Study On Stability And Anti-sliding Technology Of Deep Foundation Pit Slope At The Entrance Of Shallow Tunnel

The foundation pit at the entrance of the shallow tunnel is an important part of the construction of the diversion tunnel.Excavation of the foundation pit to the design elevation before construction of the tunnel point is an innovative way to ensure the rapid,economical and convenient construction of the tunnel.The process of excavating the foundation pit will produce slopes on both sides of the tunnel entrance.This kind of slope is "flared",resulting in a larger slope height near the entrance and a smaller slope height at the far entrance,plus the slope The excavation methods of small angles at high and high angles and large angles at low angles often result in a strong three-dimensional spatial effect at the tunnel entrance slope.The instability of the slope of the foundation pit at the entrance of the shallow tunnel will directly block the tunnel entrance and seriously affect the safety of the tunnel construction.Therefore,a reasonable analysis of the stability of the foundation pit slope at the entrance of the shallow tunnel and an effective anti-slide support It has important theoretical significance and engineering application value.Based on the field investigation of the shape design and geological conditions of the foundation pit slope at the tunnel entrance of the Tangxian-Shangshi section of the North Hubei Water Diversion Project,this paper uses theoretical derivation to analyze the sliding of the foundation pit slope at the entrance of the shallow tunnel Mechanism;using the relevant numerical simulation software to verify the support effect of the vertical steel pipe pile and slope anchor joint support system.The main work is:(1)(1)On-site investigation was carried out on the foundation pit slope of the tunnel entrance of Tangxian-Shangshi section of the water transfer project in the north of Hubei Province.To obtain the supporting method and technical parameters of the on-site slope.(2)A three-dimensional limit equilibrium analysis method for deep foundation pit slopes based on intersecting plane synthetic vector analysis is introduced.A coefficient of friction exertion is introduced to derive a three-dimensional limit equilibrium analysis method suitable for deep foundation pit slopes.The method is compared with the traditional Bishop method,and the application of geometric parameters in the stability of deep foundation pit slopes is discussed.(3)According to the on-site geomorphological characteristics and supporting methods of the foundation pit slope at the tunnel entrance of the Tangxian-Shangshi section of the North Hubei Water Transfer Project,a numerical simulation method was used to establish a combined support system with vertical steel pipe piles and slope anchor The slope model and the unsupported slope model compare and analyze the stability of the slope under the two conditions,and then verify the effectiveness of the combined support system of vertical steel pipe pile and slope anchor.