开口和闭口对静压PHC管桩贯入特性影响试验研究

为了更加精确监测开口与闭口高强预应力混凝土（PHC）管桩的沉桩过程，研究压桩力、桩身轴力、桩端阻力以及桩侧摩阻力随贯入深度的变化规律。在桩身布置低温敏光纤光栅（FBG）传感器，并在桩端安装土压力传感器，对2根闭口（P1桩，P2桩）和1根开口（P3桩）足尺PHC管桩进行现场贯入试验。试验结果表明：随着桩身贯入深度的增大，压桩力基本呈增大趋势，且P3的压桩力小于P1，P2，约为P1，P2的33.9%~79.7%；桩身轴力随贯入深度增大而逐渐减小，P3的桩身轴力小于P1，P2，压桩结束后约为P1，P2的59.16%~67.75%；桩端阻力与土层分布及土层的特性密切相关，土层越硬桩端阻力越大，且土层的变化对P1，P2的影响较大；随着贯入深度的增大，桩侧摩阻力的退化现象较明显。试验结果对道路工程中PHC管桩的应用具有重要意义。

Experimental Study on the Influence of Opening and Closing on the Penetration Characteristics of Static Pressure PHC Pipe Pile

To monitor the pile-sinking process of high-strength prestressed concrete (PHC) pipe piles more accurately and study the variation laws of pile-pushing force, pile axial force, pile end resistance, and pile side friction resistance with penetration depth, in this study, a low-temperature sensitive fiber Bragg grating (FBG) sensor was arranged on the pile body and a soil pressure sensor was installed at the pile end. The penetration characteristics of two closed (P1, P2) and one open (P3) full-length PHC pipe piles were tested in the field. The test results showed that the pile driving force increased with increase of penetration depth of the pile body, and the pile-pushing force of P3 was less than the pile-pushing force of P1 or P2, about 33.9%-79.7% of P1 or P2. The axial force of the pile body decreased gradually with increase of penetration depth. The axial force of the pile body of P3 was less than the axial force of the pile body of P1 or P2, and the end of the pile had a value of about 59.16%-67.75% of P1 or P2. The pile end resistance was closely related to the soil layer distribution and the characteristics of the soil layer. When the pile end resistance was harder, the soil layer changes had a greater impact on P1 and P2. As the penetration depth increased, the degradation of the lateral frictional resistance of the pile was more obvious. The test results have great significance for the application of PHC pipe piles in road engineering.