| With the rapid development of China’s economic construction and the construction of a large amount of infrastructure,a large number of underground chamber projects with characteristics such as large span and high side walls have been built in the fields of underground mining,underground power plants of hydropower stations,large national defense facilities,and underground nuclear waste storage warehouses.Choosing reasonable construction techniques and support measures is particularly important for ensuring construction continuity and safety and stability throughout the entire project period.At present,the anchor support schemes of large underground cavern projects at home and abroad are mostly compared and selected based on engineering analogy method and empirical method,which are limited by such defects as insufficient experience and poor adaptability of crustal stress classification standards.There are many adverse geological damage phenomena such as surrounding rock spalling,unloading rebound deformation,etc.caused by insufficient design support force in the engineering construction.Therefore,establishing a set of system support parameter indicators based on rich design experience of existing projects is of great significance for the rational design of surrounding rock support in large-scale underground chamber engineering.This paper has collected and sorted out the relevant data and anchor support design parameters of more than 50 large hydropower projects that have been built or are under construction at home and abroad,In addition,a detailed analysis was conducted on many factors that affect the efficiency of underground structural fences,and the following main research results were obtained:(1)At present,the strength stress ratio index is often used as the classification standard of crustal stress in large-scale underground cavern projects,which has certain deviation in the actual application process of projects.This paper optimizes the traditional crustal stress classification standard based on statistical relevant engineering data and onsite monitoring data,and proposes an improved crustal stress classification interval.(2)According to the statistical data of systematic support design of underground cavern engineering,the relationship between crustal stress,saturated compressive strength and systematic anchoring measures is analyzed in detail;The index of "strength stress ratio of surrounding rock support" considering the design strength of anchor bolt(cable)is proposed to assist in the classification of crustal stress and the design of systematic anchor support scheme.(3)Based on the BP neural network algorithm and MATLAB programming,an intelligent selection model for anchoring and supporting parameters of surrounding rock systems in large underground caverns is constructed.The expected output values of unknown parameters are obtained by inputting known factors,achieving automatic selection of anchoring and supporting measures for surrounding rock in large underground caverns.(4)By using three-dimensional finite element numerical analysis,the application effects of the anchoring support scheme selected by the intelligent model for the support parameters of the underground chamber surrounding rock system in this paper and the engineering analogy method were calculated and analyzed.Combined with on-site monitoring data,it was found that the system anchoring support parameters selected by the model have good suppression effects in the deformation control of surrounding rock,which is more convenient and time-saving compared to the traditional empirical analogy method,And achieve significant economic advantages. |
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