Study On Deformation Law Of Shaft Lining In Pore Water Bearing Rock

It is a growing issue that high-pressure pore water can lead to increasing damage to shaft lining structure in porous rock aquifer with the increase of burial depth.In order to improve the design theory of underground structure lining in water-bearing rock stratum,hydraulic load of underground structure in water-bearing porous rock was studied by means of numerical calculation and physical simulation based on existing researches on this problem.Study results are shown as follows.Firstly,the influence of different mechanical parameters of surrounding rock and different lining on pore water pressure has been studied.Impacts of lining size,elastic modulus and Poisson's ratio on pore water pressure were obtained by the two dimensional plane strain model built in Abaqus software with its pore pressure unit.The results show that,the greater the ratio of elastic modulus between surrounding rock and borehole wall structure(the greater the elastic modulus of surrounding rock),the smaller the equivalent hydraulic load of pore water pressure acting on the wall surface;the thicker of the borehole wall structure and Poisson's ratio of surrounding rock obey the inverse relationship with the equivalent hydraulic load is inverted.By comprehensive comparison,the influence of elastic modulus on the equivalent hydraulic load of shaft lining is the biggest,the influence of sidewall size is the second,and the least one is Poisson ratio.Secondly,the hydraulic load on shaft lining caused by pore water pressure was studied.Based on the similarity theory,a large-scale model test was designed,the actual bearing force of underground structure was preliminarily simulated.In the model test,independent loading of ground pressure or pore water pressure has been completed,and The change law and numerical level of pore water pressure were mastered with the inversion calculation.The load on the wall structure in the stable water rock mainly includes the pore water pressure and earth pressure.The pore water pressure often have different forms,under various contact conditions,the equivalent pore water pressure loaded on the wall structure are very different.When surrounding rock touch with borehole wall,the hydraulic load on shaft lining structure caused by pore water pressure is obviously lower than hydrostatic pressure,about 30% of hydrostatic pressure.Under the condition of the surrounding rock and borehole wall are stripped,the pore water will be quickly filled with stripping zone,the load on shaft lining is about hydrostatic pressure.In this case,the wall is in a non-uniform stress and unstable state.The main factor causing the shaft lining failure in stable water bearing rock stratum is the high pore water pressure,because of the high self-bearing capacity of this stratum.During the restoration of pore water pressure in surrounding rock,local delamination may occur between the borehole wall and surrounding rock and could become ‘destroy weak surface' as this area of the borehole wall bear larger hydraulic load.The fracture mode of the borehole wall in water-bearing porous rock is dominated by local seepage and broken water.This study innovatively used distributed optical fiber to continuously monitor the spatial strain of shaft lining,which improved the precision and stability of testing as well as greatly reduce the wiring.Through this experiment,we got the experience in application of distributed optical fiber to large scale geotechnical engineering,and it is beneficial to further expand the application prospects of distributed optical fiber testing system.Finally,according to the research results above,useful conclusions were put forward for the design theory of the shaft lining structure in the water bearing rock stratum.Hydraulic load is the key factor to be considered in the design of lining structure.The hydraulic load is less than that of hydrostatic pressure when the borehole wall and surrounding rock are not stripped.Therefore,the design of mine shaft lining should consider reasonable strength and rigidity,which could not only ensure sufficient stability and no stripped happened between the wall and surrounding rock,but also significantly reduce hydraulic load.