scholarly journals Slope stability analyses by circular failure chart and limit equilibrium methods: the inlet and outlet of diversion tunnel of Bolango Ulu Dam, Indonesia

2021 ◽  
Vol 325 ◽  
pp. 01015
Author(s):  
Alesandro Sejo Luden ◽  
I Gde Budi Indrawan ◽  
Dwikorita Karnawati
Keyword(s):  
Slope Stability ◽  
Limit Equilibrium ◽  
Stable Condition ◽  
Outlet Section ◽  
Inlet Section ◽  
Residual Soil ◽  
Diversion Tunnel ◽  
Stability Analyses ◽  
Limit Equilibrium Methods ◽  
Natural Slopes

The objective of this research is to evaluate the stability of the natural slopes at the inlet and outlet portals of the Bolangu Ulu diversion tunnel, Gorontalo. The natural slopes were considered stable, and therefore slope stability analyses were not carried out previously in the tunnel portal design. The slope stability analyses were carried out using the Circular Failure Chart (CFC) and Limit Equilibrium Methods (LEM). Input data for the slope stability analyses were obtained from field mapping and laboratory testing of soil and rock samples. The results show that the portal slopes consist of diorite and residual soil. Both stability analysis methods yield nearly the same results. The slope at the outlet section had the factor of safety (FOS) values of 1.29 and 1.30 based on the CFC method and LEM, respectively, indicating the slope in a stable condition. However, the slope at the inlet section had the FOS values of 1.01 and 1.07 based on the CFC method and LEM, respectively, indicating the slope in a critical condition. The results suggest that stabilization of the portal slopes, particularly the portal slope at the inlet section, is required to prevent slope failures under static and earthquake loads.

scholarly journals Numerical Analysis of Slope Stability Due to Excavation of Diversion Tunnel at Pamukkulu Dam Site, Indonesia

2021 ◽  
Vol 6 (2) ◽  
pp. 102
Author(s):  
Wakhid Khoiron Nugroho ◽  
I Gde Budi Indrawan, Dr. ◽  
Nugroho Imam Setiawan
Keyword(s):  
Slope Stability ◽  
Outlet Section ◽  
Inlet Section ◽  
Residual Soil ◽  
Basalt Lava ◽  
Tunnel Excavation ◽  
Earthquake Load ◽  
The Stability ◽  
Model Strength

Located in the Takalar Regency of South Sulawesi Province, the Pamukkulu Dam is planned to use a tunnel type as its diversion structure. One of the critical parts in the tunnel construction is the stability of portal slopes. This research aimed to estimate the effect of tunnel excavation on the stability of the portal inlet and outlet slopes under static and earthquake loads by using the finite element method. The slope stability analyses were carried out under conditions of prior to and after tunnel excavation. The input parameters used were laboratory test results in the forms of index properties and mechanical properties taken from rock core drilling samples, completed with the rock mass quality parameters based on the Geological Strength Index (GSI) classification. The Mohr-Coulomb failure criterion was used to model strength of the soil, while the Generalized Hoek-Brown failure criterion was used to model strength of the rocks. The results of rock cores analysis using the GSI method showed that the inlet tunnel slope consisted of four types of materials, namely residual soil, fair quality of basalt lava, good quality of basalt lava, and very good quality of basalt lava. Meanwhile, the outlet portal slope consisted of three types of materials, namely residual soil, good quality basalt lava, and very good quality basalt lava. The calculated horizontal seismic coefficient for the pseudo-static slope stability analysis was 0.0375. The analysis results of slope stability in the Y1 inlet section had a critical Strength Reduction Factor (SRF) value of 2.35 in a condition prior to the tunnel excavation and a critical SRF value of 2.34 after the tunnel excavation. The Y2 outlet section had a critical SRF value of 13.27 in a condition before tunnel excavation and a critical SRF value of 5.55 after the tunnel excavation. The earthquake load addition at the Y1 inlet section showed a critical SRF value of 2.05, both before and after the tunnel excavation. The Y2 outlet section showed a critical SRF value of 11.49 before the tunnel excavation and a critical SRF value of 5.54 after the tunnel excavation. The numerical analysis results showed that earthquake load reduced critical SRF values of the slopes. At the Y1 inlet section, the tunnel excavation did not have a significant effect on slope stability. It was demonstrated by an extremely small decrease in a critical SRF value of 0.43% for a condition without an earthquake load and an unchanged critical SRF in a condition with an earthquake load. At the Y2 outlet section, the tunnel excavation had a more significant effect on the slope stability. It was exhibited by the decrease in the critical SRF value of 58.18% in a condition without an earthquake load and a decrease in the critical SRF value of 51.78% in a condition with an addition of an earthquake load. However, the analysis of slope stability for both sections showed that all design slopes were above the required allowable safety factor value.

