11.4 Design and construction considerations
(1)P The overall stability of a site and movements of natural or made ground shall be checked taking into account comparable experience, according to 188.8.131.52.
(2)P The overall stability and movement of ground supporting existing buildings, new structures, slopes or excavations shall be considered.
(3) In cases where the stability of the ground cannot be clearly verified prior to design, additional investigations, monitoring and analysis should be specified according to the provisions of 11.7.
(4) Typical structures for which an analysis of overall stability should be performed are:
- ground retaining structures;
- excavations, slopes or embankments;
- foundations on sloping ground, natural slopes or embankments;
- foundations near an excavation, cut or buried structures, or shore.
NOTE Stability problems or creep movements occur primarily in cohesive soils with a sloping ground surface. However, instability can also occur in non-cohesive soils and fissured rocks in slopes where the inclination, which may be determined by erosion, is close to the angle of shearing resistance. Increased movements are often observed at elevated pore-water pressures or close to the ground surface during freezing and thawing cycles.
(5)P If the stability of a site cannot readily be verified or the movements are found to be not acceptable for the site's intended use, the site shall be judged to be unsuitable without stabilising measures.
(6)P The design shall ensure that all construction activities in and on the site can be planned and executed such that the occurrence of an ultimate or serviceability limit state is sufficiently improbable.
(7)P Slope surfaces exposed to potential erosion shall be protected if required, to ensure that the safety level is retained.
(8) Slopes should be sealed, planted or protected artificially. For slopes with berms, a drainage system within the berm should be considered.
(9)P Construction processes shall be taken into account as far as they might affect the overall stability or the magnitude of movement.
(10) Potentially unstable slopes may be stabilised by:
- a concrete cover with or without anchorage;
- an abutment of gabions, either of steel net or geotextile cages;
- ground nailing;
- a drainage system;
- a combination of the above.
(11) The design should follow the general principles of Sections 8 and 9.