Portland Bulk Terminal 5 (PBT5)
Location: Portland, Oregon, United States
Client: Canpotex/Hatch Mott MacDonald
In 2012, Hatch Mott MacDonald retained MEG Consulting to provide preliminary geotechnical input and FEL3 recommendations for the proposed rail overpass structure and storage building which forms part of the upgrade project development at the Portland Bulk Terminal 5 (PBT5) located in Portland, Oregon. The project also included a preliminary evaluation of the existing berthing structure under seismic conditions.
M+EG was responsible for all geotechnical engineering design aspects including:
• Supervision of mud rotary drilling, SPT and Shelby sampling and in-situ testing using SCPT;
• Laboratory testing (including advanced dynamic testing with cyclic simple shear tests) to provide input to the static and dynamic characterization of the foundation soils;
• Completion of 1D site-specific seismic response analyses using both equivalent linear and non-linear analysis methods (SHAKE and DESRA);
• Analysis of the susceptibility of the granular soils to initial liquefaction under the design earthquake conditions;
• Preliminary design of the ground improvement including surcharge/preload and stone columns;
• Stability and settlement analyses for the proposed rail overpass structure, new storage building, transfer towers and conveyor supports.
- The design of the bridge structure was performed based on Oregon Structural Specialty Code (2010) and Oregon Department of Transportation (ODOT) Specifications (2005 and 2011). In addition, the definition of the design response spectra was performed in accordance with ASCE 7-10 (2010) for the new storage building.
- Based on the de-aggregation data obtained from the USGS (2008), the magnitude (M) and the rupture distance (R) pairs have been determined for the shallow crustal, deep intraplate subduction and Cascadia subduction zone earthquakes. Using the M-R pairs and the probabilistic seismic hazard analysis, earthquake records have been selected and the corresponding PGA has been calculated to perform site response analyses.
- To reduce the durations of the surcharge time, wick drains were considered to be installed. Settlement analyses were performed to estimate the construction settlements and the anticipated surcharge durations with and without the installation of wick drains.
- Ground improvement using stone columns was considered in the design for mitigating the potential ground movements associated with liquefaction under the seismic design scenarios.
- The stability of the existing wharf was also analyzed under a number of different earthquake scenarios using preliminary soils information to assess the impact of liquefaction and ground movements.
- Since portions of the stockpile will progressively slough and move during the seismic loading and eventually reached a stable configuration after the strong motions have ceased, the stability of the stockpile was evaluated considering several degraded geometry.
- Both 2D/3D assessment of slope stability have been performed for static and seismic conditions.
- The site investigation work was subcontracted to Geocon Northwest Inc. Dr. Stephen Dickenson provided specialist consulting advice to M+EG for the geotechnical earthquake engineering design aspects.