Mechanism and numerical simulation of a rapid deep-seated landslide in Van Hoi reservoir, Vietnam
Keywords:Deep-seated landslide, rainfall, pore water pressure, mobility, numerical simulation, Van Hoi reservoir, Vietnam.
At approximately 5:00 AM on December 16, 2016, a rapid and deep-seated landslide was triggered by intense rainfall in the Van Hoi irrigation reservoir in Binh Dinh province, Vietnam. The landslide generated an impulsive wave with a height of approximately 20 m, resulting in severe damage to the reservoir operation station. This study investigated the mechanisms behind the landslide's initiation and simulated its initiation and motion processes through site surveys, ring shear tests, and the LS-RAPID simulation model. The physical tests were conducted on two soil samples from the sliding zone to examine the landslide mechanism. The results indicated that only sample 2 (a sand sample of completely weathered gneiss rock) showed a high level of landslide mobility due to its liquefaction phenomena resulting in a rapid pore water pressure development and a significant strength loss.
In contrast, sample 1 (a silty sand sample of residual soils) did not exhibit this behavior due to its high shear resistance value at a steady state. The findings suggest that the sliding plane of the Van Hoi landslide formed in the completely weathered gneiss layer, and the high mobility level of sample 2 is primarily responsible for its rapid movement. Notably, the LS-RAPID model successfully reproduced the landslide process using the geotechnical properties obtained in the ring shear experiments. The simulation showed that the Van Hoi deep-seated landslide was initiated from the lower middle slope at a critical value of 0.55 for the pore water pressure ratio and traveled at a high velocity of approximately 37.0 m/s. The consistency between the computer simulation results and the on-site evidence and recorded data highlights the reliability of the LS-RAPID model as a tool for assessing landslide hazards.
An T.T.P., Matsuda H., Nhan T.T., Nhan N.T.T., Tien P.V., Thien D.Q., 2021. Pore water pressure responses of saturated sand and clay under undrained cyclic shearing. Vietnam J. Earth Sci., 44(2), 181-194.
Duc D.M., Minh V.C., Yen H.H., Loc N.T., Duc D.M., 2023. Analysis of landslide kinematics integrating weather and geotechnical monitoring data at Tan Son slow moving landslide in Ha Giang province. Vietnam J. Earth Sci., 45(2), 131-146.
Loi D.H., Sassa K., Fukuoka H., Sato Y., Takara K., Setiawan H., Tien P.V., Khang D., 2018. Initiation Mechanism of Rapid and Long Run-Out Landslide and Simulation of Hiroshima Landslide Disasters Using the Integrated Simulation Model (LS-RAPID). Landslide Dynamics: ISDR-ICL Landslide Interactive Teaching Tools, Springer International Publishing, 149-168.
Luong L.H., Miyagi T., Tien P.V., 2016. Mapping of large scale landslide topographic area by aerial photograph interpretation and possibilities for application to risk assessment for the Ho Chi Minh route-Vietnam. Transactions, Japanese Geomorphological Union, 97-118.
Nhan T.T., Matsuda H., An T.T.P., Nhan N.T.T., Tien P.V., Thien D.Q., 2022. Effects of physical properties and undrained cyclic shear conditions on the pore water pressure responses of saturated sands and clays. Vietnam J. Earth Sci., 45(1), 33-48.
Sassa K., Dang K., He B., Takara K., Inoue K., Nagai O., 2014. A new high-stress undrained ring-shear apparatus and its application to the 1792 Unzen-Mayuyama megaslide in Japan. Landslide, 11(5), 827-842.
Sassa K., Nagai O., Solidum R., Yamazaki Y., Ohta H., 2010. An integrated model simulating the initiation and motion of earthquake and rain induced rapid landslides and its application to the 2006 Leyte landslide. Landslides, 7(3), 219-236.
Sassa K., Wang G., Fukuoka H., Wang F., Ochiai T., Sugiyama M., Sekiguchi T., 2004. Landslide risk evaluation and hazard zoning for rapid and long-travel landslides in urban development areas. Landslides, 1, 221-235.
Tien P.V., Luong L.H., Duc D.M., Trinh P.T., Quynh D.T., Lan N.C., Thuy D.T., Phi N.Q., Cuong T.Q., Khang D., Loi D.H., 2021a. Rainfall-Induced Catastrophic Landslide in Quang Tri Province: the Deadliest Single Landslide Event in Vietnam in 2020. Landslides, 18(6), 2323-2327.
Tien P.V., Luong L.H., Nhan T.T., Duc D.M., Quynh D.T., Lan N.C., Phi N.Q., Hao D.C., Ha N.H., Thuy D.T., 2021c. Secondary Processes Associated with Landslides in Vietnam. Proceedings of the International Conference on Innovations for Sustainable and Responsible Mining, LNCE, 108, 192-209.
Tien P.V., Luong L.H., Nhat L.M., Thanh N.K., Cuong P.V., 2021d. Landslides along Halong-Vandon Expressway in Quang Ninh province, Vietnam. Understanding and Reducing Landslide Disaster Risk, 133-139.
Tien P.V., Luong L.H., Sassa K., Takara K., Sumit M., Nhan T.T., Khang D., Duc D.M., 2021b. Mechanisms and modeling of the catastrophic landslide dam at Jure Village, Nepal. J. Geotech. Geoenviron. Eng., 147(11), 05021010.
Tien P.V., Sassa K., Takara K., Fukuoka H., Khang D., Shibasaki T., Hendy S., Ha N.D., Luong L.H., 2018b. Mechanism of large-scale deep-seated landslides induced by rainfall in gravitationally deformed slopes: A case study of the Kuridaira landslide in Kii Peninsula. Landslide Dynamics: ISDR-ICL Landslide Interactive Teaching Tools, Springer International Publishing, 793-806.
Tien P.V., Sassa K., Takara K., Fukuoka H., Khang D., Shibasaki T., Setiawan H., Ha N.D., Loi D.H., 2018a. Formation process of two massive dams following rainfall-induced deep-seated rapid landslide failures in the Kii Peninsula of Japan. Landslides, 15(9), 1761-1778.
Tien P.V., Sassa K., Takara K., Khang D., Ha N.D., Luong L.H., 2017. Simulating the Formation Process of the Akatani Landslide Dam Induced by Rainfalls in Kii Peninsula, Japan. Advancing Culture of Living with Landslides, 497-506.
Tien P.V., Sassa K., Takara K., Tam D.M., Quang L.H., Khang D., Luong L.H., Loi D.H., 2016b. The influence of rainfalls on the potential of landslide occurrence on Hai Van Mountain in Vietnam. Proceeding of the Final SATREPS Workshop on Landslides, October 13 Hanoi, Vietnam, 112-121, ISBN: 978-4-9903382-3-7.
Tien P.V., Trinh P.T., Luong L.H., Nhat L.M., Duc D.M., Hieu T.T., Cuong T.Q., Nhan T.T., 2021e. The October 13, 2020 deadly rapid landslide triggered by heavy rainfall in Phong Dien, Thua Thien Hue, Vietnam. Landslides, 18(6), 2329-2333.
W.B., 2022. Report on Environmental and Social Impact Assessment for Improving Flood Control Capacity for Large Reservoirs, Vietnam - Dam Rehabilitation and Safety Improvement Project: Environmental Assessment. The World Bank, Ha Noi, 52, 270p.