弱胶结断层岩体蠕变–冲蚀耦合突水模型

Creep-erosion coupling water inrush model of weakly cemented fault rock mass

  • 摘要: 为研究弱胶结断层岩体突水灾变过程的时空演化特征,构建了弱胶结断层岩体蠕变–冲蚀耦合突水模型。该模型拓展了连续等效介质渗流理论,分别建立了弱胶结断层岩体的蠕变子模型和冲蚀子模型,其中所建立蠕变子模型充分考虑物质间质量转化、应力–应变及应变–孔隙率之间关系;所建立冲蚀子模型充分考虑了物质质量守恒、颗粒迁移及非Darcy流动规律。根据质量守恒方程叠加原理及孔隙率–有效应力、孔隙率–蠕变材料系数、蠕变应变–孔隙率–渗透率3组影响关系实现了子模型间的耦合,并给出了一维径向渗流方向耦合模型的控制方程。设定了突水模型的定解条件,并基于COMSOL Multiphysics计算软件构建了模型在空间和时间域的数值解算方法。通过比较室内试验及模型计算的孔隙率演化结果,验证了该模型的有效性。在此基础上,求解并分析了突水过程中巷道弱胶结围岩蠕变–冲蚀特征的时空演化规律。模型计算结果表明,对于蠕变演化特征,随着时间增长,有效应力下降,蠕变应变增加,试样出现加速蠕变特征;有效应力和蠕变应变空间分布的非均匀性特征随蠕变–冲蚀耦合进程显著加强。对于冲蚀演化特征,蠕变–冲蚀耦合进程初期细小岩石颗粒在渗水作用下不断迁移流出,液化颗粒体积分数增加,渗透率和流速不断增长,弱胶结岩体内部不断形成新的导水通道,后因蠕变效应逐渐增强,冲蚀效应有所减弱,并最终陷入停滞状态;越靠近巷道内壁,冲蚀效应越强,冲蚀效应停滞后孔隙率和渗透率的空间分布呈现出明显的非均匀特征,水压空间分布在蠕变−冲蚀耦合进程中呈现出非线性–线性–非线性的变化趋势。

     

    Abstract: In order to investigate the temporal-spatial evolution properties of the water inrush disaster process of weakly cemented fault rock mass, a creep-erosion coupling water inrush model of weakly cemented fault rock mass is established. This model expands the equivalent continuum seepage theory, and a creep submodel and an erosion submodel are established respectively. The proposed creep submodel fully considers the mass conversion among materials, stress-strain and strain-porosity relationships. The proposed erosion submodel fully considers the mass conservation, particle migration and non-Darcy flow laws. According to the superposition principle of the mass conservation equations and three influence relationships (i.e., porosity-effective stress, porosity-creep material coefficient and creep strain-porosity-permeability relationships), the coupling between the submodels is realized, and the governing equations of the one-dimensional radial seepage direction coupling model are given. The solution conditions of the water inrush model are set, and the numerical computation method of the model in the temporal-spatial domain is established based on the COMSOL Multiphysics. By comparing the laboratory experimental results and the model calculation results of porosity evolution, the validity of the creep-erosion coupling model of weakly cemented surrounding rock is verified. On this basis, the temporal-spatial evolution law of the creep-erosion characteristics of weakly cemented surrounding rocks of the roadway is solved and analyzed. The calculated results show that in terms of the creep characteristics evolution, the effective stress decreases and the creep strain increases with time, and the samples exhibit the accelerated creep characteristics. The inhomogeneity of the spatial distribution of effective stress and creep strain increases with the creep-erosion coupling process. As for the evolution of the erosion characteristics, in the initial stage of the creep-erosion coupling process, the fine rock particles migrate out continuously under the effect of water flow, the volume fraction of fluidized particles, the permeability and flow velocity continuously increase, and new water-conducting channels are constantly formed in the weakly cemented rock mass. Subsequently, the erosion effect is weakened and finally stagnates due to the increasing creep effect. The closer to the inner wall of the roadway, the stronger the erosion effect. The spatial distribution of porosity and permeability after the stagnation of erosion shows obvious inhomogeneous characteristics, and the spatial distribution of water pressure presents a nonlinear-linear-nonlinear trend in the creep-erosion coupling process.

     

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