Research On Structural Stability Of Rock Bolt Crane Beam In Underground Powerhouse

For water resources and hydropower engineering,after many years of exploration and development of engineering practice,the rock-bolted crane beam,as a new type of crane beam,has been widely applied to underground powerhouse of hydropower station because of its many advantages of engineering.With the increasingly widespread application of the crane beam in the underground powerhouse,its influence on the stability of the underground powerhouse is inevitable.However,the design theory and method of the crane beam is not perfect.Therefore,it is very important to carry out the research on the structural stability of the crane beam,which is beneficial to the economic and safety of the construction of underground powerhouse in our country in the future.The conventional design method of rock wall crane beam is rigid body balance method,which can not consider the influence of the excavation of the powerhouse on the stress state of the crane beam and the adhesion of rock contact surface.In view of these shortcomings,this paper uses the three-dimensional finite difference software FLAC3D to study the structural stability of rock bridge crane.The Mohr-Coulomb elasto-plastic constitutive model is used to simulate the rock mass of the underground powerhouse,and the Coulomb sliding contact surface element is used to simulate the rock contact surface.It is achieved to truly simulate the underground powerhouse sub-step excavation and crane beam load applied.Considering the interaction between the deformation and the force of the surrounding rock,the crane beam and the anchor rod,the structure stress and stability of the of the rock crane beam of the underground powerhouse are analyzed comprehensively.The main research work in this paper is divided into the following aspects:(1)Combined with the example of Jiangsu Jurong Pumped Storage Power Station,the initial stress field is analyzed by using the multiple linear regression method.The results show that the lateral pressure coefficient of the horizontal direction has changed greatly due to the shallow depth of the plant and the main transformer hole.(2)The three-dimensional numerical model is established to analyze the influence of the excavation on the surrounding rock,crane beam and anchor,and the deformation and force law are summarized.The results show that the deformation value of the crane beam is mainly caused by the disturbance of the later excavation of the cave,and the internal stress of the beam is unevenly distributed under the excavation of the cave.The maximum tensile stress of the anchor appe,ars in the third row downstream,and the anchor is inserted into the deepest part of the surrounding rock.(3)After the crane wheel is applied to the load,the deformation and stress state of the surrounding rock and the crane beam are calculated and analyzed,and the stress distribution of the bolt is studied.The results show that the displacement and stress increment of the crane beam and the increment of the stress increment of the anchor are not large before and after loading.The load of the crane beam does not change the law of displacement and stress in the construction period.(4)The safety factor of sliding contact stability of rock wall is calculated by self-developed code.In the meantime,this paper realizes the visualization of Point Security(i.e.,the point cloud of safety)to evaluate the stability of crane beam structure from the angle of safety coefficient.The results show that the safety factor of the upstream crane beam(11～13)is larger than that of the downstream(5～6),and the bond mechanical property of the rock wall has an important influence on the overall anti-sliding stability of the crane.