| Drilling is a mechanized and automatic drilling method for mine shafts to pass through deep,thick,water-bearing,unstable strata,and it is the development direction of deep shaft sinking in the future.With the beginning of the construction of the inlet and outlet shafts of Kekegai Coal Mine by drilling method,more deep shafts will be drilled by drilling method in the western region in the future.However,with the continuous increase in the depth of the wellbore,the quality of filling behind the wall is crucial to the water prevention and control during the use of the wellbore in the future,and has become a technical problem that needs to be solved urgently during the wellbore construction process.For this reason,this paper takes Kekegai Coal Mine’s return air shaft as the engineering background,and carries out the development and engineering application research of the filling material behind the drilling shaft wall of the western water-bearing weak rock formation.Firstly,taking the return air shaft of Kekegai Coal Mine as the engineering background,the Comsol Multiphysics software was used to establish a joint interaction model of water-bearing soft surrounding rock-filling layer-drilling wellbore.Stress has the greatest influence,followed by filling material elastic modulus and filling layer thickness.It is also proposed that the filling layer after drilling the wellbore wall in the western region should ensure a certain thickness,and at the same time choose the filling material with low permeability and high elastic modulus.Secondly,based on the results of numerical simulation analysis,the principle of preparation of filling materials behind the wellbore wall was established,and two filling materials preparation schemes were selected: weighted cement slurry and high-performance micro-expansion cement mortar.Through raw material selection,orthogonal test,and range analysis,the optimal mix ratio of weighted cement slurry is obtained as cement: water: hematite powder: suspending agent: water reducing agent= 1: 0.6: 0.6: 0.015: 0.0125;high performance The optimal mix ratio of micro-expansion cement mortar is cement: water: fly ash: expansion agent: sand:water reducer = 1: 0.47: 0.2: 0.08: 1.5: 0.0128.Subsequently,the durability and triaxial seepage tests were carried out on the three materials of ordinary cement slurry,weighted cement slurry and high-performance micro-expansion cement mortar.Superior to ordinary cement slurry,the two materials have almost no appearance change and mass loss during the erosion process,and the strength loss rate is less than5%.Afterwards,a simulation test of backfilling of the wellbore wall was carried out.The results show that the high-performance micro-expansion cement mortar has a high replacement rate for drilling mud,and the early compressive strength after consolidation is greater than 10 MPa,and the 28 d compressive strength is greater than30 MPa.It has good impermeability,and is a high-quality post-wall filling material.At the same time,the test also found that mud sedimentation is easy to occur in the lower part of the filling section,and the displacement effect is relatively poor,so the height division of the filling section behind the wall is very important.Finally,a verification test of high-performance micro-expansion cement mortar filling was carried out in the return air shaft drilling project of Kekegai Coal Mine,and the construction mix ratio was obtained.The filling work behind the wall of the project site started on March 17,2023,and lasted half a month.At present,the filling work has been successfully completed.The research results of the thesis show that the high-performance micro-expansion cement mortar has the advantages of high strength,high density and good impermeability,etc.,and is an excellent backfill material for drilling wells in weak water-bearing rock formations in western China.Figure [63] Table [50] Reference [83]... |
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