Experimental study on soil improvement during construction of EPB rectangular pipe jacking with multi-cutter

The rectangular pipe jacking method is applied in the underground passage project situated in the Inner Mongolia University of Science and Technology under the condition of sandy stratum. The soil improvement effects are unsatisfactory by using the methods of adding water and the two materials of PAM solution and silt mud. The cutter head is seriously blocked, and the actual jacking speed is only 1.5 mm/min. Therefore, such methods as monitoring measurements and laboratory tests are used to optimize the old soil improvement plan. The research results are as follows: Firstly, the best concentration of PAM water solution is 2 g/L, and the better mass concentration of bentonite mud is 9%; Secondly, the best proportion of additive is that the injection ratio of slurry is 12% and that of PAM water solution is 17%; Thirdly, the jacking speed increases to 2.8 mm/min by using the optimized soil improvement plan, and at the same time, the ground settlement value does not exceed the control standard. The proposed soil improvement method can meet the requirements of rectangular pipe jacking construction.