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静压桩贯入过程中,因桩顶卸荷残留于桩身的应力较为显著。通过成层土地基中5根桩身预埋准分布式FBG光纤传感器的静压桩足尺试验,对开口PHC管桩沉桩过程中施工残余应力性状、沉桩结束17 d内桩身残余应力的发展变化情况及其对后续静载荷试验影响进行了阐述。试验表明,开口PHC管桩桩身残余应力及桩侧平均残余摩阻力随贯入深度呈折线型分布,中性面深度与贯入桩长比值介于0.66～0.92之间,其大小与桩端持力层密实度及桩端残余应力呈正相关关系。土塞效应成为制约开口PHC管桩桩端残余应力不同于其他桩型的主要因素之一;休止期内桩身残余应力逐渐趋于稳定,中性面处桩身残余应力降低幅度介于3.2%～29.88%之间,桩端残余应力降低幅度介于10.78%～32.39%之间;静载荷试验过程中不考虑施工残余应力将高估中性面以上桩侧摩阻力约53.46%,低估中性面以下桩侧摩阻力及桩端阻力分别56.62%,10%。研究成果可为进一步研究开口PHC管桩施工残余应力性状提供依据。
Static pressure pile penetration process, due to pile top unloading pile stress in the pile is more significant. Through the static pressure pile footing test of 5 pile embedded quasi-distributed FBG optical fiber sensors in stratified soil foundation, the residual stress of the open PHC pipe pile during pile sinking process, residual stress of the pile body within 17 days after the end of pile sinking The development and changes and their impact on the subsequent static load test are described. The results show that the residual stress of open PHC pipe pile and the average residual friction resistance of pile side are distributed in a straight line with penetration depth. The ratio of neutral depth to penetration pile length is between 0.66 and 0.92, Bearing layer density and pile residual stress were positively correlated. The soil plug effect is one of the main factors that restrict the residual stress of the pile end of PHC pipe pile end from being different from other pile types. The residual stress of pile body tends to be stable during the rest period, and the residual stress of the pile body is reduced by 3.2% ~ 29.88%, the reduction of pile residual stress ranged from 10.78% to 32.39%; static load test without considering the construction residual stress will overestimate the pile above the neutral side of the friction resistance of about 53.46%, underestimate the neutral Surface side of pile friction and pile resistance of 56.62%, respectively, 10%. The research results can provide the basis for further research on the residual stress characteristics of open PHC pipe piles.