| As the implementation of Chinese "western development" policy and "The Belt and Road" strategic initiatives put forward,more and more complex environmental conditions of the tunnel and underground engineering construction.Among them,the high Geo-stress and its rock burst disasters not only threaten the safety of people’s life and property,but also affect the construction and quality of the engineering,and hinder the promotion of national strategy and policy.Although there is a long history of research on high Geo-stress and its rock burst,the research on the mechanism of blasting pressure-relief is not enough,and the research on the residual stress equation of blasting pressure-relief has not been started yet.In this paper,taking a railway tunnel from Lhasa to Linzhi in Sichuan Tibet line as the engineering background,on the basis of the investigation and survey on the site,the scholars have studied the rock burst(earth pressure or mine earthquake)criterion,the tunnel(Lane)Road(hole)and other engineering blasting production and construction,the high ground stress and the conventional treatment of rock burst.With the method of theoretical derivation,calculation and analysis of example,FLAC3 D numerical simulation,a preliminary exploration is made on the residual stress equation of blasting pressure-relief for tunnels with high Geo-stress and the following achievements and understanding are mainly obtained:(1)The investigation and servey of the tunnel site revealed that the engineering geological conditions in the study area are complex and the blasting disaster is serious.According to the site survey results,the high Geo-stress and rock burst in the study area are summarized,the ideal high Geo-stress tunnel geological model is drawn,and the blasting pressure-relief residual stress equation in the two-dimensional and three-dimensional conditions is derived.(2)Through the selection of relevant parameters,the theoretical calculation of the blasting pressure-relief residual stress equation is carried out,through the analysis of the results,it is found that:(1)After blasting pressure-relief,the blasting stress wave propagated in rock mass is mainly exponentially decaying;(2)The horizontal stress components and the vertical stress components between the different blasthole have counteracted each other.In theory,the number and intensity of the blasting holes should be kept in a certain range when the blasting pressure is explained.(3)After blasting pressure-relief,the variation of the horizontal stress component and the vertical stress component size and direction is a gradual process.There is a point with zero stress,and the stress direction on both sides of the point is completely opposite,and the stress values on both sides of the point are not equal.(3)The horizontal stress and the vertical stress decline and deceleration rate all suddenly slow down at the pressure relief point of No.5 blasting,and the residual stress energy can not produce cracks on the rock mass,and the effect of unloading pressure on the tunnel,that is,No.5 unloading pressure point near the hole about 2.6m,is the maximum peri of blasting pressure relief.(4)FLAC3D3.0 is used to simulate and calculate the stress relief residual stress equation of blasting,analysis stress nephogram shows that:(1)the maximum boundary of blasting pressure relief is the boundary of the shaking area,and the distance from the blasthole is about 2.6m,which is basically consistent with the theoretical calculation conclusion;(2)By analyzing the horizontal stress nephogram of the axial section of the tunnel,the stress concentration is formed in the vault and arch bottom in a certain range of the tunnel face.This phenomenon explains the rock burst in the surrounding rock of the tunnel,which is mainly caused by the horizontal stress concentration of the surrounding rock caused by the tunnel blasting.(5)According to the numerical results of pressure relief point of blasting pressure relief residual stress equation,coMPared with the theoretical solution,concluded that,After blasting pressure relief,the stress change trend of the pressure relief line is the same,which shows the rationality of the unloading residual stress equation. |
