In this paper, mechanical properties of jet-grouted soilcrete are investigated. Jet grouting (JSG) was conducted to improve ground properties for the construction of a cross-passage between a sewerage tunnel and a manhole of the Taipei Sewer Sub-main System. Soils treated were silty sand and sandy silt. Cylindrical specimens were drilled from the site and tested in the laboratory. Experimental results show that the elastic wave velocities, modulus of elasticity, and uniaxial compressive strength of soilcrete increase with increasing dry density. Poisson's ratio of soilcrete varies from 0.05 to 0.29, which is very close to the ratio for concrete. Brazilian tensile strength of soilcrete varies from 1/7 to 1/28 of its uniaxial compressive strength. The cohesion of jet-grouted soilcrete varies from 0.40 to 4.22 MPa, and the internal friction angle varies from 20° to 44°.
The ground improvement technique termed jet grouting was first applied to soils by the Japanese about three decades ago (Miki, 1973; Yahiro and Yoshida, 1973). Currently, there are three major forms of jet grouting which involve the injection of a single fluid, two fluids, or three fluids (Kauschinger and Welsh, 1989). The Jumbo-jet Special Grout (JSG) method discussed in this article belongs to the double-fluid injection category. For this method, the grout jet sheathed in a stream of compressed air is used to breakdown soil structures and to force mixing of grout with natural soil particles. Engineering properties of soilcrete formed in the ground by jet-grouting method have been reported by Yahiro et al. (1975, 1982), Mitchell (1982), Shibazaki and Ohta (1982), JSG Association (1986), Bertero et al. (1988), Burke et al. (1989), Gallavresi (1992), Kaushinger et al. (1992), Fang et al. (1993, 1994a, 1994b, 1997), Yu (1994), and Kuo (2001).
