Research On Damage Control Of Underwater Drilling Blasting Based On Energy-Relief Blasting Technique

As an efficient and convenient excavation method,blasting has been widely used in underwater engineering.Since blasting will destroy the foundation surface of underwater rock masses and seriously affect the stability of the bedrock,there is an urgent need to propose an underwater blasting damage control technology.At present,the energy-relief blasting technique has carried out relevant model tests and engineering applications on land,and has achieved good results.Whether energy-relief blasting technique can be applied and how it can be applied to underwater drilling and blasting is a theoretical and practical problem that needs to be solved urgently in blasting engineering.In order to study the Damage mechanism of the rock mass under the underwater energy-relief blasting technique,firstly,the influence of water medium on Underwater Energy-relief blasting is analyzed theoretically.Then,with the help of water medium explosion container,the underwater energy-relief blasting with different charge is simulated and compared with conventional blasting.piezoelectric wave-based method was used to detect blasting damage at different positions of the rock mass model,and the blasting damage index at the measuring point was obtained combined with energy analysis.At the same time,the damage distribution of the rock mass model using energy-relief blasting technique is obtained through numerical simulation research.The main research results are as follows:(1)Theoretical analysis shows that when the underwater energy-relief blasting technique is adopted,the water medium in the blasthole,the energy-relief structure,and the loose sand cushion in the blasthole can consume and transform part of the explosive energy acting on the bedrock at the bottom of the blasthole.The underwater energy-relief blasting technique can theoretically control the blasting damage to the bedrock(2)Damage test results show that compared with conventional blasting technology,energy-relief blasting technique can reduce the damage of the bottom of the blasthole by33%.The attenuation speed of the damage index of the specimen using the energy-relief blasting technique on the vertical axis of the blast hole is significantly greater than that of the conventional blasting technique.(3)Experiments show that the damage index obtained by the piezoelectric wave method combined with energy analysis can truly reflect the blasting damage of the model.The blasting damage index of the model will increase with the increase of the charge,and the damage at a certain point of all specimens is inversely proportional to the distance from that point to the blast hole.(4)The numerical simulation results show that,on the cross section of the blast hole,the damage distribution presents a circular distribution with the center of the blast hole.The results show that the damage index and damage distribution range of the specimen will increase with the increase of the charge;the energy-relief blasting technique can reduce the damage of the bottom bedrock by 30.05%,and the damage attenuation speed of the energy-relief blasting technique on the vertical axis of the blast hole is higher than that of the conventional blasting technology.Numerical simulation results are basically consistent with experimental results.(5)According to the "Technical Specification for Excavation Engineering of Rock Foundation of Hydraulic Structures",it is found that energy-relief blasting technique can reduce the damage area at the bottom of the blast hole by 39.35% by numerical simulation damage nephogram.At present,the research results have been applied to the "Blasting Project of the Main Tower Foundation on the Jintang Island Side of the Xihoumen Road-Rail Bridge of Yongzhou Railway".