On the Computational Precision of Finite Element Algorithms in Slope Stability Problems

Although the finite element method (FEM) has been used extensively to analyse the slope stability problems, the computational precision and definition of failure are still two main key concepts of finite element algorithms that attract the attention of researchers. In this paper, the modified Euler algorithm and the explicit modified Euler algorithm with stress corrections are used to analyse two dimensional (2D) slope stability problems with the associated flow rule, based on the shear strength reduction method. The rounded hyperbolic Mohr-Coulomb (M-C) yield surface is applied. Effects of the element type and various definitions of failure on the computational precision of 2D slope stability problems are evaluated. Conclusions can be drawn that the modified Euler scheme is applicable when the factor of safety (FOS) is small; however, the explicit modified Euler algorithm with stress corrections is more precise if the factor of safety is relatively large. The fully integrated quadrilateral isoparametric element is better than the triangular element in terms of the precision. With respect to the definition of failure, the displacement mutation of the characteristic point combining with the continuums of the plastic zone can be regarded as a reliable definition of failure and can be widely used to perform and analyse numerical simulations of slope stability problems.

Selected components of geological structures and numerical modelling of slope stability

This paper presents the impact of selected essential aspects of geological structure on the state of slope stability as assessed by changes in the safety factor (SF). The engineering geological slope features that were analysed include: (i) changes in soil cohesion and internal friction angle, (ii) presence of a weak soil layer and its span, (iii) structural discontinuity (i.e. fault), (iv) soil permeability properties and water conditions (i.e. groundwater level, long and heavy rainfall). A certain scheme of slope stability calculations has been proposed for a case involving complex geological conditions. The numerical modelling of a hypothetic slope was performed using the shear strength reduction method based on the finite element method.

Stability of Irrigation Canal Slopes Considering the Sea Level Rise and Dynamic Changes: Case Study El-Salam Canal, Egypt

Stability of canals slopes are of paramount importance in engineering works due to its interaction with the infrastructure including roads networks and buildings. The failure of these slopes could cause human disaster, catastrophic environmental, and economic losses. The present study aims to investigate the stability of canals slopes considering the climate changes through sea level rise, fluctuation of groundwater level and the seismic actions. The study was simulated on the North Eastern part of Nile Delta aquifer, Egypt using the finite difference code of Visual MODFLOW. Moreover, the groundwater flow under the effect of sea level rise was investigated to study its effect on slope stability of El-Salam Canal, Egypt. Furthermore, the finite element program of Phase 2 was implemented, and safety factors were calculated using the shear strength reduction method (SSRM). The models are calibrated and verified through experimental work using permeability and seepage model. Moreover, the two models were applied on El-Salam Canal considering three scenarios to identify the safety factors including the effect of sea level rise (SLR), earthquake acceleration and a combination of the two scenarios. The results indicated that dynamic response values of the canal slope have different variation rules under near and far field earthquakes. Finally, the damage location and pattern of the slope failure are different in varying groundwater conditions.

Influence of bedding and backfill soil type on deformation of buried sewage pipeline

In the paper, the influence of different types of bedding and backfill soil surrounding underground sewage duct on its deformation was analysed. Impact of increased soil lateral pressure was examined by considering the construction of an embankment nearby the underground pipeline. Numerical computations of three different variants of bedding and backfill soil surrounding the pipe were carried out. Displacements and deformation of the pipe were calculated using the finite element method with adoption of elastic-perfectly plastic constitutive model of soil. Subsequent stages of the construction were taken into account. Shear strength reduction method was applied to evaluate the factor of safety of the entire system. Finally, the results and conclusions were depicted.

Numerical analysis of landslide next regional route No. 975 in Borowa before and after securing it

In the paper the problem of landslides in road engineering is discussed. An example is given of a landslide next to regional road No. 975 in Borowa. The analysed slope was modeled in the MIDAS GTS NX . The slope stability analysis and the FoS coefficient were carried out using the shear strength reduction method (SRM). In the next step a numerical analysis was carried out after the security measures were implemented. The results show the capability of numerical simulation programs.

Analysis of stability of railway embankment including horizontal forces in light of Eurocode

The subject of this paper is analysis of the influence of horizontal forces estimated on the basis of Eurocode on the stability of an exemplary railway embankment located in the horizontal curve. The work begins with an overview of the methods for determining the earthworks stability. The methods are presented along with a reference to the recommendations contained in Eurocode 7. On the basis of the Eurocode, the loads acting on the analyzed embankment are presented together. In addition to the standard vertical interactions (from the rolling stock, the weight of the track structure and ground), the calculations also take into account horizontal forces caused by: wind forces on rolling stock, centrifugal forces and nosing force of the rolling stock as well as thermal stresses in the rails. Next, there are 15 load combinations calculated according to the Eurocode guidelines. At the end of the work the values of safety factors of the embankment obtained by shear strength reduction method are presented. The obtained results show a significant influence of horizontal forces calculated on the basis of the Eurocode on the stability of the railway embankment analyzed in the work.