scholarly journals A Non-Linear, Time-Variant Approach to Simulate the Rainfall-Induced Slope Failure of an Unsaturated Soil Slope: A Case Study in Sapa, Vietnam

2021 ◽  
Vol 16 (4) ◽  
pp. 512-520
Author(s):  
The Viet Tran ◽  
Hoang Viet Hung ◽  
Huy Dung Pham ◽  
Go Sato ◽  
Hoang Hiep Vu ◽  
...  

In this study, the Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Analysis (TRIGRS), v2.1 program, and module SLOPE/W in the Geostudio package were adopted for assessing rainfall-induced slope failure. TRIGRS was developed by the United States Geological Survey to determine the time-varying groundwater table at the regional scale under rainfall infiltration. The program employs partial differential equations represented by one-dimensional vertical flow in homogeneous materials for unsaturated conditions. With the application of a simple runoff routing scheme combined with the mass balance between rainfall, infiltration, and runoff over the study area, the distribution of the transient pore-water pressures within the entire landscape was simulated considering both the surface and subsurface flow. Additionally, compared to the traditional two-dimensional approach, the topographical conditions were also considered during the groundwater simulation. For conducting the slope stability analysis, a typical cross-section was constructed based on the site description. The predicted water-tables at the observed time of failure of the typical section were extracted and used in SLOPE/W to conduct the time-dependent modelling of rainfall-induced slope failures. In this study, the non-linear method was employed for simulating unsaturated soil shear strength, and the stability of the slope was evaluated using Bishop’s simplified method. We applied the approach to the landslide event that occurred on August 5, 2019, in Sapa district, Lao Cai province, Vietnam. The event resulted in severe damage and blocked the road for days. The predicted results on the stability of the slope as the factor of safety were compared with the actual slope failure during the event. The results showed that, by inputting accurate data, the applied approach could provide valuable evidence about the time of the slope failure.

2013 ◽  
Vol 1 (3) ◽  
pp. 2547-2587 ◽  
Author(s):  
D. W. Park ◽  
N. V. Nikhil ◽  
S. R. Lee

Abstract. This paper presents the results from application of a regional, physically-based stability model: Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis (TRIGRS) for a catchment on Woomyeon Mountain, Seoul, Korea. This model couples an infinite-slope stability analysis with a one-dimensional analytical solution to predict the transient pore pressure response to the infiltration of rainfall. TRIGRS also adopts the Geographic Information Systems (GIS) framework for determining the whole behaviour of a slope. In this paper, we suggest an index for evaluating the results produced by the model. Particular attention is devoted to the prediction of routes of debris flow, using a runoff module. In this context, the paper compares observed landslide and debris flow events with those predicted by the TRIGRS model. The TRIGRS model, originally developed to predict shallow landslides, has been extended in this study for application to debris flows. The results predicted by the TRIGRS model are presented as safety factor (FS) maps corresponding to transient rainfall events, and in terms of debris flow paths using methods proposed by several researchers in hydrology. In order to quantify the accuracy of the model, we proposed an index called LRclass (landslide ratio for each predicted FS class). The LRclass index is mainly applied in regions where the landslide scar area is not well defined (or is unknown), in order to avoid over-estimation of the model results. The use of the TRIGRS routing module was proposed to predict the paths of debris flow, especially in areas where the rheological properties and erosion rates of the materials are difficult to obtain. Although an improvement in accuracy is needed, this module is very useful for preliminary spatiotemporal assessment over wide areas. In summary, the TRIGRS model is a powerful tool of use to decision makers for susceptibility mapping, particularly when linked with various advanced applications using GIS spatial functions.


2017 ◽  
Vol 17 (2) ◽  
pp. 495-500
Author(s):  
Sunhak Kim ◽  
◽  
Young-il Kim ◽  
Jaehong Kim ◽  
◽  
...  

2011 ◽  
Vol 84-85 ◽  
pp. 729-732 ◽  
Author(s):  
Jun Guo ◽  
De Qing Gan ◽  
Yu Zhang ◽  
Wei Hang Zhang

The paper analyzed major factors that influence the stability of open-pit slope and established the GM (1, N) model based on the program of Xingshan strip mine, which provided an effective method for evaluating the slope stability.


