| During the damage of the surrounding rock of the tunnel caused by the blasting vibration of the mine method,it is accompanied by the expansion of joint fractures in the surrounding rock and the seepage of groundwater.Large section tunnel flat shape and large span,generally using multiple stages of multi-step blasting excavation,repeated disturbance of surrounding rock and lining support during the construction process,flat shape makes the vault force area large,arch foot stress concentration is significant,the unexcavated area in front of the palm has a restraining effect on the deformation of the palm surface,the excavated unloaded area behind the palm face is jointly affected by the continuous blasting disturbance of the palm face and the change of groundwater seepage path after excavation,forming a spatial effect after construction,which is one of the risks focused on tunnel construction.Therefore,this paper does the following:（1）Relying on the construction of a metro tunnel in Qingdao with medium and slightly weathered granite,surface rivers and underground water-rich in local fracture zone in the actual project,the damage degree D of the Hoek-Brown failure criterion is studied and modified,and the calculation method of coupling damage degree of blasting impact and seepage action is proposed,which considers the modified parameters Mb Dand SD of GSI and coupling damage degree Dc,and more accurately reflects the rock mechanical characteristics of the coupling damage of blasting impact and seepage.（2）Through physical tests,the applicability and rationality of the modified Hoke-Brown criterion were verified,and the influence of seepage on the mechanical properties of rock after blasting disturbance was quantified.Through design tests,on-site sampling,uniaxial and triaxial tests and stress seepage coupling tests,the influence mechanism of rock weathering,osmotic action and in-situ stress on rock mechanical properties was analyzed,and the obtainedσ1,σ3 andσci were brought into the modified generalized Hoke-Brown criterion,and the relevant parameters of Mb D and SD were calculated,which verified the applicability and rationality of the modified Hoke-Brown criterion based on the degree of blasting seepage coupling damage.（3）Taking a large section of Qingdao Metro as an example,the stress-strain characteristics of surrounding rock during the construction period of urban large-section metro tunnel were analyzed by Mias GTS NX numerical simulation combined with on-site monitoring,and the spatial effect of excavation and unloading of surrounding rock of urban large-section subway tunnel was obtained by changing the construction parameters and comparing different construction conditions.（4）The modified Hoke-Brown criterion coupled damage degree calculation method and the modified parameters calculated by the triaxial test are applied to obtain the force and deformation information of the surrounding rock during on-site construction through numerical simulation,and the seepage field,stress and deformation are analyzed,the spatial effect of the surrounding rock under the coupling of blasting and seepage is studied,and the stability of the surrounding rock is evaluated. |
