Location

New York, New York

Session Start Date

4-13-2004

Session End Date

4-17-2004

Abstract

A three-story office building was located above a 35-ft slope and was supported on spread footings. The corner of the building nearest the crest of the slope experienced several inches of settlement. A subsurface exploration revealed that this portion of the building was founded on recently placed, soft fill soils. Apart from being easily noticeable on the brick veneer façade, the distress also caused serious concerns on the part of the occupants and owner regarding the continuous operability of the structure, which served as a main hub for wireless communications. A repair plan was developed that consisted of installation of micropiles outside and inside the building. The micropiles were installed around the existing footings, penetrating through the fill and into rock. Connection between the micropiles and the structure was achieved through a steel grillage attached to the column piers. Hydraulic jacks were installed between each grillage and the top of the micropiles to allow repositioning of the structure. Once the building was repositioned, the micropile-to-column connection was embedded in concrete. The work was completed in a period of approximately three weeks after the start of construction. The entire operation took place without disrupting business operations inside the building and was entirely successful, as evidenced by the settlement records of the structure. This paper describes the process of design and construction of the underpinning, the materials and equipment used for micropile installation and stressing, and the problems encountered during implementation of the proposed plan.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Fifth Conference

Publisher

University of Missouri--Rolla

Publication Date

4-13-2004

Document Version

Final Version

Rights

© 2004 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Apr 13th, 12:00 AM Apr 17th, 12:00 AM

Emergency Underpinning and Repositioning of a Four-Story Office Building

New York, New York

A three-story office building was located above a 35-ft slope and was supported on spread footings. The corner of the building nearest the crest of the slope experienced several inches of settlement. A subsurface exploration revealed that this portion of the building was founded on recently placed, soft fill soils. Apart from being easily noticeable on the brick veneer façade, the distress also caused serious concerns on the part of the occupants and owner regarding the continuous operability of the structure, which served as a main hub for wireless communications. A repair plan was developed that consisted of installation of micropiles outside and inside the building. The micropiles were installed around the existing footings, penetrating through the fill and into rock. Connection between the micropiles and the structure was achieved through a steel grillage attached to the column piers. Hydraulic jacks were installed between each grillage and the top of the micropiles to allow repositioning of the structure. Once the building was repositioned, the micropile-to-column connection was embedded in concrete. The work was completed in a period of approximately three weeks after the start of construction. The entire operation took place without disrupting business operations inside the building and was entirely successful, as evidenced by the settlement records of the structure. This paper describes the process of design and construction of the underpinning, the materials and equipment used for micropile installation and stressing, and the problems encountered during implementation of the proposed plan.