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Engineering Geology Volume 28 Issue 1-2 1990 [Doi 10.1016%2F0013-7952%2890%2990041-x] Jawad S. Al-Sulaimi; Mohammad a. Mollah; Muneer a. Matti -- Geotechnical Properties of Calcrete Soil (Gatch) in Kuwait

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  Engineering Geology, 28 (1990) 191-204 191 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands Technical Note Geotechnical Properties of Calcrete Soil Gatch) in Kuwait JAWAD S. AL-SULAIMI, MOHAMMAD A. MOLLAH and MUNEER A. MATTI Kuwait Institute for Scientific Research, P.O. Box 24885, 13109 -- Safat Kuwait) Government Laboratories and Testing Station, Ministry of Public Works, P.O. Box 8, 13001 -- Safat Kuwait) Formerly, Engineering Department, Kuwait Institute for Scientific Research, P.O. box 24885, 13109- Safat Kuwait) (Received December 11, 1986; accepted after rewsion January 1, 1989) ABSTRACT A1-Sulaimi, J.S., Mollah, M.A. and Matti, M.A., 1989. Geotechnical properties of calcrete soil (gatch) in Kuwait. Eng. Geol., 28: 191-204. This paper presents the results of a comprehensive laboratory testing program carried out to study the geotechnical properties of gatch (calcrete soil) samples. A total of 17 samples collected from 17 different sites in Kuwait City and its suburbs were used for the study. The testing program included determination of physical, index and engineering properties of gatch samples. The sensitivity of various geotechnical properties of compacted gatch was examined by testing specimens at various moisture contents and also at different soaking periods. INTRODUCTION Gatch is the local name of a partially consolidated sediment of a massive calcrete type found in many parts of Kuwait at variable depth but generally about 2 m below the surface. This deposit which can attain thicknesses of tens of meters, consists basically of quartz sands cemented predominantly by carbonates (calcite and/or dolomite). Since 1950 a huge construction program has been underway in Kuwait, in which gatch has been used principally as a sub-base material for road construction, for the formation of embankments and for fill material. Gatch is also the soil on which most building foundations rest. Considerable field and laboratory work has been carried out in the past by engineers engaged in specific projects, but so far no attempt has been made to correlate the results of these studies so as to obtain a general picture of gatch deposits. This paper presents the geotechnical properties and characteristics of gatch encountered in Kuwait City and its suburbs. A total of 17 disturbed gatch samples were randomly chosen from different areas for an intensive laboratory geotechnical testing. The program of testing included the determination of the basic and 0013-7952/90/$03.50 © 1990 Elsewer Science Publishers B.V.  192 J S AL-SULAIMI ET AL strength properties. The effect of saturation of various degrees on soil properties was also examined. GEOLOGICAL SETTING AND CLIMATE Kuwait is a small country located in the northeastern edge of the Arabian peninsula, bordered by the Arabian Gulf in the east. The eastern part of the Arabian Peninsula, known as the Arabian Shelf, consists of a sedimentary succession in which the most common rock types are sandstone and carbonate rocks (Powers et al., 1963). The area of Kuwait constitutes a part of the interior homocline of the Arabian Peninsula. The rocks exposed range in age from Eocene to Recent. The Dammam Limestone Formation, of Eocene Age, crops out along the Ahmadi Ridge about 40 km south of Kuwait City and is the oldest rock exposed m Kuwait. The Dammam Limestone is overlain by a sequence of terrigenous sediments that range in age from Miocene to Recent. These sediments are exposed in the Jal Az-Zor Escarpment northwest of Kuwait City. The rock sequence of Jal Az-Zor consists of three main formations named, from bottom to top, Ghar, Fars and Dibdibah (Fuchs et al., 1968). The Dibdibah Formation covers most of the northern area of Kuwait and consists mainly of a fluviatile sequence of cross-bedded sands and gravels usually cemented by gypsum and carbonates. The rest of Kuwait is covered by other Quaternary deposits. The climate of Kuwait is characterized by a typical desert environment, with prolonged hot dry summers and mild to cool, relatively wet winters. Annual pan evaporation is about 3500 mm per year which increases gradually from a minimum value