北京城市副中心站综合交通枢纽工程新型抗拔桩静载试验分析

ANALYSES OF STATIC LOAD TESTS FOR TENTATIVE PILES AT THE TRANSPORTATION HUB OF BEIJING SUB-CENTER STATION

为提高抗裂性能,常规抗拔桩的主筋配筋需达到一定要求,这使得该桩型造价较高。为此,研制并设计了复合预应力泥浆护壁灌注桩。基于静载抗拔试验,对新型复合预应力抗拔桩和常规钢筋笼抗拔桩的荷载-位移响应曲线进行对比分析。针对不同的灌注桩施工工艺,比如复合预应力粘结、扩底、成孔、护壁、注浆等5种形式的组合,分别比较其极限承载力。结果显示,两种新型复合预应力抗拔桩的承载能力优于常规钢筋笼抗拔桩的试验成果,其一为下部采用粘结复合预应力且扩底注浆的抗拔桩,另一种为凝结后注浆的缓凝结预应力抗拔桩。

In order to improve the crack resistance, the main reinforcement of conventional uplift piles must meet certain requirements, which makes this pile type more expensive. For this reason, one kind of composite prestressed slurry wall-protected cast-in-place piles has been developed and designed by the China Academy of Building Research Co., Ltd. Based on the static uplift test, the load-displacement response curves of the new composite prestressed uplift pile and the conventional steel cage uplift pile are compared. In view of the different construction techniques of cast-in-place piles, such as composite pre-stressed bonding, bottom expansion, hole formation, wall protection, and grouting, the five forms of combination are compared with their ultimate bearing capacity. It can be found that the bearing capacity of two new types of composite prestressed uplift pile is better than the test results of the conventional steel cage uplift pile. One is the uplift pile with bonded composite prestress and expanded bottom grouting at the lower part, and the other is the slow-setting prestressed uplift pile with grouting after setting.