超长钻孔灌注桩竖向承载力当量正态化法可靠度研究  

Study on Reliability of Obtaining Vertical Bearing Capacity of Ultra-long Bored Pile by Equivalent Normalization Method

作　　者：宋春霞[1] 任芳 张学峰[1] 尼颖升[1] 马晔[1] SONG Chun-xia;REN Fang;ZHANG Xue-feng;NI Ying-sheng;MA Ye(Research Institute of Highway,Ministry of Transport,Beijing 100088,China;Zhongyu Tiexin Transport Technology Co.,Ltd.,Hengshui Hebei 053020,China)

机构地区：[1]交通运输部公路科学研究院,北京100088 [2]中裕铁信交通科技股份有限公司,河北衡水053020

出　　处：《公路交通科技》2023年第7期136-141,共6页Journal of Highway and Transportation Research and Development

基　　金：中央级公益性科研院所基本科研业务费项目(2021-9073a);宁夏回族自治区科技厅重点研发计划项目(2022BEG07173)。

摘　　要：为了了解超长钻孔灌注桩可靠度指标状态,共收集整理了不同场地11座桥的22根超长钻孔灌注桩竖向承载力荷载试验资料,利用实测得到的219个侧摩阻力值和17个桩端承载力测试值,建立了7类土侧摩阻力和1类土桩端承载力正态分布和对数正态分布的统计概率模型。采用公路规范中摩擦桩竖向承载力计算公式,将桩顶荷载、各土层侧摩阻力和桩端反力视为变量,利用Matlab编制了基于JC法的桩基可靠度指标计算程序,对12根超长钻孔灌注桩按汽车荷载极值I型、恒载正态分布、不同荷载比情况下的可靠度指标进行了计算分析。结果表明:各类土既满足正态分布也满足对数正态分布概率模型,超长钻孔灌注桩抗力按对数正态分布时计算得到的可靠度指标均值在3.259~8.070之间,抗力按正态分布计算得到的可靠度指标均值在2.851~7.495之间,同普通桩基可靠度指标研究结果进行了对比,略高于短桩可靠度指标计算结果;由于桥梁工程地域分布广,多个工程的样本数据离散性偏大,超长钻孔灌注桩桩长增加了深度对可靠度的影响,因此超长桩可靠度指标计算结果没有明显优于短桩计算结果;利用JC法计算得到的超长桩可靠度指标分布区间合理,同时考虑到土体的离散性,建议超长桩可靠度指标标准值同上部结构相比可适当降低。In order to understand the reliability indicator status of ultra-long bored cast-in-place piles,the vertical bearing capacity load test data of 22 ultra-long bored cast-in-place piles from 11 bridges in different sites are collected.By using 219 lateral friction resistance values and 17 pile end bearing capacity test values,the statistical probability models of normal distribution and lognormal distribution of 7 types of lateral friction and 1 type of pile end bearing capacity are established.Using the formula for calculating the vertical bearing capacity of friction piles in highway specifications,regarding the pile top load,lateral friction resistance of each soil layer and pile end reaction as the variables,the calculation program of pile foundation reliability based on JC method is compiled by using Matlab,and the reliability index of 12 super long bored cast-in-place piles is calculated and analyzed under the conditions of extreme value I,dead load normal distribution and different load ratios.The reliability indicators of 12 ultra-long bored piles under the conditions of extreme type I vehicle load,dead load normal distribution and different load ratios are calculated and analyzed The result shows that(1)All kinds of soil meet both normal distribution and lognormal distribution probability model.The average reliability of resistance of ultra-long bored piles calculated according to lognormal distribution is 3.259-8.070,and those calculated according to the normal distribution is 2.851-7.495.Compared with the research result of the reliability of common pile foundation,they are slightly higher than the calculation result of the reliability of short piles.(2)Due to the wide geographical distribution of bridge projects,the dispersions of sample data of multiple projects are larger,the length of ultra-long bored cast-in-place pile increased the influence of depth on reliability.Therefore,the calculated reliability of ultra-long piles is not significantly better than that of short piles.(3)The distribution inter

关 键 词：桥梁工程 可靠度 统计分析 承载力 超长钻孔灌注桩 当量正态化法 

分 类 号：U443.154[建筑科学—桥梁与隧道工程]