Evaluation of improvement techniques for ballasted railway track model resting on soft clay

Dissertant

Abawi, Zaynah Walid Samuil

Thesis advisor

al-Suudi, Namir K. S.
al-Qaysi, Mahmud Rashid

University

University of Technology

Faculty

-

Department

Department of Building and Construction Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2010

English Abstract

More than 1400 km of new railway networks are expected to be constructed in Iraq in the near future, in addition to the full rehabilitation of the existing network.

About 60 % of the new network is located in the middle and southern parts of Iraq where most of the ground is basically sedimentary, soft to very soft cohesive soils especially in areas close to the marshes.

In such cases it is always recommended to improve the properties of the soil to increase its ability in bearing the different applied stresses and to control the expected generated settlements The present work consists of proposing and evaluating twelve methods for improving the soft soil underneath a ballasted track under monotonic loading.

Two of the twelve methods were evaluated under repeated loading.

The evaluation of each method is based on the amount of increase in bearing capacity and the reduction in settlement as compared to the untreated soil.

The proposed methods are : 1- Treatment of soft saturated soil using a top ballast layer.

2- Treatment of soft saturated soil using a top ballast layer reinforced by single georgic layer.

3- Treatment of soft saturated soil using a top ballast layer reinforced by multilayer of georgic at constant spacing.

4- Treatment of soft saturated soil using a top ballast layer reinforced by multilayer of georgic at different spacing.

5- Treatment of soft saturated soil using ordinary stone columns.

6- Treatment of soft saturated soil using ordinary stone columns incorporated with top ballast layer.

7- Treatment of soft saturated soil using ordinary stone columns incorporated with top ballast layer reinforced by single georgic layer.

8- Treatment of soft saturated soil using ordinary stone columns incorporated with top ballast layer reinforced by two georgic layers.

9- Treatment of soft saturated soil using encased stone columns.

10- Treatment of soft saturated soil using encased stone columns incorporated with top ballast layer.

11- Treatment of soft saturated soil using encased stone columns incorporated with top ballast layer reinforced by single gorged layer.

12- Treatment of soft saturated soil using encased stone columns interacting with top ballast layer reinforced by single gorged layer.

Proposed number 7 and 11 were evaluated under repeated loading.

Model tests were performed for each proposed improvement method using a special loading set up which was previously manufactured providing full control of loading increments in both monotonic and repeated patterns.

Among the twelve improvement methods it is found that improvement method number 11 (Treatment of soft saturated soil using encased stone columns incorporated with top ballast layer reinforced by single gorged layer) provided the most satisfactory results in terms of bearing improvement ratios and settlement reduction ratios under both monotonic and repeated loading conditions, as compared to the untreated soil.

Main Subjects

Civil Engineering

Topics

• Railroads
• Restoration
• Maintenance
• Soil mechanics
• Iraq

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305242