Estabilización de suelos con bacterias sporosarcina pasteurii
- Autores: Elitsa Ivanova Teneva
- Directores de la Tesis: Lluís Gil Espert (dir. tes.), Ernest Bernat Masó (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: José María Monzó Balbuena (presid.), Jordi Romeu Garbi (secret.), Dora Foti (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Mecánica, Fluidos y Aeronáutica por la Universidad Politécnica de Catalunya
- Materias:
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- Resumen
This thesis has been focused on optimizing the resistent capacity and reducing the permeability of fine and clay granular soils through the MICP (Microbiologically induced calcite precipitation). MICP is a natural biological process that induces calcium carbonate in the soil through the hydrolysis of urea by bacteria. In addition, it has several applications in the stabilization and restoration of various construction materials. Furthermore allows a high amount of CaCO3 production in a short time. The bacteria chosen to carry out the tests is Sporosarcina Pasteurii, because of its properties that favor these processes. In order to characterize the different parameters that allow optimizing bio stabilization, first several experimental studies have been carried out to determine the characteristics of the culture of the bacteria Sporosarcina Pasteurii and its application to the bio stabilization process. Secondly, unconfined uniaxial compression tests have been carried out on cylindrical soil specimens treated with MICP to assess three different experimental procedures: The first procedure consisted of subjecting the specimens to stabilization treatments with different bacterial concentrations. In the second experimental procedure, the specimens were subjected to freeze - thaw cycle and in the third, the compaction process was incorporated before or after the MICP treatment.
Thirdly, direct cutting resistance according to the UNE 103-401-98 standard has been determined from cubic soil test specimens, treated with MICP and different concentrations of bacteria.Fourth, bio stabilization technology has been applied in larger specimens and has been validated through the determination of its bearing capacity.
Finally, the influence of bio-stabilization on the permeability of soils has been studied with two experimental approaches. The results show that in the case of controlling the concentration of bacteria and the source and concentration of calcium, the final morphology of the obtained calcium carbonate crystal can be influenced; controlling the amount of unitary crystals, the size of the crystal and the formation of conglomerates may be modified. The treatments and optimum bacterial concentrations for each type of soil are also described. Increases of unconfined uniaxial compression strength reach values up to 790% and 900% for fine sand and coarse sand soils, respectively. On the other hand, the method of determination of the moisture content by means of ultrasounds is especially useful and allows distinguishing the moment in which the test pieces reach the hygrometric equilibrium. To conclude, the obtained results have been tabulated and allowed to know the optimal procedures and parameters that allow maximizing the performance of the bio stabilization depending on the properties of each one of the different types of soils studied.
