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Jet-grouting is a ground improvement method, in which liquid solidifying agent is injected into soft-ground with water and air-pressure to mix or replace the soil with the agent. The uniaxial com-pressive strengths of improved soil by Jet-grouting have uncertainties depending on the factors of the grout materials and the mixing conditions. In this study, the laboratory mixed strength tests are performed to analyze the sensitivity of the uniaxial compressive strength depending on the influence factors, e.g. mixing time and speed, water-cement ratio (W/C), and cement quantities.
The uniaxial compressive strengths of specimens increase significantly as the mixing time and the mixing speed increase. When the soil and solidification agent are mixed more than a speed of 180rpm or mixed more than 3min, variation of the uniaxial strength of the samples are decreased. Water-cement ratio (W/C), influences on the workability of field construction. When W/C ratio is less than 1.0, the uniaxial compressive strengths of the specimens decrease, as W/C increases. Variations of uniaxial compressive strength of the specimens are increased when W/C is greater than 1.0. The uniaxial compressive strength of the field grouted specimens turned out to be about 64% of the uniaxial compressive strength of labora-tory mixed specimens.