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Laboratory investigation of shaft resistance for piles socketed in basalt
ARTICLE IN PRESS
International Journal of Rock Mechanics & Mining Sciences 41 (2004) 465
SINOROCK2004 Paper 2B 16
Laboratory investigation of shaft resistance for piles socketed in basalt Xue Fan Gua,*, C.M. Haberfieldb b
a Department of Civil Engineering, Monash University, Clayton, Vic. 3168, Australia Golder Associates Pty Ltd. & Monash University, Lever 3, 50 Burwood Road, Hawthorn, Vic 3122, Australia
Abstract Understanding the shear behaviour of rock–concrete joints is important for the design and analysis of concrete structures interacting with rock, for example rock socketed piles, rock anchors and dam foundations. A significant research effort has been made to improve our understanding of the behaviour and to provide more rational methods of analysis and design. As part of this effort, researchers at Monash University have for many years been conducting fundamental research into the behaviour of the pile– rock interface, in particular on mudstone–concrete interfaces. The program has concentrated on the use of large-scale (dimensions of 600 mm 200 mm in plan) direct shear tests to simulate the concrete–rock interface, and to model the observed behaviour using theoretically based models. A computer program, Rocket(CNS), has also been developed and can be used for modelling both laboratory and field-tests results. In order to extend this research from soft rock to hard rock, a new experimental program involving basalt–concrete joints was initiated. Fifteen direct shear tests have been carried out on basalt–concrete interfaces with planer, regular triangular asperity and fractal profiles under constant normal stiffness conditions (ranging from 100 to 10 000 kPa/mm), Fig. 1. In general, the peak shear resistance of basalt–concrete interfaces was found to increase as the interface roughness (asperity angle) increased. The tests also indicated that the value of constant normal stiffness played a significant role in the development of peak shear resistance. Shear failure through asperities was only observed to occur in tests on samples comprising relatively rough interfaces and tested under high constant normal stiffness. Such failure occurred mainly within the concrete asperities. For interfaces of lower roughness and tests with lower normal stiffness, sliding and over-topping of asperities occurred. By comparison with the regular triangular asperity profiles, the response of the fractal profiles was more ductile and displayed lower peak shear resistance. The predictions of both regular profiles and fractal profiles obtained using Rocket(CNS) program give reasonable agreement with measured results.
Keywords: Shear test; Basalt; Joints; Shaft resistance; Pile; Concrete
Shear stress (kPa)
5000
4000 Testing (σ/K = 300/100) Testing (σ/K = 300/1000) Testing (σ/K = 300/10000) Predicting(σ/K = 300/100) Predicting (σ/K = 300/1000) Predicting (σ/K = 300/10000)
3000
2000
1000
0
0
5
10
15
20
Shear displacement (mm)
Fig. 1. Comparison of test results to Rocket (CNS) prediction.
*Corresponding author. Tel.: +61-3-9905-5549; fax: +61-3-9905-4944. E-mail address: [email protected] (X. Fan Gu). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.137
International Journal of Rock Mechanics & Mining Sciences 41 (2004) 465
SINOROCK2004 Paper 2B 16
Laboratory investigation of shaft resistance for piles socketed in basalt Xue Fan Gua,*, C.M. Haberfieldb b
a Department of Civil Engineering, Monash University, Clayton, Vic. 3168, Australia Golder Associates Pty Ltd. & Monash University, Lever 3, 50 Burwood Road, Hawthorn, Vic 3122, Australia
Abstract Understanding the shear behaviour of rock–concrete joints is important for the design and analysis of concrete structures interacting with rock, for example rock socketed piles, rock anchors and dam foundations. A significant research effort has been made to improve our understanding of the behaviour and to provide more rational methods of analysis and design. As part of this effort, researchers at Monash University have for many years been conducting fundamental research into the behaviour of the pile– rock interface, in particular on mudstone–concrete interfaces. The program has concentrated on the use of large-scale (dimensions of 600 mm 200 mm in plan) direct shear tests to simulate the concrete–rock interface, and to model the observed behaviour using theoretically based models. A computer program, Rocket(CNS), has also been developed and can be used for modelling both laboratory and field-tests results. In order to extend this research from soft rock to hard rock, a new experimental program involving basalt–concrete joints was initiated. Fifteen direct shear tests have been carried out on basalt–concrete interfaces with planer, regular triangular asperity and fractal profiles under constant normal stiffness conditions (ranging from 100 to 10 000 kPa/mm), Fig. 1. In general, the peak shear resistance of basalt–concrete interfaces was found to increase as the interface roughness (asperity angle) increased. The tests also indicated that the value of constant normal stiffness played a significant role in the development of peak shear resistance. Shear failure through asperities was only observed to occur in tests on samples comprising relatively rough interfaces and tested under high constant normal stiffness. Such failure occurred mainly within the concrete asperities. For interfaces of lower roughness and tests with lower normal stiffness, sliding and over-topping of asperities occurred. By comparison with the regular triangular asperity profiles, the response of the fractal profiles was more ductile and displayed lower peak shear resistance. The predictions of both regular profiles and fractal profiles obtained using Rocket(CNS) program give reasonable agreement with measured results.
Keywords: Shear test; Basalt; Joints; Shaft resistance; Pile; Concrete
Shear stress (kPa)
5000
4000 Testing (σ/K = 300/100) Testing (σ/K = 300/1000) Testing (σ/K = 300/10000) Predicting(σ/K = 300/100) Predicting (σ/K = 300/1000) Predicting (σ/K = 300/10000)
3000
2000
1000
0
0
5
10
15
20
Shear displacement (mm)
Fig. 1. Comparison of test results to Rocket (CNS) prediction.
*Corresponding author. Tel.: +61-3-9905-5549; fax: +61-3-9905-4944. E-mail address: [email protected] (X. Fan Gu). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.137