Understanding the mechanism of slope failure on a nearby highway tunnel route by different slope stability analysis methods: a case from NE Turkey

Abstract

The Arakli tunnel is located in the eastern Black Sea region where the most mass movement is observed in Turkey. Following the tunnel entrance portal excavations in basaltic tuffs on nearby the Konakonu residential area, an impending failure occurred. Because of the developed tension cracks and deformations on the ground, five houses and their gardens were damaged completely. The present study aims to investigate the mechanism of the failure. In order to do this, kinematic, limit equilibrium, and numerical stability analyses were carried out. Firstly, the kinematic analyses were performed taking into account the main joint sets for the slopes. The results of the kinematic analyses showed that planar and wedge failures were possible on the portal slope and no failure occurred on the cut slope. However, the limit equilibrium analysis showed that neither the planar nor wedge failures were expected to occur on the portal slope. The numerical stability analyses were performed to determine if circular failure is to occur in the slopes. The Phase 2 programme was used in the numerical analyses, and the Strength Reduction Factors (SRF) of the slopes were determined. According to the numerical stability analyses, the failure mode for the portal slope is composite starting with a circular surface and following a linear surface and circular for the cut slope. The stability analyses indicated that the failure mechanism was not directly controlled by the joints and might be related to the low strength parameters of the rock mass and joints. Finally, precautions were determined to make the region stable using the Phase 2 programme. After support installation, the SRF values for the portal and cut slopes increased from 1.21 to 1.63 and from 1.32 to 1.71, respectively. These results showed that the proposed support units prevent the effects of failure and were essential for the long-term stability.

The Progressive Failure Mechanism of the Tunnel-Slope System under Rainfall: An Experimental Investigation

“…Wu [17] further enriched the geomechanical model of the tunnel-slope system and finally obtained the interaction law of the tunnel-slope system. According to the above, when dividing the geological structure model of slope diseases and tunnel deformation, most experts mainly consider the rock structure characteristics, the spatial position relationship between the tunnel and the slope, and the time effect of surrounding rock deformation [18][19][20]; the combined influence of engineering disturbances and hydrogeological conditions are rarely considered.…”

Slope Stabilization of Twin-Tubes Tunnel Portal by Anchor Bolts Support System

“…This discrepancy is due to the fact that many uncertainties are involved in both the variable geological properties and the complex geomechanical properties of rock masses, especially of poor quality [3][4][5][6][7], as well as in the high initial stresses that affect them [8 -15]. However, in tunneling, there is no specific procedure to assess the behavior of the rock mass during digging with respect to the failure mechanism previously defined in the design process [16][17][18]. Hence, the stability of portal slopes should not be considered separately from tunneling [19][20][21], because the collapse that may occur during the excavation of the portal will completely stop the tunnel digging [22][23][24][25][26][27].…”

Landslide Triggered by Orthogonal Tunnel Excavation and Prevention Measures in Jimei Village, Sichuan Province, China

“…Konagai et al (2005) analyzed the landslide-induced damage to Kizawa tunnel in the 2004 Mid-Niigata Prefecture earthquake in Japan. Kaya et al (2015) conducted a comprehensive analysis to the slope failure mechanism triggered by the excavation of Arakli tunnel by kinetics, limit equilibrium method and numerical simulation. Jiao et al (2013) assessed the effect of two coal mine tunnels on an ancient landslide by using borehole data, deformation monitoring and numerical simulation, and the results show that the landslide is generally stable, partially with shallow slope failure.…”