Study On The Performance Evaluation Of Foaming Agents In PBS

Foaming agents in EPBS have been employed for more than 20 years. Especially, civil engineers have put more importance on foamed soil and there is a rapid growth in the use of foaming agent in EPBS in recent 10 years. As some factors, the use of agents is according to the experience in engineering, and there is not enough theoretical study. Now, there is no evaluation method of foam agents in EPBS in the world. Some oversea institutes have taken an active part in the study of foaming agents and foamed soil, but there is no literature about foaming agents in EPBS in our country.Presently, there is no foaming agents in our country and all foaming agents in EPBS are foreign products, so the price is very high, foaming agents are so various that the evaluation method of foaming agents in EPBS is crucial, which can help the contractors choose an appropriate foaming agent.Accordingly, this paper' emphases are placed in these unfathomed problem, and the work and research hereinafter was done:(1) Aimed at the problems encountered in EPBS because of the bad state of excavated soil, the mechanisms of those problems are studied and the best state of excavated soil is put forward.(2) The foam stability and expansion ratio are put forward according to the characteristic of foams which are two phases: gas and liquid. And the tests prove that the main factor influencing the foam stability and expansion ratio is the concentration of the foaming agent solution.(3) Aimed at the use of foaming agents in EPBS is hit-or-miss, the state of the foamed soil is tested, and the tests prove that the main factors influencing the state of the foamed soil are foam stability and foam expansion ratio.(4) The performance evaluation method of foaming agents in EPBS is put forward in terms of theoretic analysis of the test. And the results of indoor tests and field experiments prove the method correct.