Experimental Study On Hole Sealing By Slitting And Grouting In Rock Drilling

Gas drainage is not only the main measure to solve coal mine production safety and prevent coal and gas outburst but also an effective means to develop and utilize gas energy.The key technology affecting the effect of gas drainage is borehole sealing.On the basis of previous studies,according to the actual situation of gas drainage in Baiping Coal Mine of Zhengzhou coal group,and drawing lessons from the new hole sealing technology of gas drainage,drilling and sealing integration proposed by predecessors,this paper prepares borehole slit samples in the laboratory,and verifies that the borehole slit sealing technology can effectively reduce gas leakage and improve the extraction rate based on grouting test and permeability measurement test.At the same time,considering the stress state of Baiping Coal Mine after borehole sealing,the triaxial compression acoustic emission synchronous test is carried out,the full stress-strain curve and acoustic emission signal characteristics are obtained,and the mechanical characteristics of triaxial compression failure of grouting body formed after borehole sealing are analyzed.Using a micro industrial CT scanning system,combined with image processing technology,gray histogram,fractal theory and other methods,the characteristics of hole fracture network of grouting instability and failure under triaxial stress loading are analyzed qualitatively and quantitatively.Based on CT scanning data,three-dimensional numerical models including CT number and pore fracture distribution information are established through different methods,and the bridge between digital core and finite element analysis software is built to complete the interaction of data information.On this basis,permeability numerical simulation is carried out.Around and based on the above research,the main conclusions are as follows:(1)Innovatively proposed a new type of sealing technology integrating gas drainage,drilling and sealing,using a self-made grouting system to carry out grouting and sealing tests,and tested different numbers of slits and permeability of samples before and after sealing Changes.The slurry in the annular slot of the drilled hole is consolidated to form a sealing disc,which can effectively reduce air leakage.big.Excessive grouting pressure will destroy the intermolecular force of the sealing slurry,causing the slurry to lose water and form "cavities" in the borehole.(2)Under the condition of triaxial stress,the full stress-strain curves of the sealed samples all experienced a short crack compaction stage,a long elastic deformation stage,a plastic deformation stage,a peak failure stage and a post-peak residual deformation stage.When the axial deformation is larger than the axial deformation,the acoustic emission signal intensity of the sample is much higher than that in other stages during the instability failure,and the sample exhibits shear failure characteristics.(3)Micro-industrial CT scanning system is an effective technical means to study the instability and failure characteristics of sealing and drilling.It combines image processing technology,gray histogram,fractal dimension and equivalent pore network model to realize A description of the pore and fracture network characteristics of the damaged sample from a microscopic point of view.The analysis shows that the slits have a guiding effect on the development and expansion of the fractures of the samples.With the increase of the number of slits,the fracture rate and the three-dimensional fractal dimension of the damaged samples increase linearly,while the Euler number decreases linearly.(4)Both the 3D numerical model containing the CT number distribution information and the 3D numerical model containing the pore and fracture distribution information can fully display the real structural characteristics of the sample;COMSOL Multiphysics is used to simulate the permeability based on the 3D numerical model containing the pore and fracture distribution information,the simulation results are more accurate,the distribution of permeability is consistent with the distribution of pores and fractures,the more developed the pores and fractures,the greater the permeability.There are 73 figures,11 tables and 94 references.