不同厚度充填体—围岩组合体力学性质及损伤本构

为探究充填体厚度变化对充填体-围岩组合体力学性能的影响规律，开展了5种不同厚度充填体-围岩组合体试件单轴压缩试验，结合数字散斑技术对试件破坏模式的变化进行分析，建立考虑峰后应变软化阶段的分段式损伤本构模型对全过程应力-应变关系进行描述。分析结果表明，充填体厚度变化对组合试件力学性能与破坏模式影响显著。随着充填体厚度由0 mm增加至100 mm,试件峰值强度由94.6 MPa呈指数关系下降至10.1 MPa,峰值应变由0.30下降至0.06,弹性模量呈先下降后上升变化趋势；利用数字散斑技术分析发现，随着充填体厚度增加，破坏模式逐渐由脆性剪切破坏过渡为拉剪复合破坏，最终发展为由充填体内部发生“X”形剪切破坏而引起的拉伸劈裂破坏；通过改变分段式损伤本构模型的分布参数与修正系数，可较好地表征不同充填体厚度试件的全过程应力-应变曲线，验证结果表明模型适用性较好；充填体厚度越大，由充填体存在而引起的试样初始损伤越大，达到峰值应变时，损伤变量D未达到1,试件延性破坏特征越明显，破坏后残余强度越高。

Mechanical property and damage constitution of different thickness of backfill-surrounding rock combination

In order to explore the influence of the thickness change of the filling body on the mechanical properties of backfill-surrounding rock combination, uniaxial compression tests were carried out on five kinds of backfill-surrounding rock combination specimens with different thicknesses. The change of failure mode of specimens was analyzed by digital speckle correlation method and a piecewise micromechanical damage model considering the post peak strain softening stage was established to describe the complete stress-strain relation. The results showed that the mechanical properties and failure modes of specimens were significantly affected by the change of filling body thickness. As the thickness of filling body increases from 0 mm to 100 mm, the peak stress of the specimen decreases exponentially from 94.6 MPa to 10.1 MPa, the peak strain decreases from 0.30 to 0.06 and the elastic modulus decreases first and then increases. By using digital speckle correlation method, it was found that with the increase of the filling body thickness, the failure mode gradually changed from brittle shear failure to tension-shear failure, and finally developed into tensile splitting failure caused by X-type shear failure in the filling body. By changing the distribution parameters and correction coefficients of the piecewise micromechanical damage model, it could better characterize the whole process stress-strain curve of specimens with different filling body thickness. Using the data of literature 26] for verification, it was found that the model has good applicability. The greater the thickness of the backfill, the greater the initial damage of the specimen. When the peak strain was reached, the damage variable D does not reach 1, the more obvious the ductile failure characteristics of the specimen, the higher the residual strength after failure.