Research On Airblast Wave Overpressure Prediction Method Of Drilling-blasting Tunnels And Protection Technology For Wave-blocking

Drilling and blasting is one of the primary methods used to build tunnels,and for a very long time,the community and society in the vicinity of tunnel construction have been highly concerned about blasting vibration and airblast.Two essential instruments that can assist the tunnels which are confronting the issues of airblast wave,are the airblast overpressure(p_oa)prediction and the effective countermeasures of wave blocking protection.As a result,using both instruments together can lower engineering risks and do away with blasting disruption and blasting damage.This Ph D dissertation was supported by the NSFC project"Research on the damage characteristics and blast protection technology of tempered glass under the action of tunnel drilling and blasting shock waves"（51978671）.The main topic of dissertation is the propagation law and attenuation characteristics of the airblast caused by tunnel drilling and blasting.A wave blocking protection technique is recommended after a thorough investigation of the forecast and impact evaluation of airblast.The study was based on 3D numerical simulation,theoretical analysis,and field testing.The primary study is described in the following way:（1）The time domain characteristics of millisecond airblast signals were studied.The wavelet analysis method is utilized to examine the time-frequency properties of the measured airblast pressure signals as well as the time variation of the wavelet energy under various excavation techniques,blasting conditions,and explosive equivalent conditions.It was found that the delay segment and the segmental sub-signal of the airblast wave energy coincide.It demonstrates that the amount of explosive in the cutting section has the most correlation to the peak overpressure(p_max)of the airblast.Spectral analysis of the drill and blast airblast signal shows that the airblast frequency inside and outside the tunnel cavity is mainly distributed in the range of 0～150Hz,which is widely distributed in the audible range of the human ear（>20Hz）,thus leading to strong noise and disturbing the normal life of residents.（2）The mechanism of airblast inside tunnel was propagated in stages.The fluctuation propagation features of the airblast p_max,positive pressure time,and Fourier frequency with distance under various operating conditions were investigated in conjunction with the analysis of experimental data and numerical simulation.The features showed that the three propagation including three process:the spherical wave fast decay,nd the airblast catch-up superposition state,and the one-way decay stage The superposition occurred at the catch-up superposition statel.The airblast catch-up phenomenon was analyzed by the nonlinear superposition method.（3）A method for predicting the airblast of differential drilling and blasting in tunnels was proposed.Conducted a factor analysis of drilling and blasting parameters such as different explosive equivalents,extension time and detonation location,quantifying the level of influence of each factor.Determine the amount of explosives for the hollowing section as the calculation of the amount of explosives,to give the drilling and blasting airblast equivalent coefficient determination method,a comparative study of a number of drilling and blasting tunneling equivalent coefficient of the range of values.Taking the explosive equivalent and the propagation space volume as the basic parameters,the airblast energy concentration coefficient concept and the blast wave propagation proportional distance conversion method are referred to,and the blast wave overpressure formula of the Blasting Safety Regulations GB6722-2014,which is suitable for flat terrain conditions,is introduced into the tunnel boring and blasting project.（4）Based on the drill and blast airblast propagation characteristics outside the tunnel cavity,an overpressure prediction and impact zoning approach is provided.It is discovered that the drilling and blasting airblast propagation outside the tunnel cavity exhibits anisotropic variability,and the relationship between the azimuth angle and the airblast attenuation characteristics is examined.Determine the intensity and azimuth of the airblast at the cave entrance as the basic parameters,using the method of empirical formula fitting,to obtain a prediction formula for the overpressure of the drill and blast airblast outside the tunnel cave.Using the prediction formula as a benchmark,the evaluation method of the impact of airblast waves in the space near the tunnel cavity is proposed.（5）The analysis of the effect of drilling and blasting airblasts at tunnel entrances was done using the typical situation of tunnel construction near residential areas.The research used numerical simulation to examine the internal airblast propagation and evolution of the building complex close to the tunnel entrance area,analyze the factors that contribute to overpressure enhancement at critical locations like high floors,front and back elevations of floors,and narrow passages between floors,and show the value of wave blocking protection technology for drilling and blasting tunnels close to residential areas.（6）A wave blocking protective safety device is suggested for tunnels that will undergo extensive drilling and blasting.A tunnel wave blocking protection dolly device is designed and put into use with the intention of actively reducing the energy of tunnel drilling and airblast waves based on the impact of airblast waves in the tunnel opening directly in front of the residential area.The effectiveness of the protective safety device was confirmed on site to ensure construction safety through numerical simulation,and a phased implementation of the wave blocking protection technology from the tunnel entrance to the tunnel entrance and cavity body was developed.