| In many mining areas in some parts of China,there are restrictions of small coal mining on the economic and technical conditions for the production of excellent resources.A large number of high-quality coal resources are left in the small coal mine damage area.After the small coal mine or the upper goaf damage,it is difficult to continue mining,which brings serious damage to the national coal resources and ecological environment.In the process of sublevel mining,it is very difficult to support the sublevel tunnel which passes through the damaged area of small kiln because of the complexity and irregular distribution of the roof surrounding rock.At present,the study on the mechanism of grouting reinforcement of surrounding rock of broken roof is still insufficient,and the cement-based grouting materials are mostly used for grouting.The long setting time and slow increase of strength of this kind of materials are not conducive to the tunneling in a short time after grouting reinforcement,resulting in the tension of replacement of mining engineering.In order to reveal the diffusion mechanism and structural strengthening characteristics of C-S slurry in the grouting reinforcement of the surrounding rock of the broken roof,taking the main mining 2~#coal seam of hanzui coal mine as the research object,the diffusion mechanism and reinforcement characteristics of C-S liquid slurry in broken coal and rock mass are studied by means of laboratory test,theoretical analysis and numerical calculation in this paper,so as to demonstrate its reinforcement effect on the broken roof surrounding rock in the stope or roof broken area.The main contents and achievements of this paper are as follows:(1)Apparent viscosity of C-S slurries with different water cement ratio and silicate concentration was determined by rotary viscometer.The results of viscosity time-varying test showed that the apparent viscosity of the C-S slurry was a power function of time,and the apparent viscosity of C-S slurry increased with time.Through the comparison of the average gelling time before and after the critical value,based on the ratio limit of‘thick slurry and diluted liquid',the critical ratio of W/C=0.4,V_w:V_p=3.5 to determine the gelling time was obtained.Under the condition of critical ratio,the compressive strength reached 13.03MPa on the 28th day,and the peak strain was 5.16%,that is to say,the stone body showed strong deformation resistance.(2)By using the self-designed one-dimensional visual C-S slurry grouting test system for broken coal and rock mass,this paper revealed the influence of grouting parameters such as grouting pressure,grouting rate,grouting volume,page rising rate on the diffusion radius and mechanical properties,and the stage of seepage change.Based on the analysis of pore filling with different diffusion radius by MATLAB,it was found that the filling porosity meets the rule of increasing first and then decreasing,that is,the front-end density was large and the back-end density was small.The interface structure of different grouting pressure and diffusion radius is studied by means of meso test,and the influence degree of diffusion radius and grouting pressure on the consolidation capacity of C-S slurry was revealed.Through the strength test,the influence degree of the diffusion radius and grouting pressure on the structural strengthening under one-dimensional condition was revealed.(3)By using the self-designed three-dimensional deep buried C-S slurry grouting test system,this paper revealed the influence of grouting parameters such as grouting pressure,grouting volume and grouting rate on the diffusion radius and mechanical properties under the condition of deep buried.Based on the comparison and analysis of one-dimensional data,the influence of three-dimensional deep buried state on the diffusion radius and mechanical properties of double liquid grouting was revealed.Through the data analysis of the three views,the power function relationship between the diffusion radius and grouting pressure,as well as between grouting pressure and grouting volume was revealed.Through strength test,the influence degree of diffusion radius and grouting pressure on structural strengthening under three-dimensional deep buried condition was revealed.(4)On the basis of the data obtained from the laboratory test,the influence of three-dimensional single hole and C-S slurry grouting pressure on the diffusion radius and the influence of three-dimensional double hole grouting pressure and distance between grouting holes on the diffusion radius and structural strengthening were studied by using the method of COMSOL numerical calculation and considering the time-varying viscosity of C-S slurry grouting.On this basis,the influence of grouting pressure of three-dimensional single row group holes on the diffusion law was explored.The influence degree of the distance between the grouting holes of three-dimensional double row group holes on the diffusion law and reinforcement characteristics was revealed.(5)Combined with the actual pre grouting reinforcement scheme of goaf sections,COMSOL numerical calculation method was used to reveal the position of weak structural plane and the degree of interaction between grouting sections in different grouting sections,analyzed and demonstrated the feasibility and reinforcement effect of the pre grouting reinforcement scheme of broken coal and rock roof.This dissertation includes 96 figures,24 tables and 102 references. |
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