Strength And Deformation Characteristics Of Reinforced Saline Soil With Rice Straw

Saline soil in inshore has some problems, such as softening, expansion and depression, which make saline soil not meet the requirement of strength and deformation for road embankment if untreated. It could be considered that saline soil may be reinforced or solidified.Unconfined compressive strength tests and triaxial tests were carried out in order to understand the stress-strain relationship and strength property of reinforced soil and reinforced lime soil. Main contents and results are as follows:(1) The unconfined compressive strength in different conditions of reinforced soil and reinforced lime soil was tested. The best reinforced effect is of 15 mm reinforced length and 0.2% reinforced rate which the size of sample is diameter 50 mm and height 50 mm. Under the right reinforced condition, unconfined compressive strength and resistance to deformation of reinforced soil and reinforced lime soil significantly improved.(2) The unconfined compressive strength increased with the increasing of dry density. Below or above the optimum water content, the strength decreased. Homogeneous method of reinforced soil was better than the tiled. The strength of half round tubular rice straw was bigger than other form of reinforced material.(3) The unconfined compressive strength of reinforced lime soil after immersion in water decreased. With the increasing of conservation periods and lime content, the strength and water stability coefficient increased. Strength of cement soil increased after reinforced. Strength and water stability coefficient of cement soil and reinforced cement soil is less than that of lime soil and reinforced lime soil.(4) The triaxial test (UU) of reinforced soil indicated that the reinforcement improved mainly cohesion and less influence to the internal friction angle. The reinforced effect is best at reinforced length and rate of 20 mm and 0.2% separately which the size of sample is diameter 61.8 mm and height 125 mm. Rice straw may decrease availably the lateral deformation of reinforced saline soil. The reinforcement effect plays out only when soil sample arriving a certain axial strain. Strength model of reinforced soil with rice straw by WU Model theory was discussed.(5) Peak of deviator stress and cohesive increased along with dry density increasing. Peak of deviator stress, cohesive and internal friction angle of reinforced soil with 20% and 24% water content were less than that of 22%.Peak of deviator stress and cohesive of middle homogeneous and middle tiled were bigger than that of upper and lower. Homogeneous method of reinforced soil was better than the tiled.Compared with peeled rice straw, peak of deviator stress and cohesive of unpeeled rice straw were smaller. Compared with tubular rice straw, peak of deviator stress and cohesive was smaller than that of laminated rice straw, and bigger than that of half round tubular rice straw. The shear performance of reinforced soil with original rice straw was almost as same as that of anti-decayed rice straw.(6) The samples which doing CU tests showed plastic failure, their stress-strain were close to the hardening. By means of Duncan-Chang model, the stress-strain characteristic of saline soil and reinforced saline soil with rice straw can be well indicated. Cohesion of CU experiment sample was more than that of UU test. Their internal friction angle was almost the same.(7) Lime soil showed significantly 45°shear planes and brittle failure, while reinforced soil with lime showed insignificant shear planes, reflecting the weak plastic failure. Peak of deviator stress, cohesive and internal friction angle of reinforced soil with lime were almost as same as that of reinforced soil under different conditions when making samples. Cohesive and internal friction angle of cement soil and reinforced cement soil was less than that of lime soil and reinforced lime soil.After reinforced and solidified, unconfined compressive strength and shear strength parameters of reinforced soil with rice straw and lime have been significantly improved to achieve the objectives of improving strength of soil. The research results are of importance for understanding the mechanism of reinforced saline soil with rice straw. And it can be applied in dealing with high grade road embankment in Tianjin Binhai New Area while can provide technical reference for other saline soil region.