大轴力桩基托换中新旧混凝土结合面抗剪性能试验分析

桩基托换的关键在于新旧混凝土结合面的连接方法和可靠性能。本文结合某城市地铁隧道穿越高架桥桩基主动托换工程，提出了一种新型连接方式：凿毛+钻孔植筋(植筋胶)+建筑胶喷面的连接形式。设计制作了3个试件，结合面每30 cm×30 cm范围内植入一根钢筋，部分试件梁部箍筋加强，进行了重复静力加载试验。试验分析表明：此连接方式具有较高的抗剪承载力，最大可达9.208×10 3 kN/m 2；提高新浇筑梁的箍筋配筋率对提高界面抗剪承载力有较大作用；植筋在新旧结合面抗剪能力中起到了主要作用；新旧混凝土交界面上植筋所受的力较大，植筋两端受力较小；此连接形式在大轴力桩基托换中使用是安全可靠的。

Experimental study on shear bearing capacity of bond-interface between new and old concrete in underpinning engineering of high-loaded pile foundation

The core technology in pile foundation underpinning is the combination of old and new concrete surface connection method and performance. Based on the background of certain city tunnel crossing the viaduct pile foundation underpinning the engineering , this paper proposes a new mode of connection: rough surface+ planting bar drilling (adhesives ) + Spray interface adhesive. The experimental designed three specimens, the boundary surface within the scope of basic guarantee every 30 cm×30 cm into a steel bar, and part of the beam specimen strengthening, has carried on the static loading test. Conclusion: the combined surface connection way has higher shear bearing capacity of up to9.208×10 3 kN/m 2; And improving the new casting beam of stirrup reinforcement ratio has a larger effect to improve the interface shear bearing capacity; Planting bar in the old and new combination has played a major role in surface shear capacity, the border between old and new concrete surface, namely in the middle of the bar has the greater force; Planting bar located in both ends has the smaller force. Results show that the connection form construction by rough surface+ planting bar drilling (adhesives) + Spray interface adhesive is safe and reliable using in large axial force of pile foundation underpinning.