Alternative Title

Paper No. 7.20

Location

St. Louis, Missouri

Session Start Date

3-8-1998

Session End Date

3-15-1998

Abstract

A series of 20 small diameter drilled and grouted micropiles were installed at three different depths in a stiff surficial clay crust at the National Geotechnical Experimentation Site in Amherst, Massachusetts. A detailed site characterization program was performed to evaluate· the soil characteristics in the crust. Three different sizes of micropiles ranging in diameter from 76 mm to 152 mm and having lengths from 1.52 m to 4.57 m were installed vertically at the site using both continuous flight augers and hand auger techniques. Concrete was placed in the open holes using gravity free-tall. After allowing the concrete to cure for a period of 30 days, tension tests to failure were conducted on each of the micropiles. Following initial tests, some of the micropiles were retested after a resting period of one year to evaluate the recovery in tension capacity. This paper presents a description of the soil characteristics at the site including both laboratory and field test results and a description of the methods used to construct and test the micropiles. A comparison is made of the ultimate capacity obtained from the tests. The influence of drilling technique and the effect of reloading on the measured capacity are discussed.

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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Tension Tests on Drilled Micropiles in a Stiff Clay

St. Louis, Missouri

A series of 20 small diameter drilled and grouted micropiles were installed at three different depths in a stiff surficial clay crust at the National Geotechnical Experimentation Site in Amherst, Massachusetts. A detailed site characterization program was performed to evaluate· the soil characteristics in the crust. Three different sizes of micropiles ranging in diameter from 76 mm to 152 mm and having lengths from 1.52 m to 4.57 m were installed vertically at the site using both continuous flight augers and hand auger techniques. Concrete was placed in the open holes using gravity free-tall. After allowing the concrete to cure for a period of 30 days, tension tests to failure were conducted on each of the micropiles. Following initial tests, some of the micropiles were retested after a resting period of one year to evaluate the recovery in tension capacity. This paper presents a description of the soil characteristics at the site including both laboratory and field test results and a description of the methods used to construct and test the micropiles. A comparison is made of the ultimate capacity obtained from the tests. The influence of drilling technique and the effect of reloading on the measured capacity are discussed.