12.4 Design and construction considerations
(1)P Embankments shall be designed taking into account experience with embankments on similar ground and made of similar fill material.
(2)P When assessing the foundation level for an embankment, the following shall be considered, when applicable:
- reaching an adequate bearing stratum, or applying stabilising measures where this is not practicable;
- providing sufficient protection against adverse climatic effects on the bearing capacity of the ground;
- the ground-water level with respect to the drainage of the embankment;
- avoiding adverse effects on adjacent structures and utilities;
- reaching layers with adequately low permeability.
(3) Design of embankments should ensure that:
- the bearing capacity of the subsoil is satisfactory;
- the drainage of the various fill layers is satisfactory;
- the permeability of the fill material in dams is as low as required;
- filters or geosynthetics are specified where necessary to fulfil filter criteria;
- the fill material is specified according to the criteria in 5.3.2.
(4)P For embankments on ground with low strength and high compressibility, the construction process shall be specified so as to ensure that the bearing capacity is not exceeded and that excessive settlements or movements do not occur during construction (see 5.3.3 (2)P).
(5) When an embankment on compressible ground is raised in layers, piezometer measurements should be specified to ensure that pore-water pressures have dissipated to acceptably low values before the next fill layer is placed.
(6)P For embankments retaining water at different levels, the foundation level shall be chosen with respect to the permeability of the ground or measures shall be taken to make the structure watertight.
(7) If ground improvement is specified, the volume of ground to be improved should be designed with sufficient areal extent to avoid harmful deformations.
(8) When determining the weight of the embankment from the weight density of fill (see 3.3.3), care should be taken to include fill particles of size > 20 mm to 60 mm in the density tests. They are often not included but can have a considerable effect on the weight density.
(9)P Embankment slope surfaces exposed to erosion shall be protected. If berms are designed, a drainage facility shall be specified for the berm.
(10) The slopes should be sealed during embankment construction and planted thereafter, where appropriate.
(11) For embankments carrying traffic, icing on the surface of the pavement should be avoided. The thermal capacity of a pavement on an insulation layer or a lightweight fill may be high enough to avoid this.
(12) Frost penetration on the crest of an earth dam should be restricted to an appropriate level.
(13) Design of the embankment slope should consider that creep movements may occur in slopes during freezing and thawing irrespective of the slope stability under dry conditions. This is especially important in transition zones, e.g. at bridge abutments.