Seismic Analysis of Earth Slope Using a Novel Sequential Hybrid Optimization Algorithm

One of the most important topics in geotechnical engineering is seismic analysis of the earth slope. In this study, a pseudo-static limit equilibrium approach is applied for the slope stability evaluation under earthquake loading based on the Morgenstern–Price method for the general shape of the slip surface. In this approach, the minimum factor of safety corresponding to the critical failure surface should be investigated and it is a complex optimization problem. This paper proposed an effective sequential hybrid optimization algorithm based on the tunicate swarm algorithm (TSA) and pattern search (PS) for seismic slope stability analysis. The proposed method employs the global search ability of TSA and the local search ability of PS. The performance of the new CTSA-PS algorithm is investigated using a set of benchmark test functions and the results are compared with the standard TSA and some other methods from the literature. In addition, two case studies from the literature are considered to evaluate the efficiency of the proposed CTSA-PS for seismic slope stability analysis. The numerical investigations show that the new approach may provide better optimal solutions and outperform previous methods.

Semi Empirical Slope Stability Analyses of Mohmand Dam using Limit Equilibrium and Finite Element Methods

This study presents a framework for semi-empirical slope stability analysis of Mohmand dam, an important ongoing mega concrete faced rockfill dam hydropower project in Pakistan. The project comprises of 213 m high hybrid dam that will produce 800 megawatt of clean hydropower energy in addition to an effective flood mitigation. Also, it will supply water for both irrigation and drinking to the provincial capital city, Peshawar. In this study, finite element and limit equilibrium methods have been used for slope stability analysis and factors of safety have been computed for all anticipated loading conditions including earthquake loading. The rockfill samples of main dam were obtained from the construction material site of Mohmand dam and the input parameters for slope stability analysis were obtained both empirically and through laboratory testing. Results of both limit equilibrium and finite element analyses have been compared and it was observed that the latter is more conservative than the former except for earthquake loading. The implications of current findings have been demonstrated using an important case study of an independent dam site that would boost the confidence of practitioners.

Slope stability analysis of a landfill subjected to leachate recirculation and aeration considering bio-hydro coupled processes

During the operation of landfills, leachate recirculation and aeration are widely applied to accelerate the waste stabilization process. However, these strategies may induce high pore pressures in waste, thereby affecting the stability of the landfill slope. Therefore, a three-dimensional numerical analysis for landfill slope stability during leachate recirculation and aeration is performed in this study using strength reduction method. The bio-hydro coupled processes of waste are simulated by a previously reported landfill coupled model programmed on the open-source platform OpenFOAM and then incorporated into the slope stability analysis. The results show that both increasing the injection pressure for leachate recirculation and maximum anaerobic biodegradation rate will reduce the factor of safety (FS) of the landfill slope maximally by 0.32 and 0.62, respectively, due to increased pore pressures. The ignorance of both waste biodegradation and gas flow will overestimate the slope stability of an anaerobic bioreactor landfill by about 20–50%, especially when the landfilled waste is easily degradable. The FS value of an aerobic bioreactor landfill slope will show a significant reduction (maximally by 53% in this study) when the aeration pressure exceeds a critical value and this value is termed as the safe aeration pressure. This study then proposes a relationship between the safe aeration pressure and the location of the air injection screen (i.e., the horizontal distance between the top of the injection screen and the slope surface) to avoid landfill slope failure during aeration. The findings of this study can provide insights for engineers to have a better understanding of the slope stability of a bioreactor landfill and to design and control the leachate recirculation and aeration systems in landfills.

Modelling of Seepage and Slope Stability Analysis of Ribb Embankment Dam, Ethiopia

Safety against seepage is one in all the primary important steps for checking the possibility of failure of embankment dam and the stability of an embankment dam depends on its geometry, its components, materials, properties of every component, and therefore the forces to which it's subjected. This paper presented seepage and slope stability analysis against Ribb dam safety using finite element-based PLAXIS software, and so the result was compared with different standards. PLAXIS is alternative software that will be used for evaluating the protection of embankment dams due to seepage conditions. The simulated results showed the common rate of flow of seepage through the body of the dam at normal pool level was equal to 5.05*10−6 m3/s/m and through the foundation of the dam was 3.00*10−6 m3/s/m. According to Look (2014) recommendation, the seepage results within the tolerable limit. The results of the factor of safety were considered too different loading conditions. The factor of safety results during the end of construction for both static and dynamic stability analysis were 1.3063 and 1.2226, respectively. For steady-state conditions, the factor of safety obtained for static stability analysis was 1.2604, and also the dynamic analysis 1.1803. The rapid drawdown condition is analyzed with a normal pool level of 1940 m lowered to 1900 m or rapidly reduced 57% of the reservoir water. The analysis results showed that the factor of safety for the static, and dynamic analyses were 1.2021 and 1.0662, respectively. Using different recommended design standards: United States Army Corps of Engineers (USACE), British dam society (BDS), and Canadian dam association (CDA) the slope stability analysis of the Ribb embankment dam at all critical loading conditions is safe.