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Expansive soils are problematic for their relatively low load bearing capacity and extensive swelling-shrinkage deformations. Therefore, treatment of such soils is often considered to be necessary prior to construction. This paper investigates the potential of reusing waste tire textile fibers (WTTFs), a byproduct of the treatment process of end of life tires (ELTs), as reinforcement materials for treatment of expansive soils. To that end, mechanical reinforcement of sodium bentonite by WTTF inclusion has been evaluated through a set of standard compaction, direct shear, Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), and swelling-consolidation tests. Six different WTTF contents – that is, fc = 0%, 0.5%, 1%, 2%, 3%, and 4% were used and investigated. It was proven that WTTFs can improve the shear strength and UCS parameters. Swelling deformations of the soil were demonstrated to reduce by as much as 44%. At low WTTF contents, CBR was enhanced marginally. However, this parameter decreased at high WTTF contents. Therefore, it can be concluded that WTTFs can be used as economical reinforcement materials in expansive soils to enhance the strength parameters, mitigate the swelling properties, and address an environmental concern regarding WTTFs.

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2011. Estimation of the water retention curve for unsaturated clay. Can. J. Soil Sci. 91: 543Á549. Extensive laboratory tests are essential in order to determine the soil water retention curve, defined as the relationship between water content and suction, in an unsaturated soil. These laboratory tests are usually costly and time consuming. Moreover, for most practical problems, it has been found that approximate unsaturated soil properties are adequate for analysis. Thus, empirical procedures for predicting unsaturated soil parameters would be invaluable. The water retention curve can be estimated using soil properties to avoid the costs of experimental methods. Estimation of the water retention curve based on index properties is highly desirable due to its simplicity and low cost. Here, a model for the estimation of the soil water retention curve for fine soils is introduced, which takes the plasticity index and fine content into account, and is based on the Van Genuchten and Fredlund-Xing equations. The proposed equations are validated by comparing measured and simulated results. The curves predicted with these models were found to be in good agreement with the experimental results.

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Abstract. Geocell is an e ective type of geosynthetics for improving the performance of reinforced soil foundations due to provision of lateral con nement for the in ll soil. In this research, in order to study the bearing pressure-settlement response of geocellreinforced sand, a reduced-scale physical model is developed and geocells with various geometrical dimensions (height, pocket size, and width) produced from woven geotextile are used to reinforce sand bed. Strip footing model is then loaded monotonically to ultimate failure level, and the in uence of geocell geometrical properties on the improvement in bearing capacity and settlement of footing is described. The results show that by increasing height and decreasing pocket size of geocell, the bene cial e ect of geocell reinforcement increases substantially. For the highest geocell used in the tests at settlement level of 6%, improvement in bearing capacity and percentage reduction in footing settlement are obtained as 2.1 and 48%, respectively. The optimum width of geocell is determined ve times the foundation width beyond which the improvement e ect is negligible. It is also concluded that substituting a single layer of geocell reinforcement with 2 half-height and 4 quarter-height geocell layers results in 10% and 22% decrease in the ultimate bearing capacity, respectively.

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