Introduction
Contiguous pile walls are widely adopted for basement construction and underground works in congested urban areas. Their adaptability, ease of construction, and cost-effectiveness make them suitable for supporting deep excavations close to existing structures. Case studies provide valuable insights into real-world performance, design challenges, and lessons learned from contiguous pile applications.
Typical Applications in Basement and Underground Works
- Multi-level basements in urban buildings
- Underground parking structures
- Metro stations and tunnels
- Utility corridors and service shafts
Case Study 1: Deep Basement Construction in Dense Urban Area
Project Overview
A 3-level basement was constructed in a metropolitan city with adjacent residential buildings within 2–3 m of the excavation boundary.
Ground Conditions
- Fill over soft clay
- High groundwater table
Design Solution
- Contiguous pile wall with 600 mm diameter piles
- Pile spacing of 750 mm
- Multi-level ground anchors installed
Performance Observations
- Wall deflection within permissible limits
- Ground settlement less than predicted values
- Adjacent buildings showed no structural distress
Case Study 2: Underground Parking Facility
Project Overview
Construction of a two-level underground parking structure beneath an existing commercial complex.
Ground Conditions
- Medium dense sand
- Moderate groundwater inflow
Design Solution
- Contiguous piles with temporary strutting
- Dewatering system implemented
Performance Observations
- Controlled lateral movement
- Minimal groundwater seepage
- Successful completion without delay
Case Study 3: Metro Station Box Construction
Project Overview
Cut-and-cover excavation for an underground metro station.
Ground Conditions
- Mixed soil profile with weathered rock
- Variable groundwater conditions
Design Solution
- Large-diameter contiguous piles
- Combination of anchors and struts
- Instrumentation for real-time monitoring
Performance Observations
- Effective ground movement control
- Timely adjustment of support levels
- High construction safety
Key Lessons Learned from Case Studies
- Early installation of supports reduces wall deformation
- Groundwater control is critical to performance
- Proper pile spacing improves soil arching
- Monitoring allows adaptive construction
Challenges Observed
- Construction tolerance control in restricted sites
- Managing groundwater in permeable soils
- Interaction with adjacent foundations
Best Practices Identified
- Detailed site investigation before design
- Use of numerical modeling for prediction
- Implementation of observational method
- Continuous monitoring and quality control
Performance Comparison with Other Retaining Systems
- More economical than diaphragm walls for moderate depths
- Easier installation than secant pile walls
- Suitable where groundwater cut-off is not critical
Conclusion
Case studies on contiguous pile walls for basement and underground works demonstrate their effectiveness in controlling ground movement and ensuring excavation stability in urban environments. Successful performance depends on optimized design, proper construction sequencing, groundwater management, and active monitoring. These real-world experiences highlight contiguous piles as a reliable solution for basement and underground construction projects.
