The relationship among the premonitory factors of landslide dam failure caused by seepage: an experimental study

Abstract

Background: A landslide dam always has the potential for catastrophic failure with high risk for life, cost and, property damage at the downstream site. The formation of a landslide dam is a natural process; thus, minimizing the risk due to its failure is important. Landslide dam failure can be categorized into three types: seepage failure, overtopping and slope failure. As described by other researchers, the established premonitory factors of landslide dam failure are hydraulic gradients, seepage and turbidity as well as vertical displacement and inflow into the reservoir. Methodology: This study only considered seepage failure and used flume experiments to understand it. Three groups of samples which represented fine, medium and coarse particle sizes, respectively, were prepared by Silica sand S4, S5, S6 and S8 of different proportion. These samples were used to conduct the flume experiments of failure and not failure case. Result: For failure cases, it was found that GI samples have a higher hydraulic gradient and that the seepage water takes time to exit the dam body-however, the seepage water has more TSS. GII samples also had a higher hydraulic gradient, while the flow of seepage water was faster than that of the fine sample with a low TSS. For GIII samples, the hydraulic gradient was very low in comparison with the GI and GII samples. The GIII samples had TSS values that were quite a bit higher than those of the GII samples and lower than those of the GI samples. Experiments on GI samples failed at each attempt; however, the GI samples with kaolinite did not fail and had a higher TSS value. For a GII sample of a non-failed case, the hydraulic gradient was lower than for GI samples and the seepage water flow was faster but the vertical displacement was constant and TSS was on a decreasing order. For a GIII sample, the hydraulic gradient became constant after reaching its initial peak value and TSS was on a decreasing order with an initially increasing vertical displacement that would become constant. Conclusion: Seepage failure of a landslide dam can be predicted by understanding the nature of its premonitory factors. These factors behave differently in different particle size samples. The TSS trend line may be the initial factor for checking the stability of a dam crest. A landslide dam with an increasing TSS order will fail and a decreasing order may not fail. Based on all experiments, it can be concluded that the hydraulic gradient has three stages: 1) it starts to increase and reaches a peak value; 2) it starts to decrease from the peak value and reaches a minimum; and 3) it starts to increase again where the seepage water begins to come out and the vertical displacement starts to increase. Dam failures always occur when seepage water comes out with an increasing TSS and an increasing vertical displacement. Repeated experiments on samples having more fine particles show that if a landslide dam is formed by fine particles, then there would be a high chance of its failure. In case of a constant hydraulic ...

Centrifuge Modeling and the Analysis of Ancient Landslides Subjected to Reservoir Water Level Fluctuation

“…This phenomenon can also be found in the prototypes according to previous studies [19,53]. Some researchers have proved that most fine particles in the pore structure are rushed out under the seepage force action and the seepage channels gradually develop and become interconnected in the seepage process by permeability test [54,55]. It can be seen that the landslide moves or slides along these holes or fissures, which were developed or produced by seepage erosion.…”

Depositing Characteristics of Landslide Dams and Advances in the Model Test for Seepage Failure

“…Compared with the dam crest overflow failure, the seepage failure is more difficult to find and detect and easy to cover up in the dam crest overflow failure. Some researches showed that piping and internal erosion caused by seepage were one of the main causes of landslide dam failure [23,24]. The peak discharge caused by seepage failure is more remarkable for higher dams than that caused by overtopping failure [25].…”

Flume tests on the hydraulic/mechanical behavior of the Tangjiashan landslide dam considering the influences of the different debris materials in heterogeneous strata

“…Model testing has become an essential method with which to study the stability of LDs, as in the works by Gregoretti et al (2010), Awal et al (2011), Chen et al (2015), Okeke and Wang (2016), Jiang et al (2018Jiang et al ( , 2019 and Dhungana and Wang (2019). In these studies, however, the grain size distribution of the LD material was not considered, and the model LD could only re ect part of a real LD with limitations.…”