Study on the Creep Characteristics and Fractional Order Model of Granite Tunnel Excavation Unloading in a High Seepage Pressure Environment

The creep associated with unloading surrounding rock during the excavation of deep tunnels seriously affects stability tunnel, and a high seepage pressure will aggravate strength attenuation structural deterioration rock. Based on background excavation-induced deeply buried granite tunnel pressure, in this paper we carry out triaxial test that considers effects both disturbance pressure. We also analyze mechanism leading to sample failure construct fractional damage constitutive model effect. results include following findings, firstly, affect deformation for long time, circumferential expansion process is more obvious than axial expansion. Secondly, reduce bearing capacity. Under 0, 2 4 MPa pressures, long-term samples are 193.7 MPa, 177.5 162.1 respectively. Thirdly, factor increases increasing time deviatoric stress. Finally, rationality fractional-order effect verified by data. These research may provide some reference analysis environments under high-stress high-seepage-pressure.