Automatic pressure-control equipment for horizontal jet-grouting

•Automatic pressure-control equipment for horizontal jet grouting•Innovative elements: i) monitor, ii) pressure control, and iii) spoil discharge•Field test and monitoring results verify the applicability of the new equipment.

A new horizontal jet grouting equipment is proposed to eliminate the harmful effect on the surrounding environment due to the injection of large amount of water and/or grout under high jetting pressure. The components of the proposed equipment and the construction procedures are introduced. During horizontal jet grouting by the proposed equipment, the inner pressure of the soil stratum can be monitored automatically, the generated spoil can be transported out, and the impact on surroundings (such as ground upheaval and lateral displacement of the subsoil) can be mitigated. A field test involving the installation of five horizontal jet grout columns was conducted in Shanghai to demonstrate the applicability of the new equipment. In addition, monitoring instruments were installed to observe the vertical displacement of the ground surface. The measured maximum value of the ground surface upheaval was as low as 9.4 mm, which verifies that the new equipment performed as per expectations. Finally, the in-situ quality of jet grouted columns was found to be very good based upon the results of field cone penetration and unconfined compressive strength tests.