Analysis on Construction Mechanical Mechanism of Highway Tunnels with Large Span and Small Spacing

Abstract

The structure of highway tunnels with large span and small spacing has the characteristics of flat, long span, and thin arch. The load distribution and supporting mechanical characteristics of the surrounding rock are complex. The stability of the structure is affected by many processes during construction. The strength of the supporting structure is variable and prone to the instability of the surrounding rock and the cracking and destruction of the tunnel supporting structure. The comparison and verification of field monitoring data and numerical simulation analysis were carried out to analyze the construction mechanical mechanism of the large span and small spacing highway tunnels based on the construction of the Fo Yangling Tunnel in Binlai Highway, which belongs to the reconstruction and extension highway project of Zibo to Laiwu and on the Fast Lagrangian Analysis of Continua in 3 Dimensions numerical simulation software to rule out the stress and strain of the tunnel and the surrounding rock. The numerical simulation results are in good agreement with the field monitoring data. The results show that: (1) The construction of the subsequent digging tunnel significantly affects the prior digging tunnel. (2) Stress concentration tends to occur in the haunch and the foot of the tunnels and the middle surrounding rock. (3) Reasonable grouting on the surrounding rock can effectively reduce surface settlement and reduce the influence of the excavation of subsequent digging tunnel on the prior digging tunnel. (4) During construction, reasonable selection of grouting reinforcement area should be combined with the actual situation to avoid material waste. The analysis results can provide a scientific basis for the design and construction of highway tunnels with large span and small spacing.