Abstract
Y-shaped piles are a new type of pile whose cross-section is like the letter Y: they are often used in ground improvement for road or train subgrades in the eastern coastal region of China. To investigate the bearing behaviour of Y-shaped piles in saturated sand, a series of model tests under compressive and horizontal load for Y-shaped piles, C 1 circular pile (the same cross-sectional area of Y-shaped pile), and C 2 circular pile (the same perimeter of Y-shaped pile) were carried out. Comparative analysis was conducted on bearing capacity, axial force and side resistance distribution, load sharing ratio, bending moment, and lateral soil pressure distribution along the embedded length. The results show that the bearing capacity of a Y-shaped pile does not increase in proportion, and the shaft resistance is weakened to some extent in saturated sand; Y-shaped pile can effectively improve the compressive bearing capacity for the same amount of concrete. The lateral bearing capacity of a Y-shaped pile has directionality, and hanging a circular section into a Y-shaped section may improve the horizontal bearing capacity for the same amount concrete, but cannot give full play to the advantage of the larger side area for horizontal bearing capacity in saturated sand.
Highlights
Special-shaped piles often used in engineering are the: H-pile, tapered pile, Closed-Open Ended Pipe piles, belled pile, XCC pile, and Y-shaped pile
A series of model tests under compressive and horizontal load in saturated sand was carried out on a Y-shaped pile, a C1 circular pile, and a C2 circular pile; sand was pluviated into a tank containing the model piles; this was filled with water until complete soil saturation was achieved
Comparative analysis of data from load tests on Y-shaped piles and circular piles was undertaken, and the following conclusions were drawn: (1) The compressive bearing capacity of a Y-shaped pile is 1.29 times that of an equivalent C1 pile, but its perimeter is 1.56 times that of the C1 pile, so the bearing capacity of Y-shaped pile in saturated sand does not increase in proportion thereto and its shaft resistance is weakened to some extent
Summary
Special-shaped piles often used in engineering are the: H-pile, tapered pile, Closed-Open Ended Pipe piles, belled pile, XCC pile, and Y-shaped pile. The Y-shaped cast in situ pile with three concave arches was developed [15] and has a larger perimeter than a circular pile with the same cross-sectional area, so its bearing capacity can be improved significantly This technique has been applied in the soft ground improvement of some highways in Shanghai, Zhejiang, Anhui, and Jiangsu Provinces, China. Two types of piled embankment and substratum beneath the SJZA Highway were introduced: tube piles and Y-shaped piles were installed and field test results show that Y-shaped piles used in the embankment are more effective and economical [20] To facilitate their practical design, eight model tests were conducted in dry sand on Y-shaped piles and circular cross-sectional piles [21]. Comparative analysis was conducted of the bearing capacity, axial force and side resistance distribution, load sharing ratio, bending moment, and lateral soil pressure distribution along the pile length, and the results provide some suggestions for engineering practice with regard to Y-shaped piles
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