This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Journal of Geotechnical and Geoenvironmental Engineering, published
AbstractPremature failures in chemically stabilized expansive soils cause millions of dollars in maintenance and repair costs. One of the reasons for these failures is the inability of existing stabilization design guidelines to consider the complex interactions between clay minerals and the stabilizers. It is vital to understand these complex interactions, as they are responsible for the strength improvement and swell/shrink reduction in these soils, in turn affecting the overall health of the infrastructure. Hence, this research study examined the longevity of chemically stabilized expansive soils subjected to wetting/drying conditions with a major focus on clay mineralogy. Eight different natural soils with varying clay mineralogy were subjected to wetting/drying durability studies after stabilizing with chemical additives including quicklime and cement. Performance indicators such as volumetric strain and Unconfined compressive strength trends were monitored at regular intervals during the wetting/drying process. It was observed that clayey soils dominant in the mineral Montmorillonite were susceptible to premature failures. It was also noted that soils dominant in other clay minerals exhibited early failures at lower additive contents. Also, an attempt was made for the first time to address the field implications of the laboratory studies by developing a correlation that predicts service life in the field based on clay mineralogy and stabilizer dosage.
Stabilization with additives such as lime and cement has been practiced for many years and has proved effective in improving the behavior of expansive soils. Stabilizer design based on plasticity index (PI) and soil gradation is also a widely accepted method. However, some subsoils treated by this methodology have exhibited premature failures. Clay mineralogy plays an active and important role in the chemical reactions between soil and additives. A research study was conducted on six natural expansive soils with known clay mineralogy to evaluate the effectiveness of stabilization by using existing PI-based design charts. Engineering performance of treated soils was studied for long-term durability by exposing these soils to wetting and drying cycles and measuring both the volume change and the unconfined compressive strength during and at select wetting and drying cycles. Treated soil specimens containing high percentages of montmorillonite failed in durability tests when the treatments used PI-based design methods. A few treated soils did not survive the 21 wetting and drying cycles or experienced higher volumetric strains of more than the limiting value. Additional durability studies showed that soils with higher montmorillonite contents could be effectively stabilized with higher dosages of lime and cement additives. A new design chart incorporates the percentage montmorillonite content of a soil. This design chart provides an approach in selecting the optimum dosage of stabilizer to stabilize montmorillonite-dominant soils.
Expansive soil embankments are prone to shallow slope failures caused by associated swell–shrink movements. Previous studies have confirmed that seasonal changes and corresponding volumetric changes are responsible for desiccation cracking, which is a major factor behind shallow slope failures of highway embankments. For the past few years, soil stabilization proved to be an effective way to mitigate the swell–shrink property of expansive clays. The current study addresses the feasibility of guar gum biopolymer in mitigating the swell–shrink behavior of clays and in turn making it possible to adopt them as stable geomaterials. The sustainable benefits of biopolymers far exceed the environmental benefits from conventional stabilizers that contractors typically use. This paper presents a comprehensive laboratory study, followed by finite difference modeling analysis, on biopolymeric guar gum–remediated expansive soils collected from shallow slope failure-prone areas. For this study, two dam locations, at Grapevine Lake and Joe Pool Lake, Texas, that were originally constructed with expansive soils, were considered. The engineering performance of biopolymer-treated soils was evaluated and an optimum dosage was recommended for mitigating desiccation cracking at the test sites. Slope stability analyses were conducted using Fast Lagrangian Analysis of Continua in Three Dimensions software by adopting laboratory-determined strength parameters to determine the range of the factor of safety for the slopes. The variation of the factor of safety computed with the inclusion of enhanced engineering parameters from guar gum treatments revealed the advantages of adopting this treatment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.