EXPERIMENTAL STUDY ON PROPERTIES OF WEAK EXPANSIVE SOIL IMPROVED BY DISINTEGRATED SANDSTONE

Continuous distribution of weak expansive soil and collapsible sand soft sandstone exists in Jichao and Jianghuai connecting sections of the Yangtze River to Huaihe River(waterway) diversion project. In order to utilize river excavation waste to develop non-expansive soil, the feasibility of using collapsible soft sandstone to improve weak expansive soil is studied. The results show that the disintegrated sandstone is easy to become fines and has low natural water content without expansion. So it can be used as a modified material. The expansion rate, expansion force, optimum water content and the amount of incorporation are negatively related when the weak expansive soil is mixed with the disintegrated sandstone. The maximum dry density, permeability coefficient and the amount of incorporation are positively related. After the weak expansive soil is incorporated into the disintegrated sandstone, its internal friction angle develops with the inverse S-shaped curve law, and the cohesive force decreases approximately quadratic with the increase of the dosage. The shear strength of improved soil may be lower than that of natural weak expansive soil when the dosage is higher than 30%. The higher the content of coarse grains of disintegrated sandstone, the higher the cohesion and the lower the friction angle of the improved soil when the content and the size range of disintegrated sandstone are the same. The strength stability of sandstone improved soil under dry and wet cycling conditions is improved. The improvement effect of the hydrated disintegrated sandstone is better than that of the crushed disintegrated sandstone. According to the standard of no loss of strength after the improvement of weak expansive soil, the reasonable content of disintegrated sandstone is determined to be 30%. And the content of coarse-grained group in the machine crushed disintegrated sandstone has to be reasonably controlled during the construction of disintegrated sandstone improved soil.