| In recent years,with the deepening of the concept of green environmental protection,hydropower construction is developing rapidly in China because of its green and environmental characteristics.With the profound development of hydropower construction,the construction of hydropower stations will be further advanced to alpine valleys with complex geological conditions.The difficulty in excavation under conditions of narrow space,high ground stress and large sections is increasing.The blasting construction of the long and large section tunnel under high ground stress has become an unavoidable problem.Studying and solving this problem has important theoretical significance on the one hand,and it can also provide experience for similar projects on the other hand.This article takes the excavation of the diversion tunnel of the Jinping II hydropower station as its engineering background.Through theoretical analysis,on-site blasting tests,and collection and analysis of test data,the blasting excavation construction scheme and blasting control measures for high-stress and large-section tunnels under different surrounding rock conditions were studied,and the following results:(1)Through the research and analysis of the diversion tunnel blasting technology scheme,the blasting technical scheme and blasting design parameters suitable for the diversion tunnel of Jinping Project with high geostress,multi-rock burst and large section are proposed.(2)Through field production blasting tests,blasting construction plans and blasting parameters that are most suitable for the current geological conditions,tunnel section geometry and size,and construction equipment are provided for diversion tunnel blasting.After analyzing and studying the results of multiple test results for three blasting schemes for Grade Ⅱ-Ⅲ surrounding rock and Grade Ⅳ-Ⅴ surrounding rock.It can meet the needs of drilling and blasting excavation of the large cross-section diversion tunnel of the Jinping II hydropower station in different surrounding rocks,and achieves better blasting results and construction efficiency.(3)Analyze and study the controlled blasting construction of representative cross-sections such as multi-tunnel intersections,openings,large cross-section tunnels and weak foundations with high geostress and geological conditions.The construction procedures and technical solutions for controlled blasting under high ground stress conditions were obtained.The research results show that the blasting of large-section tunnels under high geostress can be controlled.Only by understanding the characteristics of blasting under high ground stress,and by adopting corresponding control methods,the blasting excavation of large-section tunnels under high ground stress can be completed successfully.The results are worthy of reference and reference for similar projects. |
