Stress Field Inversion Analysis And Safety Evaluation Based On Large Underground Powerhouse

Since the western development,there were more and more construction of hydropower development projects,most of them were developing to the underground.Underground engineering began to tend to the large scale or the giant scale due to the increase of their installed capacity.Stability evaluation of underground engineering had a relation to the construction safety and economic benefit,it always had been the core issue of scholars to study,but the initial tress field and engineering stability were closely linked with each other.Therefore,the research had important practical significance.Based on the large underground powerhouse,the main works of this article were as follows:The three-dimensional model of this region was established,according to the engineering characteristics,using gray regression method and general regression method to calculate,through the analysis based on the grey correlation,grey regression model was superior to the general regression model,whether in the inversion accuracy or in accordance with actual conditions,the adaptability of grey regression method was better.Some typical sections of underground powerhouse was selected,and the displacement monitoring data of sections was contrasted and analyzed,discovered that the change of the displacement was different when in different section,but the difference was small,also the displacement of any section followed a general regularity;excavation sequence changes had a great influence on the displacement of surrounding rock,particularly the first three layers was of the greatest impact;timely support measures could strengthen the displacement of surrounding rock tending to be stable,which laied the foundation for the stability evaluation of engineering.The displacement data monitored by using regression log method and neural network method was predicted and analyzed,from the prediction results found that prediction had the characteristics of high precision and good effect based on the neural network method,also reflected the relationship of changes between the intrinsic characteristics of forecasting object,the response on the variation law of displacement of surrounding rock increasing with time,environment,specific conditions was more precise.The application of neural network method was confirmed that was more widely.The three-dimensional model of underground powerhouse was established,and the excavation and support processes were simulated,so got changes of any layer displacement after excavation or after support.The study found that,as the layers increased,displacement of surrounding rock increased continuously,and the trend of change was from big to small,lasted to the stable state;contrasting change law of excavation and support found that thesupporting effect was obvious,for further expansion of the displacement,it played s role in restraining;points of maximum displacement mostly was in the vault,strengthened the supporting measures in this position could improve its stability.Evaluation element set and evaluation set was set up,weight coefficients were determined according to the expert experience,evaluated that whether it was safety or not by using fuzzy comprehensive evaluation method,mathematical knowledge: the law of maximum membership degree was used to evaluate,these studies concluded that the engineering was in the steady state.The research contents of this paper did provide some reference for construction of similar large-scale underground engineering.