关键词: 随钻跟管桩, 现场原位试验, 物理模拟试验, 承载性能, 桩侧摩阻力分布, 荷载传递特性

Abstract: The drilling with pre-stressed concrete pipe cased pile (referred to as DPC pile) is a new type of large-diameter (800?1 400 mm) non soil-squeezing PHC pipe pile with drilling hole, sinking pile and discharging soil occurring simultaneously. DPC pile is energy-saving and environmental-friendly. In this paper, in-situ tests, theoretical calculation analysis and physical simulation tests are carried out to compare and analyze the better vertical load-bearing capacity of this new type of pile, the skin friction distribution characteristics and the load transfer characteristics. Based on the aforementioned tests, the following conclusions are obtained. 1) In the in-situ tests, DPC pile is a type of end bearing friction pile, whose vertical bearing capacity is mainly dominated by skin friction with a proportion variation ranging from 67.84% to 72.85%. The bearing capacity of DPC pile is closely related to the grouting effect and it has been increased by 33.42% and 23.16% compared to the large diameter drill hole pile and hammered pipe pile, respectively. When the sediment thickness at the bottom of the DPC pile is small, the load-displacement curve belongs to slow deformation type (pile No. 1), otherwise it belongs to a steep drop type (pile No. 2). 2) Indoor physical model tests in sand show that the load-displacement curves of DPC pile, large diameter drill hole pile and hammered pipe pile belong to the steep drop curves under the condition that all the three types of pile mentioned above are not rock-socketed. The load-bearing capacity of DPC pile has been improved by 18.60% compared with large diameter drill hole pile. 3) The skin friction of piles with different manufacturing processes are quite different, i.e. the skin friction of DPC pile is the largest, followed by the large diameter drill hole pile, and finally the hammered pipe pile, which is related to the physical test of the simulating mud on the side of large diameter drill hole pile. The distribution rule of the skin friction of all pile types along the depth of the pile body shows a rule “a large portion in the middle and a small portion at both ends”. As the load increases, the position of the maximum skin friction gradually moves downward from the top of the pile to its deepest position until the pile foundation is damaged. 4) Under the ultimate bearing capacity, the skin friction of DPC pile is 6 061.65 N, which accounts for 74.40% of its ultimate bearing capacity (8 147.62 N). It can be implied that the DPC pile is a type of end bearing friction pile and is mainly dominated by skin friction.

Key words: the drilling with pre-stressed concrete pile cased pile (DPC pile), in-situ tests, physical simulation tests, load-bearing properties, skin friction distribution, load transfer characteristics