Experimental Study on the Effects of New Foam on the Improvement of Sandy Soil for Earth Pressure Balance Shield

In this paper, starting from the foaming amount, half-life and other indicators, the surfactant with excellent performance is optimized, and the optimal compound ratio and appropriate foam stabilizer, viscosity enhancer, and additives are studied. A new type of foam agent formula for the EPB shield is developed. The performance of the new foam agent is compared with that of domestic foam and imported foam from the aspects of foaming rate, stability, micromorphology and temperature resistance, which verifies that it meets the parameter requirements and advantages of a foam agent for shield tunneling. Then, by means of laboratory tests, such as the mixing test, friction coefficient test, adhesion resistance test, slump test and direct shear test, the improvement effect of the new foam agent is compared with existing foam agent products at home and abroad, and the improvement effect of the new foam agent on soil is evaluated. The formulation of the new foam agent is as follows: 1.6% sodium dodecyl sulfate (SDS) + 8% dodecyl dimethyl betaine (BS-12) + 7% dodecanol + 0.06% guar gum + 0.6% ammonium chloride. The foaming rate, stability, microstructure and temperature resistance of new foam meet the requirements of shield construction. New foam, imported foam and domestic foam have advantages in sand and soil improvement experiments, but from an economic point of view, the new type of bubble is better than the other two. A new type of shield foam agent is prepared to meet the needs of construction. There is a big advantage in terms of price.