August 22, 2022
Application of TRD and Jet Grouting Pile Combination Method in Shield End Reinforcement
In the process of urban subway shield construction, departure and arrival are the most dangerous links in the whole process. If not handled properly, it will cause serious engineering accidents such as flooding and collapse. In order to ensure the stability of the starting and arriving ends of the shield construction, it is necessary to formulate a reasonable reinforcement scheme in combination with the specific geological conditions. The commonly used methods include a freezing process, jet grouting pile, SMW method, etc. However, with the increase in the complexity of the urban underground situation, the single construction method can no longer meet the corresponding construction needs, and various combined new construction methods are emerging. Among them, the freezing process of construction technology level is higher and the construction cost is higher, jet grouting pile method cost is lower, but more suitable for clay, silt, and other geological conditions, for complex geological conditions of the reinforcement effect is not ideal. TRD ( Trench cutting Re-mixing Deep wall method ) was first developed by Kobe Steel Corporation in Japan in 1933. It is a construction method of underground continuous walls with equal thickness.This method has been widely used in various projects because of its good stability, good quality and high precision.
Jet grouting pile scheme
The head shaft of the shield receiving end in the steam flow section is reinforced with D600 @ 450 mm jet grouting pile, and the pile is bitten by 150 mm. The double-tube high-pressure jet grouting rig is used for construction. The jet grouting pile construction will be based on the construction of the TRD cement mixing wall. Consider whether to replace the filling in the construction area. The reinforcement range is 10 m out of the station and 12 m on both sides of the middle line. The reinforcement depth is 18.3 m below the ground, the depth of the weak reinforcement area is 6.236 m, and the depth of the strong reinforcement area is 12 m. The curing agent is P.O42.5 ordinary Portland cement, and the cement slurry adopts a water-cement ratio of 1: 1; the pressure of double pipe high-pressure grouting should be greater than 20MPa, the flow rate should be greater than 30L / min, the air pressure should be greater than 0.7MPa, the lifting speed should be 0.1 ~ 0.2m / min. After reinforcement, the 28d unconfined compressive strength Qu ≥ 0.8MPa, and the permeability coefficient k ≤ 10 ~ 7cm / s.
