Research On Mechanical Experiment And Damage Constitutional Model Of Cemented Soil Effected By Pollution

Cemented soil has been widely used in all kinds of soil improvement because of its lower cost, convinience for construction, and non-vibration, non-noise, non-upheaval of ground during constructions. However, the engineering characteristic of cemented soil usually causes the problems that the soil had been polluted or the cemented soil worked in an erosive environment. The polluted soils or the erosive ions have strong crystal decomposition functions on cemented soil, which has significant effect on the mechanical performance and durability of cemented soil. Consequently, it has great theoretic significances and engineering significances to research the mechanical characteristic changes and the chemical erosion of cemented soil and build the damage constitutional model of cemented soil under the influence of soil pollution and erosive environment.In order to adapt to two pollution instances that may be encountered in engineering, two types of cemented soil were made in lab, one of them was made from polluted soil (cemented polluted soil for short), the other was made from clean soil (cemented soil for short). The exterior configurations, failure features, unconfmed compressive strengths and stress-strain curves of both cemented polluted soil under standard curing condition and cemented soil soaked in erosive environment were contrasted in details. In consequence, polluted soil has a weaker effect on cemented soil in mechanical characteristic than erosive environment.Firstly, when SO₄^2- content was in a certain range, the compressive strengths of cemented polluted soil didn't become lower but some higher than that of clean cemented soil. With different cations, SO₄^2- has different effects on the strength of cemented polluted soil. Based on the electric scanning microscope test, the reason of SO₄^2- effect on the strength of cemented polluted soil was qualitatively analysed from both microscope aspect and chemical mechanism aspect. Based on a mass of experiment results, the limit concentrations of various irons in polluted soil and erosive environment were explained. In different erosive environment, the modified coefficients of compressive strength of various irons to cemented polluted soil and cemented soil were summerized. The influence degrees of different compounds, different anions and different cations on the strength of cemented soil were sequenced. This provided some useful references for the application, construction and design of polluted soil and cemented soil in erosive environment. Secondly, the stress-strain curves of cemented polluted soil and the cemented soil in erosive environment have significant linear-elastic stage and plastic deformation stage. Plastic deformation closely related to erosion patterns of cemented soil, the kind and the concentration of erosive irons. According to the characteristics of cemented soil elastic-plastic deformation, the author advanced the viewpoint of considering the deformation process of cemented soil in different stages. Based on the analysis of the results of cemented soil damage experiments, the change law of cemented soil damage variable was made clear and the mechanism of cemented soil damage was also discussed. Based on the stress-strain curves, the damage model of cemented soil was established. According to datums of damage experiments, the related material parameters and damage variable were determined and the damage constitutional relationship of cemented soil's sectional elastic-plastic property was obtained. This shows that it is feasible and important to introduce the elastic-plastic damage theory into the mechanical properties of cemented soil engineering.Thirdly, the chemical erosion characteristics of cemented soil in H₂SO₄ erosive environment were made clear and the chemical erosion factor of cemented soil was defined. According to the experiment datums and chemical kinetics knowledge, the chemical forecasting model of cemented soil early strength in H₂SO₄ erosive environment was established. By contrasting with the experiment result, its accuracy and reasonableness was proved. This provides the basis for forecasting the mechanical properties of cemented soil strength in H₂SO₄ erosive environment. With the establishing of this model, chemical erosion has been effectively combined with mechanical strength. According to the chemical erosion factor defined in this article, the relationship of the interior mass and hydrate in the cemented soil and H₂SO₄ consumption has been made clear, and the reaction of cemented soil and H₂SO₄ has been quantitatively understood. Meanwhile, when the mechanical parameters of cemented soil and burn rate of erosive medium in various erosive environments have been known, it is feasible to forecast the early strength of the cemented soil in relative erosive environments. This provides theoretical basis for the early strength forecasting of cemented soil pile, especially large volume of cemented soil in various erosive environments.Based on the chemical reaction mechanism and the characteristics of ions migration in various erosive environments, and considering the diffussion, penetration, and reaction of erosive ions in cemented soil, the model of ion migration in erosive environment has been established. And the analytical solution has been obtained. This model can give solutions to different erosive environments, and also provides a theoretical basis for ion migration in various erosive environments. The strength forecasting formulation of the ralationship of cemented soil strength and NaOH concentration and age in NaOH erosive environment has been also proposed. Compared with experimental values, the formulation has been proved to have high accuracy. Therefor, the formulation can be used to forecast cemented soil strength in NaOH erosive environment.