Field static load tests on drilled shaft founded on or socketed into rock
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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ABSTRACT: On the assumptions that the shear resistance increases linearly with increasing shear displacement between the uplift pile and surrounding soil, that the axis force is distributed as parabola along the pile length, that elastic distortion occurs when the pile is loaded, that the displacement of pile is in accord with that of the soil, and that the uplift pile failure is regarded as the soil failure, a rational calculation method was proposed for calculating the deformation, ultimate displacement and shear resistance of piles. The distributions of frictional resistance and the shear displacement along the pile length were obtained with the method. The comparisons were made between the measurement results and the present results. The present theoretical results agree well with the measurement results, with the average difference being less than 12% before failure. The comparisons show that the proposed method is reasonable for uplift design and engineering construction of piles.Journal of Central South University of Technology 01/2008; 15(6):906-910. · 0.36 Impact Factor
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ABSTRACT: Finite element analysis was performed to study the settlement behaviour of axially loaded piles entirely embedded in nonhomogenous rock. The elastic modulus of the rock mass was taken to increase linearly along the pile length starting from a nonzero value at the ground surface. Cases of pile-rock stiffness ratios that have not been considered in the literature were investigated. Such ratios are typical for reinforced concrete piles bored in sedimentary rocks. Results of the numerical analysis were verified through conducting static loading tests on full-scale piles in rock of well-defined physical and mechanical properties. Charts were developed to predict the elastic settlement of piles in rock. An equation was also introduced to incorporate the effect of rock nonhomogeneity in estimating the depth at which settlement becomes insensitive to the increase of pile length. A complementary numerical analysis utilizing a simple piled foundation system showed that the pile load share is sensitive to the rate of increase in rock stiffness along the pile length. The sensitivity is more pronounced for piled foundations resting on rock with high mass stiffness. On leave from Jordan University of Science and TechnologyGeomechanics and Geoengineering 01/2011;
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ABSTRACT: The load distribution and deformation of rock-socketed drilled shafts subjected to axial loads are evaluated by a load transfer method. The emphasis is on quantifying the effect of coupled soil resistance in rock-socketed drilled shafts using 2D elasto-plastic finite element analysis. Slippage and shear-load transfer behavior at the pile–soil interface are investigated by using a user-subroutine interface model (FRIC). It is shown that the coupled soil resistance acts as pile-toe settlement as the shaft resistance is increased to its ultimate limit state. Based on the results obtained, the coupling effect is closely related to the ratio of the pile diameter to soil modulus (D/Es) and the ratio of total shaft resistance against total applied load (Rs/Q). Through comparison with field case studies, the 2D numerical analysis reasonably estimated load transfer of pile and coupling effect, and thus represents a significant improvement in the prediction of load deflections of drilled shafts.Computers and Geotechnics - COMPUT GEOTECH. 01/2009; 36(3):446-453.