡过程中的变化规律。
In order to measure the shear strength of the root-soil composite easily and effectively and reduce the area of ground surface damage, a three-dimensional vegetation coverage test was carried out in the experimental area where the native vegetation was grown in Qinghai University with a modified cross-cutter In situ cross shear test and direct indoor shearing test of root-soil composite under three water contents. The results show that when the soil moisture content is the same, the average cohesion of root-soil composite measured by direct shear test in indoor is 20.39-36.49 kPa. The root-soil composite shear strength measured by in-situ cross shear test The intensity of the root-soil composite was 35.92 ~ 102.36kPa. When the vegetation coverage was the same, the average cohesion of the root-soil complex was 32.46 ~ 23.32kPa measured by the direct shear test in the laboratory. Shear strength of 109.7 ~ 68.12kPa. The results of the two tests showed that the shear strength of the root-soil composite increased with the increase of vegetation coverage and decreased with the increase of water content. The shear strength of the root-soil composite measured by the in-situ cross shear test is larger than the shear strength measured by the direct shear test with an average increase of 94.23%. The main reason for the difference between the two test results is due to the different shearing methods, the area destroyed, the number of damaged root systems and the degree of damage. Among them, the in-situ cross shear test is based on the foundation that does not destroy the soil structure and root distribution in situ, and completely cuts the root-soil complex, which can relatively accurately and directly reflect the variation rules in the process of slope landslide .