Biological stabilizers for different dispersive clayey soils

Document Type : Research Article

Authors

1 civil engineering department, Sirjan university of technology, Sirjan, Iran

2 Civil Engineering Department, Sirjan University of Technology, Sirjan, Iran

3 Civil Engineering Department, Sirjan University of Technology. Sirjan, Iran

4 PhD student in Biotechnology at International Center for Sciences, High Technology & Environmental Sciences, Kerman, Iran.

Abstract

Dispersive clays are a particular type of soil materials in which the clay fraction erodes in the presence of water by a process of deflocculating; in the state of de-flocculation, the particles remain in suspension as single units, with a consequent significant problem in geotechnical and geo-environmental projects. Dispersive soils have been found to exist in various types of climates, especially arid climates, which the extent of dispersion mostly depends on mineralogy and clay chemistry. Bentonite, kaolin, and fibrous clay soils are among the most important and useful industrial materials. Therefore, clay dispersion potential was investigated by adding dispersive materials (Sodium hexametaphosphate) and performing shear strength, crumb, double hydrometer, Pin-Hole tests, and chemical experiments. The stabilization practices using biological methods were done with Bacillus sphaericus and Bacillus pasteurii after soil divergence to assess the impact of bacteria strains on soil improvement parameters. Bases on chemical properties, Sodium Adsorption Ratio, and stabilization potential was in the order of kaolin>sepiolite>bentonite; the trend changed in accordance with clay CEC levels. The role of produced carbonate was prominent in improving mechanical and dispersivity properties. Soil chemical (exchanging Na ions) and mechanical (cohesion and friction angle) characteristics ameliorated by B. pasteurii further than B. sphaericus treatments. In general, the biological stabilization may replace the conventional soil improvement methods as an eco-friendly and efficient way toward sustainable development.

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