Query: Microbial Geotechnical Engineering Technology review

title: State of the Art Review of Microbial Induced Calcite Precipitation and Its Sustainability in Engineering Applications
abstract: Microbial induced calcite precipitation (MICP) is a promising new technology in the area of Civil Engineering with potential to become a cost effective, environmentally friendly and sustainable solution to many problems such as ground improvement, liquefaction remediation, enhancing properties of concrete and so forth. This paper reviews the research and developments over the past 25 years since the first reported application of MICP in 1995. Historical developments in the area, the biological processes involved, the behaviour of improved soils, developments in modelling the behaviour of treated soil and the challenges associated are discussed with a focus on the geotechnical aspects of the problem. The paper also presents an assessment of cost and environmental benefits tied with three application scenarios in pavement construction. It is understood for some applications that at this stage, MICP may not be a cost effective or even environmentally friendly solution; however, following the latest developments, MICP has the potential to become one.

title: Factors affecting the performance of microbial induced carbonate precipitation (MICP) treated soil: a review
abstract: Soil stabilization technology based on microbial induced carbonate precipitation (MICP) has gained widespread interest in geotechnical engineering. MICP has been found to be able to improve soil strength, stiffness, liquefaction resistance, erosion resistance, while maintaining a good permeability simultaneously. MICP processes involves a series of biochemical reactions that are affected by many factors, both intrinsically and externally. This paper reviews various influential factors for MICP process, including bacterial species, concentration of bacteria, temperature, pH, composition and concentration of cementation solution, grouting strategies, and soil properties. Through this comprehensive review, we find that: (1) the species and strains of bacteria, concentration of bacteria solution, temperature, pH value, and the cementation solution properties all affect the characteristics of formed calcium carbonate, such as crystal type, appearance and size, which consequently affect the cementation degree and distribution in geomaterials; (2) the condition with temperature between 20 and 40 degC, pH between 7 and 9.5, the concentration of the cementation solution within 1 mol/L, and high bacteria concentration is optimal for applying MICP in soil. Under the optimal condition, relatively low temperature, high pH value, and low concentration of cementation solution could help retain permeability and vice versa; (3) the effective grain size ranging from 10 to 1000 um. MICP treatment works most effectively for larger size, well graded sand; (4) the multi phase, multi concentration or electroosmotic grouting method can improve the MICP treatment efficiency. The grouting velocity below 0.042 mol/L/h is beneficial for improving the utilization ratio of cementation solution. The recommended grouting pressure is generally between 0.1 and 0.3 bar for MICP applications in sand and should not exceed 1.1 bar for silty and clayey soils.

title: MICROBIAL GEOTECHNOLOGY: EVALUATION OF STRENGTH AND STRUCTURAL PROPERTIES OF MICROBIAL STABILIZED MUD BLOCK (MSMB)
abstract: Microbial Geo technology is a new branch of geotechnical engineering that pact with the applications of microbiological methods to geological materials used in engineering. In this research, microbes were isolated and analyzed for various pozzolanic reactions as well as microbial fibrous reinforcement properties. The precipitation of CaCO3 in their micro environment by conversion of urea into ammonium and carbonate were confirmed further. The bacterial spore which is immobilized in soil matrix becomes metabolically active when revived by water entering freshly into the soil. The mycelial network of isolated fungi will provide fibrous reinforcement to the mud block. The micro organism is identified as Sporosarcina pasturii with 98% query sequence similarity. After the detailed review done by NCBI members allotted unique Accession number KP938 774 for S. pasturii. Hence now onwards this bacterium known as S.pasturii GRI Auro. The objective of the present investigation is to study the potential influence bacteria Sporosarcina pasteurii GRI Auro, and fungus Aspergillus sp. on the strength, durability and mechanical characteristics of compressed earth block. The studies are carried out in red soil. Different concentrations of microbial consortium (105,107,109 cells/ml) were introduced in mud block. Microbial Stabilized Mud Block (MSMB) were prepared by using Tara Balram soil press and cured by spraying an optimized nutrient media for 28 days. Microbial Calcite Precipitation (MCP) was identified and quantified by X ray diffraction (XRD) Fourier Transform Infrared (FT IR) analysis and visualized by Scanning Electron Microscope (SEM) Results showed that the rate of water absorption was significantly reduced and compressive strength was enhanced in microbial treated bricks. The results suggested that the microbial activities can significantly improve mechanical properties of microbial stabilized mud block. Hence microbial isolates can be used as additive to stabilize soil.

title: Discussion on the Review and Outlook of Microbial Geotechnical Mineralization Technology

title: Review on biopolymer based soil treatment (BPST) technology in geotechnical engineering practices
abstract: Various applications of biopolymer based soil treatment (BPST) in geotechnical engineering have been implemented in recent years, including dust control, soil strengthening and erosion control. Despite BPST methods can ensure the effectiveness of engineering while meeting environmental protection requirements, BPST technology requires further validation in terms of site applicability, durability, and economic feasibility. This study aims to provide a state of the art review and future prospective of BPST. Current biopolymer types, engineered and assessed in laboratory scales, are described along with site implementation attempts. The effect of biopolymers on soil behavior is reviewed with regard to geotechnical engineering application and practice, including soil consistency limits, strength parameters, hydraulic conductivity, soil water characteristics, and erosion control. The economic feasibility and sustainability of BPST application in ground improvement and earth stabilization practices is discussed. This review postulates biopolymers to be a promising new, environmentally friendly ground improvement material for geotechnical and construction engineering practice.

