Research On The Model Of Flow In Rock Fractures With Injected Sand And Its Application

Large quantities of soils and sediments are distributed widely in natural faults. Inrock fractures sediments also often get mobilized and clogged, changing thepermeability of underground fractured rock significantly. The changed permeabilitycan lead to the variation of groundwater level, which can affect the production of oil,gas and other resources. The rise of the pore pressure caused by the changed ofgroundwater level often makes liquefaction massively, and then, surface subsidenceand a series of geological disasters will break out. In this paper, the dynamic behaviorof particles and its influence on permeability of fractured rock are studied by testing,theoretical analysis and numerical simulation comprehensively. Considering thesediment effect, response model and variation range of the underground water levelcaused by the earthquake in the far field is discussed. The main research achievementsare as follows:(1) A system for testing flow in rock fracture is designed which effectively teststhe characteristics of flow in a non-contact single fracture with sand. Calculationmodel of the fracture permeability coefficient is established based on particle collisionand energy loss, and the relationship of particle volume concentration, particle sizeand flow velocity with the flow characteristic in non-contact fractures under thecondition of particle migration is obtained;(2) The test for flow in contact single fractures with sand is accomplished. Basedon the phenomena and results of the experiment, calculation model of permeabilityconsidering the particles clogging effect is set up. The particle clog distribution infracture space is obtained, and the influence of particles clog on permeability and thewater pressure distribution in fractures are researched;(3) A system for testing flow in fractured rock under normal and shear stress isdesigned, by which we effectively test the flow characteristics in a contact singlefracture with sand under different normal stress. The influence of normal stress onparticles clog distribution in fracture space and induced changes of permeability forfractured rock is established;(4) The permeability characteristic and flow distribution in herringbone fractureis researched by experiments. The calculation model for deflection flow in theherringbone fracture considering the local pressure loss is built. The effects ofcrossing angle, flow velocity and fracture aperture combination on permeability characteristic and flow distribution are analyzed by both experiment and theory;(5) Through numerical simulation method, we analyze the flow motion feature inintersection region of the herringbone fracture. Assumption of the average flowvelocity distribution in intersection region is put forward and verified. We build thesediment distribution dynamic model for flow in the herringbone fracture with sandand discuss the inequality between water and sand distribution. Combined with theexperiments of flow in herringbone intersection fracture with sand, we also discussthe relationship of flow distribution ratio, particle volume concentration, flow velocityand particle size with particle distribution;(6) Experimental Analyzing the underground water flow fluctuation in the farfield caused by seismic wave，the response model of step-like change and slowlyvarying change of well water level in the far field considering particles effect is built.The relationships of the response form and magnitude for step-like changes of wellwater level after earthquake with sediment effect and observation wells location isresearched. We also verified the availability of the model by analyzing the law ofslowly varying change for the well water level after earthquake.The research achievements in this paper can provide important references for theresearch of calculation for seepage in engineering rock mass, earthquake hydraulicresponse mechanism, earthquake underground monitoring and forecasting and so on.