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Northwest A&F University (2018)

Investigation of Solidifying Desert Aeolian Sand Using Microbially Induced Calcite Precipitation

李多;

Titre : Investigation of Solidifying Desert Aeolian Sand Using Microbially Induced Calcite Precipitation

Auteur : 李多;

Grade : Master’s Theses 2018

Université : Northwest A&F University

Résumé
Desert aeolian sand is a kind of special soil with loose structure,uniform particles and difficult to compacted,which formed in the arid and semi-arid climate in northwest China.Therefore,it is necessary to be strengthened before use as the foundation of roadbed and other building foundations.Microbially induced calcite precipitation(MICP)is a new environmentally-friendly technique for strengthening soils.This paper examines using microbially induced calcite precipitation to solidify the desert aeolian sand.Five different concentrations of solidification solution(i.e.0.5,1.0,1.5,2.0 and2.5mol/L urea-CaCl2 solutions)were used to solidifying the sand in bio-treatment.By testing mechanical properties and micro-structure,the effect of solidified desert aeolian sand in different concentrations of solidification solution was analyzed,and the mechanism of solidified aeolian sand by MICP was studied.The conclusions are summarized as follows :(1)It is feasible to use microbially induced calcite precipitation technique by Sporosarcina pasteurii to solidify desert aeolian sand,which can effectively improve the engineering properties of desert aeolian sand.(2)By drop-wise adding the bacteria solution and different concentrations of solidification solution,calcium carbonate formed in the sand specimens gradually and the sand was solidified.The formation of calcium carbonate was the primary cause of other property changes.As the concentration of solidification solution increased,the calcium carbonate content increased,resulting in sand density increase,permeability reduction and unconfined compressive strength increase.(3)The calcium carbonate filled the pores between sand particles and the volume of pores decreased,resulting in the reduction of permeability.As the concentration of solidification solution increased,calcium carbonate content increased,the permeability coefficient decreased significantly.(4)The calcium carbonate formed by low concentrations of solidification solution(i.e.0.5 to 1.0mol/L)mainly played the role of sticking on sand particles surface and filling pores.At high concentrations of solidification solution(i.e.1.5 to 2.5mol/L),based on the calcium carbonate that sticking on sand particles surface and filling pores with the distance of adjacent particles reduced,more calcium carbonate played the role of solidifying and connecting in structure.(5)Calcium carbonate crystals were calcite through XRD analyses.Micro-graphs of optical microscopy and SEM analyses show that white calcite formed in the solidified sand.The crystals were rhombic hexahedrons,which wrapped around sand particle surfaces and filling the pores

Mots clés : aeolian sand; microbially induced calcite precipitation; MICP; solidification; Sporosarcina pasteurii;

Présentation (CNKI)

Page publiée le 14 mai 2019