1887

oa Civil Engineer in South Africa - Canal construction in expansive slickensided soils

 

Abstract

The Zuikerbosch canal was required to be a high security canal designed to operate continually without down-time for maintenance. It was therefore necessary to take steps to ensure that the highly expansive slickensided clays encountered along the canal route would not produce differential soil movements sufficient to damage the thin concrete lining of the canal.


The potential heave of the expansive clays was dealt with by prewetting along the entire length of the canal.
Slope stability analyses showed that the expansive slickensided clays would have to be over-excavated beyond the lines of the canal concrete lining and replaced with an adequately thick blanket of compacted clayey sand backfill excavated from carefully selected borrow pits. The expansive soils were identified and classified as being of either high or low expansiveness by means of the commonly used parameters clay fraction, liquid limit and plasticity index. The classification was used in conjunction with visual observations of the extent of slickensiding in the soil horizons.
The canal was commissioned in May 1983 and is operating satisfactorily.

Die Zuikerboschkanaal was bedoel om 'n hoogs veilige kanaal te wees, en is ontwerp om deurentyd in gebruik te wees sonder onderbrekings vir instandhoudingswerk. Dit was dus nodig om te verseker dat die hoogs swelbare wryfspieëlklei langs die kanaalvoete nie veranderlike grondverskuiwings veroorsaak wat die dun betonvoering van die kanaal kan beskadig nie.


Om potensiële uitswelling van die swelbare klei teen te gaan, is die hele afstand van die kanaal vooraf benat.
Ontledings van die stabiliteit van die skuinstes het aan die lig gebring dat die sweibare wryfspieëlklei weer uitgegraaf sou moes word tot anderkant die lyn van die kanaal se betonvoering. En dat dit vervang moes word met 'n dik genoeg en omvattende laag verdigte kleiagtige sand uit versigtig uitgesoekte steelgroewe. Die swelbare grond is deur middel van die gangbare parameters kleibreuke, vloeistofperke en plastisiteitsgetal geïdentifiseer en ingedeel in kategorieë van hoë of lae swelbaarheid. Die indeling het gepaard gegaan met visuële waarnemings van die omvang van die wryfspieël in die grondhorison.
Die kanaal is in Mei 1983 in gebruik geneem en die bediening daarvan is bevredig.

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/content/civeng1/26/10/EJC24936
1984-10-01
2016-12-04
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