Mechanism And Technology Of Lake Mud Paste-Slurry And Grouting Wall For Large Karst Cave In Chengmenshan Copper Mine

In the process of mining,especially for karst mines,groundwater is often a problem that must be solved,and if improperly treated,it’s very likely to lead to sudden water,sudden mud and other disaster problems in the mining process.Slurry curtain is often used in engineering to treat karst groundwater.However,when the cavity volume is too large,the traditional slurry curtain treatment results in serious slurry loss,large grouting volume,high cost and difficulty in achieving good water plugging effect.To this end,this paper takes the mining area of Chengmenshan copper mine as the engineering background,in order to deal with the engineering condition of large caverns in the mining area,combined with the widely distributed local lake mud,proposed a new technology of slurry curtain wall formation,developed a paste slurry based on lake mud,determined the key performance parameters of lake mud curing paste,explored the strength growth law of the curing paste,quantitatively analyzed the interrelationship between the slurry parameters and slurry shape of lake mud curing paste,proposed a slurry curtain engineering design scheme for large karst cave in the mining area,and obtained a new technology of large karst cave water treatment and its slurry selection,slurry parameters,etc.The main research and findings of this paper are as follows:(1)Based on on-site research,this paper analyzed the hydrogeological conditions of the Chengmenshan copper mine and its characteristics of groundwater control in different mining stages,proposed the technology of lake mud paste-slurry and grouting wall for large karst cave,and conducted a feasibility analysis.According to the geological data in the area and the investigation of gushing drainage in mining,the key parameters of the technology of lake mud paste-slurry and grouting wall were analyzed with the existence of large caverns:the plastic strength of the grouted wall reaches 2 MPa,and the effective thickness of water stopping curtain wall should be greater than 6 m,to meet the resistance of 200 m head difference sealing needs.(2)This paper formulated curingpaste with lake mud as the main body,which configured in proportion to lake mud,cement,thickener,early strength agent,etc.The properties of the paste such as plastic strength,initial and final setting time were tested through indoor tests,and an evaluation system of curing paste performance was established:to ensure the application of lacustrine curing paste,the density of lacustrine base slurry should generally be greater than 1.2 g/cm~3and should not exceed a maximum of 1.45 g/cm~3;to better ensure the molding effect of the paste in the grouted wall,plastic strength was used as a key parameter to determine the ratio of the paste;during the curing of the paste,the early plastic strength value of the paste system mainly depended on the density of the base paste,and the later strength was mainly determined by the cement admixture.(3)Model tests and numerical simulations revealed the control mechanism of the performace of grouting wall for paste-slurry:in the process of paste grouting,the initial plastic strength determined the shape of the curtain wall stack,and the later strength determined the overall stability of the curtain wall;The initial plastic strength of the slurry was less than 20 k Pa to meet the requirements of grout pumping,and the plastic strength was more than 500 Pa to form a more stable wall.A control mechanism for grouting under paste water was established,which considered that the flow rate of the initial slurry outlet directly affected the effect of slurry dispersion under water,and the larger flow rate of the outlet would be easy to disperse,and controlling the flow rate of the outlet at the early stage of slurry injection could ensure the anti-dispersion ability of the slurry under water and avoided the slurry dilution caused by the violent relative motion of the slurry-water interface,which can effectively reduce the loss and consumption of slurry.Based on the research results,it proposed that it is advisable to ensure the effect of grouting into the wall by adjusting the early strength agent admixture,the height of the slurry outlet,and the appropriate slurry pumping pressure during the construction of on-site grouting into the wall.(4)Based on the results of indoor rheological tests on lacustrine curing pastes,the Herschel-Bulkley model was proposed to describe the rheology of pastes when the paste density was greater than or equal to1.25 g/cm~3,and the rheological instantiation parameters of pastes with different ratios were determined.Based on the Herschel-Bulkley rheological instantiation model,the flow equations and molding control expressions for the lacustrine cured paste slurry were derived.Based on the spherical diffusion theory,the controlling equations of paste grouting stages were constructed,the kinetic law of paste grouting wall formation process was studied,and the three-stage theory of lake mud curing paste grouting wall formation was proposed.(5)Based on theoretical analysis and numerical simulation,the wall stress and stability under hydrostatic pressure were analyzed,and the wall seepage stability was studied.Combined with the hypothesis of large cave in Chengmenshan copper mine,the technical plan of large cave slurry forming wall was designed:The drilling arrangement was analyzed,the slurry ratio design and performance regulation analysis method for large cavern grouting was proposed,and the design of grouting wall forming process and grouting quality testing and control were studied.