1. Introduction#

1.1. Definition of the stability of embankment slopes#

In general, regulations on the design and verification of embankment structures require that the safety factor (FS) associated with static stability of the work does not exceed an imposed threshold. This safety factor, whose definition can vary according to the category of calculation methods used, measure in all The cases the safety margin of the slope in relation to the state of failure. Its value often depends on the geometry of the structure and on mechanical stresses. applied and material properties. In practice, the safety factor is verified once the static loads to which the structure is subjected have been taken into account.

Slope breakage occurs when the plasticization zone of the material forms a continuous surface connecting two ends on the slope profile. This zone is thus defined as being the fracture surface. Along the fracture surface, the shear strength of the soil becomes insufficient to withstand tangential stresses [1]. Several processes can lead to slope breakage [2]:

  • Reduction in shear resistance force, for example:

    • Increase in pore pressure due to the infiltration of water into

      the book.

    • Appearance of cracks around the crest of the structure.

    • Loss of strength of the clay refill.

  • Increased shear stress, for example:

    • Loading on the crest of the structure.

    • Excavation at the foot of the slope.

    • Rapid decline in the upstream coast.

The shape of the fracture surface depends on the nature of the slope. For slopes made of homogeneous and isotropic materials, the surface of The rupture is probably circular, which leads to rotational sliding. On the other hand, if the materials constituting the slope are heterogeneous or anisotropic, the surface will be non-circular, thus leading to the staircase sliding.

Given the complexity of the failure mechanism and the influencing factors, The practice in geotechnics is to use mathematical tools (analytical or numerical) for the calculation of the safety factor. As a result, a great multitude of calculation methods have been developed during the past century. In command CALC_STAB_PENTEsont implemented two categories of methods the most popular, offering an effective tool for calculating the safety factor of slopes and visualize the fracture surface.

1.2. Reminder of CALC_STAB_PENTE features#

The CALC_STAB_PENTE command allows you to analyze the static stability of slopes by embankment modelled in 2D by two categories of method:

  • Method SRM: the method of gradually reducing parameters related to

    shear strength of the material (called method SRM). This method was proposed by Griffiths et al. in 1999 [1].

  • Method LEM: a series of methods based on limit equilibrium theory

    (named method LEM), including simplified Bishop procedures, Fellenius, Spencer procedures, and Morgenstern-Price [2].

The first (SRM) is based on a non-linear finite element calculation, and proposes to approach the safety factor by modeling the break of the slope and therefore requires more vigilance when configuring the calculation.

Nevertheless, by dividing the slope into rigid slices, the last method (LEM) is often numerically more efficient and usually recommended by regulations for the design of hydraulic structures (despite the required hypotheses on the interaction between the various slices).

The features of CALC_STAB_PENTE are explained in more detail in the document [u4.84.47].