Study On Macro - Microscopic Characteristics Of Alkali - Contaminated Red Soil

Based on the comprehensive analysis on the pollution soil, testing technology of pollution soil and microstructure of soil at home and abroad, the existing problem in the research is made clear. Considering the really existing of alkali pollution laterite and the situation of lack of pollution laterite research, the subject of "the research of macro and micro features of alkali pollution laterite" is proposed. Around this topic, condidering different influencing factors, by means of physical and mechanical experiments and microstructure experiments, physical and mechanics characteristics and micro structure characteristics of alkali pollution laterite is researched. Moreover, interaction of alkali and laterite is expounded. This paper analyses clearly the reason of change of physical and mechanics of alkali pollution laterite.This paper has a theoretical significance to safely using laterite in engineering structure field.The results of physical tests show that:the specific gravity of pollution laterite is larger than before. In same curing time, the larger the alkali concentration, the larger the specific gravity. With extended curing time, specific gravity increases first and then decreases. After alkali is added to laterite, clay content increases significantly and content of the particles and sand grains decreases obviously. With accrescent alkali concentration, clay content increases first and then decreases. Content of the particles and sand grains decreases first and then increases. With extended curing time, clay content increases first, then decreases and last increases slightly. However, content of the particles and sand grains changes in the reverse direction. Liquid limit and plastic limit of alkali pollution laterite reduce. With extended curing time, liquid limit and plastic limit reduce first and then increase.The results of mechanics tests show that:the compaction property of alkali pollution laterite becomes worse. With accrescent alkali concentration, max dry density and optimization moisture content both decrease. Shear strength of alkali pollution laterite decreases obviously.The lager the alkali concentration, the lager shear strength decreases. With extended curing time, shear strength and cohesive strength decreases first, then increases a little and decreases at last. Angle of internal friction decreases gradually. With addition of dry density, shear strength, cohesive strength, and angle of internal friction all increases, but extent of addition is smaller than pure laterite. With addition of moisture content, shear strength and cohesive strength decrease, angle of internal friction increases first and then decreases,but extent of reduction is larger than pure laterite. Alkali pollution has a larger influence in cohesive strength than in angle of internal friction.With extended curing time, compression coefficient increases first and then decreases and compression modulus decreases first and then increases.The results of microstructure tests show that:With accrescent alkali content, surface of particles of laterite turns gradually rough from original smooth state. With extended curing time, big particles gradually turns fine and number of pore decreases first and then increases. Image presents the overall structure of the sample in small magnification.Image presents characteristics of a sample such as particle, aggregate and pore in large magnification. After shear experiment and compression experiment, pore of laterite reduces, particles are in good order and integrity is good.The interaction of alkali and laterite can be divided into prophase hydrolysis action, beginning erosion action, interim cementation, late period dissolution. Four aspects’ synthesized action of microstructure characteristics, microstructure characteristics parameters, material composition characteristics and interaction of alkali and laterite change physical and mechanical properties of alkali pollution laterite.