Introduction to the process of continuous mixing wall with equal thickness cement soil
June 17, 2025
▍ Introduction to TRD construction method
The TRD method, also known as the equal thickness cement-soil underground continuous mixing wall method, operates on the principle of using a chain saw-type tool box to vertically penetrate the ground. The tool box then moves horizontally while the chain drives the tools to rotate up and down, mixing the original soil and injecting cement slurry to form a water-stopping wall of uniform thickness and strength.
TRD technology was developed in Japan in the early 1990s. It is a set of advanced engineering equipment and construction methods that can continuously build walls in all kinds of soil layers and gravel layers. It is mainly used in various construction projects, underground projects, bank protection projects, foundation reinforcement of DAMS and embankments, and seepage prevention treatment.
TRD method is suitable for cohesive soil, sand, gravel and gravel strata. It is also suitable for compact sand layer with penetration of 50~60 blows and soft rock with unconfined compressive strength not greater than 5MPa.
▍ TRD construction and process cycle
The construction technology of TRD method includes: cutting box self-penetrating excavation process, cement soil mixing wall construction process, cutting box removal and decomposition process. The cement soil mixing wall construction process of TRD method has three cycles and one cycle:
The three-cycle method involves initial excavation, withdrawal excavation, and wall-forming stirring. The chain saw cutting box first injects excavation fluid to excavate a section of the distance, then withdraws to the original position, and injects curing fluid to advance and stir to form a wall. This method is typically used in deep walls, gravel layers, or environments with underground obstacles. In the one-cycle method, the cutting box is immediately injected with curing fluid to advance and stir to form a wall. The decision to use the three-cycle or one-cycle method is based on whether the cutting box can achieve a transverse speed of 1.7m/hr.
1. Excavate the trench
Excavate the trench with excavator, the width of the trench is about 1000mm, the depth of the trench is about 1000mm.
2. Lower the pre-buried box
Use the excavator to dig a pre-buried hole with a depth of about 3m, a length of about 2m and a width of about 1m. Place the pre-buried box, and then lift the cutting box into the pre-buried box section by section. After the cutting box is fully installed, backfill the pre-buried hole, and backfill it tightly.
3. Pile machine positioning
Set up a total station on one side of the construction site and adjust the position of the pile driver. The team leader shall uniformly command the pile driver to be positioned. Before moving, check the situation above, below, left and right, and remove any obstacles in time. After moving, check the positioning and correct it in time. The pile driver should be stable and flat.
4. Connect the cutting box to the main engine
The cutting box is lifted into the pre-buried hole section by the designated crawler crane and fixed with the support platform; the TRD host is moved to the pre-buried hole position to connect the cutting box, and then the host returns to the predetermined construction position for the cutting box to be driven into the excavation process by itself.
5. Install the inclinometer
After the cutting box is driven into the designed depth, the inclinometer is installed. Through the multi-segment inclinometer installed in the cutting box, the vertical accuracy of the wall can be managed to ensure the accuracy of 1/250.
6. Wall construction by TRD method
After the installation of the inclinometer, the main engine is connected to the cutting box. Digging liquid or curing liquid is injected into the bottom of the cutting box to force it to mix and stir with the original soil to form an equal thickness cement soil underground continuous wall.
7. Replacement soil treatment
The waste slurry generated in the construction process of TRD method shall be uniformly piled up and centrally treated.
8. Pull out the cutting box
At the end of the current construction section, the cutting box shall be pulled out and reassembled for subsequent operations. The cutting box shall be pulled out at a position far away from the overhead line.
▲ TRD drilling equipment is used
▲ TRD cutting and mixing
▍ Advantages of TRD construction method
The construction depth is large
The maximum depth is 80m, and the wall width is 550mm-1200mm. There are many construction cases with a depth of 60m-70m in China.
Wide adaptability to strata
Compared with traditional construction methods, it can adapt to a wider range of strata. It can be used in general soil layers such as sand, silt, clay and gravel, and hard ground layers (pebbles, viscous mud, sandstone, limestone, etc.) with N value not exceeding 50.
The wall is of good quality
The continuous cutter saw is used to excavate vertically to the designed depth in one operation, followed by mixing and horizontal advancement. This method ensures uniform wall quality even in complex strata. Compared to traditional methods, the cement-soil wall ensures uniform mixing from top to bottom, excellent water-stopping performance, minimal dispersion, and continuous construction without joints (no poor interlocking), ensuring high continuity and water-stopping performance.
High stability
The height of the main machine is only 8.7-12 meters, with a low center of gravity and good stability. Compared with traditional construction methods, the height of the machine has no relation to the construction depth, and it has high stability and good passability. The rollover accident is "0"! During the construction process, the cutting box is always inserted into the ground, so it will never be overturned.
▲ High contrast between multi-axis, double-wheel stirring and TRD equipment
High construction accuracy
The real-time monitoring equipment tracks various parameters during the construction process, ensuring the vertical accuracy of the TRD wall throughout the construction process, a level of precision that traditional methods cannot achieve. The construction management system continuously monitors the X and Y coordinates at different depths of the cutting box, allowing for real-time adjustments to ensure the wall's precision.
The walls are of the same thickness
The wall is continuous, equal thickness and seamless connection, which is a real "wall" rather than a "fence". H-shaped steel and other core materials can be inserted at any distance to save construction materials and improve construction efficiency.
The surrounding soil has little influence
In the process of mixing and pouring cement slurry, the pressure of TRD method is smaller than that of SMW method, especially when the foundation pit is close to the protected building or pipeline subway, and the influence on the surrounding soil is less.
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