Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Additives

Study Shear Strength Characteristics of Gypseous Sandy Soil Using Additives

Hussein H. Karim; T. Schanz; Maha H. Nasif

Engineering and Technology Journal, 2013, Volume 31, Issue 8, Pages 1431-1446

The present study investigated the possibility of enhancing collapsible gypseous soil of Al-Qarma site (with relatively high gypsum content around 50%), which is located in Al-Anbar Governorate, using kaolinite and bentonite as additives. The essential idea is concentrated in mixing these additives with natural soil using different percentages (5, 10, 15 and 20% by soil dry weight) to investigate soil shear strength enhancement. The effect of such additives on soil shear strength parameters, cohesion (C) and angle of internal friction (Φ), and their behavior were studied using direct shear test. The results showed that shear strength parameters of soil sometimes increased and then decreased with increasing additives. Generally, higher shear strength parameters have been obtained from bentonite mixed soil than that of kaolinite mixed soil for the same percentages of additives. It was concluded that bentonite was much more effective in increasing C and reducing Φ than kaolinite. While, kaolinite was much more effective in reducing C than bentonite. It was also concluded that gypseous soil shear strength is improved using such additives (with only 5% kaolinite or with only 20% bentonite) which provide cohesion strength to the soil mass and also acts as a binder agent material.

Improving Collapsibility and Compressibility of Gypseous Sandy Soil Using Bentonite and Kaolinite

Hussein H. Karim; T. Schanz; Maha H. Nasif

Engineering and Technology Journal, 2012, Volume 30, Issue 18, Pages 3141-3153

The sandy soil which covers the surface layer for the investigated area consists of
high gypsum content (50%). The soil was found to be a “collapsible” soil. Thus
bentonite and kaolinite have been used as an improving agents for such soil. The
essential idea of this study represents an investigation of the possibility of using
these materials as additives with different percents (5%, 10%, 15%, and 20%) to
enhance these soils. A testing program was conducted on 9 models of untreated and
treated gypseous soil specimens to study the behavior of such mixes as well as their
effects on physical properties, collapsibility and compressibility characteristics. It
was concluded that a significant reduction in collapsibility reaching 80 to 82 % for
the 10 percent mixed kaolinite and bentonite respectively. Lowest compression
index (Cc) and recompression index (Cr) have been obtained using the same
percentages of mixed additives. Generally, best improving results have been
obtained using bentonite additive (specially the ratio 10%) for its finer grains than
those of kaolinite.