of 2.1 mm/day in winter (January) to a maximum of 13 mm/day in summer (June and July). PETROGRAPHY OF THE GATCH A typical fully developed simple soil profile m the study area can be divided into five zones or horizons. In descending order these are: (1) aeolian soil 0.5 to 10 m thick, but commonly less than 2 m; (2) up to 3 m thick of friable sand with powdery calcrete or tightly cemented calcrete lumps (nodules) up to 30 cm m diameters; (3) massive calcrete 0.2 to 2 m in thickness (gatch); (4) a mottled calcrete zone up to 2 m in thickness; and (5) unaltered parent material. Detailed accounts of the diagenesis and formtion of the different calcrete zones have been published by A1-Sulaimi (1988). The massive calcrete (gatch) is a white to light-yellowish, porcellaneous, carbonate rock. It consists of variably cemented and replaced sand particles. The carbonate in the massive calcrete (gatch) represents a substantial replace- ment of the srcinal material. Mineral grains such as quartz and feldspar are etched and replaced to varying extents by carbonate. The dominant cementing material is largely low-magnesium calcite (1-4 mole ~/o MgCO3) and]or micro- crystalline dolomite. Moderately coarse (up to 0.6 mm) dolomite usually occurs as subhedral or small euhedral rhombs whereas the low-magnesium  GEOTECHNICAL PROPERTIES OF CALCRETE SOIL GATCH) IN KUWAIT I * A ~~~~==~~l~.u=,. ,=, ~w ~~~ \~~ Fig.I. Map of Kuwait City and its suburbs showing sampling locations. pp. 193 196 KUWAIT SUBURBS ;r C - ã a C \1 0 m 1MQ .. I II I II I II I  GEOTECHNICAL PROPERTIES OF CALCRETE SOIL (GATCH) IN KUWAIT 197 calcite often occurs as microsparite and sparite. The carbonte fraction in the massive calcrete averages 60% (range 15-90~/o) with the dolomite content averaging 40% (range 5-90%). Gypsum is also observed in a few gatch samples and in some cases it effectively cements the assemblage as a result of intensive replacement of the carbonate. The main effect of the diagenetic processes on this horizon is an overall decrease in porosity and effective permeability of the gatch zone due to cementation by carbonate (A1-Sulaimi, 1988). SAMPLING AND TESTING PROGRAM This study forms an integral part of the Kuwait Institute for Scientific Research project entitled Study of the Gatch Deposits in Kuwait City and Suburbs (A1-Sulaimi et al., 1984). Over 200 samples of gatch were collected from different locations of Kuwait City and its suburbs to study the geological characteristics. Out of these a total of seventeen massive gatch samples taken from various locations (Fig.l) were made available for geotechnical analysis. The samples were collected from depths ranging between 1.0 and 6.5 m from open test pits and also during visits to various construction sites. Upon receipt of the samples in the soil laboratory a visual classification was made followed by the determination of the natural moisture content. A systematic laboratory testing program was carried out in which firstly the basic and index properties of all the samples were determined. The compaction characteristics of gatch were determined employing both standard (2.5 kg rammer) and modified (4.5 kg rammer) energies. An intensive testing program was undertaken to study the strength parameters intended for foundation design analysis, as well as suitability of compacted gatch as a subgrade material using five selected samples. These tests included performing direct shear, California bearing ratio (CBR) and permeability tests using specimens compacted by both energies. The effect of soaking on strength characteristics was studied by performing tests at different soaking conditions. PRESENTATION AND DISCUSSIONS OF TEST RESULTS Classification tests These tests were performed according to ASTM standards, and the results are summarized in Table I. The grain-size analysis indicates that sand size dominates the particle composition of the gatch, with gravel content varying between 0 nd 4%. The percentage of fine materials having the size of clay and silt particles varies between 8 and 33%. The mean grain-size diameter and specific gravity of soil solids vary from 0.15 to 0.8ram and 2.63 to 2.70, respectively. The plasticity of the gatch samples was determined on material fractions passing U.S. sieve size of 425 pro. Ten out of seventeen samples were found to be non-plastic (NP), and the remainder showed a low plasticity index (PI)
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