12.5 Ultimate limit state design

(1)P In analysing the stability of part or all of an embankment, all possible failure modes shall be considered, as stated in Section 11.

(2) Since embankments are often constructed in different phases with different load conditions, the analysis should be done phase by phase and provisions specified accordingly in the Geotechnical Design Report.

(3)P Where lightweight fill materials such as expanded polystyrene, expanded clay or foamed concrete are used, the possibility of buoyancy effects shall be considered (see Section 10).

(4)P Any analysis of embankments containing different fill materials shall adopt strength values that have been determined at compatible strains in the materials.

(5) Where roads or watercourses cross an embankment, special attention should be paid to the spatial interaction of the various structural elements.

(6) When analysing the stability of improved ground, the effect of the improving process, e.g. the disturbance of soft sensitive clay, should be considered. As the effect of the improvement is time-dependent, it should not be taken into account until a steady state has been reached.

(7)P To avoid ultimate limit states caused by surface erosion, internal erosion or hydraulic pressure, the provisions in Sections 10 and 11 shall be fulfilled.

12.6 Serviceability limit state design

(1)P The design shall show that the deformation of the embankment when subjected to characteristic actions will not cause a serviceability limit state in the embankment or in structures, roads or services sited on, in or near the embankment.

(2) The settlement of an embankment on compressible ground should be calculated using the principles of 6.6.1. Special attention should be paid to the time dependency of the settlements due to both consolidation and secondary effects.

(3) The possibility of deformations due to changes in the ground-water conditions should be taken into account.

(4) In cases where the deformations are difficult to predict, the methods of pre-loading or trial embankments should be considered, especially in cases where serviceability limit states shall be prevented.

12.7 Supervision and monitoring

(1)P Supervision and monitoring of embankments shall follow the provisions in Section 4.

(2) Monitoring should be applied to embankments in one or more of the following situations:

  • when using the observational method (see 2.7);
  • where the stability of an embankment acting as a dam to a large degree depends on the pore-water pressure distribution in and beneath the embankment;
  • where records of pollution effects of fill or traffic are required;
  • where control of adverse effects on structures or utilities is required;
  • where surface erosion is a considerable risk.

(3)P In cases where a supervision and monitoring programme is required, the designer shall present it in the Geotechnical Design Report (see 2.8). It shall be specified that the monitoring records are to be evaluated and acted upon as necessary.

(4) A monitoring programme for an embankment should contain the following records:

  • pore-water pressure measurements in and beneath the embankment;
  • settlement measurements for the whole or parts of the embankment and influenced structures;
  • measurements of horizontal displacements;
  • checks on strength parameters of fill material during construction;
  • chemical analyses before, during and after construction, if pollution control is required;
  • observations of erosion protection;
  • checks on permeability of fill material and of foundation soil during construction;
  • depth of frost penetration in the crest of an embankment.

(5) The construction of embankments on soft soil with low permeability should be monitored and controlled by means of pore-water pressure measurements in the soft layers and settlement measurements of the fill.

Eurocode 7 Geotechnical design Part 1 : General rules