Field static load tests on drilled shaft founded on or socketed into rock

The University of Hong Kong, Hong Kong, 00, Hong Kong
Canadian Geotechnical Journal (Impact Factor: 1.33). 02/2011; 37(6):1283-1294. DOI: 10.1139/cgj-37-6-1283

ABSTRACT The Mass Transit Railway Corporation proposes to construct the Tseung Kwan O Depot (TKD) within Area 86 reclamation at Tseung Kwan O as part of the Tseung Kwan O Extension. The proposed foundation for the TKD comprises about 1000 large-diameter, bored, cast in situ, drilled shafts founded on or socketed into rock. To confirm the design allowable end bearing capacity and rock socket side resistance for the drilled shaft foundations, two test piles were constructed and tested. Both test piles were instrumented with strain gauges and rod extensometers. This paper presents the static compressive load test results on both test piles. The test results indicate that an end bearing capacity of 20.8 MPa (design allowable 7.5 MPa) and rock socket side resistance 2.63 MPa (design allowable 0.75 MPa) are achieved during the pile load tests with no sign of failure.Key words: drilled shaft, static load test, end bearing capacity, rock socket, rock socket side resistance, load transfer.

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    • "Several studies have been conducted to predict the elastic behaviour of piles in homogenous rock through field testing and laboratory modelling (e.g., Carrubba 1997, Zhan and Yin 2000, Kim 2001, Mcvay and Niraula 2004, Ooi et al. 2004). Settlement of piles in homogenous rock or soil has been studied analytically assuming a linearly elastic half-space (e.g., Mattes and Poulos 1969, Poulos and Davis 1980) and utilizing simple but approximate closed-form solutions (e.g., Murff 1975, Randolph and Wroth 1978, Fleming et al. 1992, Kodikara and Johnston 1994, Motta 1994). "
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    ABSTRACT: This paper presents a shear load transfer function and an analytical method for estimating the load transfer characteristics of rock-socketed drilled shafts subjected to axial loads. A shear load transfer (f–w) function of rock-socketed drilled shafts is proposed based on the constant normal stiffness (CNS) direct shear tests. It is presented in terms of the borehole roughness and the geological strength index (GSI) so that the structural discontinuities and the surface conditions of the rock mass can be considered. An analytical method that takes into account the coupled soil resistance effects is proposed using a modified Mindlin’s point load solution. Through comparisons with load test results, the proposed methodology is in good agreement with the general trend observed in in situ measurements and represents an improvement in the prediction of the shear behavior of rock-socketed drilled shafts.
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