Time rate of swelling of compacted highly plastic clay soil from Sudan

This paper investigates the development of swelling with time for a highly plastic and potentially expansive clay from Sudan. Soil samples were prepared in the laboratory at different moisture content values. The prepared samples were placed in the oedometer ring at three density levels and then placed in an oedometer cell which allows one dimensional swelling. Swelling was observed at different time intervals to 48 hours. The data was analyzed to determine the development of swelling with time. The data analysis clearly demonstrated three stages of swelling, initial, preliminary and secondary for all tested samples except the quasi-saturated ones. The swell percent and primary swelling were very sensitive to the initial moisture content and dry density of the tested samples. Most of the swelling took place during the first 24 hours for all the tested specimens. The hyperbolic model was assessed for prediction of the percent swell. The 12 hours data was found to be very successful in predicting the percentage swell.

Pengaruh Kadar Air Awal Dan Surcharge Pressure Pada Uji Karakteristik Pengembangan Tanah Ekspansif

Expansive soils experience volumetric changes due to water content changes. These volumetric changes cause swell and shrink movement in soils, which in turn will inflict severe damage to structures built above them. A Proper understanding of how the expansive soil behaves during the wetting/drying process is essential for assessing the mitigation action of expansive soil hazard and design suitable foundation. The structures that build above expansive soil bed are susceptible to heave and to withstand swell pressure, thus the swell pressure must be considered in the design. This study focuses on swelling properties of two expansive clay from Ngawi, East Java and Wates, Yogyakarta. Laboratory test on disturbed samples is used to identified and to measured swelling properties. A series of swelling test was performed under constant soil dry density. The influence of initial water content and surcharge pressure on swelling properties (i.e swell percent and swell pressure) of compacted samples were investigated. The swelling properties test used ASTM standard 4546-03 method B. It was found that the lower initial water content the higher the swell percent, but the swell pressure seems not to be affected by initial water content. At the same initial water content, swell percent decrease with the increase of surcharge pressure, but swell pressure remains unchanged.

The Compressibility and Swell of Mixtures for Sand-Clay Liners

Sand-clay liners utilize expansive clay to act as a filler to occupy the voids in the sand and thus reduce the hydraulic conductivity of the mixture. The hydraulic conductivity and transfer of water and other substances through sand-clay mixtures are of prime concern in the design of liners and hydraulic barriers. Many successful research studies have been undertaken to achieve appropriate mixtures that satisfy hydraulic conductivity requirements. This study investigates compressibility and swelling properties of mixtures to ensure that they were acceptable for light structures, roads, and slabs on grade. A range of sand-expansive clay mixtures were investigated for swell and compression properties. The swelling and compressibility indices were found to increase with increasing clay content. The use of highly expansive material can result in large volume changes due to swell and shrinkage. The inclusion of less expansive soil material as partial replacement of bentonite by one-third to two-thirds is found to reduce the compressibility by 60% to 70% for 10% and 15% clay content, respectively. The swelling pressure and swell percent were also found significantly reduced. Adding less expansive natural clay to bentonite can produce liners that are still sufficiently impervious and at the same time less problematic.

Microfabric and mineralogical studies on the stabilization of an expansive soil using cement by-pass dust and some types of slags

This paper describes the microfabric and mineralogical aspects of the expansive soil of Al-Khod (northern Oman) treated with cement by-pass dust (CBPD), copper slag, slag-cement, and granulated blast furnace slag (GBFS). First, the engineering properties and chemical and mineralogical composition of the untreated soil were determined. The soil was then mixed with the additives at 3, 6, and 9% of the dry weight of the soil. The microfabric and mineralogical characteristics of the treated soil were determined. The high amounts of calcium ions and calcium oxide, which produces calcium ions, react with the clay particles through a cation exchange process resulting in the formation of aggregations and reduction of the swell potential of the soil. Mineralogical tests on the treated samples indicated a general reduction in all clay minerals peak intensities, particularly in the case of CBPD treated samples. The fabric of the untreated soil is composed of dense clay matrices with no appearance of aggregations or ped formations with increasing amounts of pore spaces. However, aggregations and few connectors were formed due to the addition of the stabilizers. Aggregations and bindings were formed for all of the soils treated with GBFS and for those with 9% additions of CBPD and slag-cement. The mineralogical and microfabric results were correlated with the swell percent and swell pressure of the treated samples. The formation of aggregations and reduction in clay minerals peak intensities resulted in the reduction of the swell pressure and swell percent values.Key words: microfabric, mineralogy, stabilization, expansive soils, SEM, XRD.

Computer-Aided Design for Estimating Foundation Uplift on Expansion Soils

This work presents a methodology to determine in-situ heave of foundations due to soil expansion. A total of 206 soil specimens from a semi-arid region (lrbid city in northern Jordan) were tested in the laboratory to produce a model for predicting the swell percent, SP. The results indicate that SP is strongly dependent on the placement conditions (initial water content and dry unit weight), clay content of the soil and the initial applied pressure. Utilizing this model, an Advanced BASIC computer program was written to evaluate in-situ heave. It was verified using actual field data: The program provides a Simple means for approximately determining foundation heave.