重庆地区典型土石混合体回填土区隧道围岩分级研究

Subclassification of Tunnel Surrounding Rock in Typical Soil-Rock Mixture Backfill Area in Chongqing

为对重庆地区典型土石混合体回填土区隧道围岩进行分级,通过室内基本物理性质试验获得土石混合体回填土的天然密度、干密度、含水率、含石量等基本物理参数指标,通过室内大型直剪试验和大型三轴试验获得土石混合体回填土的强度和变形等力学特性随含水率、含石量、围压等因素的变化规律,并基于室内试验结果,分别以含水率和含石量为分类指标,对重庆地区土石混合体回填土进行分类,提出适用于重庆地区土石混合体回填土的围岩分级指标和方法。主要结论有: 1)重庆地区的土石混合体回填土属于级配不良的土体;2)随着含水率的增大,土石混合体的黏聚力和内摩擦角都逐渐降低,且均表现为先快后慢的规律;3)随着含石量的增大,土石混合体的内摩擦角呈慢快慢的增大规律,而黏聚力呈先快后慢的降低规律;4)对于重庆地区的土石混合体回填土,其围岩分级指标重点选用含水率和含石量;5)对重庆地区土石混合体围岩进一步细分为Ⅳ、Ⅴa、Ⅴb 3 级,其中Ⅴa 级和Ⅴb 级分别为Ⅴ级稍好和Ⅴ级稍差围岩。

It is necessary to carry out subclassification for tunnel surrounding rock in typical soil-rock mixture backfill area in Chonging. Hence, laboratory basic physical property test is conducted to obtain the basic physical parameters of the soil-rock mixture such as natural density, dry density, water content and rock content. And then laboratory large-scale direct shear test and large-scale triaxial test are conducted to study the variation laws of strength and deformation characteristic of soil-rock mixture with water content, rock content and confining pressure. Finally, based on laboratory test results, the soil-rock backfill in Chongqing is classified by taken water content and rock content as indices, and surrounding rock classification indices and method suit for soil-rock mixture backfill in Chongqing area are put forward. Some conclusions are drawn as follows:(1) The soil-rock mixture backfill in Chongqing belongs to poorly graded soil.(2) With the increase of water content, the cohesion and internal friction angle of soil-rock mixture decrease rapidly first and then slowly.(3) With the increase of rock content, the internal friction angle of the soil-rock mixture increases, and shows a " slow-fast-slow" pattern;while the cohesion decreases rapidly first and then slowly.(4) For the backfill of soil-rock mixture in Chongqing area, the water content and rock content are priorities in key indices of surrounding rock classification.(5) The surrounding rock of soil-rock mixture in Chongqing area is further subdivided into Grade Ⅳ,Ⅴa and Ⅴb, of which Grade Ⅴa and Ⅴb are slightly better Grade Ⅴ and slightly worse Grade Ⅴ respectively.