Disturbance Effect Of Rock Mass In Layered Blasting Of Deep Buried Underground Powerhouse

At present,the problems of disturbance of surrounding rock caused by blasting load and in-situ stress unloading during excavation of deep underground powerhouses are prominent.Controlling the blasting and excavating unloading disturbance effects to ensure the safety of underground engineering structures is an important issue.Taking the excavation of the deep underground powerhouse of the Pubugou Hydropower Station as the research background,based on the analysis of the stress redistribution of the surrounding rock in the layered excavation of the underground powerhouse,the related problems such as the vibration response of surrounding rock,damage characteristics of rock mass,loose deformation mechanism of jointed rock mass,etc.are studied in the process of layered blasting.Damage characteristics,loose deformation mechanism of jointed rock mass and other related issues.Firstly,the law of vibration of surrounding rock particles induced by excavation of layered blasting of powerhouse was studied.The study found that after the ground stress was unloaded,the peak vibration velocity of the vertical particle along the side wall showed an attenuation law that first increased and then decreased;the particle vibration law of the plant arch ring was affected by its structural shape,and the vibration perpendicular to the airspace surface;The velocity of the arch top peak increases with the increase of the number of excavation layers and then decreases;and after coupling and separating of the excavation loads,it is found that as the number of excavation layers increases,the surrounding rock vibration caused by the ground stress unloading overtakes blasting effect and gradually dominates in coupling?Secondly,a dynamic tensile and compression damage constitutive model of the rock is established,and the material model is embedded through the UMAT secondary development module of LS-DYNA.The blasting load,in-situ stress unloading,and influence of coupled loads on damage distribution of power plant surrounding rock.are analyzed during the layered excavation process.The research shows that during the blasting excavation of a deep buried underground powerhouse,the surrounding rock damage is greatest near the contour of the powerhouse;when the local stress level is low,the surrounding rock damage near the excavation is mainly affected by the blasting load;The damage of surrounding rock caused by blasting load will be restrained by the compression of in-situ stress;in the excavated area,the damage of the surrounding rock is mainly caused by the redistribution of the in-situ stress.Finally,the blasting loose deformation of the jointed rock mass of the underground powerhouse was analyzed.The study found that the loose displacement of the jointed rock mass is mainly provided by the energy generated by blasting,and the joint loosened displacement under the coupling load has a non-linear relationship;when considering only the joint loosening caused by the unloading of in-situ stress,the in-situ stress level,unloading time and the unloading path have an important effect on the joint loosening displacement.Under lateral in-situ stress,loosening of rock mass during blasting excavation in high-stress areas is affected by the friction of lateral parent rock and absorption of explosive energy,and its loosening displacement is significantly reduceds;the lateral stress level increases,the joint loosening displacement is mainly provided by the energy stored in the initial geostress.