Study on filling material strength and dam failure characteristics of loess dam

Abstract Due to the special material of the loess, it is characterized by large pores and collapsibility. When the water content is low, the strength is high. However, as the water level increases after the loess dam, the soil inside the dam is continuously wetted by water. The moisture content gradually increases, some characteristics of the soil change, and the control of the dry density during construction also affects the soil properties. In this paper, the filling materials of a loess dam in Ansai, Yan'an City, Shaanxi Province were selected as the research object which is ML in the USCS classification of Loess. The effects of confining pressure, water content, and dry density on the failure characteristics and strength characteristics of unsaturated remolded loess were investigated by triaxial apparatus, while prepared soil samples at a particular water content and perform the CU(Consolidated Undrain) tests. It is found that the remolded loess samples under the conditions of low confining pressure, low water content, and high dry density show brittle failure, and obvious shear planes are formed. The stress-strain curve shows a strong strain-softening type and exhibits shear dilatancy characteristics. The unsaturated remolded loess under high confining pressure, high water content, and low dry density exhibits plastic failure and strain hardened, showing shear shrinkage phenomenon. The shear strength index of unsaturated remolded loess is affected by factors such as water content and dry density. When the dry density is kept constant, the cohesive force will decrease with the increase of water content, while the internal friction angle will decrease with the increase of water content at the lower dry density. With a dry density of 1.7g/cm 3 , the interaction between soil particles, pores and water film causes the internal friction angle to increase first, then decrease and then increase. When the water content is constant, the cohesion force will increase with the increase of dry density, and the internal friction angle will increase with the increase of dry density. Then, FLAC3D was used to conduct a numerical simulation of loess stacked dam, and it was found that with the rise of water level, the slope shear outlet of the dam with three damages gradually moved up, and the landslide volume gradually decreased, which was consistent with the on-site damage phenomenon.