Development Of New Foam Agent For EPB Shield Machine And Foamed-soil Modification

Soil improvement measures must be taken when EPB shield tunnel in the complex strata, at present, the method of foam modifying soil has been widely used in shield construction. In our country, foaming agent has not yet been developed to replace the exellent abroad products, with the accelaration of localization of shield machine, the research on foaming agent and the properties of the foamed soil are very urgent. On the R& D of a new type of foaming agent used in EPB shield and foam improving soil for tunneling in the complex strata in the subway construction. Based on the composition analyzing of imported foaming agent, the orthogonal test method is adopted to carry out the development of a new type of foaming agent used in EPB shield machine. The basic performances are compared with the homemade foaming agent, imported foaming agent and dometic foaming agent, and the quantitative evaluation criteria on the characteristics of foaming agent is put forward; taking the home-made foam, domestic foam and imports foam as soil improving materials, the experimental research on the permeability, plastic flow, shear strength, compression and external friction angle of foam improved sand and clay is carried out. Based on the comprehensive analysis of the characteristic indexes of the modified soils, the quantitative evaluation criteria on the "liquid plastic" properties of the foam modified soil is put forward; based on the research of microstructure of sand and clay, the research on micro-mechanism of foam improving sand and clay is carried out.