| Popis: |
As the most advanced soil improvement technique, foam modifying soil measures always are taken when the EPB shield tunneling in the water-rich sand and complex strata. Experimental research on foam-modified fine sand and coarse sand was carried out using self-developed foam agent, conclusions were drawn that foam can not only reduce the permeability coefficient and shear strength significantly, but also it can enhance the fluidity of the sand greatly. If appropriate quantity of bentonite or clay is injected in the sands, the water-holding capacity and liquidity will be further enhanced while the permeability coefficient of modified sands will be further reduced. Combining the experimental results of permeability, direct shear strength and fluidity of foam-modified sand, the corresponding quantitative indicators were proposed and it will provide reference for the parameters selection of sand modification in the shield tunneling construction. And some field experimental results of metro construction are introduced to show the performance of foam. |
