高應力強卸荷作用下多組裂隙巖體宏細觀力學行為

左建平 李樹忱 王兆豐

摘 要：以深部重大工程災害（礦井、水利水電工程）為研究背景，結合我國深部地下工程圍巖的復雜性，圍繞深部強卸荷作用下裂隙巖體和圍巖力學行為與演化規律的關鍵科學問題，開展了高應力強卸荷作用下多組裂隙巖體宏細觀力學行為研究。（1）深部巖體內部裂隙的結構及幾何特征復雜，提出了描述巖體多組裂隙的分形構造張量表征方法，它可表征巖體內部隨機分布裂隙的位置、大小、形狀、取向及粗糙度（分形維數），并且具有明確的物理意義；基于工業CT及體視化原理驗證了構造張量表征方法的有效性。（2）揭示了高應力強卸荷條件下深部裂隙巖體的宏細觀變形機理：常規卸載條件下，巖石變形破壞過程中的各階段（彈性變形、屈服、軟化等）轉折分明，峰殘差較大，塑性特征減弱而脆性特征增強；應力轉移卸荷條件下，巖石側向應變呈加速變形跡象，強烈的擴容最終導致巖石破壞。卸載實驗破壞差應力介于單軸和常規三軸實驗之間；常規卸載（方案III）較高應力轉移卸荷（方案II）的破壞差應力偏高，因此現有的工程設計必須重新考慮高應力轉移卸荷影響。（3）揭示了自然多組裂隙大理巖的破壞機理及強度特性差異：含裂隙巖石的破壞特征，主要受裂隙結構的控制，提出了兩個指標Rd和λ，其中Rd用于描述大粗糙尺度的影響；而λ考慮了剪力方向的影響；與完整巖石相比，含裂隙大理巖的破壞具有顯著的局部化漸進特征，且突發性更強；在統計意義上，單軸抗壓強度σ單一型>σ平行型>σ交叉型>σ混合型，并且單一型、平行型、交叉型和混合型自然裂隙巖石的單軸抗壓強度分別為完整巖石的0.72倍、0.69倍、0.59倍和0.46倍。（4）基于巖石的非線性破壞行為，從細觀力學角度出發，采用拉伸雙線性應變軟化本構模型，通過應變能密度理論與能量耗散原理建立單元破壞的判斷準則，模擬了巖石損傷破壞的峰前-峰后全過程；建立了多組貫穿裂隙巖體變形和隨機分布貫穿裂隙巖體變形的本構模型，給出兩種情況下裂隙巖體的等效彈性模量和等效泊松比，研究了巖塊和裂隙的材料性質和幾何性質對巖體等效彈性模量和等效泊松比的影響。

關鍵詞：多組裂隙巖體 宏細觀破壞機理 分形構造張量 高應力 強卸荷機理

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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