The behavior of synchronous grouting in a quasi-rectangular shield tunnel based on a large visualized model test

摘要

A quasi-rectangular shield tunnel can increase the effective usage area and decrease the degree of adverse impact from the surrounding environment relative to that of a circular shield tunnel. Synchronous grouting in a quasi-rectangular shield tunnel plays an important role in construction. This experiment used an integrated simulative experimental platform in the form of a large-sized quasi-rectangular shield tunneling machine to simulate the synchronous grouting process. Different grouting cases were implemented in this test to identify the best grouting approach in a quasi-rectangular tunnel. By installing 190 miniature soil pressure gauges in the surface of a designated organic glass segment and arranging four cameras inside the organic glass segment, the short-term and long-term grouting pressure, grouting flowing path and toroidal grouting pressure distribution were visually and accurately measured and analyzed. Moreover, settlement of each soil layer was measured to observe the influence of grouting on the ground settlement. After testing, the covering soil was removed to ensure that the final grout shape could be visibly surveyed. The results demonstrate that the key parameters of synchronous grouting in a quasi-rectangular tunnel are the grouting ratio and the position of the grouting holes. Finally, a cosine function grouting pressure formula is proposed.