Geotechnical Earthquake Engineering and Soil Dynamics V GSP 293 88 © ASCE SEM-Based Seismic Slope Stability and Mitigation Model for the Jure Landslide after the 7.8Mw 2015 Barpak-Gorkha, Nepal, Earthquake N. P. Bhandary 1 ; R. C. Tiwari 2 ; R. Yatabe 3 ; and S. Paudel 4 1 Faculty of Collaborative Regional Innovation and Center for Disaster Management Informatics Research, Ehime Univ., 3 Bunkyo-Cho, Matsuyama 790-8577, Japan. E-mail: netra@ehime-u.ac.jp 2 Faculty of Collaborative Regional Innovation, Ehime Univ., 3 Bunkyo-Cho, Matsuyama 790- 8577, Japan. E-mail: rctiwari1975@gmail.com 3 Center for Disaster Management Informatics Research, Ehime Univ., 3 Bunkyo-Cho, Matsuyama 790-8577, Japan. E-mail: yatabe.ryuichi.mu@ehime-u.ac.jp 4 Dept. of Water Induced Disaster Management (DWIDM), Pulchowk, Lalitpur, Nepal. E-mail: paudelsurendra2010@gmail.com ABSTRACT A massive landslide in the Jure village of Sindhupalchowk District, Nepal, occurred on August 2, 2014, wiping out dozens of houses and blocking the Sunkoshi River. The spectral element method (SEM) is employed here to study the stability of the slope where the landslide occurred, considering dry and wet slope conditions and pseudo-static seismic loading (with refer to 7.8Mw 2015 Barpak-Gorkha, Nepal earthquake). The results show that the Jure landslide slope becomes unsafe when the ground water table (GWT) is at the surface and peak ground acceleration (PGA) is greater than 0.2 g considering two slope cross-sections (section 2-2 and 3-3), and greater than 0.1 g for one slope cross-section (section 1-1). Based on the computational results, a correlation is made between the factor of safety (FS) and the PGA for the Jure landslide slope. Mitigation methods such as slope modification and ground water table reduction (drainage) are then proposed to increase the slope FS. The SEM results are then verified with a finite element method (FEM) technique. INTRODUCTION Nepal occupies 800km in the middle of 2400km, or one third of the Himalayan region. Within an 800km by 200km area, Nepal consists of 83% mountains, which have steep slopes, extreme relief, highly varied topography and high elevation ranges (ranging from 60 to 8848m). In addition to this, Nepal lies on the boundary of Indian and Tibetan plate, which is capable of producing large scale earthquakes in Nepal. Additionally, Nepal has adverse geological conditions (fragile geological setting), uneven patterns of rainfall and is influenced by variable groundwater. It is typical that about 93% of concentrated precipitation occurs in summer, of which 37% can occur within 24 hours. Thus, the Nepal Himalayas are a highly vulnerable, high energy environment, resulting from steep relief, active tectonics and concentrated rainfall. Due to this high energy environment and uneven precipitation, Nepal Himalayas are always prone to large scale landslides, of which the Jure landslide is one that devastated the whole village and led to the loss of hundreds of lives and properties. The massive landslide in the Jure village of Sindhupalchowk District, Nepal, occurred at 2:30 AM on August 2, 2014 wiping out dozens of homes and blocking the Sunkoshi River. The landslide runout completely dammed the Sunkoshi River for 36 days forming a lake about 3km long and 0.325km wide. Figure 1 and 2 show the location, boundary and an image of Jure Landslide. Geotechnical Earthquake Engineering and Soil Dynamics V Downloaded from ascelibrary.org by Imperial College London on 12/08/18. Copyright ASCE. For personal use only; all rights reserved.