1887

oa Civil Engineer in South Africa - Origin and some engineering properties of red soils overlying dolomitic bedrock in an area south of Pretoria : technical paper

 

Abstract

Sedimentological studies and soil engineering tests on the red soils overlying dolomitic rocks in an area south of Pretorla have revealed two distinct soil types with differences in origin and engineering behaviour. A clayey silt, comprising a mixture of aeolian and hillwash materials that have undergone substantial post-depositional alteration, occurs over most of the area and attains thicknesses exceeding 30 m in karst depressions. Sporadically overlying the clayey silt is a thin layer of sandy silt of probable aeolian origin. The clayey silt is variable in composition and engineering properties, but it is generally of low density and displays medium to severe collapse potential. The sandy silt is more homogeneous and dense. Both soil types have probably played a role in the development of sinkholes in this and similar areas, but damage to structures here is mainly the result of collapse settlement of the clayey silt.

Sedimentologiese studies en grondingenieurstoetse op die rooi gronde wat 'n dolomietgebied ten suide van Pretoria bedek, kon onderskei tussen twee grondsoorte met verskille in oorsprong en ingenieursgedrag. Kleiige slik, wat uit 'n mengsel van windvervoerde materiaal en heuwelspoelsel bestaan en betekenisvolle veranderings na afsetting ondergaan het, kom oor die grootste gedeelte van die gebied voor en bereik diktes van meer as 30 m in karstdepressies. Plek-plek oorliggend op die kleiige slik is 'n dun lagie windvervoerde sanderige slik. Die kleiige slik varieer baie in samestelling en ingenieurseienskappe, maar het meesal 'n baie lae digtheid en vertoon matige tot hewige swigpotensiaal. Die sanderige slik is meer homogeen en dig van aard. Beide grondsoorte het waarskynlik 'n rol gespeel by die vorming van sinkgate in hierdie en soortgelyke gebiede, maar skade aan strukture hier is grotendeels die gevolg van swigvassakking van die kleiige slik.

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/content/civeng1/29/3/EJC25022
1987-03-01
2016-12-06
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