Study On Mechanism And Application Of Artificial Surface In Bedrock Blasting Of Shield Tunnel

With the continuous improvement of urbanization level in China,the metro system has become the main part of green public transportation,but the construction environment is becoming more and more complex.In the eastern coastal areas of China,there are intrusions of rock or bedrock in the shield tunnels,which affect the normal construction of the shield project.At present,the pretreatment technology of "ground drilling and micro-differential blasting in the hole" is mainly adopted.However,since there is no air surface,most of the energy is transferred in the form of vibration,which will inevitably threaten the safety of the ground structure.Therefore,it is very important to improve the utilization rate of explosion energy and protect the safety of the structure.In this paper,from the perspective of creating surface,combined with the specific engineering background,the mechanism and parameter optimization of the artificial surface in the bedrock blasting construction of shield tunnel are mainly studied,and the field measurement is carried out,the following main conclusion:(1)The propagation characteristics of the blast stress wave at the interface between rock and artificial surface and the main effects of artificial surface are analyzed theoretically,including stress concentration,free surface effect and energy attenuation.Get the bigger the diameter of empty hole,for the better blasting effect.(2)Through the basic physical and mechanical properties test,the basic mechanical parameters of granite and the failure law of specimens under uniaxial compression are obtained.By using separate SHPB device,the dynamic mechanical properties of granite under different loading rate was analyzed,and the dynamic compressive strength of granite,broken characteristics with strong strain rate effect.(3)By comparing the test and optimization test,found that artificial surface can improve the blasting effect.And the larger the diameter of the hole,the closer it is to the hole,the better the effect of artificial surface.Based on the engineering background,the optimal design value of the parameters of the artificial surface is put forward.(4)Blasting construction field measurements and numerical experiments have good comparability.In the construction process,By setting the artificial surface,can effectively control the surface blasting vibration intensity,at the same time to improve rock breaking effect and well meets the need of practical engineering.This paper includes 84 pictures,35 tables,and 107 references.