SHAFT CONSTRUCTION – SCG Canada

High Pressure Jet Grouting Piles (JGP)

High pressure jet grouting is an erosion-based grouting technique using a high-pressure jet of grout to break up the soil structure and simultaneously mix the loosened soil with a cement grout to form column-shaped grouted soil bodies. The distinct advantage of jet grouting is to significantly increase the strength of the surrounding soil and/or reduce its permeability and therefore risk of water infiltration. The typical steps of to JGP construction include the following:

Advance steel drill rod downward to the designed pile depth
Activate the high pressure jet grouting system and perform jet grouting. High pressurized cement grout is injected into the soil through the monitor nozzle at the bottom of the drill. As the drilling rod and drill bit are rotating and slowly pulled up at a controlled rate, the kinetic energy of the jet grout loosens the soil and mixes the soil with the cementitious grout
In the consolidated soil, a cylindrical grouted soil column is formed by a homogeneous mixture of injected cement grout and soil. Upon reaching the desired column height, jetting is stopped and the tube is withdrawn
A central reinforcement bar, a reinforcement cage of limited dimensions or a steel profile can be inserted into the freshly formed grout column

The following parameters are monitored during the jet grouting application in real-time, which include height of the column, jet pressure, jet grout volume, rotation speed of the jet stream, rate of withdrawal of the jet string.

Installation of JGPs as a soil improvement construction method has been adopted for ground with presence of quicksand and high water table in many projects worldwide. SCG has a tracking record of successful installation of JGPs for many projects in the past. The installation of JGPs is to achieve the following:

Limit the settlement of the areas around the shafts
Stabilize the soil body around the shafts which was in the previously disturbed area
Limit underground water infiltration
Provide support for deconstructing the existing steel members in the tail tunnels and reconstructing the tail tunnel to meet the proposed MTBM tunnelling
Provide adequate strength and support for MTBM working and retrieval shafts

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