2012 ◽  
Vol 166-169 ◽  
pp. 2535-2538
Author(s):  
Ke Wang ◽  
Chang Ming Wang ◽  
Fang Qi ◽  
Cen Cen Niu

The traditional limit equilibrium method in the analysis of slope stability not only exists some subjective empirical hypothesis that can not meet the equilibrium of force and moment, but also ignores the effects of internal stress and strain on the slope stability. Furthermore, in the stability of the slope evaluation, limit equilibrium method relies too much on experience when hypothesizing the slope slip surface. So that it makes deviation on slope analysis and stability evaluation. This paper is based on simplified Bishop method used to establish the model of slope stability analysis. And it used genetic algorithms to solve the minimum safety factor and the most dangerous slip surface of slope. It was the arithmetic which simulates organisms genetic evolutionary process and it avoided the traditional methods falling into the local extreme value point easily and error propagation leading to convergence. The algorithm had advantages of higher accuracy, quick convergence and applicability. It showed that the genetic algorithm is accurate and reliable in the analysis of slope stability.


2014 ◽  
Vol 540 ◽  
pp. 177-180 ◽  
Author(s):  
Dong Fang Tian

Based on the FEM analysis of unsaturated slope seepage and strength of unsaturated soil, and adopted the assumption of rigid body limit equilibrium to calculate safe coefficient of landslides, a new slope stability analysis method is promoted and the calculation program called USSP is composed and verified. The method could consider the impact of rainfall and water change to slope stability. Compared with GeoSlope package, it is more practical in rainfall or variation of ground water level condition.


Author(s):  
Rizki Ramadhan ◽  
Munirwansyah Munirwansyah ◽  
Munira Sungkar

The Aceh Tengah / Gayo Lues-Blangkejeren road segment (N.022) Km 438 + 775 is one of the Central Cross National Roads in the Province of Aceh, which often experiences landslides due to being in hilly areas. Landslides that occur in these locations are caused by scouring of road runoff, lack of optimal drainage and the absence of outlets for drainage and soil layers under asphalt pavement consisting of loose material. Therefore, a slope reinforcement study with Counterfort type retaining wall is needed. This study aims to analyze slope stability by obtaining safety factor numbers and identifying slope failure patterns. Analysis was carried out to obtain safety factors and slope failure patterns by using 2D Plaxis and slice methods. The calculation of safety factors for Counterfort type retaining walls is done manually. The input soil parameters used are dry volume weight (gd), wet volume weight (gw), permeability (k), modulus young (Eref), paisson's ratio (υ), shear angle (f), cohesion (c) . The results of slope stability analysis on the existing conditions using the Plaxis program and the slice method with radius (r) 65.06 meters found that safety factors were 1.038 and 1.079 with unsafe slope conditions (FK <1.25). The results of the analysis after reinforced counterfort and minipile type retaining wall with a length of 12 meters found 1,268 safety factor numbers with unsafe slope conditions (FK <1,5). Thus, additional reinforcement is needed by using anchor on the counterfort. The results of slope stability analysis after reinforced counterfort, minipile and anchor type retaining walls with a length of 20 meters and a slope of 30 ° were obtained with a safety factor number of 1.513 with safe slope conditions (SF> 1.5).ABSTRAKRuas jalan batas Aceh Tengah/Gayo Lues-Blangkejeren (N.022) Km 438+775 merupakan salah satu ruas jalan Nasional Lintas Tengah Provinsi Aceh, yang sering mengalami terjadi tanah longsor karena berada di daerah perbukitan. Longsoran yang terjadi pada lokasi tersebut disebabkan oleh gerusan air limpasan permukaan jalan, kurang optimalnya drainase dan tidak adanya outlet untuk pembuangan air serta lapisan tanah di bawah perkerasan aspal terdiri dari material lepas. Oleh karena itu, diperlukan kajian perkuatan lereng dengan dinding penahan tanah tipe Counterfort. Kajian ini bertujuan untuk menganalisis stabilitas lereng dengan mendapatkan angka faktor keamanan dan mengidentifikasi pola keruntuhan lereng. Analisis dilakukan untuk mendapatkan faktor keamanan dan pola keruntuhan lereng yaitu dengan menggunakan program Plaxis 2D dan metode irisan. Perhitungan faktor keamanan untuk dinding penahan tanah tipe Counterfort dilakukan secara manual. Adapun parameter  tanah input yang digunakan adalah berat volume kering (gd), berat volume basah (gw), permeabilitas (k), modulus young (Eref), paisson’s rasio (υ), sudut geser (f), kohesi (c). Hasil analisis stabilitas lereng pada kondisi eksisting menggunakan program Plaxis dan metode irisan dengan jari-jari (r) 65,06 meter didapatkan akan faktor keamanan sebesar 1,038 dan 1,079 dengan kondisi lereng tidak aman (FK < 1,25). Hasil analisis setelah diperkuat dinding penahan tanah tipe counterfort dan minipile dengan panjang 12 meter didapatkan angka faktor keamanan 1,268 dengan kondisi lereng tidak aman (FK < 1,5). Dengan demikian, maka diperlukan perkuatan tambahan dengan menggunakan angkur pada counterfort. Hasil analisis stabilitas lereng setelah diperkuat dinding penahan tanah tipe counterfort, minipile dan angkur dengan panjang 20 meter serta sudut kemiringan 30° didapatkan angka faktor keamanan 1,513 dengan kondisi lereng aman (SF > 1,5).Kata kunci : longsoran; counterfort; plaxis 2D; faktor keamanan.


