Study On The Seepage Evolution Law Of Aquifer Accompanied By Sand Loss In The Process Of Water And Sand Inrush

Water and sand inrush is a thorny problem that plagues the safety production of many large coal bases in western my country.In this paper,the method of combining theoretical analysis and laboratory simulation test is used to explore the permeability performance of the aquifer in the process of sand loss from the point of view of the force movement of sand particles,in order to explore the starting mechanism of water inrush and sand inrush and the sand inrush.The mechanism provides theoretical and experimental basis,and then guides the prevention and control of sand breaking disasters,so as to achieve the purpose of safe resource development and ecological environmental protection.A series of work has been carried out from this:According to the structure of the loosely accumulated sand particles in the aquifer,the parameter "Hiddenness" is introduced to describe the state of the sand particles,the starting behavior of the sand particles is theoretically analyzed,and the theoretical starting water velocity of the sand particles is given,and The starting behavior of sand particles under special accumulation forms is analyzed,and the flow velocity is regarded as the fundamental factor that causes sand particles to start.A water-sand start-up test is designed to discuss the critical conditions for the start-up of sand particles.After testing the starting flow velocity of five groups of samples with different proportions under the three-stage compression displacement,the relationship between the starting flow velocity and the Talbol series n and porosity is given through data analysis,and the starting flow velocity range of the test is given.In order to explore the changes in the internal permeability of the aquifer during the water inrush and sand collapse,the improved variable mass permeability test system was used to carry out variable mass permeability tests by changing the initial porosity,initial water pressure gradient,sand particle size and other conditions,Quantitative analysis of water flow parameters,sand loss,porosity changes and other parameters in the process.In the process of sand loss,the water pressure gradient and flow rate of the sample slowly change from the initial value,followed by sudden changes,and finally stabilized.At the same time,it is proved that the greater the initial water pressure gradient,the greater the initial porosity,and the smaller the sand particles,the greater the possibility of water inrush and sand collapse.With the weakening of hydraulic conditions,the influence of initial porosity on permeability in the whole process increases.Considering the influence of the internal permeability of the aquifer and the crack channel on the water and sand burst,the water and sand gushing test system that can realize the variable channel size is designed,and the water and sand burst with different aperture channels is carried out based on the steady state permeability method.Out of the test.The water and sand flows under different initial water pressure gradients are obtained,and the sensitivity parameter method is used to analyze the hydraulic sensitivity of the seepage process.With the increase of the initial water pressure gradient,the peak value of the hydraulic sensitivity curve for each channel size gradually increases,and the peak time will also advance with the increase of the channel size,and its early performance becomes more obvious with the decrease of the initial water pressure gradient.On the basis of the previous experiments,comprehensively use the capillary model assumptions and model permeability equations,consider the changes in the porosity and permeability of the aquifer structure caused by the loss of internal sand particles,and introduce the capillary permeability equation,tortuosity,specific surface area,etc.Contents,the model was revised based on the test data,and the dynamic permeability model of the aquifer was established.Substituting the critical flow velocity results obtained from the sand initiation test into the model equation to solve the problem,the sand initiation conditions under different initial water pressure gradients are understood in the form of porosity conditions,and the interval where the critical porosity is located is given by mathematical analysis.It can provide a reference for index selection in the actual process of aquifer reformation.