Study On Reasonable Horizon Of Grouting Of Horizontal Directional Borehole To Seal Water Flowing Fractured

There is a very thick water-rich Luohe formation aquifer in the coal-bearing strata of Gao Jiabao coal mine.Under the conditions of limited height mining and advanced exploration and water release in the first panel area of the mine,the water inflow in the goaf still reaches about 800m3/h.In order to minimize the water inflow in the mine and reduce the threat of water damage,the water plugging engineering test was carried out by using horizontal directional drilling grouting on the surface to seal the water guide crack in the overlying rock.Due to the different development characteristics of mining-induced fractures in different strata,the different levels of horizontal directional drilling will lead to the retention characteristics of grouting materials in different fracture channels in different layers,thus affecting the final water plugging effect.Therefore,it is very important to study and determine the reasonable horizon of horizontal directional drilling for improving the effect of grouting water plugging.By means of simulation experiment,theoretical analysis and field measurement,the distribution of water-conducting fissure zone in the first panel area of Gao Jiabao coal mine,the development characteristics of fissure exposed by directional drilling in different strata,the characteristics of grouting and the selection of optimal grouting strata were studied.In this paper,the development height of water-conducting fracture zone in overburden rock under different working conditions is studied by using the "height conducting" discrimination method based on the position of key strata and numerical simulation experiment,and the spatial distribution characteristics of water-conducting fracture zone in one working face are obtained.Due to the obvious differences in the development of water-conducting fractures in different regions,the same horizontal directional drilling will expose mining-induced fractures with different development characteristics,thus resulting in different grout flow characterization and sealing characteristics.On the basis of using the physical simulation experiments of different drilling reveal fracture and serous fluid diversion characteristic are studied,the drilling in the drilling process within different strata by mining the lateral to expose of the mining-induced fracture in three typical types: first,the borehole drilling first revealed abutment pressure caused by pressure shear fracture,because of the small opening,communication is bad,so easy to seal;Secondly,it is revealed that the v-shaped upper end tension crack caused by rock fracture rotation has a large crack opening,and the grouting slurry is easy to spread along the fracture plane and difficult to plug.It is revealed again that the inverted v-shaped bottom end tension fracture caused by rock strata fracture rotation is easy to communicate with the lower separation fracture,and the slurry needs to reach the plane diffusion radius in the separation layer to achieve sealing;Finally,closed fractures with small opening in the middle compaction zone are revealed.Secondly,on the basis of the first type,after the borehole reveals the upper end tensile crack,it is possible to reveal the separation crack between the upper and adjacent rock layers due to the perforation.When the grouting slurry blocks such separation crack,it is necessary to make the grouting slurry reach its diffusion radius to achieve smooth drilling.Thirdly,in the region above the water-conducting fracture zone,penetrating drilling is carried out to reveal the abscission fractures.In this region,the abscission fractures have a relatively small amount of closed space,so it is relatively easy to plug the abscission fractures with grouting under this trajectory.Considering the retention capacity of mining-induced fracture to grouting material,the effectiveness of grouting plugging and the reliability of drilling construction,this paper puts forward the method of determining the optimal level of grouting water plugging by horizontal directional drilling.That is to say,the selected stratum should be conducive to the retention of water plugging material in the crack channel without slurry running.Drilling in the corresponding stratum should reveal the main crack channel of water conduction,and the lithology of the drilling strata should keep the wall rock stable.Based on this,the optimal drilling horizon of horizontal directional drilling for water plugging in Gao Jiabao coal mine is determined,which provides a reference for the water plugging project.