Study On Foam Soil Conditioning Technology For Epb In Fully Weathered Granite

During the construction of earth pressure balance shields,there are plenty of common problems such as cutting tool wear seriously,clay clogging,etc.,and when shields cross rich water stratum spurt problems cloud even occur,which would lead to instability of the excavation surface and excessive surface settlement,and proper use of soil conditioning technology can better solve the above problems encountered in the excavation of shield machine.This paper intends to use the basic experiment of foam and the macro application of shield tunneling machine to fully research the physical properties of the foam,the changing rules of the physical and mechanical properties of the improved muck,and the foam soil conditioning technology for FPB in fully weathered granite.The research results can provide direct reference and technical support for the soil conditioning of shield tunnel in the urban metro area.The main research results are as follows:(1)Through on-site investigation and analysis of the construction difficulties of shield construction in the fully weathered granite stratum of the Guangzhou Metro Line 21,a summary of effective construction measures was concluded.(2)Through the investigation of the foam generation mechanism,the effects of different pressure conditions,gas-liquid ratio and foam concentration on the physical and mechanical properties of the foam produced by the foaming material were obtained.The optimal foaming method for the foaming agent was obtained through systematic analysis.(3)By the project soil,an indoor test was conducted through the self-made test equipment,the influence of formation ions on the properties of foaming agent was obtained,and the actual pressure state of the soil was simulated,and the influence law of factors such as moisture content of the test soil,foam injection rate,gas-liquid ratio of the foam,and foaming agent concentration on physical and mechanical properties such as workability,shearability,and compressibility were obtained.The basis for the selection of parameters for the foam soil conditioning was proposed and the recommended parameters for the improvement of the formation were obtained.(4)Based on the Guangzhou Metro Line 21 project,the tunneling parameters of the shield machine such as thrust,torque,excavation speed,face temperature,and screw temperature before and after the replacement of foaming agent on site were collected,and the impact of different modifiers on shield tunneling were analyzed,and the applicability of the obtained foam modification parameters was verified.