Comparison between the efficiency of ordinary and geogrid encased stone columns

Dissertant

Kazim, Sarah Imad

Thesis advisor

al-Suudi, Namir K. S.
al-Qaysi, Muhammad Mustafa Mahmud

University

University of Technology

Faculty

-

Department

Department of Building and Construction Engineering

University Country

Iraq

Degree

Master

Degree Date

2012

English Abstract

One common approach used for treatment of soft saturated soil is the installation of stone columns.

The load capacity of the stone columns depends mainly on the shear strength of the surrounding soft soil, the dimensions and configuration patterns used, in addition to the construction techniques.

The geosynthetic encasement of stone columns is another ideal solution for enhancing the performance and improving the strength and stiffness of stone columns.

The present work investigates the behaviour of the soft soil reinforced with ordinary and encased stone columns with geogrid underneath plain strain condition.

Model tests were performed with different area replacement ratios and different configuration patterns of the stone columns, in addition to different relative densities of the backfill stone aggregate.

A total number of 25 model tests were carried out on a soil with undrianed shear strength ranging between 15-20 kPa.

The models consist of eight stone columns at area replacement ratio of (0.196) in square pattern, and four stone columns at area replacement ratio of (0.098) in three configuration patterns (at center in square pattern, at corner in rectangular pattern and in triangular pattern) were conducted for both tests of ordinary stone columns (OSC) and geogrid encased stone columns (ESC).

The configuration of eight ordinary stone columns (OSC) with square pattern revealed maximum bearing improvement ratio of 1.49 and maximum settlement reduction ratio of 0.19 at area replacement ratio of 0.196 and backfill relative density of 71%.

For the same configuration minimum values were achieved, namely, bearing improvement ratio of 1.19 and settlement reduction ratio of 0.59, at a relative density of 23%.

The four ordinary stone columns at the triangular configuration pattern with area replacement ratio of 0.098 at relative density of 71% demonstrated close agreement not exceeding 3% in comparison with the results of the eight stone columns at relative density of 23% in square pattern.

The four ordinary stone columns with triangular configuration showed marginal difference as compared to the four ordinary stone columns at the corners of rectangular configuration.

These two configurations are slightly higher than the four ordinary stone columns with square configuration at the center.

The configuration of eight encased stone columns ESC in square pattern revealed bearing improvement ratio of 1.5 and settlement reduction ratio of 0.19 at relative density of 71%.

As the density is reduced to 23%, the results of bearing improvement ratio and settlement reduction ratio were very comparable to the model test with 71% relative density, and no significant difference was noticed for this particular configuration.

The four encased stone columns exhibited maximum results of bearing improvement ratio of 1.38 and settlement reduction ratio of 0.26 when the configuration of the four columns is at the corners.

The other four encased stone columns with square configuration at the center and the triangular configuration revealed comparable results and marginal difference was noticed between the two configurations.

Comparing the results of encased stone columns with corresponding ordinary stone columns, maximum improvement were observed for the case of eight encased stone columns prepared at relative density 23%.

The obtained results are analyzed using finite element (Plaxis 3D Foundation).

Theoretical prediction for the total applied load on single stone column demonstrated acceptable results with the model test results.

Main Subjects

Engineering & Technology Sciences (Multidisciplinary)

Topics

• Mathematical models
• Soil mechanics

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-419297