基于新型加卸载本构模型底板损伤规律研究

Study on damage law of floor based on new constitutive model of cyclic loading and unloading

应力路径对底板岩石力学性能有重大影响,而隔水层的力学特性是其厚度的决定性因素之一。本文认为岩石材料是一种能量非均匀耗散结构,以此为基础建立了修正平行杆模型,将宏、细观损伤变量和损伤演化方程相互联系,体现了循环加卸载过程中岩石的"非线性"、"随机性"和"刚度退化"特性。结合Drucker-Prager屈服准则,建立了一种新型循环加卸载本构模型。根据不连沟矿工程实际建立数值计算模型,通过UMAT二次开发,计算采矿过程中底板的损伤响应。结果表明,工作面煤壁下的底板损伤深度随顶板悬露面积的增加而增加,随顶板垮落而减小。而采空区内形成张拉裂隙,并释放应力波,导致底板损伤深度二次加深。上述因素使得损伤深度以Logistic函数形式波动增长,最终不超过18.5 m的概率超过90%。

The stress path has a significant effect on the mechanical properties of the floor rock, while the mechanical properties of aquifer are one of the decisive factors in its thickness. In this article, the rock material is regarded as a kind of energy non-uniform dissipative structure. A modified parallel bar model is established based on that which links the macro and meso-damage variables and the damage evolution equation. It embodies the mechanical characteristics of ＂nonlinear＂, ＂randomness＂ and ＂stiff- ness degradation＂. A new constitutive model in the condition of cyclic loading and unloading is estab- lished by combining the Drucker-Prager yield criterion. A numerical calculation model has been estab- lished according to the engineering practice of Buliangou mine. We develope the constitutive model by the UMAT. The results show that the damage depth of the floor under the mining face increases with in- creasing the hanging roof area, and decreases with the roof collapse. The stress wave releases during theformation of the tensile fractures in the goaf, and leads to the damage depth to deepen again. The dam- age depth of the floor fluctuates in the form of Logistic function and the probability that the damage depth less than 18.5 m is more than 90%.