Study On The Effectiveness Of Soil Conditioning Of EPB TBMs In Unfavorable Geology

Based on the earth pressure balance shield tunneling interval between jiangcheng avenue station and laoguancun station of the third section of the first phase of wuhan rail transit line 6,and aiming at the construction influence of bad soil layers encountered in the interval,the improvement of soil foaming agent and its effect on shield tunneling were studied.In this paper,the basic physical and mechanical properties and strength tests of bad soil were carried out to study the bad mechanical properties of soil.The flow plasticity test of foamed breading and clay was carried out by using foam additives,and the quantitative standard of foaming agent properties and the bad geological body improvement method with the collapse value as the evaluation standard were put forward.On this basis,the field application analysis of earth pressure balance shield tunneling was carried out,and the relationship between the construction parameters of shield tunneling and foam additives was studied,which effectively verified the rationality of the indoor test results.Through this study,the following main conclusions are obtained:(1)The main causes of affecting foaming agent bubbles decay half-life and expansion rate,puts forward the quality evaluation of foam agent laboratory quantitative indicators,namely the generated bubble foam agent under the normal pressure within 3 min defoaming rate not greater than 10%,and the half-life is greater than or equal to 5 min,at the same time bubble foaming rate of inflation is greater than or equal to 8 times,according to the object of this study "jiang avenue station-old clearance between village station" of the adverse soil conditioner foam suitable ratio is 3% ~ 5%;(2)Foam can significantly enhance the flow plasticity of breccia and clay,and water content is the key factor affecting the collapse value of breccia clay.(3)The application of earth pressure balance shield tunneling was carried out by using the ratio of foaming agent provided by indoor tests.The relationship between monitoring parameters on the site of shield tunneling and foaming agent was comprehensively analyzed,and the application parameters of foaming agent in the construction of shield tunneling with earth pressure balance were given,that is,the concentration was 3% and the incorporation ratio was 30%~40%.