Research And Application Of Smooth Blasting Technology In Xiong Chong Tunnel

Smooth blasting technology has been proposed for more than 60 years,Has been widely used and developed.Smooth Blasting Technology is a Kind of Controlled Blasting,Smooth contours can be formed after blasting.It will not cause large disturbance to the surrounding rock.It is used more in tunnel excavation projects.XiongChong Tunnel is a large-section deep-buried double-hole tunnel,It is one of the Highway construction tunnels around Wuzhou,The surrounding rocks are siliceous sandstones,joints and fissures are developed,and some sites are highly weathered,with poor integrity.Blasting effect is not ideal,resulting in a lot of economic losses.This paper aims to study the application of smooth blasting technology for Xiongchong tunnel,The research methods and applications of smooth blasting technology in Xiongchong tunnel are introduced.Firstly,the rock breaking mechanism during blasting was analyzed theoretically.The process and law of crack initiation,propagation and crack arrest of surrounding rock in the three major theories of explosion stress wave superposition theory,explosion gas action theory and the interaction of stress wave and explosion gas are introduced.Based on this,the principle of smooth blasting is explained.The factors affecting the smooth blasting technology,such as the peripheral hole spacing,the coefficient of non-coupling,the thickness of the smooth blasting detonating layer,the density of the charge line,the length of the plugged hole,and the charge structure,were analyzed.Provide guidance for selection of parameters for subsequent smooth blasting test.Then the geological conditions of the surrounding rock of Xiongchong tunnel were investigated,relevant data were collected,the distribution of joints was statistically analyzed,the distribution law of joint fractures in surrounding rock was found out,and the full-section excavation method was used to conduct tests according to the condition of surrounding rock.The thickness of the smooth blasting detonating layer,the density of the line charge,and the distance between the Peripheral holes are the major factors affecting the smooth blasting.According to the requirements of orthogonal test principle L9(33),9 groups of experiments were designed.It covers 3 factors and 3 levels of main tests,and the design is scientific and reasonable.According to the calculation formula of hole network parameters.Taking into account the actual situation of the Xiongchong tunnel,select a reasonable value of the hole network parameters.using detonating cords and other blasting equipment for testing.After the test,Data collected after the test.ANSYS/LS-DYNA software was used to simulate the blasting process of the smooth blasting detonating layer in Xiongchong tunnel before the experiment,and the fracture extension map and stress cloud diagram at each time step were obtained.To study the damage process of surrounding rock during smooth blasting of Xiongchong tunnel.The smooth blasting test of the Xiongchong tunnel was carried out under strict control of the accuracy of the pore network parameters,and the test was successful.The average value of overbreak and underbreak is 13.1cm,and the average semi-pore rate is 71%and all results are greater than 50%.All indicators meet the expected requirements.The analysis of simulation results of blasting blasting shows that the cracks developed in the interior of the smooth blasting detonating layer,and the blasting of the cracks on the Overlying surrounding rocks is weak.Multi-objective grey decision-making was used to process the test data.The pros and cons of each test parameter were compared to find out the best parameter combination and determine the optimal pore network parameter selection range.The best perimeter hole spacing is 45-50cm,the best smooth blasting detonating layer thickness is 49-59cm,the best line charge density is 0.16-0.20kg/m,and the best shot hole density coefficient is 0.8-0.85.After the new drilling parameters were applied to tunnel excavation,the economic benefits and safety were greatly improved.