Research On The Same Scale Model Test And Evaluation Of Foundation Grouting Effect In The Immersed Tube Tunnel

Zhoushan Shenjiamen Harbour tunnel is the domestic first ocean underwater tunnels using immersed tube construction method. Its foundation will be treated by tube grouting method. At present, the problems of underwater foundation grouting process for the large-scale concrete tube sections of immersed tube tunnel, which include construction technology, function mechanism, application effect and other related aspects, are studied less in our country. There is no similar experience of engineering practice. In order to study the related technology parameters of foundation grouting and the applicability and reliability of non-destructive monitoring methods for immersed tube tunnel, and then establishing a rapid, simple, accurate and economic non-destructive method for detecting grouting effect, the same scale model test of foundation grouting has been carried out for Zhoushan Shenjiamen Harbour immersed tube tunnel, real-time monitoring methods and evaluation systems of the filling effect have been established in this paper. The research contents are divided into two parts as follows:1. Field grouting model test: Based on determined grout mix, designed geometry size of foundation and tube, foundation trench and its back silting conditions and on-site working conditions, the same scale model test have been using in studying the diffusion characteristics of grouting, strength characteristics of mortar, monitoring some data (such as grouting pressure, grouting volume and diffusion radius etc.) and their relationship analysis. The relevant technology requirements and parameters of foundation grouting construction have been proposed for Zhoushan Shenjiamen immersed tube tunnel.2. Research on method of detection and evaluation for on-site grouting effect: The effect of grouting has been detected using non-destructive testing method (such as ground-penetrating radar and surface wave instrument, etc.). By compared with the results of observations, the non-destructive detection method of grouting filling effect for immersed tube bottom has been explored.Test studies have shown that can reach a predetermined range of grouting and ensure general anti-floating performance of tunnel tube sections when the maximum grouting pressure is 10kPa in the model test, the horizontal direction distance is 6m and the longitudinal direction distance is 5.75m for the grouting pipe hole. It can detect effectively flow state of grout and infer grout spread to reach the interface position in the grouting process using ground-penetrating radar and surface wave method. In comparison, the surface wave method is more intuitive and reliable.