Orange County Branch Newsletter
Continuing Education/GeoInstitute OC
Continuing Education Seminar on Ground Improvement for Challenging Sites in Orange County
By: Clint Isa, GeoInstitute Chair
ASCE-Orange County Continuing Education Committee (CEC) and GeoInstitute (GI) co-hosted a half-day seminar at the City of Irvine Council Chamber on March 13, 2015. The seminar consisted of three presentations that focused on several ground improvement methods that were employed for recently constructed projects in Orange County. The presentations were given by local geotechnical and civil engineering professionals - Mr. Ted Miyake, PE, who is a principal engineer at NMG Geotechnical, Inc. in Irvine, California; Mr. Ali Fayad, PE, who is a senior civil engineer for the Orange County Public Works Department - Flood Control Division; and Mr. Russ Lamb, PE, GE, who is chief geotechnical engineer for Stoney Miller Consultants in Irvine, California.
To start the seminar, Mr. Miyake presented case studies for two podium-style apartment developments in Irvine, California where compacted aggregate piers were used to mitigate loose and/or soft soil conditions. Mr. Miyake first discussed the installation methodology and engineering principles of compacted aggregate piers, and highlighted the importance of close collaboration between the geotechnical consultant, structural engineer, and contractor during the design phase of an aggregate pier project. He then presented the constraints (both technical and financial) and geotechnical subsurface conditions for each of the case studies and discussed why compacted aggregate piers were selected for each site. Of particular interest were the cost savings relative to mat foundations, and the practicality of implementing compacted aggregate piers to control settlement and improve bearing capacity where conventional foundation systems would be considered infeasible. Mr. Miyake concluded his presentation by discussing typical quality assurance/quality control procedures during installation of compacted aggregate piers, including in-situ modulus testing for post-installation stiffness verification.
As a follow-up to his presentation during the ASCE OC Branch Luncheon in September, 2014, Mr. Fayad discussed some of the finer geotechnical aspects of the East Garden Grove Wintersburg Channel (EGGWCH). Specifically, his presentation focused on the “soil mixed sandwich” that was designed to form the new walls for a portion of the Wintersburg Channel improvements. The soil mixed sandwich consisted of a zone of deep soil cement mixing (DSCM) confined by two parallel rows of sheet piles. Mr. Fayad discussed the effects of liquefaction settlement, lateral spreading, and nearby faulting on the design, and how the soil mixed sandwich addressed those issues. The project site also presented interesting construction challenges that were primarily driven by the limited construction space and the proximity of the improvements to nearby residential areas. Mr. Fayad described how the construction challenges were overcome by using an assembly line approach to install the sheet pile rows using silent piling methodology, after which the DSCM was placed within the confines of the sheet piles in a hexagonal pattern to form the final product.
Implementation of the improvements also needed to consider temporary surcharges generated by the construction equipment and the overall project geometry, which included portions of the DSCM columns that were installed 10 to 15 feet above adjacent grades. Mr. Fayad then went on to describe the process of designing and implementing DSCM construction validation guidelines, which were complicated by the lack of precedent for the proposed layout. Finally, Mr. Fayad gave a brief summary of the performance of the channel improvements during the seismic and rainfall events that occurred during the first quarter of 2014.
During the last segment of the seminar, Mr. Lamb presented the numerous geotechnical challenges associated with the Newport Marina project located in Newport Beach, California, which consisted of a waterfront, multi-level structure with subterranean parking. The primary design considerations consisted of liquefiable soils; the impact of shallow groundwater on foundation design and selection, basement wall design, and construction dewatering; and temporary shoring. Some of the construction challenges discussed by Mr. Lamb included the proximity of the project to old buildings and infrastructure that were sensitive to construction vibrations, and the impact of the oceanfront environment and tidal influences on construction operations.
To address the numerous design and construction challenges, multiple foundation and shoring systems were recommended to help tailor the design solutions to the most appropriate areas of the project. Foundation types included micropiles and auger-cast piles used in combination with mat foundations; shoring systems consisted of sheet piles installed using press-in and/or water jetting techniques, king pile systems, and secant pile systems. Several monitoring programs were implemented to check construction vibrations, shoring deflection, and groundwater drawdown; load testing was also performed on the various deep foundation components to check initial design capacities.
The following are the presentations described above:
On behalf of the CEC and GI, I would like to offer special thanks to our seminar sponsors for their generous support: California Nevada Cement Association (Platinum); Western Ground Improvement, NMG Geotechnical, Inc., and Hayward Baker (Gold); Giken, Blue Iron, Gregg Drilling and Testing, and Vertical Earthworks (Silver).