冲击荷载与静荷载作用下的单桩承载特性

对灌注桩试桩分别进行了高应变冲击试桩试验和单桩轴向抗压静载试验,并对动静载试验的结果进行了对比分析。结果表明:试桩静载试验荷载-沉降曲线呈缓变型,桩侧摩阻力先于桩端阻力发挥,且桩端阻力随桩端位移的增加表现出硬化特性; 桩侧各土层达到极限摩阻力所需的桩土相对位移差异较大,且摩阻力随相对位移的增大分别呈理想弹塑性、双曲线型和软化模型变化; 桩端持力层强度越高,冲击试验实测桩底速度信号负向反射越显著; 桩端持力层强度越低,实测桩底速度信号正向反射越显著; 高应变拟合分析的承载力普遍低于静载试验,而拟合分析的桩顶位移远小于静载试验单桩极限承载力对应的桩顶位移; 极限端阻力随桩岩阻抗比的增大而增大,且桩端持力层存在有效阻抗面积; 所得结论对于提高拟合分析土参数及单桩极限承载力的计算精度和可靠性具有重要意义。

Bearing Behaviors of Single Pile Under Impact and Static Loads

The high strain impact pile test and single pile axial compression static load test were carried out for cast-in-place piles, and the results of dynamic and static tests were compared and analyzed. The results show that the load-settlement curve of the static load test varies gradually, and the side resistance of pile develops earlier than tip resistance. The tip resistance shows hardening characteristics with the increase of tip displacement. The relative displacement between pile and soil required for reaching the ultimate frictional resistance is very large. With the increase of relative displacement, the frictional resistance changes as ideal elastoplastic, hyperbolic and softening model respectively. The higher the strength of pile end bearing stratum is, the more significant the negative reflection of the measured velocity signal at pile bottom of the impact test is. The lower the strength of pile end bearing stratum is, the more obvious the positive reflection of the measured velocity signal at pile bottom is. The bearing capacity of high strain fitting analysis is generally lower than that of static load test. The fitting analysis displacement of pile top is much smaller than that of static load test corresponding to the ultimate bearing capacity of single pile. The ultimate tip resistance increases with the increase of pile rock impedance ratio, and the bearing stratum has an effective impedance area. The research results have great significance in improving the calculation accuracy and reliability of the fitting analysis of soil parameters and ultimate bearing capacity of single pile.