摘要
舟山某石化基地工程,场地大面积填土厚度达10 m,填土以下深厚软土厚度达50 m。在场地超载预压卸载后对新打设的预应力管桩进行下拉荷载测试,研究桩土相对位移以及桩土相对位移速率对试桩下拉荷载、负摩阻力系数和中性点的影响。结果表明:下拉荷载与桩土相对位移呈正相关性,下拉荷载增长速率随桩土相对位移速率减小而减小,当桩土相对位移速率减小至0.1~0.2 mm/d时,下拉荷载趋于稳定;根据单桩悬吊法测得的不同桩长桩身负摩阻力平均值,提出负摩阻力系数及中性点的计算方法。实测表明:随着时间增长,负摩阻力愈大,但远小于正摩阻力极限值,中性点深度愈大,至一定深度后趋于稳定。最后,基于JGJ 94—2018《建筑桩基技术规范》负摩阻力综合安全系数法所建议的单桩承载力特征值验算了预制桩,验算表明桩基满足工程安全要求。
Field tests of drag loads for prestressed pipes pile were performed in a petrochemical engineering in Zhoushan in which the backfill and underlying soft soil were 10 m and 50 m respectively.After unloading of surcharge preloading,prestressed pipe piles with different length were piled.Based on field tests,influences of relative displacement and relative displacement rates between piles and soil on drag loads,coefficients of negative friction and neutral points were studied.The results showed that there existed a positive correlation between drag loads and relative displacement between piles and soil.Growth rates of drag loads decreased with decrease of relative displacement rates between piles and soil.When relative displacement rates between piles and soil reduced to 0.1 to 0.2 mm/d,drag loads tended to be stable.Average values of negative friction could be tested by the suspension method.The calculation methods about coefficients of negative friction and neutral points were proposed according to the measured values in different pile length.The field test results showed that negative friction increased with time and the depth of neutral points in piles would increase as well.In the end,the increase of the depth for neutral points tended to be stable,negative friction was much less than the ultimate value of positive friction.The characteristic value of the bearing capacity of single piles was checked by the comprehensiely safe factor method considering the negative friction from JGJ 94-2018 Technical Code for Building Pile Foundation,the results showed the piles could meet safety requirements.
作者
余建飞
张静
杨石飞
YU Jianfei;ZHANG Jing;YANG Shifei(Zhejiang Petroleum&Chemical Co.,Ltd.,Zhoushan 316021,China;SGIDI Engineering Consulting(Group)Co.,Ltd.,Shanghai 200093,China)
出处
《工业建筑》
CSCD
北大核心
2022年第1期143-149,64,共8页
Industrial Construction
关键词
下拉荷载试验
大面积填土
深厚软土
负摩阻力系数
中性点
桩基承载力
field test of drag load
large filling
deep soft soil
coefficient of negative friction
neutral point
bearing capacity of pile foundation
