| Summary: | Thesis (MScEng)--University of Stellenbosch, 2003. === ENGLISH ABSTRACT: Tunneling in busy urban areas is becoming a common practice, caused by the everincreasing
number of commuters. This causes a decline in the service level that the
surface transportation systems provide in cities. Tunneling induces movement of the
soil directly surrounding the tunnel. These movements are translated into surface
movements, which are translated into structural displacements of the surrounding
surface infrastructure. These displacements, for which the infrastructure may not have
been designed, put a question mark on the infrastructure aesthetics, serviceability, as
well as structural stability.
Burland and Wroth (1974) proposed a simple analytical damage assessment approach
(Limiting tensile strain method (LTS)) to aid in the design of tunnels with respect to
the structural integrity of the affected surface infrastructure. This study is concerned
with the accuracy of this approach applied to the damage assessment of laterally
unconfined, solid masonry walls, subject to a sagging mode of settlement deformation
with no soil to wall friction. It is also concerned with the proposal of modifications to
the approach, where deemed necessary.
Finite element models of solid masonry walls are built and analysed in order to
determine the accuracy of the simple analytical damage assessment approach with
regard to the prediction of strains in solid masonry walls subject to tunneling-induced
displacements. The predictions are found to be accurate for walls ofL/H ratio equal to
2 and larger. For walls of L/H ratio smaller than 2, the predictions are found to be
underestimates.
The simple analytical damage assessment approach is unable to account for the
stiffness of the soil directly under the foundation of the wall. The stiffness of the soil
plays a major role in the stress and strain distributions in the wall. It is therefore
deemed necessary to modify the simple analytical damage assessment approach by
accounting for the soil to wall interaction and the effect it has on the settlement
damage to solid masonry walls. The soil to wall interaction is found to reduce the
number of mitigating measures originally recommended for the walls, by the simple analytical damage assessment approach, as it accounts for the bedding of the wall into
the soil previously unaccounted for.
This study has reached the point where it is able to accurately predict whether a
laterally unconfined, solid masonry wall, subject to a sagging mode of settlement
deformation with no soil to wall friction will experience magnitudes of strain
surpassing the yielding strain of the material. This was fundamentally achieved by
developing a better representation of the strains in solid masonry walls as well as
accounting for the inherent soil to wall interaction
This study is intended to pioneer the proliferation of similar studies for various other
structures. A methodology, applicable for similar investigations envisaged for other
structures, is hereby developed. === AFRIKAANSE OPSOMMING: Tonnels in besige stedelike gebiede is besig om 'n allerdaagse verskynsel te raak
a.g.v. die skerp toename in pendelaars. Die rede hiervoor is die afname in die
kwaliteit van bogrondse vervoerdienste. Tonnels veroorsaak beweging van grond
direk in aanraking met die tonnel. Hierdie bewegings versprei na die oppervlak wat
strukturele verplasings veroorsaak. Vir n' struktuur wat nie vir hierdie verplasings
ontwerp is nie, ontstaan vrae oor die estetika, diensbaarheid asook die stabiliteit van
die struktuur.
Burland en Wroth (1974) het 'n eenvoudige analitiese skade-assesseringsmetode
voorgestel (Limiting tensile strain method (LTS)) vir die ontwerp van tonnels m.b.t.
die strukturele integriteit van die geaffekteerde oppervlak se infrastruktuur. Hierdie
studie handeloor die akkuraatheid van dié benadering, toegepas op die assessering
van skade op lateraalonbeperkte, soliede messelwerkmure, onderhewig aan die
deurbuigings mode van versakkingsdeformasie, met geen grond tot muur wrywing.
Eindige element modelle van messelwerkmure is gebou en geanaliseer om die
akkuraatheid van die eenvoudige analitiese skade-assesseringsmetode te bepaal, m.b.t.
die voorspelling van die vervormings in messelwerkmure onderhewig aan
grondverplasings veroorsaak deur tonnels. Die voorspellings is akkuraat in mure met
lengte tot hoogte (L/H) verhoudings van 2 en hoër. Vir mure met LIH verhoudings
van minder as 2, word daar gevind dat die voorspellings onkonserwatief is.
By die eenvoudige analitiese skade-assesseringsmetode word die styfheid van grond
direk onder die fondasies van die muur nie in ag geneem nie. Die grondstyfheid speel
'n kardinale rol by die spannings- en vervormingsverdelings in die muur. Dit is
daarvoor nodig om die eenvoudige analitiese skade-assesseringsmetode aan te pas om
die grond tot muur interaksie in ag te neem. Die interaksie tussen die grond en die
muur veroorsaak 'dat a minder of geen skade voorkomende maatreëls getref hoef te
word as wat oorspronklik deur die envoudige analitiese skade-assesseringsmetode
voorgestel sou word. Dit neem die inbedding van die muur in die grond in ag, wat
voorheen geïgnoreer is. Die studie het 'n punt bereik waar dit akkuraat kan voorspelof 'n lateraalonbeperkte,
soliede messelwerkmuur, onderhewig aan die deurbuiging mode van
versakkingsdeformasie en met geen grond tot muur wrywing, vervormings hoër as die
swigvervorming van die material salondervind. Dit is bereik deur 'n beter
voorstelling van die vervormings in soliede messelwerkmure asook die in agneming
van inhirente grond tot muur interaksie.
Die studie is veronderstel om die voorganger te wees vir soortgelyke studies toegepas
op verskeie ander struktuurklasse. Die sistematiese metode wat hier ontwikkel is kan
toegepas word op die ander struktuurklasse.
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