修正密度法分析混凝土桩复合地基路基绕流滑动稳定性
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摘要
混凝土桩复合地基路基主要失稳模式为绕流滑动,除路基整体剪切滑动稳定分析外,还应进行路基绕流滑动稳定分析。基于混凝土桩主要通过桩帽反力和桩侧摩擦力提高路基稳定性的特点,对混凝土桩复合地基路基绕流滑动稳定分析提出修正密度法。该方法将路堤和地基土作为分析对象,根据改进HEWLETT法确定桩帽荷载,按照格栅挠度等于桩土沉降差的原则计算格栅向桩帽转移的荷载,然后按照桩间土荷载率对桩帽顶面以上路堤密度进行修正。根据混凝土桩底刺入破坏时竖向受力平衡条件确定用于绕流滑动稳定分析的中性面,然后将桩侧正、负摩擦力换算到桩间土密度中。对桩帽反力和桩侧摩擦力经上述等效处理后,可利用现有路基常规稳定分析软件分析混凝土桩复合地基路基的稳定性。滑塌路基实例证明,修正密度法分析结果与工程实际符合较好。
Stability of flow slide of embankment with concrete-pile composite foundation should be analyzed besides overall-shear slide since the main failure mode is flow slide. Revised density method is proposed for flow slide since stability of embankment is enhanced mainly by counterforce of pile caps to embankment and frictional stress of piles. As embankment and ground soil being used for analysis for revised density method, load transferred to pile cap by soil arch is gotten according to modified HEWLETT method. Load transferred to pile cap by reinforcement is calculated on the basis of the relationship that deflection of reinforcement is equal to differential settlement between pile and soil. The density of embankment up pile cap is revised according to ratio of load on soil. The neutral plane for frictional stresses during flow slide is gotten according to equilibrium condition of vertical forces of a concrete pile with bottom punching failure. The frictional stress of piles is transformed into soil density among piles. Then the stability of flow slide of embankment can be analyzed with natural density outside composite foundation and revised density of fill and composite foundation by use of present normal stability analysis software after the above equivalent transformation. It is shown that the result of revised density method coincides with a slid embankment with concrete-pile composite foundation, but the results according to present codes can't coincides with a slid embankment with concrete-pile composite foundation.
Stability of flow slide of embankment with concrete-pile composite foundation should be analyzed besides overall-shear slide since the main failure mode is flow slide. Revised density method is proposed for flow slide since stability of embankment is enhanced mainly by counterforce of pile caps to embankment and frictional stress of piles. As embankment and ground soil being used for analysis for revised density method, load transferred to pile cap by soil arch is gotten according to modified HEWLETT method. Load transferred to pile cap by reinforcement is calculated on the basis of the relationship that deflection of reinforcement is equal to differential settlement between pile and soil. The density of embankment up pile cap is revised according to ratio of load on soil. The neutral plane for frictional stresses during flow slide is gotten according to equilibrium condition of vertical forces of a concrete pile with bottom punching failure. The frictional stress of piles is transformed into soil density among piles. Then the stability of flow slide of embankment can be analyzed with natural density outside composite foundation and revised density of fill and composite foundation by use of present normal stability analysis software after the above equivalent transformation. It is shown that the result of revised density method coincides with a slid embankment with concrete-pile composite foundation, but the results according to present codes can't coincides with a slid embankment with concrete-pile composite foundation.
引文
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[2]刘吉福.刚性桩地基路基稳定性研究[R].天津:天津大学,2015.
[3]刘吉福,郑刚,安关峰.折减荷载法分析刚性桩复合地基路基绕流滑动稳定性[J].广西大学学报,2013,38(1):176-181.
[4]黎爱清.CFG桩加固某软土路基的病害分析[J].铁道标准设计,2012(6):36-39.
[5]莫景逸,黄向平.某矿料堆场地基失稳原因分析[J].水运工程,2013(10):212-217.
[6]刘力.刚性桩加固路堤稳定分析方法研究[D].天津:天津大学,2010.
[7]陈云敏,贾宁,陈仁朋.桩承式路堤土拱效应分析[J].中国公路学报,2004,17(4):1-6.
[8]曹卫平,胡伟伟.桩承式加筋路堤三维土拱效应试验研究[J].岩土力学,2014,35(2):351-358.
[9]刘吉福,郭舒洋,肖昌建.管桩垂直度偏差检测及其对竖向承载力的影响[J].广东公路交通,2015(5):39-42.
[10]龚晓南.复合地基理论及工程应用[M].北京:中国建筑工业出版社,2002.
[11]刘吉福,郑刚,安关峰.稳定路基中刚性桩抗弯能力验算简易方法[J].岩土工程学报,2013,35(8):1387-1396.