Improvement Efficacy of RJP Method in Shanghai Soft Deposit

This paper presents a case history on the efficacy of Rodin Jet Grout (RJP) construction in the soft deposit of Shanghai. The RJP columns were employed to improve the soft deposit in a deep excavated pit. The excavation depth was about 43 m. Jet grouting reached to the depth of 50 m, in which the soil types varied from soft clay, silt, stiff silty clay (SSC), and sand. Field construction was performed with different construction parameters such as jetting pressure, nozzle diameter, and retrieving speed. The diameter and mixing uniformity of the columns was measured and checked layer by layer during the excavation of the pit. The results showed that except for the layer SSC, the column diameter is over 1.8 m with the largest diameter of 3.3 m in soft clay layer at a depth of 15.3 m. In cohesive soil layer, mixing quality is good. However, in cohesiveless soil, although the eroding range reached 2.0, the soil and cement was separated and mixing uniformity was poor.