Location

Arlington, Virginia

Session Start Date

8-11-2008

Session End Date

8-16-2008

Abstract

This paper presents design and construction aspects of two similar circular Liquefied Natural Gas (LNG) impoundment basins in deep soft clays. Each basin has a design spill containment volume of 70,630 cubic feet. The inside diameter of each basin is 60 ft; bottom of the excavation is 32 ft below grade and the excavation retained permanently by concrete secant pile walls. The circular wall is constructed of 3 ft nominal diameter concrete piles overlapping adjacent piles by 6 in; the wall penetrates 60 ft below grade. Excavation stability during construction is the primary concern in soft clays; an inadequate retention system could experience large wall movements and stresses as well as excavation bottom heave often resulting in failure. A finite element analysis (FEA) was performed to evaluate overall stability of the wall and excavation using axis-symmetric model and to design an excavation-wall system which yields a minimum factor of safety of 1.3 during construction. Soil model parameters were established from back-analysis of performance data from a near-by instrumented dike. The conventional stability analyses were performed to verify the results of FEA; it appears that the method proposed by Bjerrum et al (1956) corresponds well with FEA results. The FEA demonstrated that the circular wall is in compression, in agreement with the theoretical analyses, resulting in negligible movements of wall and ground behind the wall.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Sixth Conference

Publisher

Missouri University of Science and Technology

Publication Date

8-11-2008

Document Version

Final Version

Rights

© 2008 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

Share

 
COinS
 
Aug 11th, 12:00 AM Aug 16th, 12:00 AM

Design and Construction of Circular Secant Pile Walls in Soft Clays

Arlington, Virginia

This paper presents design and construction aspects of two similar circular Liquefied Natural Gas (LNG) impoundment basins in deep soft clays. Each basin has a design spill containment volume of 70,630 cubic feet. The inside diameter of each basin is 60 ft; bottom of the excavation is 32 ft below grade and the excavation retained permanently by concrete secant pile walls. The circular wall is constructed of 3 ft nominal diameter concrete piles overlapping adjacent piles by 6 in; the wall penetrates 60 ft below grade. Excavation stability during construction is the primary concern in soft clays; an inadequate retention system could experience large wall movements and stresses as well as excavation bottom heave often resulting in failure. A finite element analysis (FEA) was performed to evaluate overall stability of the wall and excavation using axis-symmetric model and to design an excavation-wall system which yields a minimum factor of safety of 1.3 during construction. Soil model parameters were established from back-analysis of performance data from a near-by instrumented dike. The conventional stability analyses were performed to verify the results of FEA; it appears that the method proposed by Bjerrum et al (1956) corresponds well with FEA results. The FEA demonstrated that the circular wall is in compression, in agreement with the theoretical analyses, resulting in negligible movements of wall and ground behind the wall.