水平撞击下桩土复合体系动力作用特性试验研究

Experimental Study on Dynamic Interaction Characteristics of Pier-Pile Composite System under Horizontal Impact

以重载车辆撞击公路跨线桥桥墩为研究背景,基于动力相似试验原理以及微粒混凝土等相似试验材料,构建重载车辆水平撞击作用下的缩尺试验模型。基于4种不同水平撞击试验工况,系统分析了不同撞击动量作用下桩土复合体系动力响应以及桩土接触面动力相互作用特性,并基于超声波损伤识别理论,分析研究了不同水平撞击能量作用下桩身动力损伤演化规律。结果表明:当撞击速度较低时,撞击力峰值随撞击速度的增大呈非线性增长,当撞击速度超过某一水平时,撞击力峰值增长率趋于稳定;水平撞击动量与撞击能量愈大,桩身的撞击损伤程度愈严重,桩身动力损伤指标D与水平撞击动量p和撞击动能Ek均呈二次函数关系;水平撞击荷载作用下,桩身破坏模式主要表现为被撞击一侧的拉伸破坏,桩身正反两侧桩土接触面会产生较大量值的瞬态动土压力增量,提高桩侧土体的抗压强度可有效提高桩土复合体系抗水平撞击能力。

Based on the principle of dynamic similarity test and similar test materials such as particulate concrete,a scale test model under horizontal impact of heavy vehicles is established.And based on four different horizontal impact test conditions,the dynamic response of pile-soil composite system under different impact momentum and the dynamic interaction characteristics of pile-soil interface are analyzed systematically.Based on the ultrasonic damage identification theory,the dynamic damage evolution law of pile under different horizontal impact energy is analyzed.The results show that when the impact velocity is low,the peak value of impact force increases nonlinearly with the increase of impact velocity,and when the impact velocity exceeds a certain level,the growth rate of peak value of impact force tends to be stable.The greater the horizontal impact momentum and impact energy,the more serious the impact damage degree of pile.The dynamic damage index D of pile is quadratic function with horizontal impact momentum p and impact kinetic energy Ek.Under the horizontal impact load,the main failure mode of the pile is tensile failure on the impacted side,and a large amount of transient earth pressure increment will be generated on the pile-soil interface on both sides of the pile.Improving the compressive strength of the soil on the pile side can effectively improve the horizontal impact resistance of the pile-soil composite system.