Study On The Technique Of Blasting Vibration Reduction In The Middle Section Tunnel At Hard Rock That Closing To The Existing Building

With the continuous development of China's economy,the urban population density continues to increase,and alleviating urban traffic pressure has become a problem that large cities need to focus on in the process of economic development,forcing the government to invest a lot of money in the construction of urban rail transit.Meet the needs of urban transportation;the metro is an important transportation construction method in the construction of rail transit.At present,many large cities in China are building or are about to build subway tunnels;in tunnel excavation methods,drilling and blasting method is a common construction method.This is because the drilling and blasting method is considered to be the most suitable construction method for hard rock areas in terms of economy,technology,and other technical aspects;however,the drilling and blasting method is inevitably accompanied by strong earthquake effects.It has an adverse effect on the existing building structure and stability on the ground and may even result in damage.In particular,in the case of existing buildings,excavation of medium-section tunnels in hard rock areas will have higher requirements for the control of blasting vibrations.This will allow conventional emulsification.Explosive blasting excavation method can not meet blasting vibration effect control requirements,must seek other excavation tunnel construction that meet the requirements of the subway tunnel;imported from South Korea SWELLNEX metal expanders can be well controlled blasting vibration effect.Meet the requirements of excavating subway tunnels in the construction environment of existing buildings.This article relies on the underground construction of the underground excavation section of the Qingdao Railway Station on the third line of the first phase of the Qingdao Metro Line 3.This section passes through the existing Metro Line 2 station and the Yiqun underground shopping mall,which is the front station interval and transfer path.The floor of the existing building is close to the adjoining surface of the tunnel,and the tunnel roof below the main section of the Metro Line 2 station is even close to the floor of the 2nd line,and the surrounding rock is disturbed during the excavation of the subway line 2 in the early stage.The integrity of the surrounding rock has been reduced,and the blasting vibration effect needs to be strictly controlled.There are many methods of tunnel blasting excavation using the drill-and-blast method.This paper mainly studies the explosive blasting method,metal expansive blasting method and static crushing method.By combining the theoretical analysis with the field test,the advantages of metal expansive blasting excavation method and static crushing method in blasting excavation method are summed up,and the construction details that need attention during use are summed up;The explosive blasting excavation method and metal expansive blasting excavation method have their own advantages in the aspects of blasting vibration damping effect,and are compared and verified with actual monitoring results on the spot.The specific research content can be summarized as the following aspects:(1)For the safety assessment of existing buildings and surrounding rocks,according to the safety standards for the control of blasting vibration effects at home and abroad,in conjunction with the construction environment of Qingdao Metro Line 3,the corresponding blasting under the construction environment of the tunnel project studied in this paper is formulated,vibration speed safety standards.(2)Explosion excavation tests of metal expansive agent and static crusher are conducted at the construction site,and the blasting vibration velocity is monitored in real time to observe the crushing effect of the surrounding rock.Two types of blasting modes are summarized and the advantages and disadvantages of the two types of blasting excavation are analyzed.As well as construction details that need attention during construction,it is concluded which blasting method is more suitable for tunnel blasting excavation construction in the construction environment studied here.(3)In order to ensure that the proposed blasting safety vibration rate can be met and the desired tunnel blasting excavation effect can be achieved,a number of metal expansive agent blasting tests are performed at the site,and the results of each test are summarized and improved to determine the blast hole layout,spacing,depth,and blasting excavation sequence.(4)Using the display dynamic analysis software ANSYS/LS-DYNA3 D,simulate and analyze the explosive blasting excavation method and the metal expansive blasting excavation method,and calculate which construction method meets the blasting vibration speed requirement.The coincident simulation results of the construction method are compared with the on-site monitoring results to verify the respective advantages and disadvantages of the two blasting methods.(5)To synthesize the features of the three blasting methods and sum up the construction methods that are most suitable for tunnel blasting excavation in close proximity to the existing building construction environment.