Study on stability of exit slope of Chenjiapo tunnel under condition of long-term rainfall

• Published in: Environmental earth sciences 2021-09, Vol.80 (17), Article 590
• Main Authors: Hou, Tian-shun, Duan, Xiang, Liu, Hao-yu
• Format: Article
• Language: English
• Subjects: Biogeosciences; Damage; Displacement; Drainage; Drainage engineering; Dredging; Earth and Environmental Science; Earth science; Earth Sciences; Environmental Science and Engineering; Excavation; Geochemistry; Geology; Gravel; Highways; Hydrology/Water Resources; Landslides; Landslides & mudslides; Mathematical analysis; Original Article; Plastic zones; Plastics; Polls & surveys; Rain; Rainfall; Safety; Safety factors; Seepage; Shear strength; Shutdowns; Simulation; Slope stability; Soil erosion; Soils; Surveying; Terrestrial Pollution; Traction; Tunnels
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-021-09895-x

The exit slope of Chenjiapo Tunnel is located directly above the exit of Chenjiapo Tunnel on Enshi to Laifeng expressway. During the excavation of the exit of the right line of the tunnel, the left side of the front edge of the slope slips. Under the joint action of excavation and rainfall, a large landslide of 6.27 × 10 4 m 3 and a huge unstable slope of 8.69 × 10 5 m 3 are formed. The landslide body and unstable slope body not only cause the tunnel to be shut down, but also directly threaten the operation safety of the later expressway. Therefore, to study the stability change process of the exit slope of Chenjiapo tunnel under the condition of long-term rainfall, the finite element calculation of the slope is carried out by GeoStudio software. The results show that under the condition of long-term continuous rainfall, the safety factor of the slope decreases with the increased rainfall time, but the reduction rate gradually slows down, and finally tends to be stable. The safety factor of the slope is reduced from 1.187 in the natural state to 1.015, which indicates that the slope is still in a stable state under the condition of long-term continuous rainfall, but the safety reserve is not high, and it is easy to lose stability and damage due to the influence of external adverse factors. As the rainfall continues, the seepage line inside the slope is rising, and the saturated area of the soil at the toe of the slope is increasing. Until the slope begins to drain outwards, the seepage field inside the slope is basically stable. The maximum horizontal displacement of the slope increases with the increased rainfall time, but the increase rate gradually slows down until it tends to be stable. The maximum horizontal displacement of the slope occurred in the middle surface of the slope at the beginning of the rainfall, and gradually transferred to the toe of the slope within 7 days of the rainfall and continued until the end of the rainfall. At the end of the rainfall, the maximum horizontal displacement of the toe of the slope is 0.128 m, and the toe of the slope will be damaged first. At the beginning of the rainfall, the plastic zone of the slope is only scattered at the slope surface and the slope toe. And then as the rainfall continues, the distribution range of the plastic zone in the slope surface, the slope toe and the slide zone gradually widen, and the slope stability gradually decreases. The maximum horizontal displacement and plastic zone of the sl