灌浆料对预制承插式桩芯与钢管桩黏结性能影响试验研究

Experimental study on influence of grouting material on bond behaviorbetween prefabricated pile core and steel pipe

高桩码头的桩芯、桩帽为桩顶连接关键结构,而传统水上现浇施工通常面临作业难、施工质量影响因素多等问题。预制承插式桩芯桩帽结构由水上现浇转变为工厂预制,通过超高性能混凝土灌浆料与钢管桩形成桩顶结构,避免了水文条件对其施工的影响。通过物模试验开展预制桩芯-桩帽结构的破坏模式及灌浆料配比研究,结果表明:竖向荷载下桩顶结构的灌浆料与预制桩芯界面黏结不动,仅灌浆料与钢管之间产生相对滑移,灌浆料与钢管内壁的界面黏结性能相对薄弱;灌浆料与钢管的黏结强度随钢纤维掺入而减小,随膨胀剂掺入而增大;塑性膨胀剂掺量0.08%、中后期国标Ⅱ型膨胀剂掺量12%组合为最优配比,其界面黏结强度在28 d内呈增长趋势,28 d后趋于稳定。

The pile core and cap of high pile wharf are the key structures of pile top connection,and the traditional cast-in-place construction on water usually faces operational difficulties and construction quality problems.The prefabricated pile core and cap structure is changed from cast-in-place to prefabricated in factory,and the pile top structure is formed by grouting material and steel pipe piles,which avoids the influence of hydrological conditions on its construction.In this paper,the failure mode and grouting material ratio of precast pile core and cap structure are studied by physical experimental.The results show that the interface between grouting material and precast pile core of pile top structure is immobile under vertical load,only the relative displacement between grouting material and steel pipe is generated,and the interface bond behavior between grouting material and inner wall of steel pipe is relatively weak.The bond strength between UHPC grouting material and steel pipe decreases with the incorporation of steel fiber and increases with the incorporation of expansion agent.The combination of 0.08%plastic expansion agent and 12%national standard II expansion agent is the optimal ratio.The interfacial bond strength shows an increasing trend within 28 days and tends to be stable after 28 days.