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Numerical analysis on the failure of landslide dam resulting from seepage-induced stiffness
degradation (A research progress)〇Raden Harya Dananjaya, Gonghui Wang
Landslide is a prominent disaster in hilly areas; it can harm the environment and people. The need to understandfailure mechanisms of slope for countermeasure is urgently needed. In this research, a numerical method will be
used to examine the failure mechanism of a landslide dam. both serial and parallel SPH-based codes were developed
and their performances were examined. Subsequently, a Kleefsman’s dam break test code was conductednumerically, and its experimental data sheets were used to validate the code. The result shows that the GPU parallelcode increases performance by more than ten times faster than its serial CPU code. Moreover, in Kleefsman’s dam
break test, no obvious difference was found in both numerical and experimental results, although our code has a lagtime of around 0.06 s.
Failures occurring on landslide dams or embankments

flow. An SPH-based program is developed. Several testare problematic disasters, especially in hilly areas. Forcases have been conducted to validate the developed

example, in January - March 2021, several landslidecode. A GPU offloading algorithm is opted fordams were formed and then failed in Indonesia,

increasing performance besides its serial algorithm.

resulting in 84 casualties and damage to 694 houses. To
prevent and mitigate this kind of disaster, a better
understanding of the initiation and movement
mechanisms of these landslide dams or embankments
will be of great importance. It has been well understoodthat the failures of landslide dams and embankmentscould be initiated due to internal erosion, surfaceovertopping erosion, and slope instability. However, a(a)comprehensive study of combining these three failure
mechanisms is still rare. In this study, a numerical studyof the combination of these failure mechanisms isconducted to obtain 1) the role of internal erosion andsurface erosion on change of hydraulic gradient,
stiffness degradation, and pore pressure leading tolandslide dam failure and 2) the effect of soil erosionand deposition on surface evolution of the landslide(b)Fig. 1 Numerical validation set up based on Kleefsman et al.,(2005): a) top, b) side view.

dam leading to slope instability.

Results
1. Performance analysis
The result of the performance test between serial CPU

Methodand parallel GPU code is shown in Fig. 2. It shows that

The first step to numerically investigating the landslide

GPU offloading code can increase performance anddam failure mechanism is to develop a numerical code

accelerate the computational time by more than ten

that incorporates soil-water interactions and multiphaseresults have a strong correlation, they have highpearson’s coefficient of correlation, i.e., 0.917, 0.815,
and 0.95 for H1, H2, and H3, respectively.

times than its serial code (Fig. 2)

Fig. 2 Comparison of GPU offload code and CPU serial code.
(a)2. Kleefsman’s dam break
To this end, a weakly compressible SPH has beendeveloped, and a Kleefsman dam break case has been
conducted (Fig. 1). The results show that the developed
numerical code can mimic the test case, although there
is a small time-lag between the numerical andexperimental results, i.e., 0.06 s (Fig. 3). The
discrepancy can arise due to the chosen SPH parametersettings

andparticle

resolution.

However,(b)thediscrepancy can be reduced by calibrating the code.

(a)

(c)
Fig. 4 Comparison of water level from experimental (Kleefsman
et al., 2005) and numerical results after calibration: a) H1, b) H2,and c) H3.

(b)Fig. 3 Snapshot of 3D dam-break: a) Kleefsman et al., (2005) at
0.4 s, b) this study at 0.46 s.

The comparison of water levels between experimental(Kleefsman et al., 2005) and numerical results areshown in Fig. 4. In this figure, the numerical model canpredict the dam break water profile evolution precisely,
although tolerable small difference is observed. In Fig.
5, it’s shown that the numerical and experimental

Fig. 5 Correlation of numerical (after calibration) andexperimental results (Kleefsman et al., 2005).