不同层理倾角炭质板岩巴西劈裂试验及数值研究

Investigation on Brazilian tests and simulations of carbonaceous slate with different bedding angles

炭质板岩中层理软弱结构面对其破坏性态具有重要影响。以陕西岷县木寨岭隧道富含黏土矿物炭质板岩为研究对象,开展不同层理倾角炭质板岩巴西劈裂试验,并采用内聚力模型进行数值分析,研究结果表明:(1)不同层理倾角炭质板岩荷载−位移曲线形式具有一定相似性,具有压密―近线弹性―破坏跌落的基本特征;(2)随试样层理由Divider型及0°、30°、45°、60°、90°变化,其对应抗拉强度为1.65、1.59、1.12、0.89、0.76、0.66 MPa,且该试样抗拉强度显著偏小,受固有缺陷、富含黏土矿物受加工时水岩作用及放置时间等损伤效应的影响;(3)破坏形态受层理影响显著,可分为张拉破坏、剪切破坏和基质及层理面间的拉剪组合破坏;(4)三维数值计算结果显示,内聚力模型所预测的炭质板岩巴西劈裂破坏过程和室内试验结果相比,具有较好的吻合度。所得内聚力模型断裂力学参数能够为相关岩性及工程的数值计算提供参考。

Bedding structural planes play a dominated role in the failure process of carbonaceous slate under loading/unloading conditions.In this work,specimens with the clay mineral rich carbonaceous slate were sampled from Muzhailing tunnel of Shaanxi province in China.A series of Brazilian split tests for the rock specimens was conducted and the corresponding numerical simulations were performed using the cohesive zone model(CZM),in which different bedding angles in the rock were taken into account.This study indicates that the load-displacement relations of the rock specimens with different bedding angles under loads are similar to each other.All of them demonstrates identical basic characters that includes the initial stage,the rock specimens compaction,nearly linear elasticity,and finally complete collapse.The tensile strength of different specimens with bedding angles of 0°,30°,45°,60°,90° and divider are 1.59,1.12,0.89,0.76,0.66,1.65 MPa,respectively.The anisotropy coefficients are 2.41 and 2.50(divider),and the deterioration of such tensile strength is significantly related to the intrinsic defects and damage due to the water-rock effects.Furthermore,the failure modes and patterns of the rock specimens strongly depend on bedding structures,which can be classified as approximately pure tension failure,shear failure,and mixed tension-shear failure.Additionally,the three-dimensional numerical results show that the predicted split failure processes of carbonaceous slate by the CZM model are in a fair agreement with the results of laboratory tests.Therefore,the fracture mechanical parameters of CZM are valuable for similar tunneling engineering as a reference.