Study On The Damage And Rupture Repair Of Shaft Lining Concrete

As the main throat connecting the ground and the underground in mining,the vertical shaft plays the role of transportation channel and enclosure structure.Therefore,ensuring its safety and stability during service is important for coal mining and the reuse of underground space in abandoned mines in the future.Very important meaning.The thick topsoil causes the upper soil layer to consolidate and settle due to the drainage of the stratum,thereby generating a vertical additional force acting on the outside of the shaft wall.As the soil layer continues to settle,the vertical additional force gradually increases,and cracks occur in the concrete of the shaft lining,causing damage to the concrete of the shaft lining.As the cracks propagate and penetrate,the shaft lining begins to appear macroscopic cracks,deformations and even ruptures.In this paper,the fracture of the shaft lining concrete is taken as the dividing line,and the evaluation method of the damage state of the shaft lining concrete before the rupture and the repair method of the shaft lining after the rupture are carried out research.This paper studies the damage evolution model of the concrete in the cylindrical structure of the shaft wall by establishing a theoretical model and laboratory tests.Subsequently,the repair effect of the rebuilt shaft wall repair method based on the inner wall restraint method was studied and evaluated through the methods of engineering application,field measurement,indoor test and numerical calculation.The main research work and results of this paper are as follows:(1)Based on the equivalent strain theory of damage mechanics and Weibull distribution,the structural parameters of the inner and outer diameter of the cylinder and the initial elastic non-damage are considered into the equation,and the damage evolution equation suitable for the force state of the cylinder structure is obtained.After comparing the conventional triaxial compression test curve of the sandstone cylinder in the literature with the theoretical calculation curve,it is found that the two have a good agreement before the peak stress,and the two curves after the peak stress are quite different.Subsequently,the parameter analysis of the damage evolution equation was carried out,and it was found that increasing the inner diameter(diameter-thickness ratio)would promote the damage evolution process,and increasing the confining pressure would inhibit the damage evolution.In addition,it is also found that the diameter-tothickness ratio and confining pressure have little effect on the peak damage of the sandstone cylinder at the moment of peak strain.(2)Through analysis,the extremely long shaft wall structure is simplified into a concrete cylindrical structure sectioned along the depth under equal confining pressure.By adjusting the confining pressure of the cylindrical sample in the chamber,it is similar to the radial and circumferential stress distribution along the wall thickness of the shaft wall at vertical depths of 100 m,125m,145 m,and 165 m.Without considering the size effect,pass The indoor concrete cylinder triaxial compression test has obtained the approximate damage evolution curve of the shaft wall concrete at the vertical depth of 100 m,125m,145 m,and 165 m.It is found that similar to the results of the sandstone cylinder sample,the peak damage degree of the concrete cylinder at the peak strain moment of triaxial compression under different confining pressures changes little.Therefore,for the shaft lining concrete at different depths,a unified peak damage degree can be used as the shaft wall Early warning value of concrete damage.For practical engineering applications,the vertical strain can be obtained by the sensors installed inside the concrete of the shaft wall,and the damage state of the concrete here can be obtained.(3)Aiming at the fracture of the main shaft lining of a Coal Mine,the reconstruction method of the shaft lining based on the inner wall restraint method was applied,the reinforcement mechanism and characteristics of this method were analyzed,and the construction technology and construction process were given.In addition,a monitoring system for the deformation of the rebuilt shaft wall was established,and strain data of the rebuilt shaft wall was obtained.Through the analysis of the monitoring data,it was found that the overall force of the rebuilt shaft wall was relatively stable.In addition,using the vertical strain data and the damage evolution equation in the previous chapter,the damage evolution curve of the concrete shaft lining at the three corners at a vertical depth of 150 m is obtained.The damage evolution curve can be more intuitive to find the shaft lining.Continuous vertical compression,the degree of damage D continues to increase.(4)In order to study the shear resistance of the bonding interface in the method of repairing damaged shaft walls with grouting concrete,direct shear tests of the bonding interface of composite specimens under different normal pressures and ages were carried out.It is found that the shear strength increases with the increase of the normal stress,and the relationship is basically linear.The shear strength of the bonding interface between grouting concrete and old concrete shows obvious early strength.The average shear strength of 3d and 7d can reach 70% and 85% of the 28 d shear strength respectively.Therefore,the grouting concrete and the original shaft wall concrete have better adhesion.(5)In order to study the influence of the method of rebuilding the shaft wall based on the inner wall restriction method on the stress state of the shaft wall.Based on the engineering background of the reconstruction method of the shaft wall of the Xuzhuang Coal Mine's inner wall restraint method,numerical calculations have been carried out.It is found that this method has obvious effects on the improvement of the radial and circumferential stresses of the inner wall concrete,but it has a significant effect on the main factor causing the shaft wall damage.The stress has basically no effect.However,considering that this method has the advantages of convenient construction,short construction period,simple materials,etc.,this method still has a good repair effect for projects that require short-term emergency reinforcement of the shaft wall.