Study On Macro - Microscopic Characteristics Of Phosphorus - Stained Red Soil

The movement and transformation of laterite contaminated by phosphorus have been discussed. Soil column migration tests are carried out on Yunnan laterite with sodium hexametaphosphate associated with the influence of the depth of soil column tests. Mechanical characteristics of laterite contaminated by phosphorus are investigated.Compaction, shear, consolidation and penetration tests are carried out on Yunnan laterite with sodium hexametaphosphate associated with the influence of the concentration of sodium hexametaphosphate and dry density.Moreover, the mechanism towards laterite contaminated by phosphorus could be accounted for the action of phosphorus and laterite. The research results could provide a theoretical significance reference for engineering practice.The movement and transformation tests have been proved that the relative quality and clay content are larger after phosphorus is added to laterite. The relative quality and clay content decrease as the depth of soil column increase. The liquid limit, plastic limit and plasticity index decrease as the depth increase, a minimum value appears in the boundaries moisture content.The beta sodium tecto-dioxoferrate is generated. A maximum value appears in the phosphorus content. The ferrous oxide content has seriously changed on the surface of soil column. The iron and aluminum ion concentration of soaking solution on the surface of soil column gradually increase as time gone, and few iron and aluminum ion are found in seepage solution.The microstructure images show that the structural units of laterite contaminated by phosphorus have changed from compactly squamose structure to honeycomb structure and then become incompactly bee coagulation structure, a maximum value appears in the void ratio of the microstructure images. The iron and aluminum element are the main cementing materials of laterite.The cementing accumulations enclose the grain surface of laterite. The grain areas of the microstructure images decrease, but pore areas increase, a minimum value appears in the orientation and fractal dimention of grain of laterite.The mechanical test results show that phosphorus contamination has changed the mechanical characteristics of laterite. With the increasing phosphorus concentration, the maximum dry density of laterite increases gradually, and the optimum water content decreases gradually, and the optimal time is appeared. The cohesion and internal friction angle of laterite contaminated by phosphorus decreases, and the consolidation increases, but the penetration decreases.The microstructure units cement well in but coupling bad out. New structures of laterite are produced between the grain and pore. The cementing accumulations still enclose the grain surface of laterite. Combining with the SEM images that produced after mechanical tests, the microstructure image parameters of laterite contaminated by phosphorus are better after mechanical test. the change of mechanical characteristics of laterite contaminated by phosphorus may be the structural weakness of laterite.The mechanism towards laterite contaminated by phosphorus could be accounted for hydrolyzation, adsorption-complexation, reduction-oxidation and salification.The changes of transportation, transformation and mechanical characteristics of laterite contaminated by phosphorus may be the result of those comprehensive actions.