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

Xingzhou Chen (), Quan Zhang, Xinchao Ding, Lili Chen, Wei Du, Hai Jiang and Sheng Gong
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Xingzhou Chen: School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Quan Zhang: School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Xinchao Ding: Northwest Engineering Corporation Limited, Xi’an 710065, China
Lili Chen: School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Wei Du: School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Hai Jiang: School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Sheng Gong: School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China

Sustainability, 2023, vol. 15, issue 5, 1-16

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

Keywords: hydraulic tunnel; unloading seepage; excavation disturbance; rock materials; creep test; granite (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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