Model tests on large-section and shallow soil rectangular pipe jacking

During the construction of pipe jacking tunnels, the simultaneous injection is a key in controlling the surface deformation and jacking force. At present, the traditional researches on the simultaneous injection are mainly limited to those on the slurry materials and the friction coefficient, while the researches on the flow of the slurry itself and its filling mechanism are rarely involved. By establishing the pipe-slurry-soil system and the model test platform, the results of a laboratory reduced-scale model test on the simultaneous injection of slurry of super-large rectangular pipe jacking are introduced. It is shown that different slurries have different effects on the quality of the protective slurry screen, which contains the traditional thixotropic slurry (consisting of bentonite, CMC (carboxy methyl cellulose) and soda ash) and HS-3 compound slurry and polyacrylamide compound slurry. The settlements of different parts of soils and the pipe jacking forces are measured to observe the influences of the protective slurry screen on the ground settlements and the pipe jacking forces. The effects of the simultaneous injection on the ground displacements and the jacking forces of a large-section rectangular pipe-jacking tunnel with shallow overburden are explored. The test results show that the jacking forces can be reduced by about 40% under the simultaneous injection.