砂土及黏土场地钻井船插桩对邻近桩的影响
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摘要
为研究黏土场地和砂土场地中桩靴贯入及拔出对邻近桩的影响,开展了2组在不同场地中进行插、拔桩靴的室内模型试验,分析了桩靴贯入、拔出过程中桩靴贯入阻力、拔出阻力、土体位移及桩身弯矩的变化规律。结果表明,黏土场地桩靴贯入阻力随桩靴贯入深度增加而增加,达到某一极限值后基本保持稳定;砂土场地桩靴贯入阻力随桩靴贯入深度呈线性增大。黏土场地中桩靴拔出阻力基本保持不变,在邻近泥面处突变,几乎减小为零;砂土场地中桩靴拔出阻力在初始阶段迅速增大然后迅速减小,达到最大值的一半后开始以一定的速率均匀减小,对比拔桩阻力的实测值与理论值,发现桩靴贯入土体后减小了土体强度。通过在土层中埋置土体位移测量装置,发现桩靴贯入在黏土场地的深度方向影响较大,砂土场地中则对水平方向影响较大;两种场地中均发生不同程度的回淤现象,且砂土场地更为明显。不同形式土体位移进一步导致不同的邻近桩响应,具体表现在黏土场地中桩身上部正弯矩较大,桩身下部负弯矩较小;在砂土场地中桩身上部正弯矩较小,桩身下部负弯矩较大;插桩过程中最大桩身弯矩逐渐增大,且发生位置逐渐下移,当桩靴贯入到一定深度后最大桩身弯矩基本保持不变;拔桩过程中砂土场地的邻近桩响应不明显,桩身弯矩出现轻微减小。研究结果可为钻井船平台桩靴计算竖向承载力和抗拔极限力提供依据,同时为评价不同场地中桩身响应提供技术参考。
Two 1 g model tests in the laboratory are carried out to investigate the influences of the spudcan penetration and extraction on the adjacent piles in the sand and clay. The variations of the spudcan penetration and extraction resistance,the soil displacement and the pile shaft bending moment distributions during the spudcan penetration and extraction are analyzed in this study. It is found that the penetration resistance of the spudcan in the clay initially increases with the increase of the spudcan penetration depth and then gradually keeps stable after reaching a certain limit value,while in the sand it keeps linear increasing with the penetration depth. The extraction resistance in the clay keeps constant until the spudcan is lifted near the soil surface,where it drops to zero. In the sand,the spudcan extraction resistance rapidly increases at the initial stage,and then decreases rapidly. After reaching the maximum value,it begins to uniformly decrease at a certain rate. A comparison between the calculated and the measured values of the spudcan resistance indicates that the soil strength is weakened by the spudcan penetration into the soil mass. It is found from soil mass displacement measuring system that the spudcan in the clay has a greater influence in the vertical direction and has a greater influence in the horizontal direction in the sand.And there are different degrees of the back-siltation at both sand and clay sites,and at the sand site the backsiltation is more obvious. Different soil movement distributions lead to different responses of the adjacent pile: in the clay,the positive bending moment in the upper part of the pile shaft is larger,and the negative bending moment of the lower part of the pile shaft is smaller. And the positive bending moment in the upper part of the pile shaft in the sand is smaller and the negative bending moment in the lower part of the pile shaft is larger. In the process of pile penetration,the maximum bending moment along the pile shaft gradually increases with the spudcan penetration and its position moves downwards at the same time. When the spudcan penetrates to a certain depth,the maximum bending moment remains basically unchanged. However,the adjacent pile only displays a slight decrease in its bending moment during the spudcan extraction. The research results given by this paper can provide a reference for the calculating vertical bearing capacity and ultimate uplift force of the spudcan of the drilling ship platform,and a reference for evaluating the pile shaft response in different soil masses.
Two 1 g model tests in the laboratory are carried out to investigate the influences of the spudcan penetration and extraction on the adjacent piles in the sand and clay. The variations of the spudcan penetration and extraction resistance,the soil displacement and the pile shaft bending moment distributions during the spudcan penetration and extraction are analyzed in this study. It is found that the penetration resistance of the spudcan in the clay initially increases with the increase of the spudcan penetration depth and then gradually keeps stable after reaching a certain limit value,while in the sand it keeps linear increasing with the penetration depth. The extraction resistance in the clay keeps constant until the spudcan is lifted near the soil surface,where it drops to zero. In the sand,the spudcan extraction resistance rapidly increases at the initial stage,and then decreases rapidly. After reaching the maximum value,it begins to uniformly decrease at a certain rate. A comparison between the calculated and the measured values of the spudcan resistance indicates that the soil strength is weakened by the spudcan penetration into the soil mass. It is found from soil mass displacement measuring system that the spudcan in the clay has a greater influence in the vertical direction and has a greater influence in the horizontal direction in the sand.And there are different degrees of the back-siltation at both sand and clay sites,and at the sand site the backsiltation is more obvious. Different soil movement distributions lead to different responses of the adjacent pile: in the clay,the positive bending moment in the upper part of the pile shaft is larger,and the negative bending moment of the lower part of the pile shaft is smaller. And the positive bending moment in the upper part of the pile shaft in the sand is smaller and the negative bending moment in the lower part of the pile shaft is larger. In the process of pile penetration,the maximum bending moment along the pile shaft gradually increases with the spudcan penetration and its position moves downwards at the same time. When the spudcan penetrates to a certain depth,the maximum bending moment remains basically unchanged. However,the adjacent pile only displays a slight decrease in its bending moment during the spudcan extraction. The research results given by this paper can provide a reference for the calculating vertical bearing capacity and ultimate uplift force of the spudcan of the drilling ship platform,and a reference for evaluating the pile shaft response in different soil masses.
