11 Overall stability
(1)P The provisions in this Section shall apply to the overall stability of and movements in the ground, whether natural or fill, around foundations, retaining structures, natural slopes, embankments or excavations.
11.2 Limit states
(1)P All possible limit states for the particular ground shall be considered in order to fulfil the fundamental requirements of stability, limited deformations, durability and limitations in movements of nearby structures or services.
(2) Some possible limit states are listed below:
- loss of overall stability of the ground and associated structures;
- excessive movements in the ground due to shear deformations, settlement, vibration or heave;
- damage or loss of serviceability in neighbouring structures, roads or services due to movements in the ground.
11.3 Actions and design situations
(1) The list in 2.4.2 (4) should be taken into account when selecting the actions for calculation of limit states.
(2)P The effects of the following circumstances shall be taken into account, as appropriate:
- construction processes;
- new slopes or structures on or near the particular site;
- previous or continuing ground movements from different sources;
- climatic variations, including temperature change (freezing and thawing), drought and heavy rain;
- vegetation or its removal;
- human or animal activities;
- variations in water content or pore-water pressure;
- wave action.
(3)P In ultimate limit states, design free water and ground-water levels, or their combination, shall be selected from available hydrological data and in situ observations to give the most unfavourable conditions that could occur in the design situation being considered. The possibility of failure of drains, filters or seals shall be considered.
(4) The possibility of emptying a canal or water reservoir for maintenance, or due to dam failure, should also be considered. For serviceability limit states, less severe, more typical water level or pore-water pressure may be used.
(5) For slopes along waterfronts, the most unfavourable hydraulic conditions are normally steady seepage for the highest possible ground-water level and rapid draw-down of the free water level.
(6)P In deriving design distributions of pore-water pressure, account shall be taken of the possible range of permeability anisotropy and variability of the ground.