Based on orthogonal experimental design, the key solidification controlling technology of Solidified/Stabilized (S/S) sludge with high total organic content (TOC) by cement, lime and metakaolin was explored by macroscopic tests, chemical components measurements and microscopic analysis. The macroscopic tests show that, the permeability coefficient is mainly affected by initial water content and lime content, and the unconfined compression strength is mainly affected by cement content and lime content. The chemical components measurements show that, the solidification effect of S/S sludge with high TOC is controlled by organic matter consumption, and organic matter consumption is determined by the alkaline environment from the cement and lime hydration reactions, which is mainly affect by the initial water content and lime-metakaolin content ratio. The microscopic analysis results show that, lime consumes parts of organic matter while excess lime produces weak Ca(OH)2 crystal fluffy sheet structure, matakaolin produces pozzolanic reactions with cement and lime instead of soil particles, and consumes the weak Ca(OH)2 crystal fluffy sheet structure produced by superfluous lime. The research has confirmed key controlling points of S/S sludge in case of high TOC, which will provide theoretical guidance and technical support for S/S sludge promotion with high TOC.
To develop a model material suitable for analysing the stability of sandstone slopes during strong earthquakes, an orthogonal test was designed by selecting seven physico-mechemical parameters, a combination of dynamic and static parameters, as research indexes. Then, the influence of the proportion of each component in the model material on each test index was determined by sensitivity analysis, and the quantitative relationship between physico-mechanical parameters and component proportions was established by multiple linear regression analysis to develop a model material similar to sandstone. Finally, a sandstone slope along the Duxiang Expressway was taken as an example, and the proportions of the components suitable for a model of the rock mass in this area were determined. The test results showed that (1) the physico-mechanical parameters selected for the dynamic and static tests were used to effectively develop model materials for dynamic geotechnical model tests; (2) samples of model materials composed of barite powder, quartz sand, ferric powder, gypsum and cement met the requirements for dynamic testing of geotechnical models of sandstone slopes; and (3) through sensitivity analysis of various factors and multiple linear regression analysis, the required model materials were efficiently configured, and the failure mode, failure process and physico-mechanical parameters of the model materials accurately simulated the original rock materials.
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