Ecological Engineering 60 (2013) 142–149
Contents lists available at ScienceDirect
Ecological Engineering
j ourna l ho me pa g e: www.elsevier.com/locate/ecoleng
Stress-deformation and compressibility responses of bio-mediated
residual soils
Min Lee Lee
∗
, Wei Soon Ng, Yasuo Tanaka
Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kuala Lumpur 53300, Malaysia
a r t i c l e i n f o
Article history:
Received 5 January 2013
Received in revised form 3 July 2013
Accepted 6 July 2013
Available online 14 August 2013
Keywords:
Compressibility
Stress-deformation
Bio-mediated soil
Residual soil
Calcite precipitation
a b s t r a c t
Bio-mediated soil improvement technique has attracted increasing interest from geotechnical engineers
in recent years. This paper investigates the stress-deformation and compressibility responses of bio-
mediated soil at laboratory scale. A typical residual soil was subjected to microbially-induced calcite
precipitation (MICP) under various treatment durations, concentrations and flow pressures of cemen-
tation reagents. The experimental results showed that the stiffness and peak strength of soil were
significantly improved by the MICP treatment. The amount of calcite precipitated showed a linear correla-
tion with recompression index (C
r
), reasonable correlations with peak strength (
p
) and total settlement
(S
c
), but a poor correlation with compression index (C
c
). Under a high applied stress (exceeds the yield
stress of soil), the MICP treatments become ineffective in improving the compressibility characteristics of
soil attributed to fracturing of calcite bonds. Cementation reagent with a low flow pressure (i.e. 0.2 bar)
contributed to more favorable stress-deformation and compressibility responses than those of high flow
pressures.
© 2013 Elsevier B.V. All rights reserved.
1. Introduction
Bio-mediated soil has recently emerged as a new sustainable
technique of soil improvement. The technique takes advantages
of natural bio-activities, technically termed as microbially induced
calcite precipitation (MICP), to improve engineering properties
of soils. The MICP process has also shown promising applica-
tions in other construction materials, i.e. improvements of strength
(Siddique et al., 2008; Raijiwala et al., 2009) and durability (De
Muynck et al., 2008; Achal et al., 2011) of concrete/mortar, and
durability of brick (Sarda et al., 2009).
In general, MICP can be achieved by urea hydrolysis, aerobic
oxidation, denitrification, sulfate reduction, etc. van Paassen
et al. (2010) suggested that urea hydrolysis possesses the highest
calcite conversion rate compared to other studied processes. Urea
hydrolysis refers to a chemical reaction where urea (CO(NH
2
)
2
)
is decomposed by urease enzyme that can be either supplied
externally (Nemati and Voordouw, 2003) or produced in situ by
urease-producing microorganism (DeJong et al., 2006; Whiffin
et al., 2007; Martinez et al., 2011). The latter process requires
urease positive type bacteria, i.e. genera Bacillus, Sporosarcina,
∗
Corresponding author. Tel.: +60 3 41079802; fax: +60 3 41079803.
E-mail addresses: mllee@utar.edu.my (M.L. Lee), just ws@hotmail.com
(W.S. Ng), yasuo@utar.edu.my (Y. Tanaka).
Spoloactobacilus, Clostridium or Desulfotomaculum (Kucharski et al.,
2008). The corresponding chemical reaction involves 1 mol of urea
decomposes into 2 mol of ammonium:
CO(NH
2
)
2
+ 2H
2
O → 2NH
4
+
+ CO
3
2-
(1)
The release of ammonium (NH
4
+
) increases pH, and eventu-
ally creates an ideal environment for calcite precipitation with the
presence of calcium ion (Ca
2+
) from the supplied calcium chloride:
Ca
2+
+ CO
3
2-
→ CaCO
3
(2)
The calcite (CaCO
3
) precipitated is responsible for improving
inherent engineering properties of soil through biocementation
and bioclogging. Biocementation is defined as an improvement of
soil strength by production of particle-binding materials through
microbial means, while bioclogging is a reduction of hydraulic con-
ductivity of soil or porous rock by pore-filling materials generated
by microbial processes (Ivanov and Chu, 2008).
Studies pertaining to the topic of bio-mediated soil improve-
ment had been reported by numerous researchers. DeJong et al.
(2010) provided an overview of potential applications of this new
technique in improving engineering properties of soil. Various
microscopy techniques were used to quantitatively assess the dis-
tribution of calcite during the soil improvement. Qian et al. (2010)
used three types of urease-producing bacteria to consolidate sand
grains. They found that the precipitation program was essential for
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http://dx.doi.org/10.1016/j.ecoleng.2013.07.034