单轴压缩条件下溶蚀岩体力学特性数值试验研究

Numerical test on the mechanical properties of dissolution rock mass under the uniaxial compression condition

工程尺度的溶蚀岩体难以开展室内外力学试验,导致溶蚀岩体的力学参数获取存在困难,因此基于岩石矿物含量特征、室内力学试验和岩体结构面特征,采用三维颗粒流离散元法,通过建立等效孔隙型溶蚀岩体模型进行单轴压缩数值试验,进而分析其力学特性和变形破坏机制。研究表明:采用改进平行黏结模型,基于细观矿物特征,通过元胞自动机算法剔除颗粒可建立孔隙型溶蚀岩体模型;加载前期,岩体结构面首先快速破坏而产生以剪切为主的微裂纹;随加载进行,岩块内逐渐产生以拉裂纹为主的破坏,其微裂纹呈指数增加,而结构面微裂纹先激增后趋于稳定;相同轴向应变时,岩块内拉裂纹随溶蚀率增加而增加,而结构面剪切微裂纹减少;岩体的变形破坏分为结构面快速破坏、岩块弹性变形、岩块塑性变形和岩体完全破坏等4个阶段,其破坏形式随溶蚀率增加而从整体均匀性破坏转化为局部结构性破坏;溶蚀使岩体强度降低,溶蚀率与单轴抗压强度和变形模量分别呈反比和负指数函数关系。

It is difficult to carry out laboratory and field mechanical tests on engineering-scale dissolution rock mass,which leads to great difficulty in obtaining mechanical parameters of the dissolution rock mass.Therefore,based on the characteristics of rock mineral content,laboratory mechanical tests,and rock mass structural plane characteristics,three-dimensional particle flow of discrete element method was adopted to conduct a uniaxial compression numerical test by establishing an equivalent dissolution rock mass model.Finally,the mechanical properties and deformation failure mechanism are analyzed.Based on the characteristics of meso-minerals and macro-structural planes,the research shows that the establishment of an equivalent dissolution rock mass model can truly reflect the mechanical behavior of it.In the early stage of loading,the structural plane of rock mass was quickly destroyed to produce micro-cracks mainly of shear.However,with the loading progressing,tensile failure occurred gradually in the rock mass,and its micro-cracks increased exponentially,while the micro-cracks of the structural plane surged first and then stabilized.Under the same axial strain,the internal tensile cracks in the rock block increase by the dissolution rate,but the shear microcracks on the structural plane decrease.The deformation and failure of the rock mass can be divided into four stages:rapid failure of the structural plane,elastic deformation of the rock,plastic deformation of the rock,and complete failure of the rock mass.The failure form of the rock mass transitions from the overall-uniform failure to the local-structural failure with the increase of the dissolution rate.dissolution reduces the strength of rock mass.The dissolution rate is inversely proportional to the uniaxial compressive strength,and has a negative exponential relationship with the deformation modulus.