Foundations for buildings and structures founded on black Cotton Soils shall be designed in accordance with Section 1.2 or 1.3.
1.1 Exception: Foundation design need not comply with Section 1.2 or 1.3 where one of the following conditions is satisfied:
a) Removal of Black Cotton Soils: Where black Cotton Soil is removed- the soil shall be removed to a depth sufficient to ensure a constant moisture content in the remaining soil. Fill material shall not contain black Cotton Soils.
Exception:
Black Cotton Soils need not be removed to the depth of constant moisture, provided the confining pressure in the black Cotton Soils created by the fill and supported structure exceeds the swell pressure.
b) Stabilization approved building official:
Where the active zone of black Cotton Soils is stabilized-the soil shall be stabilized by chemical, dewatering, presaturation or equivalent techniques.
1.2 Foundations:
Foundations placed on or within the active zone of black Cotton Soils shall be designed to resist differential volume changes and to prevent structural damage to the supported structure. Deflection and racking of the supported structure shall be limited to that which will not interfere with the usability and serviceability of the structure. Foundations placed below where volume change occurs or below black Cotton Soils shall comply with the following provisions:
1. Foundations extending into or penetrating black Cotton Soils shall be designed to prevent uplift of the supported structure.
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Foundation Failure:Supported on Black Cotton Soil in United States
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b) Stabilization approved building official:
Where the active zone of black Cotton Soils is stabilized-the soil shall be stabilized by chemical, dewatering, presaturation or equivalent techniques.
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Post Tensioned Slabs are the Best Solution for Slab-On-Ground Foundations on Black Cotton Soil
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Foundations placed on or within the active zone of black Cotton Soils shall be designed to resist differential volume changes and to prevent structural damage to the supported structure. Deflection and racking of the supported structure shall be limited to that which will not interfere with the usability and serviceability of the structure. Foundations placed below where volume change occurs or below black Cotton Soils shall comply with the following provisions:
1. Foundations extending into or penetrating black Cotton Soils shall be designed to prevent uplift of the supported structure.
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| Failure of foundation wall due to "clay bowl effect" of backfill black cotton soil |
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Distribution of black cotton soil around North America
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1.3 Slab-on-ground foundations: Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on black Cotton Soils shall be determined in accordance with WRI/CRSI Design of Slab-on-Ground Foundations or PTI Standard Requirements for Analysis of Shallow Concrete Foundations on black Cotton Soils. Using the moments, shears and deflections determined above, nonprestressed slabs-on-ground, mat or raft foundations on black Cotton Soils shall be designed in accordance with WRI/CRSI Design of Slab-on-Ground Foundations and post-tensioned slab-on-ground, mat or raft foundations on black Cotton Soils shall be designed in accordance with PTI Standard Requirements for Design of Shallow Post-Tensioned Concrete Foundations on black Cotton Soils. It shall be permitted to analyze and design such slabs by other methods that account for soil-structure interaction, the deformed shape of the soil support, the plate or stiffened plate action of the slab as well as both center lift and edge lift conditions. Such alternative methods shall be rational and the basis for all aspects and parameters of the method shall be available for peer review.
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