Alternative Title

Paper No. 2.28

Location

St. Louis, Missouri

Session Start Date

3-8-1998

Session End Date

3-15-1998

Abstract

A case history is presented for slope stabilization of channels using piles. The Kansas City District, Corps of Engineers has used various pile designs and types of piles for projects along the Blue River Channel in Kansas City Missouri to stabilize sections of unstable channel slopes in previous slide areas, since June of 1986. Low existing soil shear strengths and limited rights-of-way precluded use of more conventional stabilizing methods. Although a pile analysis method had been used for initial projects, with several piles instrumented with slope indicator devices, an improved analysis method was needed. In July of 1994, through a design analysis, the Kansas City District, Corps of Engineers developed a pile design procedure for the stabilization of a failed slope, along the Blue River Channel, known as the Gregory Blvd Project. The method utilizes both Limit Equilibrium slope stability methods and P-Y curve methods for pile analysis, and takes into account earth pressure theory. The method includes a trial and error procedure for determining the driving forces from a sliding mass of soil. The driving forces were then calculated at a concentrated point on the slide plane, coincident with the location of the piles, or where the piles intersect the slide surface, using limit equilibrium procedures with the most critical slide surface and at the desired factor of safety for the stabilized slope. For projects discussed, shear strengths, were determined from a back analysis of the existing slopes at failure using F=1.0. Laboratory test results generally did not yield usable values. The slope stability computer programs UTEXAS2 and UTEXAS3, using Spencer's Procedure was used in all analyses. The driving forces, thus determined, are then input into the pile analysis (LPILE) program, using both a triangular and a uniform load distribution along with the appropriate soil strength parameters for generating the P-Y curves within the program. Depth of pile embedment below the slip surface, size of the piles, position of the piles in the slope and the required spacing are then determined. Actual instrumented field data located on piles are presented as well as comparisons with predicted results, using the pile procedure analysis technique. The case studies demonstrate the importance of proper formulation of the analysis and of modeling the soil using the correct P-Y soil parameters for the pile.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Fourth Conference

Publisher

University of Missouri--Rolla

Publication Date

3-8-1998

Document Version

Final Version

Rights

© 1998 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Mar 8th, 12:00 AM Mar 15th, 12:00 AM

Pile Design Procedure for Stabilizing Channel Slopes

St. Louis, Missouri

A case history is presented for slope stabilization of channels using piles. The Kansas City District, Corps of Engineers has used various pile designs and types of piles for projects along the Blue River Channel in Kansas City Missouri to stabilize sections of unstable channel slopes in previous slide areas, since June of 1986. Low existing soil shear strengths and limited rights-of-way precluded use of more conventional stabilizing methods. Although a pile analysis method had been used for initial projects, with several piles instrumented with slope indicator devices, an improved analysis method was needed. In July of 1994, through a design analysis, the Kansas City District, Corps of Engineers developed a pile design procedure for the stabilization of a failed slope, along the Blue River Channel, known as the Gregory Blvd Project. The method utilizes both Limit Equilibrium slope stability methods and P-Y curve methods for pile analysis, and takes into account earth pressure theory. The method includes a trial and error procedure for determining the driving forces from a sliding mass of soil. The driving forces were then calculated at a concentrated point on the slide plane, coincident with the location of the piles, or where the piles intersect the slide surface, using limit equilibrium procedures with the most critical slide surface and at the desired factor of safety for the stabilized slope. For projects discussed, shear strengths, were determined from a back analysis of the existing slopes at failure using F=1.0. Laboratory test results generally did not yield usable values. The slope stability computer programs UTEXAS2 and UTEXAS3, using Spencer's Procedure was used in all analyses. The driving forces, thus determined, are then input into the pile analysis (LPILE) program, using both a triangular and a uniform load distribution along with the appropriate soil strength parameters for generating the P-Y curves within the program. Depth of pile embedment below the slip surface, size of the piles, position of the piles in the slope and the required spacing are then determined. Actual instrumented field data located on piles are presented as well as comparisons with predicted results, using the pile procedure analysis technique. The case studies demonstrate the importance of proper formulation of the analysis and of modeling the soil using the correct P-Y soil parameters for the pile.