二重钢管混凝土桩头的性能研究

Study on bearing capacity of doubled steel tubular pile

介绍了包括单钢管桩,带肋单钢管桩及二重管钢管桩在内的共12个试件的轴心静压试验.讨论了加强肋、桩尖形状、外管突出长度参数对极限承载力和变形性能等力学性能的影响.结果表明,现行的单钢管桩属于界面的粘结破坏,承载力低,变形能力弱,不能充分发挥材料特性.用加强肋可以明显改善承载力,但对变形性能的影响较弱.二重管钢管桩大幅提高了极限承载力和变形性能.将外管的末端切成45°的楔形可以增大承载力,提高闭塞效应系数.承载力和闭塞效应系数随外管突出长度的增加而增大,实际工程中可取D长度.

A new kind of doubled steel tubular pile for inner excavation method was proposed. It consists of inner tube, outer tube, and concrete bulb. Three series of compressive experiment were carried out with 12 pieces of specimens. The parameters include： reinforcing rib, tip shape, and extension length of outer tube （OTE length）. Single pipe pile shows sliding failure at interface and cannot utilize the strength of material ; the bearing capacity and deformation ability are low. The reinforcing rib can enhance the bearing capacity, but have little influence on the deformation ability. As a result, doubled steel tubular pile has high bearing capacity and good construction, and has advantages over bored steel tube piles. The wedge-shaped end of outer steel tube shows more excellent bearing capacity and plugging effect than that of specimen with flat shape end. The bearing capacity and plugging effect increase with the longer of OTE length. At the point of OTE length D, the plugging effect factor is about 3 and it meets the demand of design.