Laserfiche WebLink
1 1932.003 <br />Late ra I E a rth Pressures <br />The following parameters are recommended to be used for the design of retaining <br />structures less than 6 feet in height based on the assumed type of low expansive, <br />granular backfill material as described above. <br />Table 1 - Retaining Wall Design Parameters <br />Condition Equivalent Fluid Unit Weight (psf/ft) <br />Active Earth Pressure <br />At-Rest Earth Pressure <br />Allowable Passive <br />Earth Pressure <br />Coefficient of Sliding Friction <br />Unrestrained walls that are free to rotate or deflect may be designed using the active <br />earth pressure. The at-rest condition should be used for restrained walls that are fixed <br />against rotation. The atrest pressure should also be used for design of walls <br />supporting settlement-sensitive structures, such as adjacent roadways and structures. <br />Resistance to lateral loads will be provided by the friction acting along the bottom of the <br />footing and the passive pressure along the front of the foundation and footing key (if <br />included in design). The lateral passive resistance should be used in design only if the <br />footings are cast in direct contact with vertical side walls within structural compacted fill <br />and the support characteristics of the soils in front of the footing will not degrade with <br />time. Protection of the soils typically consists of covering the ground surface with an <br />impervious surface. <br />The above-recommended lateral pressures were based on a soil total (compacted) unit <br />weight of 125 pounds per cubic foot (pcf) and an angle of internal friction of 32 degrees. <br />Revision to the parameters may be necessary if the soils used in construction exhibit <br />different properties. <br />Backfill for retaining walls should be compacted to a minimum of 90 percent relative <br />compaction based on ASTM Test Method Dl557. Relatively light construction <br />equipment should be used to backfill the retaining walls and the walls are recommended <br />to be externally supported during backfilling and compaction operations. <br />3 € <br />Leighton <br />38 (Level Backfill) <br />64 (2H:1V Backfill) <br />55 (Level Backfill) <br />92 (2H:1V Backfill) <br />250 with a maximum of 2,500 psf <br />(Level grade in front of wall) <br />0.30