| When the excavation of local projects exposes the water-bearing sand layer and the buildings(structures)are in or need to cross the water-bearing sand layer,the technology of stratum grouting to block water and reinforce stratum is often adopted.However,due to the complexity of the fluid-solid coupling between the sandy soil and slurry,the theoretical research on slurry diffusion mechanism and grouting design at home and abroad seriously lags behind the engineering practice,and related safety accidents often occur due to improper grouting parameter design and construction.Therefore,this paper takes the ground drilling grouting in Guotun Coal Mine as the engineering background,comprehensively adopts indoor test,theoretical derivation,model test,numerical simulation and field engineering application,etc.,and systematically studies the slurry diffusion mechanism of penetration grouting in water-rich sand layer,which has important theoretical significance and application value for guiding the design and construction of grouting parameters in water-rich sand layer.The main work and achievements of this paper are as follows:(1)Based on the physical parameters of the thick sandy soil and water bearing layer samples in Guotun Coal Mine,the sandy soil used in the sand layer permeability test and penetration grouting model test was prepared according to the particle size distribution and the content of cohesive soil.A new test device for sand layer permeability test has been developed.75 groups of sand layer permeability tests have been carried out based on the optimization method of better condition results.According to the test results,a new permeability index formula and criteria that comprehensively consider five factors,namely,sand particle size,cement particle size,slurry water cement ratio,clay content and slurry pressure,have been obtained by fitting.(2)The particle retention mechanism of the deep infiltration effect was expounded at the microscopic scale,and a theoretical model of the mass transformation of the sand skeleton,cement particles and water in the deep infiltration system based on the law of mass conservation was constructed,and the unified solution of space-time variation function of three parameters of cement particle volume fraction,infiltration coefficient and sand porosity in the whole system under the action of deep infiltration effect of penetration grouting was given.It is shown that the porosity of sand increases nonlinearly in the form of “S” with the increase of grout diffusion distance.The influence of different percolation coefficient values on sand porosity has obvious spatial difference,and the area near the grouting tube has the greatest influence.(3)Considering the tortuosity effect of the slurry diffusion paths,a theoretical model of the cylindrical diffusion of the sand layer penetration grouting was established,and the theoretical calculation formulas of the slurry diffusion radius and initial grouting pressure and the distribution function of the slurry pressure in the diffusion area were obtained.Combined with the indoor penetration grouting test data,it was found that the attenuation of slurry pressure shown obvious stages,and the attenuation speed of slurry pressure in the area close to the grouting pipe was significantly faster than that in the area far away from the grouting pipe.(4)Using the self-developed penetration grouting cylindrical diffusion model test device,taking sand particle gradation,grouting pressure and water-cement ratio of the slurry as control factors,6 groups of cylindrical diffusion model tests of penetration grouting of water rich sand were carried out.The grouting diffusion radius is 7.5 ～ 33.5cm,and the theoretical calculation value of the grouting diffusion radius under the test conditions is 6.10% ～ 10.97% larger than the test value,which is smaller than the existing theoretical calculation error.The research shows that during the grouting process,the soil pressure attenuated in the direction of slurry diffusion,and the soil pressure attenuated faster at the position closer to the grouting pipe than at the position farther from the grouting pipe.After stopping grouting,the attenuation speed of soil pressure and pore water pressure is fast at first and then slow.(5)The applicability of the cylindrical diffusion model of radial tube flow was verified by the results of the ground drilling grouting test in Guotun Coal Mine.The theoretical error of initial grouting pressure is -9.41% ～ 13.75% and the theoretical error of diffusion radius is -20.63% ～ -14.50%.The research shows that the grouting pressure attenuates rapidly near the grouting tube and slowly at a distance from the grouting tube.In the first 30% of the diffusion radius,the slurry pressure attenuates rapidly by about 70%,and in the last 70% of the diffusion radius,the slurry pressure attenuates slowly by about 30%;The diffusion radius has a nonlinear negative correlation with the height of the grouting section and the comprehensive injection rate of the formation.The attenuation rate is relatively slow,and there is no obvious stage.(6)The parameter design method of ground drilling grouting for non-stop production of water-rich sand layers around the existing wellbore was proposed.The principle and main points of the grouting hole-pressure relief hole combined intermittent grouting reinforcement technology were described.The layout of drilling holes around the main shaft,auxiliary shaft and air shaft was designed.The theoretical formula of the cylindrical diffusion model of radial tube flow was embedded in COMSOL Multiphysics software.The numerical simulation of the grouting process of main W1 hole,main W2 hole and main W3 hole was carried out.The safety and effectiveness of ground drilling grouting were verified by the monitoring results of vertical and circumferential deformation of shaft wall and horizontal deviation of shaft during grouting of main shaft.Figure [90] Table [38] Reference [171]... |
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