Speaker
Description
Microbially induced calcite precipitation (MICP) is believed to have a great potential to provide eco-friendly solutions to a wide range of geotechnical problems, e.g. mediation of contaminations, improvement of soft underground, erosion control and so forth. Recently, plenty of experimental and numerical investigations have been conducted by many researchers to get a better insight into the processes involved in MICP. Among the current MICP research, especially in the modelling perspective, less attention was paid to the temperature effects. In general, the temperature can affect on the one hand, the chemical reaction rate and on the other hand, the bacterial activities [1-4]. Considering that in the MICP field application, the soil temperature varies along with the underground's depth and changes due to the groundwater flow, thus except for the bio-chemo-hydro-mechanical (BCHM) processes there is still a need to investigate the temperature influence (T).
In the present study a coupled numerical model is developed with the main purpose to investigate the relevant coupled processes, specifically the temperature influence on the microbially induced calcite precipitation (MICP) in soil. The model development is based on the continuum approach in porous media, where the porous media is assumed to be fully saturated. The hydrolysis of urea, the calcite precipitation, bacterial decay and attachment, the transport of bacteria, urea, calcium, and ammonium in the pore fluid, the porosity and permeability reduction are considered. Specifically, to address the temperature influence, the hydrolysis rate of urea is assumed to increase linearly with the temperature elevation. Meanwhile, the inactivation of urease capacity of bacteria with the increased temperature is considered by using an Arrhenius-Type relation. The model is implemented in the open-source finite-element simulator OpenGeoSys (OGS). The spatial discretization is done using the standard Galerkin-Method, while the fully implicit backward Euler-Method is applied for the temporal discretization.
To calibrate, validate, and demonstrate the model's capability, we apply this model to simulate a set of laboratory experiments. The numerical results indicate that the temperature could significantly impact the efficiency and the spatial homogeneity of the calcite precipitation. Thus, as stated in [4], in the application one could improve the performance of MICP by control of the treatment temperature. The numerical simulation could be adopted as a useful tool for the design of such temperature-controlled MICP treatment.
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