Study On The Influence Of Loading And Unloading Wave On The Deformation And Failure Of Deep Underground Caverns

In recent years,with the rapid development of China's economic construction,underground projects have continuously challenged the depth records.In the special geological environment with large depth,in addition to the impact of blasting on the rock mass,the redistribution of the transient stress caused by the strong unloading of the excavation body will also affect the stability of the surrounding rock.These disturbances propagate in the surrounding rock in the form of loading stress waves and unloading stress waves,affecting the safety and stability of the surrounding rock.The influence of blasting loading and transient unloading on the deformation and failure of the surrounding rock is considered from the perspective of the stress wave.From the point of view of the stress wave,it is of very important research value to consider the influence law of blasting loading and transient unloading on the deformation and failure of surrounding rock.This article first summarizes the research status of blasting excavation process of deep rock mass at home and abroad,and briefly describes the basic characteristics of deep underground rock mass and deep cavern.The theoretical analysis of the blast load and transient unloading is discussed.The mechanics model and action process of the charge,and from the point of view of wave dynamics,the stress wave propagation in the rock during the excavation process and the interaction mechanism between loading and unloading stress waves are described.Then,based on the fluid-structure interaction and implicit-explicit continuous algorithm,the finite element software was used to simulate and analyze the influence of the initial ground stress on the blast loading unloaded stress wave in the case of plane strain.The direction has a significant influence on the loading and unloading stress waves generated during the explosion process.The relationship between the initial loading and disturbance and the relative unloading disturbances are quantitatively analyzed.The calculation of the stress amplitude and disturbance time on the initial ground stress is given.The formula provides higher calculation accuracy for subsequent calculations.Finally,with the background of the excavation of the side wall of the underground powerhouse of Baihetan Hydropower Station as an engineering background,using dynamic finite element analysis software,combined with geological site exploration data and blasting monitoring data,the influence of loading and unloading stress waves on deformation and failure of underground caverns was studied.law.The study found that it is very necessary to fully consider the unloading effect when simulating deep rock mass blasting.In actual blasting,the range and magnitude of displacement distortion caused by the superposition of both unloading and stress waves are greater than that of any single factor.The displacement is mainly contributed by the loading stress wave and the impact scope is small,while the vertical displacement is mostly contributed by the unloaded stress wave,and the range of influence is large.In the plastic zone,the plastic deformation of the surrounding rock can be mainly caused by the blasting wave,and the unloading.On this basis,the wave aggravated the plastic failure of the surrounding rock of the cavern.The results of this dissertation have important engineering significance for controlling the stability of surrounding rock in blasting excavation of deep rock mass,reducing the damage and deformation of surrounding rock and ensuring the safety of underground construction.