引文
[1] SICILIANO R J,HAMILTON J M,MURFF J D,et al. Effect of jack-up spudcans on piles[J]. Offshore Technology Conference,1990,OTC 6467.
[2] CRAIG W H. Spud-can foundations:Installation with deep penetration and subsequent removal[J]. Proceedings of the ICEGeotechnical Engineering,1998,131(3):146-151.
[3] STEWART D P.Influence of jack-up operation adjacent to a piled structure[J]. Proceeding International Symposium Frontiers in Offshore Geotechnics,2005:543-549.
[4] XIE Y. Centrifuge model study on spudcan-pile interaction[D]. Singapore:National University of Singapore,2009.
[5]田兆丰.钻井船插、拔桩对邻近桩影响的模型试验[D].天津:天津大学,2017.(TIAN Zhaofeng. Model tests on effects of spudcan penetration and extraction on adjacent piles[D]. Tianjin:Tianjin University,2017.(in Chinese))
[6]吴永韧,鲁晓兵,王淑云,等. Spudcan基础贯入对固定平台基础影响[J].中国海洋平台,2008,23(1):35-38.(WU Yongren,LU Xiaobing,WANG Shuyun,et al. Effects of spud-can on pile foundation of fixed platform[J]. China Offshore Platform,2008,23(1):35-38.(in Chinese))
[7] JTJ 254—98港口工程桩基规范[S].(JTJ 254—98 Code for pile foundation in port engineering[S].(in Chinese))
[8] SNAME. Recommended practice for site specific assessment of mobile jack-up units[S]. Society of Naval Architects and Marine Engineers. Technical and Research Bulletin 5-5A. New Jersey,2007.
[9] PURWANA O A. Centrifuge model study on spudcan extraction in soft clay[D]. Singapore:National University of Singapore,2007.
[10] MEYERHOF G G,ADAMS J I. The ultimate uplift capacity of foundations[J]. Canadian Geotechnical Journal,1968,5(4):225-244.
[11]张其一.自升式平台桩基土体变形规律与破坏机理分析[J].中国海洋大学学报,2012,42(11):111-116.(ZHANG Qiyi. Analysis of deformation law and failure mechanism of pile foundation of jack-up platform[J]. Periodical of Ocean University of China,2012,42(11):111-116.(in Chinese))
[12]陶常飞.曹妃甸浅滩海洋工程地质特征及插桩深度研究[D].青岛:中国海洋大学,2008.(TAO Changfei. Reasearch on the characteristics of marine engineering geology and the depth of pile penetration in Caofeidian Shoal[D]. Qingdao:Ocean University of China,2008.(in Chinese))
[13]王琦.自升式平台插桩物理模型试验及分析[J].中国水运,2014,14(3):364-366.(WANG Qi. Model test and analysis of jack-up platform penetration[J]. China Water Transport,2014,14(3):364-366.(in Chinese))
[2] CRAIG W H. Spud-can foundations:Installation with deep penetration and subsequent removal[J]. Proceedings of the ICEGeotechnical Engineering,1998,131(3):146-151.
[3] STEWART D P.Influence of jack-up operation adjacent to a piled structure[J]. Proceeding International Symposium Frontiers in Offshore Geotechnics,2005:543-549.
[4] XIE Y. Centrifuge model study on spudcan-pile interaction[D]. Singapore:National University of Singapore,2009.
[5]田兆丰.钻井船插、拔桩对邻近桩影响的模型试验[D].天津:天津大学,2017.(TIAN Zhaofeng. Model tests on effects of spudcan penetration and extraction on adjacent piles[D]. Tianjin:Tianjin University,2017.(in Chinese))
[6]吴永韧,鲁晓兵,王淑云,等. Spudcan基础贯入对固定平台基础影响[J].中国海洋平台,2008,23(1):35-38.(WU Yongren,LU Xiaobing,WANG Shuyun,et al. Effects of spud-can on pile foundation of fixed platform[J]. China Offshore Platform,2008,23(1):35-38.(in Chinese))
[7] JTJ 254—98港口工程桩基规范[S].(JTJ 254—98 Code for pile foundation in port engineering[S].(in Chinese))
[8] SNAME. Recommended practice for site specific assessment of mobile jack-up units[S]. Society of Naval Architects and Marine Engineers. Technical and Research Bulletin 5-5A. New Jersey,2007.
[9] PURWANA O A. Centrifuge model study on spudcan extraction in soft clay[D]. Singapore:National University of Singapore,2007.
[10] MEYERHOF G G,ADAMS J I. The ultimate uplift capacity of foundations[J]. Canadian Geotechnical Journal,1968,5(4):225-244.
[11]张其一.自升式平台桩基土体变形规律与破坏机理分析[J].中国海洋大学学报,2012,42(11):111-116.(ZHANG Qiyi. Analysis of deformation law and failure mechanism of pile foundation of jack-up platform[J]. Periodical of Ocean University of China,2012,42(11):111-116.(in Chinese))
[12]陶常飞.曹妃甸浅滩海洋工程地质特征及插桩深度研究[D].青岛:中国海洋大学,2008.(TAO Changfei. Reasearch on the characteristics of marine engineering geology and the depth of pile penetration in Caofeidian Shoal[D]. Qingdao:Ocean University of China,2008.(in Chinese))
[13]王琦.自升式平台插桩物理模型试验及分析[J].中国水运,2014,14(3):364-366.(WANG Qi. Model test and analysis of jack-up platform penetration[J]. China Water Transport,2014,14(3):364-366.(in Chinese))