Soil Conditioning of Waterless Sand–Pebble Stratum in EPB Tunnel Construction
Due to large porosity, high soil friction, less cohesion, low flow of waterless sand–pebble stratum and the problem of very difficult in achieving a soil pressure balance in the shield front during the earth pressure balance (EPB) shield construction process, the soil conditioning for EPB excavation in the waterless sand–pebble stratum along Urumqi rail transit line 1(L1) is studied. A series of laboratory tests are performed to investigate and assess the properties of selected additives and the conditioned soils. The additives test results show that foam A with relative higher half-life, foaming ratio and adhesion thickness can be adopted preferentially; the most optimal mass concentration ratio of three types of bentonites (named S1, S2 and S3) slurry are 1:6, 1:10 and 1:15, respectively when funnel viscosity is around 64/s. The slump test results showed a trend of increasing after first decreasing to zero when using a single additive such as water or bentonite slurry indicate single additive cannot achieve a better soil conditioning effect. Slump value can reach about 230 mm when conditioned the soil with 14% water content and only added 15% of the foam (concentrate rate is 3%), and the conditioned particles on the surface sediment are evenly dispersed, which is able to achieve an ideal effect in the shield. Economic and reasonable soil conditioning ratio is the water content to 14% + 6% bentonite (bentonite ratio is 1:15, funnel viscosity is 65.08/s) + 5% foam with the concentrate rate of 3%. The results can be used to provide guidelines for the excavation by use of EPB machine under such soil conditions.
KeywordsShield Soil conditioning Laboratory tests Waterless sand–pebble stratum EPB
The authors acknowledge the financial support provided by Urumchi Construction Project of Science and Technology (No. H151312001) and Natural Science Foundation of China (No. 41302223), Science and Technology Plan Projects of Chongqing Administration of Land, Resources and Housing (KJ-2015047), Chongqing No. 3 colleges and universities youth backbone teachers funding plans and Chongqing Research Program of Basic Research and Frontier Technology (cstc2016jcyjA0074, cstc2016jcyjA0933, cstc2015jcyjA90012), Scientific and Technological Research Program of Chongqing Municipal Education Commission (KJ1713327, KJ1600532). China Railway Engineering Equipment Group Co., LTD greatly acknowledged for the test support of this paper.
- Chao M, Gong QM, Jiang HT, Zhou YP (2013) Research on micro-structural mechanism of conditioning the excavated soil in earth pressure balanced TBM. In: ICPTT 2012 © ASCE 2013, pp 1619–1656Google Scholar
- Jancsecz S, Krause R, Langmaack L (2009) Using the slump test to assess the behavior of conditioned Soil for EPB tunneling. Environ Eng Geosci 8(3):167Google Scholar
- Jiang HT, Gong QM, Du XL (2013) Experimental study on soil conditioning in cobble layer by use of earth pressure balanced machine. Chin J Geotech Eng 35(2):284–292Google Scholar
- Langmaack L (2000) Advanced technology of soil conditioning in EPB shield tunnelling. MBT PublicationGoogle Scholar
- Martinelli D, Chieregato A, Onãte Salazar CG, Barbero M, Peila D (2015) Conditioning of fractured rock masses for the excavation with EPB shields. In: Proceedings of the 13th international congress of rock mechanics. International Society for Rock MechanicsGoogle Scholar
- Oggeri C, Vinai R (2012) Soil conditioning and ground monitoring for shield tunnelling. Rev Min 18(4):2–14Google Scholar
- Peña Duarte MA (2007) Foam as a soil conditioner in tunnelling: physical and mechanical properties of conditioned sands. Ph.D. Thesis, University of OxfordGoogle Scholar
- Peron JY, Marcheselli P (1994) Construction of the ‘Passante Ferroviario’ link in Milan. Italy. lots 3P, 5P, and 6P: excavation by large EPBS with chemical foam injection. In: IMM (ed) Proceedings of Tunnelling ’94. Chapman & Hall, London, pp 679–707Google Scholar
- Williamson GE, Traylor MT, Higuchi M (1999) Soil conditioning for EPB shield tunneling on the south bay ocean outfall. In: Proceedings of RETC rapid exaction and tunneling conference, pp 897–925Google Scholar