Experimental study on shear mechanical properties of soil-rock mixture-bedrock interface
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摘要: 填方体-下伏基岩接触面间的剪切强度是控制高填方体或堆积体边坡稳定性的重要因素,界面强度参数取值是高填方工程设计的重要参数之一。通过较系统地室内大型直剪试验探讨了接触面粗糙度对土石混合料-基岩接触面剪切力学特性的影响。结果表明:在低法向应力作用下,剪应力-剪切位移曲线前期呈现出应变硬化现象,后期呈现出塑性应变现象,且接触面粗糙度越大接触面发生剪切破坏时变形越小;在高法向应力作用下,曲线呈现出应变硬化现象,无明显峰值;相同法向应力水平作用下,接触面粗糙度越大,土石混合体-基岩接触面剪切刚度越大。剪切界面上块石的破碎形态可分为完全破碎、部分破碎和表面磨损3种,随着接触面粗糙度的增加,剪切界面上块石的破碎总数也增加。接触面的抗剪强度、内摩擦角和表观黏聚力随着接触面粗糙度的增加而增大,相比于内摩擦角,接触面的表观黏聚力增大较为明显。接触面粗糙度对剪切带宽度有影响作用,表现为接触面粗糙度越大,剪切带越宽。Abstract: The shear strength of the interface between the fill and the underlying bedrock is an important factor to control the stability of high fill or accumulation slopes. The value of the interface strength parameter is one of the important parameters for the design of high backfills. The effect of the contact surface roughness on the shear mechanical properties of the soil-rock mixture-bedrock contact surface is explored through the systematic large-scale indoor direct shear tests.The test results show that under the action of low normal stress, the shear stress-shear displacement curve shows strain hardening in the early stage and plastic strain in the later stage, and the greater the roughness of the contact surface, the more the contact surface deforms when shear failure occurs. Under the action of high normal stress, the curve shows strain hardening without obvious peaks. Under the same normal stress level, the greater the contact surface roughness, the greater the shear stiffness of the soil-rock mixture-base rock interface. The crushing morphology of the rock at the shear interface includes three types: complete crushing, partial crushing, and surface abrasion. As the contact surface roughness increases, the total number of rock crushing at the shear interface also increases. The shear strength, internal friction angle and apparent cohesion of the contact surface increase with the increase of the roughness of the contact surface. Compared with the internal friction angle, the apparent cohesion of the contact surfaces increases significantly. The roughness of the contact surface has an effect on the width of the shear band, which shows that the larger the roughness of the contact surface is, the wider the shear band is.
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Keywords:
- soil-rock mixture /
- bedrock interface /
- roughness /
- shear characteristic /
- broken stone
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表 1 土石混合体及灰岩基本物理参数指标
Table 1 Basic physical parameter indexes of soil-rock aggregate
土体类型 物理参数指标 干密度/(g·m-3) 孔隙比 天然含水率/% 天然密度/(kg·m-3) c/kPa φ/(°) 弹性模量/GPa 单轴抗压强度/MPa 土石混合体 1788 0.24 9.32 2110 23.9 10.54 — — 灰岩 — — — 2730 1433 35.67 29.14 68.09 表 2 台阶基岩界面力学参数指标
Table 2 Mechanical parameter indexes of step bedrock interface
试件 编号 坡率 台阶高/cm 台阶宽/cm 粗糙度Y/mm J斜面α/(°) 1 1∶2 25 50 0.399 26.56 2 1∶1.75 25 43.75 0.431 29.74 3 1∶1.5 25 37.44 0.462 33.69 表 3 室内大型直剪试验方案
Table 3 Indoor large-scale direct shear test schemes
试件编号 粗糙度C 法向压力/kPa 1 0.399 200,400,600,800 2 0.431 200,400,600,800 3 0.462 200,400,600,800 表 4 界面抗剪强度
Table 4 Interface shear strengths
项目 试件编号 1 2 3 抗剪强度 =200 kPa 179.0500 224.2300 264.8700 =400 kPa 356.9700 401.5600 460.8900 =600 kPa 490.3700 536.6700 575.6700 =800 kPa 605.5600 694.8200 794.5600 粗糙度 0.3990 0.4310 0.4620 相关系数R 0.9899 0.9975 0.9874 表观黏聚力/kPa 54.7500 77.6000 98.0400 内摩擦角/(°) 35.2400 37.7200 40.4300 -
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