title: Review of the use of microorganisms in geotechnical engineering applications
abstract: Until recently, engineers either ignored or neglected the role of microorganisms in geotechnical engineering. The microbially induced calcite precipitation (MICP) research technique is an innovative and relatively green technology which consists in a biological process through which microorganisms react with minerals (calcium source and cementation reagent) to produce calcite (CaCO 3 as a byproduct that modifies and improves the engineering properties of soil. Laboratory and field results obtained from various studies are promising and viable, suggesting potential for various engineering applications. This research technique has also been considered to be useful in many engineering applications such as improvement of construction materials, cementation of porous media, improvement in strength and stiffness of engineering soils, hydraulic control of engineering facilities (waste containment) liquefaction, and erosion mitigation. In this review, the various methods of production of calcium carbonates (calcite) the role played by bacteria, various state of the art procedures that have evolved in this research area, as well as ongoing studies are reported. Furthermore, the use of the MICP technique in remediation of contaminants and other environmental concerns is also presented. The advantages and challenges (in form of undesired byproducts) of this research technique are highlighted herein.

title: Review on geotechnical engineering properties of sands treated by microbially induced calcium carbonate precipitation (MICP) and biopolymers
abstract: This study reviews the fundamental mechanisms of biological soil improvement methods microbially induced calcium carbonate precipitation (MICP) and biopolymer treatment (BPT) Extensive experimental data on various geotechnical properties of sands treated by MICP and BPT are compiled, including the unconfined compressive strength, Mohr Coulomb shear strength parameters, and permeability. Furthermore, the variations in these engineering parameters are correlated to calcium carbonate content for MICP and biopolymer content for BPT, which provides insights into the extent of biological modification in engineering properties of sands, potential applications, and limitations.

title: Applications of Microbial Processes in Geotechnical Engineering.
abstract: Over the last 10 15 years, a new field of "biogeotechnics" has emerged as geotechnical engineers seek to find ground improvement technologies which have the potential to be lower carbon, more ecologically friendly, and more cost effective than existing practices. This review summarizes the developments which have occurred in this new field, outlining in particular the microbial processes which have been shown to be most promising for altering the hydraulic and mechanical responses of soils and rocks. Much of the research effort in this new field has been focused on microbially induced carbonate precipitation (MICP) via ureolysis, while a comprehensive review of MICP is presented here, the developments which have been made regarding other microbial processes, including MICP via denitrification and biogenic gas generation are also presented. Furthermore, this review outlines a new area of study: the potential deployment of fungi in geotechnical applications which has until now been unexplored.

title: Introduction of Microbial Biopolymers in Soil Treatment for Future Environmentally Friendly and Sustainable Geotechnical Engineering
abstract: Soil treatment and improvement is commonly performed in the field of geotechnical engineering. Methods and materials to achieve this such as soil stabilization and mixing with cementitious binders have been utilized in engineered soil applications since the beginning of human civilization. Demand for environment friendly and sustainable alternatives is currently rising. Since cement, the most commonly applied and effective soil treatment material, is responsible for heavy greenhouse gas emissions, alternatives such as geosynthetics, chemical polymers, geopolymers, microbial induction, and biopolymers are being actively studied. This study provides an overall review of the recent applications of biopolymers in geotechnical engineering. Biopolymers are microbially induced polymers that are high tensile, innocuous, and eco friendly. Soil biopolymer interactions and related soil strengthening mechanisms are discussed in the context of recent experimental and microscopic studies. In addition, the economic feasibility of biopolymer implementation in the field is analyzed in comparison to ordinary cement, from environmental perspectives. Findings from this study demonstrate that biopolymers have strong potential to replace cement as a soil treatment material within the context of environment friendly construction and development. Moreover, continuing research is suggested to ensure performance in terms of practical implementation, reliability, and durability of in situ biopolymer applications for geotechnical engineering purposes.

title: Systematic Literature Review on Data Driven Models for Predictive Maintenance of Railway Track: Implications in Geotechnical Engineering
abstract: Conventional planning of maintenance and renewal work for railway track is based on heuristics and simple scheduling. The railway industry is now collecting a large amount of data with the fast paced development of sensor technologies. These data sets carry information about the conditions of various components in railway track. Since just before the beginning of the 21st century, data driven models have been used in the predictive maintenance of railway track. This study presents a systematic literature review of data driven models applied in the predictive maintenance of railway track. A taxonomy to classify the existing literature based on types of models and types of applications is provided. It is found that applying the deep learning methods, unsupervised methods, and ensemble methods are the new trends for predictive maintenance of railway track. Rail geometry irregularity, rail head defect, and missing rail components detection were the top three most commonly considered issues within the application of data driven models. Prediction of rail breaks has received increasing attention in the last four years. Among these data driven model applications, the collected data types are the most critical factors which affect selecting suitable models. Finally, this study discusses upcoming challenges in the predictive maintenance of railway track.