Micro - Microscopic Characteristics Of Alkali - Contaminated Red Soil Under Soaking Condition

The research object of this paper is Yunnan red clay, using sodium hydroxide as a contaminant, under the soaking condition, the simulation outgoing and ingoing of lye, and under the soaking condition studying on microscopic characteristics of alkali contaminated laterite, according to the change of shear characteristics, compression properties, permeability characteristics, micro characteristics, the corrosion mechanism of alkali contaminated laterite is discussed. The main conclusions are as follows.Shear test results show in lye ingoing condition shear strength and its index of the alkali pollution laterite are lower than the prime laterite when the alkali concentration is low; when the alkali concentration is high, they are higher than the prime laterite; With alkali concentration increases, the Shear strength and its index of the alkali pollution laterite are gradually increase. With the extension of ingoing time, at low concentration, Shear strength and its index of the pollution laterite changes slowly, and exist minimal value. At high concentrations, they are increase significantly, and exist maxima value, In lye outgoing condition, Shear strength and its index of the alkali pollution laterite are lower than the prime laterite when the alkali concentration is low. With the increase of concentration, they are recovery increases. After a long time to move out, under high concentration, the restoring force is weakened, they are lower than the prime laterite. The same concentration of lye, with the extension of outgoing time, they are higher than the prime laterite, when the time of outgoing is long enough, they are lower than the prime laterite, and the higher the concentration, the greater the amount of lower.Compression test results show that in lye ingoing condition compression coefficient of the alkali pollution laterite is higher than the prime laterite when the alkali concentration is low. Its is lower than the prime laterite when the alkali concentration is high, With the extension of ingoing time, compression coefficient of the alkali pollution laterite are gradually increase when the alkali concentration is low, and exist great value. It is gradually decrease when the alkali concentration is high, and exist minimal value. In lye outgoing condition, compression amount and compression coefficient of the alkali pollution laterite are increase when the alkali concentration is low, with the increase of concentration, it is gradually low. With the extension of outgoing time, compression amount and compression coefficient of the alkali pollution laterite are lower than the prime laterite, and exist minimal value. When the time is long enough to move out, compression coefficient are higher than the prime laterite.Permeability test results show that in lye ingoing condition permeability coefficient of the alkali pollution laterite is decreases with the increase of concentration. With the extension of ingoing time, the permeability coefficient of the alkali pollution laterite is increase, at low concentrations, exist great value. In lye outgoing condition, within a short period of time, permeability coefficient of the alkali pollution laterite is a great value with the increase of concentration, and extreme value is higher than the prime, permeability coefficient of the alkali pollution laterite are gradually increases with the increase of concentration, and minimal value is lower than the prime.Microstructure analysis showed that in lye ingoing condition with the increase of concentration or with the extension of ingoing time, grains size of the alkali pollution laterite become small and increase, Void ratio, fractal dimension and orientation degree are reduce, particle alignment uniformity and tightness are enhancement. After stress, grains size of the alkali pollution laterite Become big and decrease, fractal dimension and the degree of orientation is further reduced, and the lower the concentration the greater the amount. In lye outgoing condition, with the concentration increasing, pore ratio and particle size are first decreases and then increases, fractal dimension and orientation degree are first increase and then decrease, The soil particles is disarray and connectivity become weak in a certain period. After stress, with the increase of concentration or with the extension of outgoing time, void ratio, fractal dimension and orientation are first decreases and then increases, Force and contaminated soil pore ratio, fractal dimension, orientation degree with migration out of concentration and emigration time decreases, the low concentration of accepting and a micro structural parameters change greater. At low concentration, the parameters of the micro structure before and after the stress changed greatly.Mechanism of action is about between alkali and laterite. The essence of alkali contaminated laterite lies in the interaction between the alkali and the laterite. Its action mechanism can be used alkali soil reaction, salt solution, salts adhesion and formation of new colloid, salt dissolved ion balance to explain. The combined effects of these four stages changed the shear, compression, permeability and microstructure of alkali contaminated red soil.