路堤挡墙与预应力管桩连接方法现场试验研究

采用预应力管桩（PHC）作为路基挡土墙基础，可发挥PHC桩质量保证率高、抗压性能好的优势，挡土墙承担水平荷载的要求也给PHC桩基础与基底的连接模式提出了问题。依托广东广清高速公路扩建工程进行现场试验，研究PHC桩基础分别采用有盖板的垫层式和无盖板的嵌入式承连挡土墙基底模式的作用机制。研究表明：垫层式与嵌入式连接的PHC基础桩间土均承担主要荷载，嵌入式连接外桩与桩间土应力比更大，是垫层式两倍左右，嵌入式内、外桩承载力发挥率差别更加明显；垫层式连接基础不能阻止墙体发生偏转，嵌入式连接通过桩体的约束作用控制墙体保持位置状态稳定；垫层式与嵌入式连接的挡墙受力主要表现为底板底面沿路基方向承受拉应力，在垂直路基方向底板底面未出现零压力区；两种连接模式墙体水平位移差别不大，桩间土是承担水平荷载的主体。

Field test research on method for connecting embankment retaining wall and prestressed pipe piles

The advantage of high quality assurance rate and good compression resistance of PHC pipe pile can be exploited by using them in the foundation of retaining wall of embankments. It puts forward a new research about the connection mode between PHC pile and retaining wall base. Based on in-situ tests in Guang-Qing Expressway extension project, the mechanism of the connection between the base of retaining wall and PHC pile is studied. Two connecting mechanisms, one with cover plate, called the cushion type and the other without cover plate, called embedded type, are studied. The research suggests that both cushion type and embedded connection between PHC pile foundation soil bear the main load, embedded links between pile and pile soil stress are larger, which are about twice of the cushion type, bearing capacity rate difference of inside and outside the pile for embedded type is more apparently. Deflection of the retaining wall cannot be prevented with the cushion type connecting mechanism, as opposite to the embedded type, in which the wall can be kept in a stable state by the constraint resulting from the piles. For both connecting types, the base of the retaining wall bears tension force along the embankment direction and non zero-compression zones exist in this surface. There is very little difference in horizontal displacement for two connecting types, and the horizontal load is mainly carried by the soils around the piles.