Geomechanical Model Experiment Study on Deformation and Failure Mechanism of the Mountain Tunnel in Layered Jointed Rock Mass

Abstract

The Minxian tunnel is a key engineering of the Weiyuan-Wudu expressway that is excavated in layered jointed carbonaceous slate rock mass. During the construction process, the surrounding rocks of the tunnel encountered serious large deformations and failure, which brought about great difficulties to the safety and cost of the tunnel. In order to study the deformation and failure mechanism of the surrounding rocks, a physical model test was conducted, and integrated methods including strain gauges, a digital camera, and noncontact full-field digital imaging correlation technique were used to record the response information of the surrounding rocks. The evolution process of surrounding rocks failure was simulated successfully in the model test, and the deformation characteristics were basically consistent with the actual engineering. The modelling results show that concentrated stresses in the surrounding rocks were very uneven due to developed stratified and jointed rock mass structure. The maximum and minimum concentrated stresses appeared at the vault of the tunnel and left of inverted arc area, and concentration factors were 3.11 and 1.98, respectively. The main forms of surrounding rocks deformation and failure were large area spalling of surface, severe circumferential fractures, serious bending deformations of thin rock layers, and collapse of overlying strata. The maximum displacements occurred at left sidewall and right shoulder of the tunnel and the corresponding actual displacements were 460 mm to 500 mm. Caving and failure took place firstly at several key positions with maximum concentrated stresses or displacements and subsequently gave rise to massive collapse of surrounding rocks.

Development of Transversely Isotropic Elastoplastic Constitutive Model in FLAC3D and Its Application in Tunnel Engineering

“…After substituting the partial derivative of Equation (1) into Equation (10), the plastic shear strain in each principal direction can be obtained: 4 Geofluids…”

“…In recent years, extensive research has been conducted on the deformation and failure characteristics of layered rock mass [1][2][3][4][5][6][7]. Xia et al [1] studied the bearing deformation and failure process of layered rock mass through a model test and revealed the eccentric pressure failure phenomenon of surrounding rock.…”

Analytical expression of displacement of circular double tunnels in transversely isotropic rock mass in unstable rock zone of southwest mountainous area

“…Under the assumption that any tunnel section is parallel to the isotropic plane, the analytical solution for stress and displacement around any tunnel has been derived [28][29] . There is also comprehensive research on the stress distribution, deformation, and failure characteristics of surrounding rock in layered rock masses [30][31][32][33][34][35] .…”

Numerical Analysis on the Influence of Joint Density on the Stability of Complex Jointed Roadway Surrounding Rock

“…Wang et al [15] comprehensively examined the effects of roadway shape and fault dip angle on roadway damage, studying the initiation position and propagation path of cracks under the respective influences. Guo et al [16] analyzed the deformation evolution process of layered jointed roadway surrounding rock models and found that the distribution of stress concentration zones in the surrounding rock is highly uneven due to the unique characteristics of layered joint structures.…”