Technical Principle

The front-end device of the MJS method

The MJS Method is a foundation treatment technique capable of multi-directional construction. It utilizes high-pressure jet grouting equipment with multi-directional capacity, integrated with drilling tools that provide active sludge discharge and ground pressure control. During the process, high pressure jets cut the soil while hardening slurry is simultaneously injected and mixed to form reinforced elements of specified strength. By monitoring ground pressure and employing active sludge discharge, the method achieves precise pressure management, effectively minimizing construction impact on the surrounding ground and environment. The core of the MJS method lies in its active sludge discharge system and ground pressure monitoring, both of which are enabled by a novel front-end slurry preparation device (see figure below).

 

The device integrates 7 dedicated nozzles (high-pressure slurry, main air, lower cutting, upper cutting water, reverse suction water, and 2 reverse suction air nozzles), along with a pressure sensor and active sludge discharge port. The high-pressure slurry nozzle injects cement slurry, with the main air nozzle using compressed air to assist cutting. The lower cutting nozzle sprays hardening control agent while drilling; the upper cutting nozzle pre-cuts clay or stabilizes silt. The reverse suction water nozzle generates negative pressure, while the reverse suction air nozzles create an air-lift effect.

The system monitors stratum pressure in real time via the pressure sensor and coordinates with the discharge valve for flow control. The active sludge discharge port removes sludge to ground level using negative pressure and air lift effect. This design enables precise pressure management, reducing nozzle load while improving pile formation quality and construction efficiency.

Porous Pipe

The front-end slurry-making device is bolted to the multi-channel pipe, with their internal channels aligned and interconnected. In addition to the connecting passages, the pipe incorporates 11 dedicated channels for supplying air, water, hardening materials, hydraulic oil, and electricity to the front-end device, as well as for slurry discharge, as illustrated in the figure.

Construction Principle

The MJS Method can perform foundation treatment operations at any angles (including full-circle, semi-circle and fan-shaped) in any directions such as vertical, horizontal and inclined. The active sludge discharge and precise management of underground pressure make the horizontal foundation treatment construction under water-rich conditions safe and feasible, as shown in the figure below.

Construction Case

Nanjing Metro Line 7 Project, Underground Excavation Project of Zhongsheng Station in Section 4 of D7-TA02 Bid Section

General Contractor: China Railway No.3 Engineering Group Co., Ltd.

Project Time: May 2020

Construction Unit: Shanghai Guanglian Environmental Geotechnical Engineering Co., Ltd.

Horizontal Technical Parameters: φ2600mm semicircle (180°/84 pieces) and φ1500mm full circle (360°/8 pieces); horizontal reinforcement length: 17-27 meters.

Cement Content: Divided into three sections along the pile length based on cement content, with the contents being 45%, 50%, and 60% respectively.

Compressive Strength: The average compressive strength is 3MPa for 45% cement content, 3.24MPa for 50% cement content, and 4.75MPa for 60% cement content.