Abstract
Biogeotechnology is a recent area of study that deals with the improvement of engineering properties of soils in an eco-friendly and sustainable approach through the use of microorganisms. This paper first, reviewed the concept of bio-mediated soil improvement technique, components involved and the roles they played. Two processes of bio-mediation soil improvement techniques i.e. microbial-induced calcite precipitation (MICP) for producing bio-cement via ureolysis and bio-desaturation for generating specifically biogenic nitrogen gas via denitrification, their mechanisms of occurring and factors influencing them were described in details. An overview study was done on soil liquefaction. Conventional methods employed for mitigations of liquefaction hazards were reviewed and their limitations were drawn. The use of the de-saturation process for mitigation of soil liquefaction was adequately addressed. Mitigation of liquefaction using biological processes, in particular, MICP and/or bio-desaturation were introduced. The findings from the previous works have shown that both the two techniques are capable of improving liquefaction resistance of soils. Most of the results have shown that presence of biogenic nitrogen gas in soils treated with denitrifying bacteria is able to induce partial desaturation in the soil which consequently increases the cyclic shear strength, reduces pore water pressure and changes the soil behaviour from compressive to dilatant. Finally, potentials, challenges, and recommendations for future studies were identified.
Highlights
Earthquake and its associated phenomena such as soil liquefaction must occur inevitably but, their effects can be mitigated to reduce loss of life, properties and injuries [1]; [2]
Apart from that, a process known as bacteriogenic mineral plugging used for prevention of oil leakages from reserviour was even patented in the U.S bacteria have been utilized in remediation of cracked concrete and masonry structures ([10], [11], [12])
The results and observations made with regard to the application of bio-desaturation and microbial calcite precipitation for soil mitigation can be captured in the following points:
Summary
Earthquake and its associated phenomena such as soil liquefaction must occur inevitably but, their effects can be mitigated to reduce loss of life, properties and injuries [1]; [2]. [5] had reported the improvement of resistance to liquefaction of poorly graded Ottawa sand which was biologically treated with urease producing bacteria Sporosarcinapasteurii; [4] had utilized various concentration of Sporosarcinapasteurii and its nutrients to increase liquefaction of poorly graded sand; again Feng and Montoya, (2017) have reported that liquefaction resistance increases with the increase in shear wave velocity when two different sandy soils were treated at the same cementation level using bio-mediated soil improvement technique; [3] have improved the liquefaction resistance of sand soil via desaturation process through production of nitrogen biogenic gas; [2] had use biogas and bio-sealing processes to demonstrate liquefaction resistance of sand soil; [7] have used microbial induced denitrification and precipitation (MIDP) by employing denitrifying bacteria to induce desaturation and bio-cementation formation via denitrification process as two stage process
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