| Coal mining in the mining area is accompanied by a variety of safety problems,such as shaft damage,surrounding rock fracture,borehole collapse,sand gushing in the well and other destructive phenomena that affect the stability and safety of shaft engineering construction have occurred many times in many mining areas.The coal mine in the west of Shaanxi Province is located in the Quaternary sand layer,which has the characteristics of loose rock mass structure,high water permeability and no viscosity.Therefore,it is equipped with a drilling rig foundation structure to place the drill bit,bear the drilling rig and maintain the stability of the wellhead to prevent the collapse of the shaft side.However,at present,the relevant research on the foundation of vertical shaft drilling rig in western coal mines is very rare,and the foundation of drilling rig plays an important role in reducing the degree of shaft stress damage,ensuring the work safety in shaft construction and reducing the construction cost of vertical shaft.Therefore,taking the western coal mine drilling rig foundation as the research object to study its structural stress characteristics and optimization has its practical significance,which can provide relevant theoretical value and reference significance for similar projects.Based on the construction of drilling rig foundation shaft in kekegai coal mine,Yulin City,Shaanxi Province,this paper studies the stress characteristics and optimization of drilling rig foundation structure in coal mine by means of theoretical analysis,test and numerical simulation.The main research is as follows:(1)Based on the existing load calculation principle and the analysis of the stress structure of the drilling rig foundation,a new load calculation formula is deduced.Then the example analysis and comparison are carried out,and it is concluded that the variation trend of the calculated value of the derived formula with the wellbore depth is consistent with the distribution law of the earth side pressure of the original formula,which is larger than that of the original formula,and the difference between them is also increasing with the increase of the wellbore depth.After that,by comparing with the soil lateral pressure data of indoor model test,it can be seen that under the same conditions,the calculated value of the derived formula is more consistent with the test data,which verifies the applicability and correctness of the derived formula.Finally,the load calculation formula of drilling rig foundation shaft is obtained.(2)The indoor model test method is used to design the test scheme for the construction under the drilling rig foundation of the return air shaft,and the test results of the stress and deformation of the shaft excavation under condition I(Construction under the lock Foundation),condition II(shaft wall)and condition III(drilling rig foundation structure)are obtained through the test.Then through analysis and comparison,it is concluded that the stress distribution law of the drilling rig foundation shaft is basically consistent with that of the conventional shaft,which increases with the increase of the shaft depth,which is similar to the triangular distribution.At the same time,the stress distribution in the same horizontal section is uniform and the values are consistent.Comparing the maximum stress under different working conditions,it can be seen that the drilling rig foundation structure reduces the stress of the vertical shaft by about 1 / 4 compared with working condition 2.(3)Midas GTS / NX software is used to establish the numerical simulation of the vertical shaft construction process,analyze the data of the finite element numerical simulation of the vertical shaft construction process under working conditions 1,2 and3,and obtain the stress and deformation situation and distribution law under different working conditions.The variation trend of surface subsidence and bottom hole uplift gradually increases with the increase of drilling depth under different working conditions,showing a parabolic distribution.By comparison,it is found that the bottom hole uplift value of condition 1 greatly exceeds the construction deformation specified in the project.The bottom hole uplift of condition 2 is reduced by about 50%compared with condition 1,but still does not meet the allowable value of the specification.Finally,compared with conditions 1 and 2,condition 3 greatly reduces the uplift value and reaches the specified allowable deformation.At the same time,the stress distribution law of working conditions 2 and 3 shows a quasi triangular distribution.After comparison with the stress value of the test results,it is verified that the stress value of the test model should be small,the stress change law is consistent,and it also presents a quasi triangular nonlinear change with depth,which is evenly distributed and consistent in the same horizontal section.Considering some errors and influencing factors,it can be considered that the two results are equal within the allowable range of errors,which proves the accuracy and reliability of the experimental model and numerical simulation,and the research results can be used as a reference.(4)The process of vertical shaft construction under different wall thickness is simulated by numerical simulation software.Based on the original drilling rig foundation scheme,the stress and deformation results of the optimized measures with shaft wall thickness of 0.8m and 1.0m are analyzed.It is concluded that the magnitude of shaft wall stress will increase with the decrease of shaft wall thickness.Compared with the original scheme,the reinforcement with bite pile wall thickness of 1.0m and0.8m can reduce the surface settlement,reduce the shaft bottom uplift by 12%,and increase the shaft wall stress by 16% and 46%.Finally,the comprehensive comparison shows that the wall thickness of 1.0m is the best for the optimization measures of drilling rig foundation structure in this paper,which not only meets the construction safety of the project,but also reduces the project cost and improves the economy.Figure [51] table [10] reference [53]... |
PDF Full Text Request