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Study of pullout behaviour of soil nails in completely decomposed granite fill

by Pradhan, Bandana

Abstract (Summary)
(Uncorrected OCR) Abstract of thesis entitled

Study of Pullout Behaviour of Soil Nails in Completely Decomposed Granite Fill

Submitted by Bandana Pradhan

for the degree of Master of Philosophy at The University of Hong Kong

in August 2003

Soil nailing is a technique for reinforcing slopes by installing closely spaced passive slender inclusions into the soil to increase its shear strength. It has been extensively used in slopes comprising in-situ or compacted soils. However, its uses in slopes comprising loosely compacted or uncompacted fill slopes are limited, because there is a lack of quantitative understanding of the behaviour of soil nails in such fills.

A laboratory study of pullout resistance of grouted soil nails was therefore conducted to investigate the behaviour of soil nails in completely decomposed granite (CDG) soil fill. Pullout tests were carried out in a large test box (length 2m x width 1.6m x height 104m). The vertical pressure was varied by means of hydraulic jacks. During the tests the degree of compaction and degree of saturation were also varied. The study focused on the development of pullout resistance of soil nails during the pullout, and the soil-nail interface characteristics, especially in loose fill at natural moisture content. The peak pullout force and the pre-peak and post-peak load-displacement behaviours were established by pulling the nails in displacement-rate controlled

manner.

The results of the study indicate that the pullout load-displacement curves have distinct peak values, followed by a reduction in the post-peak stage both in loose and dense fills. A large portion of the pullout resistance is mobilized within a very small displacement. There is an increase in the pullout resistance as the overburden pressure and the degree of compaction increase. The apparent soil-nail interface friction angles are very close to the friction angles of the soil. However, the apparent interface adhesion depends on the degree of saturation and the degree of compaction of the soil.

Bibliographical Information:

Advisor:

School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:soil stabilization china hong kong slopes mechanics fills earthwork

ISBN:

Date of Publication:01/01/2004

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