Effect of Relative Compaction on Water Absorption and Gypsum Dissolution in Gypsum-Rich Clayey CBR Samples
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Effect of Relative Compaction on Water Absorption and Gypsum Dissolution in Gypsum-Rich Clayey CBR Samples Sabah S. Razouki 1 & Dina K. Kuttah 2 Accepted: 19 March 2020/ # The Author(s) 2020
Abstract A clayey gypsiferous soil of CL group according to the Unified Soil Classification System was studied for the effect of relative compaction on water absorption and gypsum dissolution during long-term soaking. The soil has a gypsum content of about 33%. Two sets of soil samples were prepared at optimum moisture content of 11.75% of the modified Proctor compaction test. The first set received 100%, while the second received about 93.5% relative compaction with respect to modified Proctor. These samples were soaked for 4, 7, 15, 30, and 120 days under 40 lbs (178 N) surcharge load. The moisture content was determined at top, quarter points, midpoint, and bottom of each soil sample. The test results revealed that for each compaction effort, the moisture content along each soaked soil sample is not uniform and increased with increasing soaking period. This increase in moisture content is greater for soil samples compacted at the lower compaction effort. The moisture content at top of each soil sample is greater than at the bottom, and the least moisture content took place at the middle of the sample. The dissolution of gypsum, at the top of soil samples, was greater than that at the middle. A multiple regression equation was developed relating strongly the decrease in gypsum content along the clayey CBR samples, with compaction effort and increase in average moisture content along the samples due to soaking. Similarly, strong correlation was obtained from the multiple regression developed between absorbed water, soaking period, and compaction effort. The paper shows that the water absorption and gypsum dissolution decrease with increasing relative compaction as the soil becomes denser. Keywords CBR samples . Compaction effort . Gypsum . Moisture . Soaking . Soluble salts
* Dina K. Kuttah [email protected] Sabah S. Razouki [email protected] Extended author information available on the last page of the article
Transportation Infrastructure Geotechnology
1 Introduction Gypsiferous soils are found in arid lands such as the Middle East, North Africa, southern central Australia, former inland lakes in Western States of the USA, and also in Europe especially in Spain and former USSR (Van Alphen and Romero, 1971; Hunter, 1988; Kota et al., 2007; Salih, 2013; Bao and Zhang, 2016). Verheye and Boyadgiev (1997) reported that, worldwide, gypsiferous soils cover approximately 100 million ha. The presence of gypsum in soils affects most of their properties, causing several physical and chemical problems (Hunter, 1988; Mashali 1996; Razouki and El-Janabi, 1999; Razouki and Kuttah, 2004a, b; Herris et al. 2005; Razouki et al., 2012a; Najah et al. 2013a and Razouki and Kuttah 2019). This is especially important in soils from semi-arid and arid areas, where gypsum behaves as a semi-soluble soil constituent (FAO, 1990). G
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