Experimental study on the change laws of water repellency and shear strength of water repellent core materials modified by octadecylamine

Abstract The quality of the core-wall is the key to the normal operation of earth-rock dams. In this paper, the water repellent core materials were produced by standard sands combined with water repellent laterite modified by octadecylamine. The water-repellent degree and shear strength tests were carried out to obtain the change laws of water content, soil-rock ratio and octadecylamine content of shear strength of the specimens. It is shown that: (1) when the content of octadecylamine is 0.6%, the water drop penetration time (WDPT) of the specimens decreased gradually with the increase of soil-rock ratio in dry condition. The maximum WDPT is 2966s and the minimum WDPT is 2182s, which are severely water repellent. With the increase of water content, the change laws of WDPT increased firstly and then decreased, and the WDPT reached the peak value when the water content was from 10–15%, which are extremely water repellent. (2) With the increase of water content, the shear strength of the specimens increased continuously, in which the effect on soil cohesion is more than the effect on internal friction angle. (3) With the increase of soil-rock ratio, the shear strength of the specimens increased gradually and the maximum increasing range was 92.36% when the soil-rock ratio was less than 5%. (4) With the increase of octadecylamine content, the shear strength of specimens decreased gradually, and the maximum decreasing range was 12.44%. The soil-rock ratio and water content has a greater effect on shear strength, while the octadecylamine content has a less effect on shear strength.