Experimental study on soil improvement using local microorganisms
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ORIGINAL PAPER
Experimental study on soil improvement using local microorganisms Mohsen Mohammadizadeh 1
&
Rasoul Ajalloeian 1,2 & Bahram Nadi 1 & Shahla Soltani Nezhad 3
Received: 28 June 2018 / Accepted: 18 May 2020 # Saudi Society for Geosciences 2020
Abstract Bio-mediated soil improvement has been recently introduced as a novel link between biotechnology and geotechnical engineering. Microbial induced carbonate precipitation (MICP) is one of the most promising bio-mediated methods which have been developed based on biologically driven urea hydrolysis. In the present study, an indigenous bacterium that can be used in MICP is identified in the native soil of Sirjan, Southern Iran. This bacterium, called Acinetobacter calcoaceticus Nima (ACN), was compared with the standard Sporosarcina pasteurii (SP), with respect to their performance in the improvement of the mechanical properties of biologically treated soil samples. During a 40-day period of the experiment, direct shear and shear wave velocity tests were conducted to investigate the influence of the treatments on soil properties. Also, stereo microscope images were used to investigate the precipitation on the interparticle contacts. It was observed that the bio-mediated techniques can significantly improve the mechanical properties of the soil samples. For instance, while the shear wave velocity of the bacteria-free soil was measured as 175 m/s, SP-treated soil has the shear wave velocity of 526 m/s. This value was even higher for the ACN-treated samples (588 m/s) indicating that the local bacteria performed considerably better than the standard SP when used for the native soil. Keywords Bio-mediated soil improvement . Microbial induced carbonate precipitation . Urease-producing microorganisms . Direct shear test . Shear wave velocity . Stereo microscopy
Introduction Soil materials usually do not meet engineering requirements, mainly in terms of shear strength and deformability. Responsible Editor: Sanjay Kumar Shukla * Rasoul Ajalloeian [email protected] Mohsen Mohammadizadeh [email protected]; [email protected] Bahram Nadi [email protected] Shahla Soltani Nezhad [email protected] 1
Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
2
Department of Engineering Geology, The University of Isfahan, Isfahan, Iran
3
Department of Biology, Jiroft Branch, Islamic Azad University, Jiroft, Iran
Consequently, soil improvement techniques, also known as ground treatment, have been extensively used in many geotechnical engineering projects. Traditionally, there exist two main categories of ground improvement techniques namely mechanical compaction and chemical stabilization (Ibragimov 2015). The selection of the appropriate improvement method is accomplished based on various criteria such as soil type, percentage of fines, area and depth of the improvement, and availability of the material. A common approach is the use of Portland cement, lime, and chemical stabilizers, such as epoxi
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