Deformation And Stability Of Columnar Jointed Foundation And Reinforcement Mechanism Of Super-High Arch Dam

Adaptability of foundation rock mass is of great significance for safety and stability of super-high arch dam.In terms of columnar jointed rock mass,the mechanical properties and those impacts on the engineering foundation have drawn widespread attention,which is one of the hot topics in area of rock mechanics and engineering and hydraulic structure.To protect the quality of foundation surface and overall stability of arch dam,it is worth researching the mechanical properties of columnar jointed rock mass,as well as the evolution law of unloading relaxation.In this dissertation,to reveal the deformation and stability of columnar jointed foundation and reinforcement mechanism,the structural and mechanical properties and equivalent continuum model of irregular columnar jointed rock mass are analyzed.The unloading relaxation characteristics and mechanisms of columnar jointed foundation are further studied,as well as field reinforcement control and overall stability of arch dam.The main results are concluded as follows.(1)A new method for constructing irregular columnar joints network is proposed.Based on the geometry features of columnar jointed rock mass,a new method for producing irregular columnar joints network with different regularity is proposed using Lloyd relaxation,regularity index and vertex merging algorithms.Based on the field statistics of columnar joints,the irregular columnar joint network is successfully produced using key geometry indexes,such as average diameter of columns,the distribution of side numbers and side lengths.With analysis of discrete element method and joint deformation tensor,the irregular columnar jointed rock mass shows transverse mechanical properties and the stable size of equivalent mechanical parameters is 3 m×3 m.(2)An equivalent continuum model of irregular columnar jointed rock mass is proposed.Based on the equivalent method of joint deformation tensor,the random joints in the irregular columnar joint plane are reasonably simplified into three joint sets and the equivalent deformation parameters of joints are determined.Under the framework of equivalent compliance,the equivalent continuum model consisting of persistent and nonpersistent joint sets is proposed considering the joint space and connectivity rate,as well as the corrected coefficients for stress concentration and shear strength of staggered joints.The proposed model is verified to describe the anisotropic characteristics of irregular columnar jointed rock mass compared with discrete element method and field results.(3)The unloading relaxation and reinforcement control mechanisms of columnar jointed foundation are revealed.Four types of unloading relaxation characteristics of columnar jointed foundation are summarized.Using the equivalent continuum model,the unloading relaxation degree and mechanism of columnar jointed foundation are analyzed based on monitoring and excavation simulation.Different reinforcement measures are verified for preventing unloading relaxation of columnar jointed foundation and for overall stability of arch dam.Considering the stress condition of foundation surface and the state of transverse joints,the optimization time of consolidation grouting at riverbed foundation is suggested in early period of dam construction.The relaxed rock mass at the riverbed has little influence on the stress status of corridors close to the foundation confinement zone,and the overall stability of arch dam meets the requirement.