Soil Stabilization by Microbial Activity

Posted: August 26th, 2021

Student’s Name

Instructor’s Name

Course

Date

Soil Stabilization by Microbial Activity

Introduction

The need to improve soil shear strength is among the goals of many construction engineering projects. As much as there exist varied methods of increasing the stability of the soil, the application of biological techniques such as microbial activity seems to rank the best in preferential treatment. The utilization of microbial activity is environmentally friendly, therefore considered to yield positive results. To attain soil stabilization, civil engineers have been compelled to look into various mechanical properties of soil. Thus, the ingredients’ concentrationis regarded as a significant determinant of the shear strength of the soil.

Application of Biogeo-Technology in Soil Stability

According to Saffari et al., the recent emergence of the study of biogeo-technology has brought forth two biological methods of improving soil stability, namely bio-stimulation and bio-augmentation (406). These biological techniqueshave facilitated the increase of soil shear strength in the following ways. There is a need to involve the biogeochemical process in microbial activity because soil shear strength is a function of two factors, namely soil cohesion and friction angle. It has been established that whereas the internal friction angle of soil varies due to varying degrees of grain shape and boundary,  its cohesion changes relatively to a change inthe bonding pattern of soil particles (Saffari et al. 406). Apart from that, research has established that increasing bacterial concentration alsopromotes soil cohesion as well as its friction angle and vice versa (Saffari et al. 406). As a result, there is increased soil shear strength.

Bio-Stimulation Method

Natural soil environment consists of numerous microorganisms essential in enhancing cementations or binding material that is widely regarded as the best by-products of microbial metabolic path processes (Saffari et al. 408). To attain a raised strength of the soil, there is an introduction of the required type of nutrient and precipitating agent into the soil to promote both the growth and metabolic activity of microorganisms (Saffari et al. 408). In this technique, biogeo-technology is essential because it optimizes the use of thestabilizing soil agents in a bid to createorganic binding materials. Indeed, the bio-stimulation method is associated with the creation of natural biding materials, thus resulting in improved soil engineering properties.

Bio-Augmentation Method

According to Saffari et al., this method entails inducing some other kinds of microorganisms that may not be readily present in the soil structure (409). These microorganisms such as cyanobacteria, microalgae, and sulfate-reducing bacteria are presumed to work relatively in soil bymakingnatural binding materials. An introduction of varied bacteria into the soil via a microbially induced calcium carbonate precipitation (MICP) processbrings about different metabolic paths useful in producing binding materials (Saffari et al. 409). The involved metabolic pathways, namely de-nitrification, urea hydrolysis, and sulfate production and iron reduction, are considered the biological patterns of encouraging soil microbial activity. The by-products of the bio-augmentation techniqueare composed ofvaterite crystals, calcite, and aragonite (Saffari et al. 409). Hence, they help bind the soil particles to achieve cohesion as well asa proper friction angle.

Conclusion

According to Saffari et al., the employment of the MICP process in construction engineering has been seen as a useful measure of soil stability (409). The reason is that the use of MICP promotes the reinforcement ofself-healing and controlled corrosion in sustainable concrete, thus leading tobetter concretedurability (Saffari et al. 409). Moreover, the application of the MICP method has been useful in geotechnical engineering as an efficient biological technique of mitigating soil liquefaction mitigation. As a result, both bio-augmentation and bio-stimulation methods have extensively enhanced soil microbial activity, promotingshear strength as well as reduced soil permeability of coarse-grained soils (Saffari et al. 409).

Work Cited

Saffari, Rahim et al. “Biological Stabilization of a Swelling Fine-Grained Soil: The Role of Microstructural Changes in the Shear Behavior.” Iranian Journal of Science and Technology: Transactions of Civil Engineering, Shiraz, vol. 41, no. 4, 2017, pp. 405-414.