Deformation And Failure Mechanism Of Surrounding Rock In Underground Double Caverns Based On Discrete Element Method

With the development of cities and the advancement of science and technology,relying solely on ground engineering projects has been unable to meet the needs of modern society.People are paying more and more attention to the development and utilization of underground space.Because of this,hydropower projects underground powerhouses,diversion tunnels,High-speed rail tunnels,urban rail transit tunnels and other underground buildings have mushroomed.However,the structure of underground buildings is not simple,and the form is not a single one.It does not exist only in a single cavern.It is often in the form of double caverns and caverns.In such a complex underground cavern situation,the surrounding rocks The deformation and destruction mechanism is very complicated.Therefore,it is very important to study the failure mechanism of underground caverns and to predict the form of damage through numerical simulation methods,so as to guide the excavation and lining operations of caverns and greatly improve the economical efficiency,safety and reliability of cavern excavation linings.Therefore,based on discrete element method UDEC software,the displacement response,principal stress distribution and plastic zone distribution of underground double caverns under different geometries and rock masses are simulated.The interaction and prediction between the two caverns are analyzed.The research results also have certain guiding significance for the analysis of the Jinping I underground powerhouse cavern group.The analysis conclusions can provide a certain theoretical basis for the construction and stability analysis of the underground cavern group,especially the double caverns.The research work is as follows:(1)Based on the UDEC software,the numerical simulation of the failure mechanism of the double caverns with different shapes,depths and holes is performed.The analysis found that under the same conditions,the circular cavern is more vulnerable to damage than the gatehole shape,but the deformation of the surrounding rock of the circular cavern is more symmetrical;with the increase of the hole diameter or depth,the stress condition of the cave floor is As a result,the stress on both sides of the cavern deteriorated and the overall stability of the surrounding rock became worse.When the sizes of the cavernous double caverns are small,the double caverns with different diameters are the same size as the double caverns.The chamber is more conducive to overall stability,but it requires special support for the spandrel at the location of the rock pillars.With the increase of the size of the hole,the displacement change value is more significant,which is opposite to the effect of the buried depth;the size of the hole is larger.The difference in the deformation and destruction of the surrounding rock between the double caverns with the same size and size of the double holes with different diameters and the same diameters is smaller.(2)Simulate and analyze the influence of rock mass structure on the stability of the surrounding rock of double caverns.Analysis of the stability of the surrounding rock of double caverns with dip angles and spacings of different joints revealed that the large spacing joints improved the stress condition of the intermediate rock pillars,which was conducive to the stability of the surrounding rock of the double caverns;the dip angle of the joints in the caverns increased,and the double caverns The sidewalls are unfavorable,which is conducive to the bottom of the chamber and the rock pillars.When the joint dip angle is 90°,it is the most unfavorable to the stability of the cavern;Cave stability is not only affected by joint dip and pitch,but also related to the combination of joints and caverns.(3)Combined with the engineering example of the underground powerhouse of Jinping I hydropower station,the excavation simulation of underground powerhouse caverns was performed.It was found that the displacement response,principal stress distribution,and plastic zone distribution were basically consistent with research rules of the double-chamber wall rock failure mechanism.The research result on the failure mechanism of the surrounding rock of the cavern also have a certain guiding effect on the stability analysis of the surrounding rock mass in the underground caver group.