Port of Christchurch Wharf and Seawall Stabilization

Lyttelton, New Zealand


Raito, Inc.

The Lyttelton Port of Christchurch (LPC) in New Zealand is a critical piece of infrastructure that acts as the biggest importer of exporter of goods to the South Island.  Between 2010 and 2011,  LPC suffered a series of earthquakes exhibiting strong ground shaking that severely damaged the physical infrastructure including the main container wharves, Cashin Quay 2 (CQ2) and Cashin Quay 3 (CQ3).    Q2 and CQ3 were built in the 1960s by dumping large rubble-rock fill over of liquefiable sands to induce intentional slope failures to remove the weak areas; however, there was still much liquifiable material left and ground motions experienced were much higher than anticipated.  Seismic-induced lateral spreading of over 1.6 ft was measured along CQ2 and CQ3 which caused significant deformation to the wharf decking and piles rendering it inoperable.

TERRA Engineers was responsible for the innovative design as part of a Design-Build project with Raito, Inc.  The design  involved using Cement Deep Soil Mixing (CDSM), steel h-pile reinforcement, tieback anchoring, and an armored finish to stabilize the backlands and provide a finished reinforced seawall.  A key challenge to the project was the installation of CDSM through the large rock obstructions left in place from the construction.  TERRA performed engineering analyses to ensure the CDSM and reinforcement was sufficient to carry significant earth pressure loading under heavy container storage, port operations equipment, and ship mooring loads according to port codes. Analyses included:

  • Pseudo-Static and Static Limit Equilibrium analysis of CDSM Designs under Several Loading Scenarios
  • Monte-Carlo Simulation on Potential Configurations of CDSM Footprints Based on Vertical Drilling Tolerance
  • Structural Analysis of Steel Reinforcement for Bending and Shear Capacity
  • Finite Element Analysis of Earth Pressure Loads for Slope Stability and Tieback Design
  • Sizing and Lateral Capacity of Deadman Columns
  • Sensitivity Study of Key Parameters to Ensure a Robust Design

TERRA also provided on-site construction-phase engineering services during the Test Section to monitor movements of the existing seawall and analyse results for potential problems; develop as-built drawings;  record field-logs of coring operation and selection of CDSM core specimens for strength testing; and analyzing the unconfined compression strengths test results on CDSM.

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