Strengthening sandy soils by microbial methods
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ICAGE 2016
Strengthening sandy soils by microbial methods Erdal Akyol 1 & Ömer Bozkaya 1 & Nazime M. Dogan 2
Received: 4 October 2016 / Accepted: 20 July 2017 # Saudi Society for Geosciences 2017
Abstract Some contemporary methods and materials are available in geotechnical engineering to improve the engineering performance of soils. Bacterial calcium carbonate cementation could be an innovative application by bonding at the particle contacts and increasing the shear strength. Bacteria type is the most effective factor on the calcium carbonate precipitation while incubation time, concentration, and pH were minor effects. The increasing urea concentration reduces the amorphous phase and increases the crystalline phase with vaterite. Meanwhile, the increasing incubation time is very effective transforming the vaterite crystals to calcite. Paenibacillus favisporus U3 forms the maximum calcium carbonate precipitation among the tested ones, and it is utilized for the geotechnical studies. The unit weights of the samples are not changed noticeably by the bacterial procedure. The uniaxial compressive strength of the tested core samples are varying in a quite large range from 66.8 to 204.1 kPa. The young modulus of the treated samples reaches up to 89.4 MPa. The Vp and Vs sonic velocity values rise up to 985 and 443 m/ s, respectively. The images prove the homogeneous distribution of bacterial carbonate cement material among the soil grains, and it fills the gaps up to 0.5 mm size. The improvement provided by the bacterial treatment is sufficient to support the project loads in very large areas like transportation
This article is part of the Topical Collection on Georesources and Environmental Management * Erdal Akyol [email protected]
1
Engineering Faculty, Pamukkale University, 20070 Denizli, Turkey
2
Science & Art Faculty, Pamukkale University, 20070 Denizli, Turkey
projects and factory sites. The method can be employed in the associated geotechnical engineering applications. Keywords Bacteria . Biological mineralization . Soil strengthening
Introduction In recent years, a large number of contemporary methods and materials are available in geotechnical engineering to improve the engineering performance of soils. They are miscellaneous in the matter of environmental impact, penetration depth, treatment uniformity, cost, etc. Naturally, they have benefits and drawbacks and researches are required on soil improvement to find out new materials and methods. Microorganisms play substantial roles in geological processes. A role of bacteria on calcium carbonate precipitation was learned by Nadson (1903). Since then, a large number of researchers have studied interactions between microorganisms and minerals (Douglas and Beveridge 1998; Dong et al. 2000; Lower et al. 2001; Frankel and Bazylinski 2003; Edwards and Bach 2005; Braissant et al. 2007; Achal and Pan 2011; Biswas et al. 2015; Mueller 2015; Kuznetsov 2015). The method is widely employed in many applications like wastewater treatment (Hammes et al. 2003), biorem
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