Gross and Net Soil Pressures
In RISAFoundation, the Allowable Soil Bearing value is controlled by the Soil Region. This value is always taken as a Gross allowable soil...
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RISAFoundation can apply soil overburden to a mat slab to account for the weight of the soil above the foundation. Simply enter a Soil Overburden pressure value for your foundation design in the Slabs spreadsheet. The soil overburden load is utilized to help the mat slab resist overturning during the analysis.
The soil overburden pressure is multiplied by the area of the slab and is scaled to reduce the magnitude by the areas of and pedestals and stem walls.
In the example above, a soil overburden load of 0.5ksf is applied to a 15’x15’ slab with four rectangular 1.5’x1.5’ pedestals. The total load due to soil overburden is calculated as follows:
The soil overburden is included in the dead load applied and the effect of the overburden is reflected in the total Point Reaction result spreadsheet by an increase in total load.
Below is the total reaction without Soil Overburden due to slab self-weight only.
The total reaction including Soil Overburden and self-weight shows a difference of 108 kips we calculated from the total overburden load.
The effect of the soil overburden can also be quickly verified in the total slab soil pressure results.
Varying Soil Properties in RISAFoundation
Admin : Jul 14, 2011 12:00:00 AM
While RISAFoundation has a Default soil properties (Subgrade Modulus and Allowable Bearing), it is possible to create regions of varying soil...
Passive Resistance for Mat Slabs
RISAFoundation includes the added ability to enter a passive pressure for slabs. The passive pressure represents soil pressure along the perimeter...