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

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.