Blasting vibration response characteristics of tunnel support structures in horizontally layered rock masses under initial in-situ stress

Yu Jianxin; Liu Wenjin; Zhang Xin; Zhang Hao

doi:10.16186/j.cnki.1673-9787.2023070026

Abstract：Objectives To analyze the stability of surrounding rock during tunnel blasting excavation in hori-zontally layered rock masses under initial in-situ stress.Methods Using LS-DYNA finite element software,numerical models were established under three different in-situ stress levels and three sets of blasting pa-rameters.The dynamic stress distribution and vibration velocity response at typical positions of the tunnel support structures were computed and analyzed.Results The results show that during tunnel blasting excava-tion in horizontally layered rock masses,the peak particle velocity(PPV)of surrounding rock behind the tunnel face increases with higher in-situ stress and changes in blasthole types.For cut-hole blasting,the maximum PPV increases by 1.86 times at 10 m behind the tunnel face,and for auxiliary-hole blasting,by 1.83 times at 15 m.The PPV at the spandrel of the tunnel face under cut-hole blasting is 4.61 times higher than that of auxiliary-hole blasting and 41.17 times higher than that of peripheral-hole blasting.As the in-situ stress increases,the difference between lateral and vertical compressive stress in various parts of the support structure also increases.At 30 MPa in-situ stress,the maximum lateral and vertical compressive stresses in the support structure reach 186.55 MPa and 176.39 MPa,respectively.Among the three blasting types,cut-hole blasting induces the highest PPV at the vault and spandrel,while peripheral-hole blasting yields the lowest.The dynamic tensile stress of anchor bolts shows a nearly linear relationship with different blasting parameters:the peak tensile stresses are 14.21 MPa for cut-hole blasting,5.88 MPa for auxiliary-hole blasting,and 1.36 MPa for peripheral-hole blasting,displaying a decreasing trend.Conclusions In tunnel excavation of a horizontally layered rock masses,increased in in-situ stress leads to higher peak stresses in the support structures.Among different blasting parameters,cut-hole blasting produces the stron-gest vibration response.