Sustainable Ground Improvement Technique for Geo-Disaster Mitigation - Sustainable Practices in Geoenvironmental Engineering - page 451

applied in situ into the soil subgrade or soil mantle, thus essentially rendering it a soil
stabilization procedure.

12.4 Artificial Diagenesis
The term artiicial diagenesis is deined as the cementation process due to microbially but
artiicially induced production of carbonates—a process similar to that of natural diagen-
esis. Artiicial diagenesis, as a technique for strengthening soil (ground improvement) has
been used successfully by Bachmeier et al. (2002), Ciurli et al. (1996), and Fukue et al. (2011).
The most eficient technique utilizes ureolytic microbes that produce the enzyme urease .
It is useful to note that while there are many species of ureolytic microbes, the ureolytic
ability of the microbes varies widely with species.
Artiicial diagenesis can be used to mitigate geo-disasters by strengthening soils and
weathered rocks. The concept is simple; soils can be rendered as rock by artiicial dia-
genesis. Figure 12.8 illustrates the main elements of the technique. Ureolytic bacteria are
cultivated with the appropriate medium. If the medium is not the proper one, cultivation
will not be complete. When successful cultivation has been achieved, the culture solution
is mixed with the reactive solution consisting of CaCl 2 , MgCl 2 , NaCl, buffer materials, etc.,
before injection into the soil.

Bacteria

Reactive solution

CaCl 2
MgCl 2
Buffer solution

Culture solution

Cultivation with
appropriate medium
NaCl

Mixture

Soft soil

FIGURE 12.8
Procedure for application of artiicial diagenesis in soil mantle.