Description:
Open-cut excavation involves digging without internal support or bracing structures, allowing for large-scale excavation equipment and efficient construction of the main structure. This method is fast and cost-effective, suitable for sites with low groundwater levels and ample space.
No retaining or bracing structures required (except for high-permeability strata, where water cutoff structures are necessary).
Easy excavation and quick soil removal.
Convenient for internal civil structure construction.
Lower construction costs.
Higher soil removal volume; backfilling may increase costs if no stockpile area is available.
Limited excavation depth (generally ≤10m).
Requires low groundwater levels or dewatering measures if no water cutoff structure is used.
Needs open space with no nearby protected structures.
Slope protection measures may increase costs during rainy seasons or long construction periods.
Description:
This method is environmentally friendly, producing no pollution, noise, or vibration. It is cost-effective and allows for unobstructed excavation and construction inside the pit.
No internal bracing required.
Lower construction costs.
Low strength of cement-soil mixing piles (typically 0.8 MPa).
Significant environmental impact during construction.
Requires trapezoidal overlapping construction.
High cement consumption (13–15%).
The large construction site is needed.
Significant wall deformation.
Description:
This technique forms piles of various diameters (single, double, or triple-fluid systems) and can bypass underground utilities. It serves as a water cutoff curtain and can create self-supporting walls, eliminating the need for internal bracing.
Suitable for soft soils, clay, silt, sand, loess, and gravel.
Not ideal for soils with large boulders, hard clay, or organic content.
Used in foundation reinforcement, deep excavation waterproofing, slope stability, and underground pipeline reinforcement.
Functions as a gravity retaining wall or water cutoff structure.
Higher strength than cement-soil mixing piles (1.2–2.0 MPa).
Less environmental impact.
Flexible obstacle avoidance.
Larger diameters (0.6–2.5m).
Higher cost than cement-soil mixing piles.
High cement consumption (20%).
Description:
Best for low-water-table cohesive soils, this method uses soil-wall interaction for stability, offering fast construction and minimal environmental impact.
Temporary/permanent retaining structures.
Slope stabilization, foundation underpinning.
Fast construction, no internal bracing.
Lower deformation than gravity walls.
Cost-effective.
Requires layered excavation.
Waterproof curtains are needed in high-water-table soft soils.
Difficult quality control; low nail load capacity.
Description:
Minimal footprint, no additional retaining structures, and low impact on surroundings.
Wet Caisson: Uses slurry or compressed air.
Dry Caisson: Workers excavate inside.
Cost-effective, structurally robust.
Difficult to correct large caisson deviations.
Challenging soil removal in wet conditions.
Significant ground settlement.
Types:
By construction: Pile, panel, composite.
By material: Reinforced concrete, plastic concrete, steel.
Applications:
Depths >10m.
Permanent structural walls with high waterproofing needs.
Top-down construction.
Used for shallow slopes/excavations.
Low noise/vibration alternatives are available.
Composed of drilled/bored piles.
Requires capping beams for stability.
Installed in pre-drilled holes for tension resistance.
Ideal for unobstructed excavation.
Choosing the right underground construction method depends on soil conditions, depth, groundwater, and project requirements. Each technique offers unique benefits, from cost-effective open-cut excavation to robust diaphragm walls for deep projects. Proper selection ensures safety, efficiency, and cost control.
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