地下洞室围岩喷钢纤维混凝土抗弯细观机理的三维离散元分析

喷混凝土的抗弯性能是其支护地下洞室围岩强度的重要反映。针对丰宁抽水蓄能电站地下厂房洞室群的钢纤维混凝土喷层,采用三维离散元分析了其抗弯细观机理。在数值分析过程中,提出了基于Voronoi随机多边形的三角分割建模方法;引入了Monte-Carlo法,建立了钢纤维随机分布模型。数值模拟采用了库伦摩擦节理本构模型来表征混凝土材料介质之间的粘结-开裂效应,采用Cable单元来模拟钢纤维作用。结果表明:数值模拟曲线与室内试验曲线基本一致;钢纤维混凝土的弯曲破坏由拉破裂主导,拉破裂路径总体铅直向上,但会受钢纤维作用的影响;在钢纤维混凝土弯曲破坏过程中,钢纤维的屈服大多是由于其与混凝土之间的粘结力达到屈服值,这与室内试验中有较多钢纤维被拔出的现象结论一致。研究结果为丰宁抽水蓄能地下厂房支护结构稳定性提供了重要理论支撑,同时也是室内试验的重要补充内容。

Three-dimensional Discrete Element Study on Meso-mechanism of Bending Resistance of Steel Fiber Reinforced Shotcrete for Surrounding Rock of Underground Cavern

The bending resistance of shotcrete is an important reflection of its support strength. Steel fiber reinforced concrete is adopted as the shotcrete for the underground powerhouse of Fengning pumped storage power station. In this study, numerical bending test of the shotcrete is carried out by using 3D discrete element code. During the numerical bending test, a triangulation modeling method based on the Voronoi tessellation is proposed. The Monte-Carlo method was used to establish the random distributed steel fibers, Coulomb-sliding joint constitutive model to represent the linking-breaking effects between concrete mediums, while Cable model to simulate the reinforcement effects of steel fibers. Numerical results are basically consistent with laboratory test curves. The bending failure of the steel fiber reinforced shotcrete is dominated by tensile fractures. The tensile fracture path is generally vertically upward, but is affected by the action of steel fibers. In the process of the bending failure of steel fiber reinforced shotcrete, the yield of steel fibers is mostly due to the yield of the bonding force between steel fibers and concrete, which echoes laboratory tests when many steel fibers are pulled out.