Study On Multi-phase Multi-field Coupling Mechanism Under Deep Bionic Mining In Western Mining Area

The large-scale coal base in western China is rich in reserves,with the large-scale and efficient mining of shallow resources,some mines have entered the stage of deep mining,and it will be an inevitable trend for shallow and middle-deep mining to turn to deep mining.The overlying rock structure is destroyed by deep coal mining,and the bedrock water enters the working surface and discharges along the water diversion fissures,resulting in the loss of deep water resources,destroying the groundwater circulation system,and then indirectly affecting the groundwater ecological environment.Quaternary phreatic layer is the key aquifer for the survival of surface ecology in the western mining area,and there are no good treatment measures and means at present.However,the concept of coal-water bionic co-mining provides the possibility for the protection of deep groundwater resources and the reduction of surface ecology.In this paper,by constructing a "flexible isolation layer",modelling the pre-harvest relationship between the surface ecology and ecological sustainability requirements,transforming the mining destruction transmission zone,controlling the impact range of mining fissures,maintaining or reconstructing the water environment conditions that satisfy the natural groundwater circulation and surface ecology.The post-harvest groundwater and surface ecology can be maintained or even better than the "original state".At the same time,the water resources of deep bedrock fissures are liberated by mining fissures to explore the law of "initiation-expansion-penetration" of overlying mining fractures and water diversion fissures induced by bionic mining in deep coal seams.The evolution process of flexible isolation layer constructed by bedrock grouting in the lower part of aquifer and the coupling law of stress field,crack field and seepage field of overlying strata are analyzed,and the coupling mechanism of multi-phase and multi-field in bionic mining under different deep conditions is studied.To achieve safe exploitation and comprehensive development and utilization of groundwater,so as to achieve the purpose of protecting surface ecology.The main results are as follows:(1)Based on the similarity theory and block theory,it is proposed for the first time to build a similarity model through modularization,and consider that the traditional similarity model has the advantages of easy side collapse,non-repeatability,material waste,long test cycle,cumbersome process,high laying process requirements,labor Due to the disadvantages of high strength and other disadvantages,a new set of similar modular experimental materials,techniques and methods for rapid modeling have been designed.The model uses a block substrate as a module and a gel material as an inter-module binder.Among them,the block substrate is composed of A glue(latex),B glue(JS,that is,polymer composite material),cement and It is composed of quartz sand and additives,and the cementing material is a mixture of fine sand,gypsum,and white powder,that is,additives;through the production of new material modules with different ratios and experimental specimens of cementing materials,compression and shear resistance were developed respectively.The physical and mechanical properties and electron microscope scanning test analyzed the compressive strength,elastic modulus,internal friction angle and cohesion of the new material,and optimized the mixing ratio of similar experimental materials in bionic mining.(2)In order to control the influence range of mining fissures more effectively,the stress load of overlying rock in the upper part of isolation layer is determined by using the calculation method of Taishagji vertical ground pressure,and the analytical solution of the thickness of "flexible isolation layer" is solved by using the theory of elastic foundation beam.Which provides a theoretical basis for calculating the thickness of the isolation layer in the new similar simulation experiment.(3)Using the new similar simulation experiment method proposed in this paper,a complete similar test platform system of "coal-water bionic co-mining" is established.The technologies such as multi-phase and multi-field coupling bionic mining,deep coal seam mining,isolation layer fracturing and isolation layer grouting are realized.Based on the similar experimental study of the system,the development height and law of water diversion fracture zone in coal seam roof,the pressure step,the evolution characteristics of overlying rock,the fracturing and grouting time sequence of flexible isolation layer and the water blocking effect of post-mining grouting in flexible isolation layer are analyzed.Through the study of multi-phase and multi-field coupling mechanism under deep bionic mining in western mining area,this paper not only expands the understanding of the relationship between deep coal mining,groundwater circulation and surface ecology in western mining area.The proposed new experimental materials and technological methods also provide favorable technical support for follow-up industrial experiments and industrial applications,and have important reference value.