ABSTRACT
In Bangkok, Thailand, the soils consist of a layer of soft clay underlain by interlayers of stiff clay and sand. The groundwater level is often observed a few meters below the ground surface. Unexpected incidents, such as water inflow from the sand aquifers and excessive deformation from the soft clay, could occur during TBM breakthroughs in such soil conditions. The jet grouting technique is commonly utilized for ground improvement to avoid these issues. This paper focuses on an evaluation of jet grouting design and construction methods related to water leakage issues for TBM breakthroughs. The design and construction data collected from the MRTA Orange Line East Project in Bangkok, Thailand, were used to evaluate key jet grouting design and construction parameters for TBM launching and arrival. A large-diameter jet grouting technique was used to form jet grouted blocks at the TBM launching and arrival areas. Regarding the design method, it was found that the cohesion of the jet grouting mixture is one of the key parameters that affect the jet grouted block dimension. The permeability and dimension of the jet grouted block are also essential design parameters when the tunnel is subjected to high water pressure at a greater depth. Regarding the construction method, it was concluded that to minimize construction issues a combination of many construction techniques, such as jet grouting, sealing rings, concrete blocks and flood of the chamber, should be applied to provide safer TBM breakthroughs.
