高应力强卸荷作用下多组裂隙岩体宏细观力学行为

摘 要：以深部重大工程灾害（矿井、水利水电工程）为研究背景，结合我国深部地下工程围岩的复杂性，围绕深部强卸荷作用下裂隙岩体和围岩力学行为与演化规律的关键科学问题，开展了高应力强卸荷作用下多组裂隙岩体宏细观力学行为研究。（1）深部岩体内部裂隙的结构及几何特征复杂，提出了描述岩体多组裂隙的分形构造张量表征方法，它可表征岩体内部随机分布裂隙的位置、大小、形状、取向及粗糙度（分形维数），并且具有明确的物理意义；基于工业CT及体视化原理验证了构造张量表征方法的有效性。（2）揭示了高应力强卸荷条件下深部裂隙岩体的宏细观变形机理：常规卸载条件下，岩石变形破坏过程中的各阶段（弹性变形、屈服、软化等）转折分明，峰残差较大，塑性特征减弱而脆性特征增强；应力转移卸荷条件下，岩石侧向应变呈加速变形迹象，强烈的扩容最终导致岩石破坏。卸载实验破坏差应力介于单轴和常规三轴实验之间；常规卸载（方案III）较高应力转移卸荷（方案II）的破坏差应力偏高，因此现有的工程设计必须重新考虑高应力转移卸荷影响。（3）揭示了自然多组裂隙大理岩的破坏机理及强度特性差异：含裂隙岩石的破坏特征，主要受裂隙结构的控制，提出了两个指标Rd和λ，其中Rd用于描述大粗糙尺度的影响；而λ考虑了剪力方向的影响；与完整岩石相比，含裂隙大理岩的破坏具有显著的局部化渐进特征，且突发性更强；在统计意义上，单轴抗压强度σ单一型>σ平行型>σ交叉型>σ混合型，并且单一型、平行型、交叉型和混合型自然裂隙岩石的单轴抗压强度分别为完整岩石的0.72倍、0.69倍、0.59倍和0.46倍。（4）基于岩石的非线性破坏行为，从细观力学角度出发，采用拉伸双线性应变软化本构模型，通过应变能密度理论与能量耗散原理建立单元破坏的判断准则，模拟了岩石损伤破坏的峰前-峰后全过程；建立了多组贯穿裂隙岩体变形和随机分布贯穿裂隙岩体变形的本构模型，给出两种情况下裂隙岩体的等效弹性模量和等效泊松比，研究了岩块和裂隙的材料性质和几何性质对岩体等效弹性模量和等效泊松比的影响。

关键词：多组裂隙岩体 宏细观破坏机理 分形构造张量 高应力 强卸荷机理

Abstract：Under the researching background of deep engineering disasters in mining，hydraulic and hydropower engineering，combining with the complexity of the surrounding rock of deep underground constructions in China，a research on macroscopic mechanical behavior of the multi-cracked rock under the deep high stress was carried out.（1）Based on the complexity of structures and geometric characteristics of the internal crack，a tensor method， which could describe the fractal structure of the multi-cracked rock，was put forward.（2）The macroscopic deformation theory of the deep fractured rock mass was revealed.Under conventional unloading conditions， turns over each stage （elastic deformation，yield，softening，etc.）of the rock deformation and failure process are obvious，peak residual stress is larger， the plastic characteristics become weak，and the brittle characteristic reinforces.（3）Differences of the failure mechanism and strength characteristics of the nature multi-cracked marble were analyzed.The failure mechanism of the cracked rock，is mainly controlled by the crack structure with two indicators Rd and λ put forward，which Rd is used to describe the influence of the large roughness scale and λ is a parameter considering the influence of the shearing direction.Comparing with the intact rock， the multi-cracked rock failure has an obvious localizing gradient changing process，and sometimes it suddenly becomes stronger. In statistical， the uniaxial compressive strength，σ，has a feature like，σ single>σ parallel>σ cross>σ mix.The uniaxial compressive strength of the rock with single crack， parallel cracks，crossing cracks and mixed cracks is，respectively，0.72，0.69，0.69，and 0.46 times as it of the intact rock. （4）Based on the nonlinear behavior of the rock，from the angle of the microscopic mechanic，using bilinear strain tensile softening constitutive model， by understanding of the judging criteria of the cell damage establishing on the strain energy density theory and the principle of energy dissipation，the whole damage process of the rock was simulated， the constitutive model of the cut through multi-cracked rock and the random crossing cracked rock were established，the equivalent poisson′s ratio and the elastic modulus of the cracked rock in two cased above were given， the influence of material properties geometric properties of the rock or cracks on the equivalent poisson′s ratio and the elastic modulus were studied systematically.

Key Words：Multiple fractured rock； Macro-micro failure mechanism； Fabric structure tensor； High stress； Unloading mechanism

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