Study On The Seepage Characteristics And Application Of High Pressure Grouting In Micro-fractured Soft Rock Under Deep Mine

With the continuous reduction of my country's shallow coal resources,deep coal mining is the main direction of my country's future coal mine development.In the environment of high in-situ and strong mining stress,there are a large number of fractures in the surrounding rock of the roadway,including large and medium-sized fractures with large fracture openings and micro-fractures with small fracture openings.With the large deformation and continuous rheology of the soft rock roadway,the fractures in the surrounding rock are prone to squeeze and close to form a large number of underdeveloped low-permeability micro-fractures.Conventional grouting support cannot achieve the expected reinforcement effect.This dissertation relies on the national key research and development plan(2017YFC0603004),with deep well micro-fractured soft rock roadway grouting support as the background,through a combination of indoor experiment,theoretical analysis,numerical simulation and field monitoring,the grout in the deep mine micro-fractured soft rock in-depth research on seepage characteristics has been made,and the following innovative research results have been achieved:(1)A series of ultrafine cement slurry characteristics experiments were carried out,and the rheological and stability characteristics of cement slurries with different particle sizes and additive content of superplasticizers,ultrafine fly ash and ultrafine silica fume were obtained.Through the orthogonal test to analyze the sensitivity factors,the proposed addition range of ultrafine fly ash,ultrafine silica fume and superplasticizer was proposed,which provides a basis for the selection of grouting fluid performance for micro-fractured rock masses.(2)Developed a set of test system that can realize micro-fracture high pressure grouting,carried out a variety of ultrafine cement slurries under different grouting pressures and fracture opening conditions,the seepage test research,analyzed the changing law of the grouting pressure and cumulative grouting amount with the opening of fractures,the criterion for the infiltration effect of cement slurry is put forward;the influence mechanism of high-pressure grouting on the infiltration effect is studied,and the minimum injectable fracture openings b_min and the minimum non-infiltration fracture opening b_crit of different ultrafine cements and the law of slurry infiltration under two critical fracture openings were obtained..(3)Based on the fluid-solid coupling effect of grout seepage and micro-fracture deformation,the theoretical model of micro-fracture high pressure grouting percolation is established through the control equations of grout flow and fracture deformation.Based on the step-by-step algorithm,a micro-fracture high pressure grouting process analysis and calculation program was developed on the MATLAB software platform to realize the description of the grout seepage distance and the change of the fracture opening during the grouting process.Numerical experiments on micro-fracture grouting seepage under different grouting pressures and fracture openings were carried out,and the spatial distribution of grout pressure,fracture openings and the variation of grout seepage distance during the seepage process were obtained.(4)Taking the grouting support of deep soft rock roadway as the engineering background,according to the analysis of the influence factors of the roadway deformation and failure characteristics,a deep mine soft rock roadway micro-fracture high pressure grouting support plan was proposed.The grouting time and grouting pressure were considered.The optimization design of grouting parameters,combined with on-site monitoring data,verifies the effectiveness and scientificity of the high pressure grouting support scheme,which provides a reference for the grouting support of deep mine micro-fractured soft rock roadways.The dissertation incudes 83 figures,27 tables and cites 196 references.