The Influence of pile batter angle, soil unit weight and soil moisture content on the ultimate axial tensile load capacity of micropiles

Du Toit, Francois (2020-03)

Thesis (MEng)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Battered piles are commonly adopted to resist overturning moments acting on the foundations of high-rise buildings and tower structures. Urbanization at an exponential rate is leading to an increase in the construction of high-rise buildings coupled with confined operating spaces and challenges regarding site accessibility. Micropiles are 300 mm or less in diameter, have various applications, require compact installation rigs and ancillary equipment and are thereby ideal for foundation engineering solutions in confined spaces. Battered micropiles are often utilized to act under tension, however several theories exist regarding the effect of batter angle on ultimate axial tensile load capacity, while literature addressing the effect of soil unit weight and moisture content is seldom. The aim of this study was to gain insight into the effects of batter angle, soil unit weight and soil moisture content on the ultimate axial tensile load capacity of a micropile. The aim was achieved through in situ tests, laboratory tests and scale model simulations. A variation in ultimate axial tensile load capacity of 28.87% was observed over a 30° change in batter angle during in situ testing conducted on micropiles. Soil-soil and soil-grout direct shear test results suggested that soil unit weight does not have a significant impact on the development of the soil-grout interface of a pile shaft and scale model simulation results revealed that soil unit weight affects the magnitude of variation in ultimate axial tensile load capacity associated with a change in batter angle, while soil moisture content greatly influences ultimate axial tensile load capacity through soil suction.

AFRIKAANSE OPSOMMING: Heipale word gereeld op nie-vertikale hoeke installeer om draai momente op die fondasies van ho¨e geboue en toringstrukture teen te werk. Verstedeliking teen ’n eksponensi¨ele tempo lei tot ’n toename in die konstruksie van ho¨e geboue, gekoppel met beperkte werkspasie en moeilikhede aangaande terein toegang. Mikroheipale is 300 mm of minder in deursnit, het verskeie toepassings, benodig kompakte installasie masjienerie en aanvullende toerusting en is daarom gepas vir fondasie ingenieurswese oplossings in areas met beperkte spasie. Nie-vertikale mikroheipale word gereeld in spanning geplaas, maar verskeie teori¨e bestaan egter aangaande die invloed van heipaalhoek op laaikapasiteit, terwyl literatuur aangaande die invloed van grondeenheidsgewig en grondvoginhoud seldsaam is. Die doel van hierdie studie was om insig te verkry oor die effek van heipaalhoek, grondeenheidsgewig en grondvoginhoud op die laaikapasiteit van ’n mikroheipaal. Die doel was bereik deur in situ toetse, laboratorium toetse en skaalmodel simulasies. ’n Variasie in laaikapasiteit van 28.87% was opgemerk oor ’n 30° verskil in heipaalhoek tydens in situ toetse uitgevoer op mikroheipale. Grond-grond en grond-sement direkte skuiftoetse stel voor dat grondeenheidsgewig nie ’n beduidende invloed het op die ontwikkeling van die grond-sement kontak op ’n heipaal skag nie en skaalmodel simulasies het getoon dat grondeenheidsgewig die grootte van die variasie in laaikapasiteit be¨ınvloed wat gepaard gaan met ’n verandering in heipaalhoek, terwyl grondvoginhoud grootliks laaikapasiteit beinvloed deur grondsuiging.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107756
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