Determination Method of Reasonable Reinforcement Parameters for Subsea Tunnels Considering Ground Reinforcement and Seepage Effect

Zhenyu Sun,Dingli Zhang,Qian Fang

doi:10.3390/app9173607

Abstract

The key issue for construction of subsea tunnels through unfavorable geological conditions is to determine a reasonable reinforcement scheme, while the core problem for the reinforcement design is to accurately evaluate the mechanical behavior of surrounding rock with ground reinforcement. Considering that advanced curtain grouting and full-face grouting are widely used in subsea tunnels, a mechanical model for the subsea tunnel surrounding rock accounting for both ground reinforcement and seepage effect was established. According to the distribution and extent of the plastic zone(s), six potential configurations were appropriately analyzed, which were validated by numerical simulations and analytical solutions for simplified settings from the literature. The sensitivities of the reinforcement parameters were examined, and by taking into account the tunnel radial displacement and the seepage quantity as the main objectives, the multi-objective optimization of the reinforcement parameters was put forward via the stratified sequencing method. Finally, application of the proposed method to the Qingdao Jiaozhou bay subsea tunnel project in China was explained. Research results could provide insightful ideas for the quantitative design of the ground reinforcement of subsea tunnels and may have reference value for their construction safety through unfavorable geological conditions.

Highlights

When subsea tunnels pass through unfavorable geological conditions, the stability of the surrounding rock is reduced under the combined action of the seepage and ground stressor fields, and, it could dramatically respond due to the excavation disturbance
The determination of reasonable ground reinforcement has a significant impact on the surrounding rock stability of subsea tunnels
The method was applied to the Jiaozhou bay subsea tunnel project in Qingdao

Summary

Introduction

When subsea tunnels pass through unfavorable geological conditions, the stability of the surrounding rock is reduced under the combined action of the seepage and ground stressor fields, and, it could dramatically respond due to the excavation disturbance. To ensure successful tunneling through weak zones, ground reinforcement methods including grouting, concrete backfilling, and freezing are necessarily exploited [3]. Among these approaches, grouting is often preferred because of its advantages of being a mature technology, having a low cost, and exhibiting good outcomes [4]. Researchers have shown that ground reinforcement can significantly improve stability and water resistance of the surrounding rock, as a result, construction safety is ensured [5,6]. Ground reinforcement has become a strategic technology for subsea tunnels crossing through weak zones, whose design concepts are of particular importance

Methods

Results

Conclusion