CSA S6.1-2019 pdf free download

CSA S6.1-2019 pdf free download.Commentary on CSA S6 : 19 , Canadian Highway Bridge Design Code.
C6.12.1 General
Ground pressure should be calculated using characteristic values of geotechnical parameters (Bowles, 1988; Barker et aL, 1991; CFEM, 2006; NAVFAC DM-7.01, 1986; Clayton and Militsky, 1986). The uncertainty (Fenton et al., 2005b) associated with the density of the backfill, earth pressure theories, and the position of the centroid of the earth pressure is accounted for through the use of load factors based on pressures and loads calculated using unfactored geotechnical parameters. The procedures used in the 1988 edition of the Code, where soil strength parameters and load factors are applied together, do not apply to the 2019 edition of the Code.
In the calculation of earth pressure forces, distinctions must be made between overall stability, bearing resistance, overturning and sliding resistance, and the forces acting in the design of the individual components of the retaining structure. Different pressures are specified for design, depending on the deformation of the structure. There are also forces within the earth resulting from compaction pressures, and dead load and live load effects. In the computation of earth pressure, the nature and drainage properties of the backfill material should be carefully determined. Frost pressures, swelling pressures, or hydrostatic pressure can develop in the backfill material. These pressures act on the retaining structure and cannot be reliably determined; because of this, the use of free-draining granular backfill is preferred.
The following comments are relevant to Clause 6.12.1:
• When computing earth pressures, moist density of the backfill should be assumed above the groundwater table, and submerged or saturated density below the water table.
• For free-draining granular soil or backfill, the same strength parameters can be assumed for short- term and long-term conditions. For fine-grained cohesive soil or backfill, earth pressures tend to increase with time due to softening or swelling and for this reason cohesive backfill Is normally avoided. If cohesive soil is used as fill, the design should employ conservative effective stress strength parameters assuming C’ equal to zero and using an equivalent angle of internal friction ‘. Pore pressure effects in the soil must also be considered as should expansion due to frost.
• The magnitude of earth pressure of retained earth during placement depends on the displacement characteristics of the structure relative to the supporting soil or rock. Accordingly, earth pressure due to fill can range from an active pressure to a pa5sive pressure. Active earth pressure is the minimum value of lateral earth pressure that a soil mass can exert against an unrestrained structure. Passive pressure is the maximum value of lateral earth pressure and occurs when the structure moves into or against the soil mass.
If the movement of the structure during placement of the backfill is minimal, the pressures developed correspond to an at-rest earth pressure condition, and will include residual stresses due to compaction effects (Clayton and Militsky, 1986; Ingold, 1979). The active, at-rest, and passive pressure conditions are used as a design convenience to describe backfill pressures.CSA S6.1-2019 pdf free download.