Study On Reinforcement Mechanism And Damage Performance Of Cemented Soil Stabilized With Nanometer Material

Cemented soil has been extensively used to ground treatment, however, engineering experiences suggest that low strength and large deformation has restricted its further application in the engineering. To improve engineering properties, many additives have been added to cemented soil. With the progress of nanometer technology, nanometer materials have been applied to modify cement-based materials, so it is a trail to introduce nanometer material with particular characteristics to cemented soil as a new kind of additive. In the paper, three kinds of nanometer materials are used for the cemented soil. Based on laboratory tests and theoretical analysis, the paper discussed reinforcement mechanism of the cemented soils stabilized the nanometer materials, which will provide research foundation for further application of the nanometer materials in cemented soil.Based on analysis on research existing status and application foreground of nanometer materials in cemented based material, the paper firstly discusses the microstructure properties of the three nanometer materials and compares them with the corresponding ordinary crystals. By unconfining compression strength tests of the cemented soil stabilized with the nanometer materials, influencing rules of nanometer material addition ratio and curing period on the strength are individually analyzed. The results suggest that nanometer silica fume (nanometer SiOx) can greatly improve the strength of cemented soil at various curing period, nanometer aluminium fume (nanometer AljOs) can not improve the strength, and nanometer titanium fume (nanometer TiO2) still reduce the strength until curing period of 90d. According to testing results, the stress-strain curve of the cemented soil stabilized the nanometer silica fume is fitted using a quadratic parabolic curve and expression equation for upward sector of the stress-strain curve is given.Through strength tests and XRD tests for cemented stone, the paper presents action mechanism of the nanometer materials in the cement hydration and hardening process: pozzolanic effect, filling effect, acceleration action for the cement hydration, and improving action for microstructure. From the four aspects, the modified mechanism of the nanometer silica fume and ordinary silica fume in cement paste are compared. The analysis results show that the particular properties of the nanometer silica fume include particle fineness, crystal structure and surface hydroxy, etc.A serial of laboratory tests are performed to study physical and mechanic properties of the clay with the addition of the nanometer silica fume. Based on testing results and soil theory, the modified mechanism of the nanometer silica fume in the clay is proposed: water molecule adsorption action, cementation action and filling action.Combining the SEM tests, the microstructure features of the cemented soil of nanometer silica fume are concluded. On the basis of analysis on the pairwise action of cement paste, nanometer silica fume and clay, the paper proposes the reinforcement mechanism of the cemented soil stabilized with nanometer silica fume. The reinforcement mechanism includes cementation action of cement hydrate, ionic exchange and quadrate reaction of clay particle, pozzolanic effect, filling effect and cementation action of nanometer silica fume. According to the reinforcement mechanism, some experimental phenomena and rules in the strength tests of cemented soil and cemented stone are explained. The paper also discusses the applicability of the nanometer silica fume in the cemented soil as an additive.Based on the analysis of micro-damage mechanism and damage performance of the cemented soil stabilized with nanometer silica fume, an elasto-plasticity damage model under uniaxial compression condition is established. Damage evolution laws are analyzed by the load-unload tests. Analysis results show that obvious damage occurs in the inner of the cemented soil stabilized with nanometer silica fume and the added nanometer silica fume can improve the damage...