2000 ◽  
Vol 22 ◽  
Author(s):  
I. R. Humagain ◽  
K. Schetelig ◽  
M. P. Sharma ◽  
B. N. Upreti ◽  
M. Langer

The proposed Kathmandu-Hetauda Road alignment passes through Thankot, Chitlang, Kulekhani, Bhimphedi, and Bhaisedobhan. It is the shortest as well as least hazardous route very suitable for a standard highway. It has the following three tunnel sections: the Thankot Tunnel (3.2 km long), the Kulekhani Tunnel (500 m long), and the Chisapani Tunnel (3.8 km long). The alignment passes through the Kathmandu Nappe, Upper Nawakot Group of the Lesser Himalaya, and the Siwaliks. It also crosses the Main Boundary Thrust and the Mahabharat Thrust, four major faults/shear zones, and a major fold axis. The areas of plane sliding, wedge sliding, and toppling are delimited on the basis of the study of discontinuities along the proposed alignment. The stability analysis show s that 60-75% of the total road length is stable, 20-30% is fair, 5- 15% is weak, and 2-5% is critical.


2013 ◽  
Vol 13 (11) ◽  
pp. 2833-2849 ◽  
Author(s):  
D. W. Park ◽  
N. V. Nikhil ◽  
S. R. Lee

Abstract. This paper presents the results from the application of a regional, physically based stability model: Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis (TRIGRS) for a region on Woomyeon Mountain, Seoul, South Korea. This model couples an infinite-slope stability analysis with a one-dimensional analytical solution to predict the transient pore pressure response to the infiltration of rainfall. TRIGRS also adopts the geographic information system (GIS) framework for determining the whole behaviour of a slope. In this paper, we suggest an index for evaluating the results produced by the model. Particular attention is devoted to the prediction of routes of debris flow, using a runoff module. In this context, the paper compares observed landslide and debris flow events with those predicted by the TRIGRS model. The TRIGRS model, originally developed to predict shallow landslides, has been extended in this study for application to debris flows. The results predicted by the TRIGRS model are presented as safety factor (FS) maps corresponding to transient rainfall events, and in terms of debris flow paths using methods proposed by several researchers in hydrology. In order to quantify the effectiveness of the model, we proposed an index called LRclass (landslide ratio for each predicted FS class). The LRclass index is mainly applied in regions where the landslide scar area is not well defined (or is unknown), in order to avoid overestimation of the model results. The use of the TRIGRS routing module was proposed to predict the paths of debris flow, especially in areas where the rheological properties and erosion rates of the materials are difficult to obtain. Although an improvement in accuracy is needed, this module is very useful for preliminary spatio-temporal assessment over wide areas. In summary, the TRIGRS model is a powerful tool of use to decision makers for susceptibility mapping, particularly when linked with various advanced applications using GIS spatial functions.


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