Company:
GMU Geotechnical, Inc.
Status:
Awarded
Awarded:
Geotechnical Project of the Year
Additional Files
Additional photo - Parking Structure Excavbation
Additional Photo - Excavation Adjacent Existing Island Hotel
Peer reviewed paper
Additional Information

This submittal is for the geotechnical engineering evaluation of the foundation design for the developments at 650 & 670 Newport Center Drive.

20 Story Office Tower and 8 Story parking Structure @ 650/670 Newport Center Drive

Project Location:

Office Tower - 650 Newport Center drive, Newport Beach, CA
Parking Structure (adjacent) - 670 Newport Center Drive, Newport Beach, CA

Project Description:

This submittal involves the geotechnical engineering evaluation of a 20-story steel moment framed office building with an adjacent 8-story parking structure with 4-stories below grade.  The office tower is supported on a structural mat slab, and the parking structure is supported on conventional foundations. 
The geotechnical engineering aspects of the foundation design were complex and involved the following:  1) a variable geotechnical subsurface profile involving adversely oriented geologic structure; 2) potential surcharge effects of the mat slab on the adjacent parking structure walls; 3) shoring/tie-back design for the parking structure walls; 4) geotechnical construction sequencing considerations; 5) detailed settlement evaluations of the mat slab for the office tower and the conventional foundations for the 8-story parking structure; and, 6) construction performance monitoring of mat slab settlement, basement subgrade heave and tie-back wall movements.

Project Justification:

This project is outstanding and worthy of award for three reasons:  1) geotechnical engineering complexity;  2) the unique analyses required to be performed for the development; and, 3) post construction documentation and monitoring that involved a contribution to the geotechnical engineering community.
Because of the subsurface complexities, the high structural loading and stresses and the relative proximity of the two structures, a considerable amount of non-standard geotechnical engineering analyses needed to be performed.  The main non-standard analyses involved the shoring design evaluation, settlement analyses of the parking structure foundations and the settlement analyses of the mat foundation for the office tower. 
Given the high earth lateral loads and the height of the parking structure excavation, robust shoring consisting of soldier piles with 4 rows of tie-backs needed to be constructed.  In addition, many of these tie-backs were drilled below existing structures.  Consequently, in addition to standard geotechnical parameters, geotechnical tie-back design also included evaluation of the tie-back system for post construction lateral deflections and an evaluation of tie-back passive movements during installation.  In addition, the tie-backs had to be designed such that construction of the tower could begin as soon as possible following completion of the shoring.  Settlement of the parking structure foundations were complicated by the fact that the subgrade (4 stories subterranean) would undergo a state of elastic heave following the excavation.  This heave was greater at the center than at the edges and thus created non-uniform conditions which had to be considered in the analyses.  Settlement of the mat foundation for the 20-story tower was complicated by loading differential between the core and the outside edge of the foundation.  Because of this differential loading a unique evaluation had to be developed to evaluate potential settlements.
Construction monitoring deformation surveys were performed for the parking structure shoring, the parking structure basement subgrade, and the mat slab.  The mat slab monitoring consisted of monitoring the lab as structural loading was taking place to confirm the design settlement estimates.  Following construction, the deformation readings were then compared to three different methods of settlement analyses performed during design.  The settlement analysis method which resulted in the highest degree of accuracy involved the use of Cone Penetrometer Testing (CPT).  The overall results were then summarized in a peer reviewed paper that was published at the 3rd International Symposium on Cone Penetrometer Testing in 2014.

Special Circumstances:

The project resulted in a closer working relationship with Dr. Peter Robertson , Ph.D., PE, GE - one of the leading experts in the world in performing geotechnical engineering analyses with CPT data.  Dr. Robertson provided valuable insight and suggestions in evaluating the CPT data used in the engineering analyses for this project.  It also resulted in a closer working relationship with the geotechnical reviewer for the City of Newport Beach - Dr. Ken Bagahi, Ph.D., PE, GE.

Project Attachments:

See uploaded professional paper published regarding the mat slab settlement evaluation using CPT data and additional project photos.

Award Citation::

Geotechnical Evaluation of 20 Story Office Tower and Adjacent 8 Story Parking Structure at 650/670 Newport Center Drive - The project Involved complex and unique geotechnical engineering analyses for the evaluation of a 20 story office tower and adjacent 8 story parking structure with 4 stories below grade and the publication of a professional paper which contributed to the geotechnical engineering community.

Suggested Award Summary:

Geotechnical Evaluation of 20 Story Office Tower and Adjacent 8 Story Parking Structure at 650/670 Newport Center Drive - The project Involved complex and unique geotechnical engineering analyses performed for the evaluation of a 20 story office tower and adjacent 8 story parking structure with 4 stories below grade and the publication of a professional peer reviewed paper which contributed knowledge and understanding to the geotechnical engineering community.  Complex geotechnical engineering analyses included: 1) shoring/tie-back design evaluation involving construction deformation and potential effects of tie-backs being drilled beneath existing structures,  2) settlement of below grade parking structure foundations considering a reduction in density and compression characteristics due to basal heave,  3) settlement analysis of a mat foundation system with variable bearing pressures for the 20 story tower and 4) geotechnical design considerations for construction sequencing due to the proximity of the tower to the below grade portion of the parking structure.  Construction monitoring was performed for both the parking structure and the mat slab.  Recorded mat slab settlements were then evaluated with 3 different settlement methods to evaluate which method was most accurate.  The results indicated the method involving the utilization correlated constrained modulus values from Cone penetrometer testing was the most accurate.  The results of the post construction study were then published in the proceedings of the 3rd International Symposium on Cone Penetrometer Testing in 2014.

CEC

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