摘要
冲刷会带走桥梁桩基础附近的土体,导致基础在水平向和竖直向的承载力大大降低.最常用的分析冲刷对桩基础影响的方法是在剩余土体性质保持不变的情况下把冲刷掉的土体移除.然而这种方法忽略了剩余土体在冲刷前后所受的应力状态的变化,剩余土体的性质在不同应力历史条件下是不同的,这样剩余土体能给桩基础提供的土阻力也是不一样的.本文主要研究的是冲刷条件下在砂土中的水平向受荷桩考虑了剩余土体应力历史后承载性能的变化.首先通过迭代求得冲刷后砂土的相对密度和侧向土压力系数;其次根据砂土参数之间存在相关性,求得冲刷后有效重度、摩擦角、砂土的地基反应模量等参数并对砂土中的p-y曲线修正;最后基于前人的现场试验,将利用修正过的p-y曲线计算得到的结果和利用原始p-y曲线计算得到的结果进行比较,最终的结果表明,超固结比的改变对侧向土压力的影响最大,砂土由正常固结到超固结的状态转变增加了桩基础的侧向土压力,忽略了应力历史的影响,导致在设计冲刷作用下水平向受荷桩的参数时偏保守.
Scour is the removal of soils around pile foundations of bridges,resulting in reduced capacity of thefoundations in either lateral or vertical direction. A common way to analyze the scour-affected pile foundations is toremove the scoured soil layers while keeping the properties of the remaining soil unchanged. However,this approachignores the fact that the remaining soil experiences the different stress histories before and after scour,which can beexpected to change the properties of the remaining soil. As a result,the resistance of the remaining soil provided tothe pile foundation may be different. The present study focused on the response of laterally loaded pile foundations insand under scour considering the stress history of the remaining sand. Relative density and coefficient of lateral earthpressure of the sand were evaluated when it changed from a normally consolidated(NC)soil to an over-consolidated(OC)soil due to scour. The relative density was then used to estimate other properties of sand,e.g.,unit weight,friction angle,and modulus of subgrade reaction of the sand based on their correlation. The lateral load-deflection(p-y)curve for a pile in sand was modified. A field test was referenced as an example to compare the calculatedresults from the modified p-y curves with those from the initially developed p-y curves for the tested sand. The resultsshow that the change in the over-consolidation ratio(OCR)resulted in the most significant effect on the lateral soilresistance among all the effects due to the changes in the properties of the remaining sand. The sand changing froman NC to OC state increased the lateral soil resistance to the pile foundation. Ignoring the stress history would resultin a conservative design of laterally loaded piles under scour.
出处
《河南科学》
2017年第12期2014-2022,共9页
Henan Science
基金
中央级公益性科研院所基本科研业务费重点基金项目(Y316018)
关键词
砂土
冲刷
应力历史
侧向土压力
水平向受荷桩
sand
scour
stress history
lateral soil resistance
laterally loaded piles
