含“架空”结构土石混合体力学特性试验及变形破坏机理研究

Soil-rock mixture containing macropore structure (SRMCMS) widely exists in south and western China. The SRMCMS exhibits complex structural characters and mechanical performance. The SRMCMS is the mainly factor that induces geological disaster such as collapse, landslide and debris flow. Currently, the formation mechanism and the long-term deformation performance of the SRMCMS is not well understood. The correlation between mechanical parameters of the SRMCMS obtained from experiments and geological disaster occurrence needs to be discerned. A synthetic method, which includes field investigation, theoretical analysis, laboratory test and numerical simulation, is employed in this project. The model shafts, which can alter angle and gradient, are first manufactured. Then, the model simulation test is conducted by the model shafts to identify the formation mechanism of the SRMCMS. Furthermore, the mechanical behaviors of the SRMCMS are studied by the experiments that are conducted by large scale triaxial apparatus designed by applicant and direct shear apparatus. In addition, the failure law, a new identification method of the mechanical parameters, the mechanism of deformation, and the nonlinear rheological model to consider creep characteristics will be also detailed studied on the basis of the experimental results. Finally, the size of the representative element (REV & REA) in different conditions of geometrical combination is determined, and the design theory and design criterion of the SRMCMS formation, deformation and failure can be obtained, which can directly serve for the design theory and design criterion of engineering. The expected results can not only remedy the defects of the current research in which the formation mechanism, strength parameters identification and long-term deformation theories of the SRMCMS is neglected, but also provide the theoretical proof for prediction, prevention and control of the geological disaster due to the SRMCMS.

含“架空”结构土石混合体广泛分布于我国西南地区，其组成结构及力学特性是崩塌、滑坡和泥石流等地质灾害频发的主要诱因。目前的研究成果对其力学特性及变形破坏机理的解释远远不够，通过室内及现场试验得出的力学参数尚无法直接采用；据此，课题将从土石混合体的形成结构、分布特征及力学特性入手，采用现场调查、理论分析、室内试验及数值模拟等技术手段，研制可改变倾角的多坡度模型槽并进行模型试验，根据试验结果提出“架空”结构层形成机理的见解；采用自主研制的大型三轴仪和大直径直剪仪对其力学特性开展试验，依据试验结果提出力学参数系统识别方法、变形破坏机制理论、能反映瞬时变形的非线性流变模型及不同结构组成条件下表征单元的确定方法；提出适于工程应用的设计理论和准则。预期成果可弥补当前土石混合体研究中忽略“架空”结构层形成机理及其力学特性认识的不足，从而对含“架空”结构土石混合体导致的地质灾害的预测、预防及控制提供依据。

含“架空”结构土石混合体广泛分布于崩塌、滑坡、泥石流致灾区域，具有复杂的结构特征和力学性能。当前，由于对其形成机理、力学特性及变形破坏特征的研究远远不够，通过室内及现场试验得出的力学参数尚无法直接采用。鉴于此，课题在实施过程中以具体工程中的崩塌堆积体为研究对象，从土石混合体的形成机理、分布特征及力学特性入手，采用了现场调查、理论分析、室内试验及数值模拟相结合的技术手段开展了一系列的研究工作，取得以下成果：（1）研制了可改变倾角的多坡度模型槽并开展模型试验，依据试验结果揭示了“架空”层的形成条件和机理；（2）采用大型直剪仪对其力学特性开展试验，依据试验结果提出了力学参数系统识别方法，揭示了变形破坏机制理论，构建了非线性数值模型，并建立了不同结构组成条件下表征单元的确定方法；提出了适于工程应用的设计理论和准则；（3）揭示了不同胶结材料、材料含量对含“架空”层土石混合体剪切破坏的影响机理。课题研究成果弥补了土石混合体研究中忽略“架空”层形成机理及其力学特性认识的不足，为含“架空”结构土石混合体导致的地质灾害的预测、预防及控制提供了理论依据。