Soil Improvement for Earth Pressure Balance Shields Construction in Watered Sandy Stratum

Abstract:

In order to improve the residue in shield construction, slump tests for watered sandy stratum in Shenzhen were conducted by using foam, bentonite and polymer. Based on the results of field test, laboratory tests including electron microscope scanning, permeability test and compression test were performed. The variation of soil sample properties as meso structure, the seepage and squeezing were analyzed. Based on the tested data, the effects of additives on improving plasticity fluid and capability of retaining water of sandy strata as well as the balance mechanics of shield work face were discussed in detail. As reasonable proportion, bentonite with mass ratio of 1∶7, incorporation 8% to 10% were determined providing valuable experience for shield construction in the similar strata.

Key words:watered sandy stratum; earth pressure balance shield; soil improvement; electron microscope scanning; permeability test