Abstract
In recent years, traditional material for coastal erosion protection has become very expensive and not sustainable and eco-friendly for the long term. As an alternative countermeasure, this study focused on a sustainable biological ground improvement technique that can be utilized as an option for improving the mechanical and geotechnical engineering properties of soil by the microbially induced carbonate precipitation (MICP) technique considering native ureolytic bacteria. To protect coastal erosion, an innovative and sustainable strategy was proposed in this study by means of combing geotube and the MICP method. For a successful sand solidification, the urease activity, environmental factors, urease distribution, and calcite precipitation trend, among others, have been investigated using the isolated native strains. Our results revealed that urease activity of the identified strains denoted as G1 (Micrococcus sp.), G2 (Pseudoalteromonas sp.), and G3 (Virgibacillus sp.) relied on environment-specific parameters and, additionally, urease was not discharged in the culture solution but would discharge in and/or on the bacterial cell, and the fluid of the cells showed urease activity. Moreover, we successfully obtained solidified sand bearing UCS (Unconfined Compressive Strength) up to 1.8 MPa. We also proposed a novel sustainable approach for field implementation in a combination of geotube and MICP for coastal erosion protection that is cheaper, energy-saving, eco-friendly, and sustainable for Mediterranean countries, as well as for bio-mediated soil improvement.
Highlights
At present, coastal erosion is a major problem all over the world
Urease activity is closely related to the bacterial cell growth and it was revealed that a high bacterial cell concentration enhanced the amount of calcite precipitated by the microbially induced carbonate precipitation (MICP) method
It was concluded that the urea hydrolysis rate was directly proportionate to the concentration of bacteria, which is an important factor for the success of the MICP application [23,24]
Summary
Traditional measures consisting of hard and soft defense protection systems are adopted to protect from this disintegration. All of these coastal design and structures have been identified as being expensive to build and sustain because of the scarcity of materials, energy, time, cost, and environmental concern. Countermeasures against coastal erosion protection have been studied by many researchers [1], including hard and soft structures focusing on urea degradation bacteria. All these methods have an adverse effect on the surrounding landscape, environment, and ecosystem [2]; eco-sustainability is another major concern
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