Experimental Investigation on the Sand Deposit Foundation of an Immersed Tube Tunnel by Using a Sand Flow Model

Abstract

Abstract Sand flow is a mainstream construction method to treat the foundation of immersed tunnel. The characteristics of the sand deposit foundation, including its size and compactness, as well as fullness degree, are key indicators for estimating the effect of foundation treatment on the immersed tube tunnel. In this study, three series of model tests were conducted. The characteristics of fullness degree and compactness were elaborated. In addition, tunnel uplift and its prevention, the effect of surface roughness of tunnel on the compactness and size of sand deposit, and the effects of different injection sequences on the fullness degree were investigated. Valuable practical suggestions were drawn from the test results. First, the incidence of tunnel uplift can be avoided by monitoring the hydraulic pressure under the bottom of tunnel with water pressure gauges. Second, the surface roughness of tunnel should be decreased to allow for a sand deposit with a large radius and consequently enhance construction efficiency. Third, the difference in injection sequences barely influences the fullness degree of sand deposit; therefore, injection sequences can be flexibly designed to provide convenience for construction.