Investigation of subsidence phenomena by GPR technique and geotechnical evaluation in Baghdad City

Other Title(s)

التحري ع ظاهرة التخسفات بتقنية الاختراق الراداري الأرضي و التقييم الجيوتكنيكي في مدينة بغداد

Dissertant

al-Shijiri, Sabah Jasim Dahbush

Thesis advisor

al-Atrakchi, Fathi Fadil
al-Rawi, Fityan Rashid

Comitee Members

Fattah, Muhammad Yusuf
al-Khersan, Imad Hasan Rida
al-Yasi, Amin Ibrahim Hassun Hamzah
al-Mukhtar, Khalid S.
al-Fayyd, Jasim Muhammad Thabit Ibrahim

University

University of Baghdad

Faculty

College of Science

Department

Geology Department

University Country

Iraq

Degree

Ph.D.

Degree Date

2013

English Abstract

Two sites are chosen in Baghdad City in order to investigate the subsurface soil conditions that cause subsidence at these Sites.

The first site is located at Mohammed Al –Qassm (Site -1) in Karada District and while the second is at the intersection roads at Yarmook District (Site-2).

Ground Penetration Radar (GPR ) is used as a non destructive and powerful geophysical technique to depict the underground situations in addition soil samples were collected from the drilled boreholes to evaluate the geotechnical properties of the soil at the studied sites.

GPR survey has been carried out along 22 traverses, (14) of which are at Site-1 and the other at Site-2 (8) traverses.

Most radargrams of the raw data (preprocessing) do not exhibit the presence of a weak zones.

But after processing of the raw data through using suitable filters and other interpretation tools, such as RAMAC and RadExplorer softwares, the surface images become so clear and reflect the weak zone under the ground surface Two Adjacent weak zones are displayed very clear at depths of 1.55, 1.62, 2.56 and 2.94 m at site -1 through using antenna frequency of 100 MHz.

The dielectric constant and the velocity of the material at site-1 ranges (22.0 to 36.7) and (46 to 70) m/μs respectively.

When antenna frequency of 500 MHz was used, a weak zone was also recognized at the shallow depths of (0.24, 0.31, and 0.51) m.

The radargrams raw data belong to site-2 reflect the presence of a weak zone in case of the three antenna frequencies are used.

The weak zone is very clear 3 at a depth of 3.29 m and the material dielectric constant and velocity values are consequently 23 and 63 m/ μs when the antenna frequency of 250 MHz is used.

The same of weak zone was also detected at depth of 0.67 m and with dielectric constant and velocity of weak soil are equal to 5.8 and 125m/ μs.

The water table depth at the two sites is defined from GPR Radargrams at a depth of (2.38 and 2.96 m.) with using of(100) MHz antenna.

The physical, engineering and chemical properties of the soil at these two sites to depth of 10 meters in addition to their influences on the occurrences of the soil subsidence were evaluated.

The physical tests include particle size analysis, Atterberg limits, moisture content, specific gravity, dry density and wet soils.

The engineering tests include consolidation and direct shear tests.

Also, the chemical tests include carbonate, sulphates, chloride, organic content and Ph value .All these tests are done depending upon American and British specifications.

Grains size analyses of soil are found less than 75 microns for both sites which indicate a dominant fine grains soil with slight coarse grains.

The Atterberg limits for the soils are also determined and their results clear that the soil at site-1 and site-2 are highly-medium plastic and cohesive respectively.

The values of moisture content at site -1 and site -2 are moderate while the consistency index for site -1 and site -2 are stiff soil.

The relationships between the depth and standard penetration test were constructed.

The maximum and minimum values are 22 and 3 for site 1 and for site -2 they are 24 and 3 which means that the soil ranges from loose to compact, therefore gets the subsidence.

Main Subjects

Earth Sciences, Water and Environment

No. of Pages

210

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-609707