Mitigation of Earthquake-Induced Liquefaction via Microbial Denitrification: A Two-Phase Process

Abstract

Microbial denitrification, or dissimilatory reduction of nitrate, offers the potential of a sustainable and cost-effective method for mitigation of earthquakeinduced liquefaction. Carbonate precipitation via microbial denitrification is a slow process and may take years to precipitate enough carbonate to provide the desired degree of mitigation. Fortunately, large amounts of nitrogen gas are generated immediately upon the onset of denitrification. As desaturation by biogas generation is in itself a liquefaction mitigation mechanism, liquefaction mitigation via microbial denitrification may be viewed as a two-phase process: an initial phase wherein desaturation via biogas generation provides mitigation and a second phase in which sufficient carbonate precipitation has occurred to provide mitigation via particle cementation and/or an increase in dilatancy. Microbial denitrification is suitable for remediation under and around existing facilities because it is non-disruptive. An advantage of microbial denitrification compared to hydrolysis of urea (ureolysis), another technique for microbial precipitation of carbonate, is that its primary byproducts are benign (non-toxic). Another advantage of microbial denitrification is that denitrifying bacteria are ubiquitous in the subsurface. Laboratory test data demonstrates the ability of microbial denitrification to both desaturate the soil and induce carbonate precipitation, leading to an increase in strength and dilatancy, substantiating the concept of microbial denitrification as a two-phase process for mitigation of earthquake-induced liquefaction.

Applications of Microbial Processes in Geotechnical Engineering

“…Accumulation of these intermediates should be avoided as nitrite and nitric oxide are toxic and inhibit microbial growth and nitrous oxide is a very strong greenhouse gas (Almeida, Julio et al 1995;Chung and Chung 2000;Zumft, 1997;Madigan et al 2012, Pham et al, 2016. Kavazanjian et al, 2015, Hamdan et al 2017Pham et al 2016), for which the catabolic reaction is written as:…”

“…Although biogenic nitrogen gas may be considered as a by-product of MICP via denitrification, as described in the previous section, several recent studies have investigated the potential use of biogenic nitrogen gas alone for ground improvement (He et al 2013;He and Chu 2014;Kavazanjian et al 2015, Pham et al 2016, O'Donnell, 2017a. The most common biogenic gases that are formed in the subsurface are methane (CH 4 ), nitrogen (N 2 ), hydrogen sulphide (H 2 S), and carbon dioxide (CO 2 ).…”

“…The presence of gas can significantly reduce the hydraulic conductivity of soils, even if it fills up a small fraction of the pore space (Ronen et al, 1989;Baird & Waldron, 2003;Mahabadi and Jang, 2014;Mahabadi et al 2016). Biogenic nitrogen gas production may also mitigate both static liquefaction (He and Chu 2014;Pham et al 2016) and earthquake-induced liquefaction (Rebata-Landa and Santamarina 2012; He et al 2013;Kavazanjian et al 2015). The gas phase increases the compressibility of the pore fluid (Biot, 1941;Tsukamoto et al 2002;, which dampens pore pressure build up during monotonic and cyclic undrained loading (Yang et al 2004;Yegian et al 2007, He andChu 2014) It has been shown that small levels of desaturation can increase liquefaction resistance significantly Okamura and Soga, 2006).…”

“…Considering the durability of the gas phase and that its potential to mitigate liquefaction may be limited, a number of authors suggest the use of biogenic gas formation as the first step in a combined two-stage process of desaturation and carbonate precipitation via denitrification (O'Donnell, 2017a,b). In particular, this has been considered for mitigating liquefaction, where gas formation provides enhanced resistance in the short term and calcium carbonate precipitation provides enhanced resistance in the long term (Kavazanjian et al 2015;Khodadadi et al 2017;O'Donnell 2016).…”

Bio-desaturation and bio-sealing techniques for mitigation of soil liquefaction: a review

“…Soil liquefied as a result of loss of strength or stiffness associated with earthquake and this leads to the structural failures such as settlement of buildings, landslides, dams' failure [44]. Soil liquefaction also can cause less damaging effect such as settlement and flooding large areas, ground deformation, lateral deformation of slightly inclined ground [45] etc. Soil liquefaction has first drawn the attention of engineers after Nigata -Japan earthquake in 1964.…”