Risk/event source



Deep excavation assuring protected environment

1) Controlling foundation pit deformation;

2) Limiting ground movement (sudden ground loss or subsidence)

Geotechnical conditions

Spatial geo-material variation & uncertainties (different site conditions)

Inverse analysis based on observations during excavation to confirm actual & design assumption; Enhance soil strength by grouting; Turn to appropriate construction method to suit unanticipated condition

Leakage & hydraulic failures

End-plate method connection for diaphragm wall joints; With relief wells release confined aquifer pressure; Waterproof curtain by mixed-in-place technology; Prevent uplifting by hybrid of jet grouting & deep soil mixing

Global and/or localized soil and excavation support structure failure

Zoned construction method (quick excavation, prompt propping, casting rigid floor slab timely); Provide sufficient wall embedment & adequate passive resistance (including stiffness of retaining wall-strut system, soil/anchor length with soil voids filled by grout); Increase unlading moduli of basal stratum with ground improvements

Selection of proper constitutive model (model simplification and omissions)

Consider optimum compromise to account for path- and state-dependent soil properties; Insufficient level of detailing and design accuracy

Surrounding existing condition

Structural and geotechnical failure of existing piles

Construction of isolation/barrier piles to reduce imposed external passive loading (bending moment and forces) on piles

Abrupt loss of foundation bearing capacity

Avoid over-excavation to prevent toppling; Compensation grouting

Tensile strains induced in a building

Component and system fragility assessment for limiting tensile strain (reliability analysis approach)

Differential foundation settlement; movement and rotation at pile head

Renovation, backfilling and underpinning to limit distortions in the sagging and hogging zones

Project-delivery system

Uncertainties in performance measurements as required by the contract

Risk transfer through negotiated exception clauses included in the bid or through claims

Amount of risk willingly taken by the owner

The traditional design-bid-build is ineffective in minimizing adversarial relationships

Poor on-site management & communication

Continues performance & productivity monitoring with 4-eye principle; Turn to Design-Build or Construction-Management at work mode of project delivery

Political and financial related

Change of related-low and regulations; Price escalations, payment delays, etc.