The failure of concrete retaining block (CRB) walls

Agostini, Loren (2016-12)

Thesis (MEng)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Concrete retaining block (CRB) walls have been identified by ECSA (the Engineering Council of South Africa) as a class of structures prone to failure. In South Africa, four major CRB wall failures occurred in Gauteng in one month alone. By identifying trends in the failures, engineers obtain a better understanding of how a CRB wall system works and how these retaining walls fail. This insight will assist engineers in designing more reliable retaining walls that will satisfy all the foreseen structural, environmental and construction demands. This study focuses on failed gravity and reinforced soil CRB walls in provinces throughout South Africa, including the Eastern Cape, Kwa-Zulu Natal and Gauteng. Through an extensive review of 18 case histories of failed CRB walls, common trends and aspects that typically cause problems with the walls are identified. The case histories were obtained from ECSA and private consulting engineering companies. The outcomes of the case histories focus on a description of the failure, identification of the problem and any designrelated issues. To further review the case histories effectively, the walls are classified and described according to specific criteria, and the basic failure mechanism(s) are identified. The information collected from this study is compared to the outcomes of previous studies. Furthermore, the outcomes of this study are described in such a manner as to be added to the database of the previous studies. The previous studies form part of the GSI (Geosynthetic Institute) database and focus on failed reinforced soil CRB walls on a global scale. Variations in the different studies are highlighted as the methods of classification, specifically regarding the backfill and the basic failure mechanism(s), are unique to each of the studies. An overall look into the previous and present studies allows the author to make recommendations to improve the current shortcomings in the design and construction of CRB walls, as well as the manufacturing of CRB wall components. The major design and construction-related issues identified in both studies are very similar, with a few variations. The current study recognises 11 major design and construction-related issues pertaining to gravity and reinforced soil CRB walls. These issues specifically focus on the components of the system including the type and placement/compaction of the backfill, an adequate drainage system and the placement thereof, construction drawings and specifications, performance monitoring, disruption of the system and the design itself.

AFRIKAANSE OPSOMMING: Betonblok keermure (CRB mure) is deur ECSA (die Ingenieurswese Raad van Suid-Afrika) geïdentifiseer as ʼn tipe struktuur wat geneig is om te faal. In een enkele maand was daar vier gevalle in Gauteng, Suid Afrika waar blok keermure gefaal het. Deur ooreenkomste in falings te identifiseer, kan ingenieurs ʼn beter begrip kry van hoe hierdie keermure werk en hoe hulle geneig is om te faal. Met hierdie insig kan ingenieurs meer bertroubare blok keermure ontwerp wat al die voorspelde strukturele, konstruksie en omgewingseise bevredig. Hierdie studie fokus op swaartekrag en versterkte grond blok keermure wat gefaal het in verskillende provinsies in Suid Afrika, insluitende die Oos-Kaap, Kwa-Zulu Natal en Gauteng. Tipiese tendense en aspekte wat probleme veroorsaak in die ontwerp en konstruksie van blok keermure kan geïdentifiseer word deur ʼn uitgebreide analise van 18 gevallestudies van falings van blok keermure. Die 18 gevallestudies was by ECSA en private konsultasie ingenieursfirmas verkry. Die uitkomstes van elkeen van die gevallestudies fokus op ʼn beskrywing van die faling, identifisering van die probleem en enige ontwerp verbonde probleme. Die gevallestudies is geklassifiseer en beskryf volgens spesifieke kriteria en die basiese falings meganismes is geïdentifiseer vir verder ondersoek. Die uitkomstes van hierdie studie kan nou vergelyk word met die uitkomstes van vorige studies. Die uitkomstes van hierdie studie is op ʼn soortgelyke manier beskryf as vorige studies sodat dit by die databasis van die vorige studies bygevoeg kan word. Vorige studies is deel van die GSI (Geosynthetic Instituut) databasis en fokus op versterkte grond mure wat wêreldwyd gefaal het. Daar is variasies tussen die twee studies omdat daar ʼn verskil is in die metodes wat gebruik word om die mure te klassifiseer. Die klassifikasie van die grond en basiese falings meganismes is uniek vir elke studie. Deur middel van ʼn algehele ondersoek van vorige en huidige studies kan voorstelle gemaak word om die konstruksie- en ontwerp-verbonde tekortkominge, asook kwessies met die vervaardiging van die komponente van blok keermure te verbeter. Tydens die studie en in vergelyking met vorige studies is daar ʼn beduidende tendens in konstruksie- en ontwerp-verbonde probleme opgemerk. Hierdie studie erken 11 beduidende konstruksie- en ontwerp-verbonde probleme met betrekking tot swaartekrag en versterkte grond blok keermure. Die bogenoemde konstruksie- en ontwerp-verbonde probleme fokus op komponente van die sisteem, kompaksie en plasing van die grond, ʼn voldoende dreinering stelsel, die uitleg van die dreinering stelsel, konstruksietekeninge en spesifikasies, prestasiekontrole van die konstruksie van die blok keermuur, ontwrigting van die blok keermuur sisteem asook die ontwerp van die blok keermuur.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100087
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