An efficient approach for locating the critical slip surface in slope stability analyses using a real-coded genetic algorithm

2010 ◽  
Vol 47 (7) ◽  
pp. 806-820 ◽  
Author(s):  
Yu-Chao Li ◽  
Yun-Min Chen ◽  
Tony L.T. Zhan ◽  
Dao-Sheng Ling ◽  
Peter John Cleall
Keyword(s):  
Genetic Algorithm ◽  
Slope Stability ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Search Performance ◽  
Critical Slip Surface ◽  
Stability Analyses ◽  
Limit Equilibrium Methods ◽  
Real Coded Genetic Algorithm ◽  
Search Approach

A real-coded genetic algorithm is employed to develop a search approach for locating the noncircular critical slip surface in slope stability analyses. Limit equilibrium methods and the finite-element-based method are incorporated with the proposed search approach to calculate the factor of safety. Geometrical and kinematical compatibility constraints are established based on the features of slope problems to prevent slip surfaces from being unreasonable. A dynamic bound technique is presented to improve the search performance with more effective exploration within the solution domain. A number of examples are investigated that demonstrate the proposed search approach to be efficient in yielding accurate solutions to practical slope stability problems. The proposed search approach is stable and highly correlated with the results of independent analyses. Furthermore, this paper demonstrates the successful application of a real-coded genetic algorithm to noncircular critical slip surface search problems.

The Mt. Gamalama Instability in Generating Landslides in Ternate Island, Indonesia

2020 ◽  
Author(s):  
Saaduddin Saaduddin ◽  
Jurgen Neuberg ◽  
Mark Thomas ◽  
Jon Hill
Keyword(s):  
Slope Stability ◽  
Limit Equilibrium ◽  
Stable Condition ◽  
Static Condition ◽  
Characteristic Parameter ◽  
Parameter Analysis ◽  
Limit Equilibrium Methods ◽  
A Value ◽  
South West ◽  
History Of

<p>Mt. Gamalama has a history of volcanic tsunamis that have occured in 1608 and 1840. Regarding its geomorphology, Mt. Gamalama has very steep flanks, and landslides entering the sea could be the potential mechanism of tsunami generation which could threaten the coastal population and submarine infrastructure in the vicinity of Mt. Gamalama.</p><p>The potential volumes and types of landslides are estimated by a study of the Mt. Gamalama instabilities using the Generalized Hoek-Brown failure criterion which is applied in<em> Slide2D</em> (Rocscience), a 2D slope stability program using limit equilibrium methods. This procedure will result in a so-called <em>Factor of Safety</em> or FoS which represents a value of the Mt. Gamalama slope stability level.</p><p>The critical FoS values ranging from 1.945 to 3.361 have been obtained for four sections i.e., north, south, west and east side of the Mt. Gamalama edifice and are considered in relatively stable condition. These values hold for a static condition only under the force of gravity and in the absence of any volcanic activities. The application of seismic coefficients of 0.103 and 0.658, magma pressure of 2-17 MPa, and various angles of a dyke intrusion decreases the Mt. Gamalama stability and might cause landslides. Based on posture parameter analysis of modeled landslides, the landslide volumes could reach 10<sup>6</sup> -10<sup>9</sup> m<sup>3</sup>. Furthermore, regarding the morphometric characteristic parameter analysis, the landslide mobility could enter the Molucca seaand generate tsunamis.</p><p>Keywords: Gamalama, volcanic instability, volcanic landlsides, volcanic tsuamis</p>

Some difficulties associated with the limit equilibrium method of slices

1983 ◽  
Vol 20 (4) ◽  
pp. 661-672 ◽  
Author(s):  
R. K. H. Ching ◽  
D. G. Fredlund
Keyword(s):  
Slope Stability ◽  
Factor Of Safety ◽  
Limit Equilibrium ◽  
Stability Limit ◽  
Limit Equilibrium Method ◽  
Soil Conditions ◽  
Side Force ◽  
Limit Equilibrium Methods ◽  
Equilibrium Method ◽  
The Stability

Several commonly encountered problems associated with the limit equilibrium methods of slices are discussed. These problems are primarily related to the assumptions used to render the inherently indeterminate analysis determinate. When these problems occur in the stability computations, unreasonable solutions are often obtained. It appears that problems occur mainly in situations where the assumption to render the analysis determinate seriously departs from realistic soil conditions. These problems should not, in general, discourage the use of the method of slices. Example problems are presented to illustrate these difficulties and suggestions are proposed to resolve these problems. Keywords: slope stability, limit equilibrium, method of slices, factor of safety, side force function.

Seismic Coefficients for Simplified Deepwater Slope Stability Assessment Under Earthquake Loading

2021 ◽  
Author(s):  
Aurelian C. Trandafir
Keyword(s):  
Finite Element ◽  
Slope Stability ◽  
Shear Strain ◽  
Limit Equilibrium ◽  
Slope Instability ◽  
Earthquake Loading ◽  
Complex Deformation ◽  
Correlation Relationship ◽  
Stability Analyses ◽  
Seismic Coefficient

Abstract Pseudostatic limit-equilibrium based slope stability analyses are carried out on a routine basis to evaluate stability of submarine slopes under earthquake loading. For slopes in deepwater settings, a major challenge in performing pseudostatic slope stability analyses is selection of an appropriate seismic coefficient. Most published displacement-based methodologies for seismic coefficient selection were developed using simplified sliding block models for seismic slope performance evaluation that are unable to capture the complex deformation mechanism of deepwater slopes during earthquakes. To address this challenge, this study employs two-dimensional dynamic finite-element based deformation analysis to investigate the earthquake response of submarine clay slopes characterized by morphology, stratigraphic architecture and geotechnical properties representative for the deepwater environment. Finite-element computed seismic slope performance indicators, including horizontal peak ground acceleration at the seafloor and earthquake-induced maximum shear strain within the slope, along with horizontal seismic coefficients required to trigger slope instability in limit-equilibrium based pseudostatic stability analyses are used to develop a rational shear strain-based correlation relationship for deepwater slope seismic coefficient selection.

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