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Strong Correlation between the Bearing Capacity and CBR of a Gypsiferous Subgrade Soil Subjected to Long-Term Soaking
Al-Nahrain University.
Al-Nahrain University.ORCID iD: 0000-0003-0478-1150
Construction and Housing Ministry, Baghdad, Iraq.
National Center for Construction Laboratories and Researches, Baghdad, Iraq.
2005 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Presented in this paper is a correlation between the bearing capacity of a gypsiferous subgrade soil with the corresponding CBR value. The geotechnical tests carried out on this soil indicate that the soil is sandy lean clay of CL group according to the USCS and A-6 (6) group according to AASHTO Soil Classification System. The soil contains about 33% gypsum content. For this purpose, thirty six CBR samples were prepared at optimum moisture content (of the modified AASHTO compaction test) namely 11.5% at compactive efforts of 1, 2 and 4.56 times that of the Proctor compaction (standard AASHTO). These samples were soaked for 0, 4, 7, 15, 30, and 120 days under the effect of 40 lbs (178 N) surcharge load. For each soaking period, three pairs of CBR soil samples were prepared, one for each compactive effort. The first CBR sample from each pair was used to determine the CBR value while the second CBR sample was used to obtain triaxial soil samples for unconsolidated undrained tests to arrive at the corresponding shear strength parameters. The present paper reveals that for each soaking period, there is a linear increase of the ultimate bearing capacity with increasing compactive effort, while a significant drop in the ultimate bearing capacity of the tested soil took place with increasing soaking period. The paper reveals also that there is a strong linear correlation between the estimated ultimate bearing capacity and the corresponding CBR value indicating that the Rosenak's equation correlating the bearing capacity with CBR value is very conservative.

Place, publisher, year, edition, pages
2005. p. 11-19
Keywords [en]
Gypsum, Subgrade, Clay, Soil, Resilient Modulus, Compaction, Moisture content, California bearing ratio, Bearing capacity
National Category
Soil Science
Research subject
60 Road: Soil and geotechnics, 62 Road: Soil mechanics
Identifiers
URN: urn:nbn:se:vti:diva-13215OAI: oai:DiVA.org:vti-13215DiVA, id: diva2:1241278
Conference
The Seventh International Conference on the Bearing Capacity of Roads, Railways and Airfields, Trondheim, Norway, 27-29 June 2005
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2018-11-20Bibliographically approved
In thesis
1. Effect of Compactive Effort on the Behaviour of a Gypsiferous Subgrade Soil
Open this publication in new window or tab >>Effect of Compactive Effort on the Behaviour of a Gypsiferous Subgrade Soil
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Presented in this thesis is a study of the effect of compactive effort and long-term soaking on strength, stiffness and deformation characteristics of a gypsiferous subgrade soil from Kirkuk city.

The tested soil is sandy lean clay (CL) according to the Unified Soil Classification System and A-6 (6) soil according to AASHTO soil classification system. The soil contains about 35% total soluble salts (T.S.S.) and about 33% gypsum.

The compaction characteristics of the tested soil indicate that the AASHTO compaction curves are of double peaks having two maximum dry unit weights and two optimum moisture contents.

To study the effect of compactive effort and long- term soaking on the properties of the tested soil, ninety-six CBR soil samples were prepared, fourty eight CBR samples for each moulding optimum moisture content of 2% (dry optimum moisture content DOMC) and 11.5% (wet optimum moisture  content WOMC). For each moulding moisture content and each soaking period of (0, 4, 7, 15, 30 and 120 days), eight CBR samples were prepared, two for each case of the four chosen compactive efforts of 12, 25, 56 and 70 blows/layer.

Unconsolidated undrained and consolidated undrained triaxial tests (with pore water pressure measurements) were carried out on samples extracted from CBR samples as well as on samples compacted in manufactured mould at WOMC to determine the cohesion and friction of tested soil using the triaxial cell.

For samples compacted at DOMC, various unconsolidated undrained shear box tests were carried out to determine c and ø of the tested soil.

The full load-penetration curve obtained from CBR test was used to determine the resilient modulus. In addition, the ultrasonic tests were carried out on CBR samples to estimate the resilient modulus, and good agreement between both approaches was noticed especially for samples compacted at WOMC.

Vertical swelling / settlement measurements were carried out on each CBR sample during soaking using 0.002 mm dial gauge.

The moisture content determinations were carried out in this study to determine the effect of compactive effort on the distribution of moisture along the CBR soil sample during soaking of samples compacted at WOMC and DOMC. Similarly, the total soluble salts tests (T.S.S.) and the gypsum content tests were carried out for the same purpose.

Place, publisher, year, edition, pages
Baghdad: Al-Nahrain University, College of Engineering, Civil Engineering Department, 2004. p. 180
Keywords
Gypsum, Soil, Clay, Compaction, California bearing ratio, Triaxial, Moisture content, Pore water pressure
National Category
Geotechnical Engineering
Research subject
60 Road: Soil and geotechnics, 62 Road: Soil mechanics
Identifiers
urn:nbn:se:vti:diva-13231 (URN)
Public defence
2004-06-07, Baghdad-Iraq, 09:00 (English)
Opponent
Supervisors
Note

Approved by the Swedish National Agency for Higher Education,decision no. 54- 03038 -09 in 2009-12-09

Available from: 2018-09-04 Created: 2018-08-23 Last updated: 2018-11-21Bibliographically approved

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Kuttah, Dina K

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