Stress concentration ratiol of model stone columns improved by additives

Dissertant

al-Waily, Makki Jafar Muhammad

University

University of Technology

Faculty

-

Department

Department of Building and Construction Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2007

English Abstract

In this work, laboratory experiments have been carried out to study the value of the stress concentration ratio, n, which is defined as the ratio of vertical stress acting on the stone column to that acting on the surrounding soil. A laboratory setup was manufactured in which two proving rings are used to measure the total load applied to the soil-stone column system and the individual load carried directly by the stone column. Stone columns made of crushed stone were installed in very soft clays having undrained shear strength ranging between 6 and 12 kPa.

Two ratios of the length to diameter (L / D) were tried, namely (L / D=6 and 8), and additives of sand and cement were mixed with the crushed stone in some experiments.

The cement used was mixed with crushed stone and very little amount of water. The testing program consists of 72 tests on single, two, three and four columns to study the stress concentration ratio, the bearing improvement ratio, (qtreated / quntreated), the settlement reduction ratio, (Sr) or (Streated / Suntreated) and the efficiency of the group of stone columns, The experimental tests showed that crushed stone columns with (L / D = 8) provided a stress concentration ratio n (1.4, 2.4, 2.9 and 3.2) for the soil having a shear strength cu = 6 kPa, treated with single, two, three and four columns, respectively.

The values of n where decreased to (1.2, 2.2, 2.5 and 2.7) when the (L / D= 6).

The values of n increase when the shear strength of the treated soil was increased to (9 kPa and 12 kPa), The stone column, (crushed stone + 10 % cement) with (L / D = 8) cement provided an increase in the bearing improvement ratio (qtreated / quntreated) of 3.70 for the soil of shear strength (cu = 6 kPa) treated four columns. It was also found that the stone column, (crushed stone + 10 % cement) with (L / D= 8) provided a settlement, reduction ratio S of (0.31, 0.10, 0, 09 and 0.06) for the soil of shear strength (cu = 6 kPa) treated with single, two, three and four columns, respectively. The crushed stone provided with efficiency (L / D = 8) higher than those with (L / D= 6).

The values of efficiency decrease with increasing, he shear strength of the treated soil. It was concluded that the (crushed stone + I0 % cement) is most effective technique than other techniques (stone only, stone + 30 % sand).

Main Subjects

Civil Engineering

Topics

• Mechanics
• Soil physics
• Soil mechanics

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305458