【作者】 郭杰；

【导师】 万玲；

【作者基本信息】 重庆大学 ， 力学， 2017， 硕士

【摘要】 岩石作为天然地质材料,其内部含有大量的微裂纹,微裂纹的演化对岩石的性质有很大的影响,基于微缺陷变形及演化的细观损伤模型能够较为准确的反映材料的损伤行为,因此建立能够反映岩石类材料内部微裂纹扩展变化的细观损伤模型有很重要的理论和实际意义。本文考虑花岗岩内穿透型微裂纹的损伤演化,建立了相应的细观损伤模型。首先,将穿透型微裂纹置于受到远场拉伸应力的无限大弹性基体内,建立起整体坐标系和裂纹面所在的局部坐标系,并对其进行位移、应力等的坐标变换。其次,考虑二维拉应力状态下穿透型微裂纹的变形、扩展,推导出具有任意空间取向的单个微裂纹引起的应变,通过应用Taylor方法假设微裂纹随机分布并引入概率密度函数,得到微裂纹系统所引起的应变。最后,将理论计算结果与单轴拉伸实验的结果相比较,验证了理论模型的可靠性。另外,建立了穿透型微裂纹受远场压-剪应力时的细观损伤模型。即取任意空间取向和完全随机分布,得到单个闭合穿透型微裂纹引起的应变,将穿透型裂纹的偏折扩展简化处理,得到单个微裂纹偏折扩展引起的应变。采用Taylor方法考虑所有随机分布的穿透型微裂纹引起的应变,合理的引入概率密度函数,得出二维压应力状态下穿透型微裂纹系统引起的应变。采用该模型分析了岩石单轴压缩试验和岩石三轴压缩试验,理论计算结果与试验结果吻和较好,从而验证了模型的正确性。最后,应用有限元软件对压应力条件下含预制裂纹板进行数值了模拟。根据最大周向应力准则,确定裂纹的偏折方向,求得裂纹偏折扩展路径,最终得到了一个扩展方向趋近于竖直方向的裂纹。得出裂纹引起的应变的数值模拟结果,并与理论计算结果相比较分析。更多还原

【Abstract】 As a kind of crude geological material,rocks often contain nunmerous microcracks,and the deformation of microcracks play important roles in their constitutive behavior and should be considerredin the description of deformation of materials.Therefore,it is of important theoretical and practical application significance to establish a detailed damage model which are able to describethe changes of microcracks in the rock material.Therefore,this paper considers the evolution of the microcracks within granite and establish a detailed damage model.First,the penetrating microcracks are placed in an infinite elastic matrix subjected to tensile stresses of the far field.Local Coordinate system for the crack surface and Global Coordinate system are established respectively.Considering the deformation and extension of penetration microcracks,Secondly,the strain caused by single crack with arbitrary spatial orientation is derived,and then the strain caused by all microcracks can be derived by employing the Taylor’s scheme and an appropriate probability density function.Finally,the present model is verified by a uniaxial tensile experiment.Besides,the deformation and growth of microcracks under far-field compressive stress are considered,and the micromechanical damage model is established.The additional compliance strain induced by single closed penetrating microcrack is derived.A simplified method to calculate the kinked deformation of the closed microcrack is presented.The strain caused by all microcracks under far-field compressive stress is derived by employing the Taylor’s scheme and an appropriate probability density function.Then the present model is verified by a uniaxial compression experiment and a triaxial compression experiment.Finally,a crack-containing plate under compressive stress is simulated by employing commercially finite element software ABAQUS.The propagation direction of the closed microcrack can be calculate by the maximum circumferential stress criterion,then the crack propagation path can be obtained.It is found that the crack propagation direction at final stage is almost vertical to the crack original faces.Then the additional compliance strain induced by this crack is derived,and compared this results with the theoretical results.更多还原