Blog

Deep Excavation Engineering: Key Construction Techniques and Safety Measures

With the development of high-rise buildings and underground spaces, excavation engineering—especially deep excavation projects—has become increasingly large-scale and complex, presenting numerous technical challenges. This field is also one of the most accident-prone areas in construction. Below, we outline the key construction points for excavation engineering.

01 Hazard Identification and Control in Excavation Engineering

Major Hazards

  1. Excavation affecting adjacent structures or facilities requires special protection.

  2. Continued use of structures beyond their designed service life.

  3. Modifications to the original design, such as deepening, expanding, or changing usage conditions.

  4. Nearby construction activities (e.g., pile driving, excavation, dewatering) affect excavation support safety.

  5. Adjacent water sources.

General Hazards

  1. Poor-quality materials, defects, structural damage, or other adverse conditions affecting safety.

  2. Vibrations or shear forces from support structures or pile construction can cause soil liquefaction or seepage failure.

  3. Severe leakage in waterproof curtains.

  4. Major roads within the excavation influence zone or potential leaks from underground pipelines.

  5. Reduced effectiveness of soil nails or shallow prestressed anchors during rainy seasons.

  6. Sidewalls consisting of miscellaneous fill or special soil types.

  7. Excessive heaving during excavation.

  8. Vibrational loads on sidewalls.

  9. Failure or progressive collapse of internal bracing.

  10. Lateral impact loads on support structures.

  11. Power outages, drainage system failures during typhoons or heavy rainfall.

  12. Excessive deformation or ground cracks due to soil nail or anchor creep.

Hazard Control Measures

  • Pre-construction control: Develop risk mitigation measures in construction plans.

  • Construction process control: Strictly supervise and implement corrective actions.

Comprehensive Safety Management

  1. Implement safety responsibility systems and establish management protocols.

  2. Conduct safety training to enhance worker awareness.

  3. Strengthen safety expertise among management personnel.

  4. Apply preventive measures tailored to identified hazards.

02 Selection of Excavation Support Methods

Shallow Excavation (Depth <5m)

Common methods include:

  • Anchor and inclined strut supports: Suitable for large but shallow excavations.

  • Short pile and lagging wall supports: Used where partial slope cutting is insufficient.

  • Steel sheet pile supports: Ideal for low groundwater levels in cohesive or sandy soils.

Deep Excavation (Depth ≥5m or Complex Conditions)

Common methods include:

  • Soldier pile walls & diaphragm walls: For high-safety-grade excavations.

  • Cement-soil mixing walls: For medium-risk excavations.

  • Top-down arched walls: For low-risk excavations (not suitable for soft clay).

03 Key Excavation Techniques

Unsupported Excavation

  • Suitable for open areas with moderate depth.

  • Soft soils: Limit layer thickness to 2m and depth to 6–7m.

  • Hard soils: Layer thickness ≤5m (no depth limit).

Supported Excavation Methods

  • Bowl excavation: Central digging first, preserving slopes for temporary support.

  • Island excavation: Peripheral digging with central soil retained for stability.

Construction Guidelines

  1. Follow “layered excavation, immediate cushioning” principles.

  2. Combine excavation with slope reinforcement.

  3. Use manual digging where machinery is impractical.

  4. Pause excavation 200–300mm above the final grade for manual leveling.

  5. Conduct pre-excavation monitoring for safety assurance.

04 Common Accidents and Mitigation

Excessive Displacement or Collapse

  • Displacement: Halt excavation, backfill if necessary.

  • Collapse: Install temporary steel sheet piles with shotcrete.

Base Heave or Soil Eruption

  • Heave: Backfill and reinforce the base soil.

  • Eruption: Install barrier piles and dewater.

Support Structure Defects

  • Leaks: Use grouting or polyurethane injection based on severity.

  • Void formation: Fill cavities via compaction grouting.

Adjacent Building Damage

  • Cracks/settlement: Halt work, consult experts, and reinforce soil via pressure grouting.

05 Excavation Monitoring

Monitoring Point Layout

  • Place horizontal/vertical displacement points along perimeter (3+ per side, ≤20m spacing).

Monitoring Techniques

  • Lateral soil movement: Measure via inclinometer tubes (accuracy ≥0.25mm/m).

  • Groundwater levels: Use piezometers (accuracy ≥10mm), distinguishing shallow/deep aquifers.

By adhering to these practices, excavation projects can mitigate risks and ensure structural and environmental safety.

Recent Posts