砂土中桶形基础静压沉贯过程桶-土受力分析
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摘要
在砂土中采取负压沉贯桶形基础易出现液化、砂沸等现象,导致沉贯失败,而采用静压下沉则可有效避免此现象发生。在室内设计了不同尺寸桶形基础静压沉贯模型试验,探讨了沉贯过程中桶体内外土压力的变化情况,结合数字图像处理技术获取了桶形基础下沉过程中的土体位移场。试验结果表明:桶形基础在沉贯深度达到1倍口径时开始出现土塞效应,沉贯结束时土塞填充增量比值约为0.7;沉贯过程中贯入力与内壁土压力随深度线性增加,而当贯入深度达到0.5倍桶裙高时则呈现指数级增长;桶内土塞高度与口径相关,口径为10 cm时土塞高度达到15 cm,闭塞效果最为显著;桶内存在土拱效应,沉贯时首先在桶体端部形成被动土拱,随着贯入深度增加,被动土拱被破坏而形成主动拱。
liquefaction and sand boiling are common failure phenomenon during the suction penetration for bucket foundation. However, the jacked penetration can avoid such failure phenomenon. The jacked penetration tests of bucket foundation with different sizes is designed in the laboratory. The earth pressure internal and outer the bucket body is discussed in the process of penetration, meanwhile, the soil displacement field is obtained by using digital image processing technology. Test results show that the soil plugging effect of bucket foundation appears when the penetration depth reached 1 times of the diameter of bucket, and the incremental filling ratio of soil plug is about 0.7 after penetration. The penetration resistance and the inner earth pressure of bucket increase linearly with the penetration depth during the penetration, then exponentially grow when the penetration depth reaches half times of the height of bucket shirt. The soil plug is more effective with 10 cm in diameter of bucket, and the height of soil plug is 15 cm. There is a soil arching effect inside the bucket, a passive soil arch is formed first at the end of bucket, then destroyed as the penetration depth increase, and the active soil arch form.
liquefaction and sand boiling are common failure phenomenon during the suction penetration for bucket foundation. However, the jacked penetration can avoid such failure phenomenon. The jacked penetration tests of bucket foundation with different sizes is designed in the laboratory. The earth pressure internal and outer the bucket body is discussed in the process of penetration, meanwhile, the soil displacement field is obtained by using digital image processing technology. Test results show that the soil plugging effect of bucket foundation appears when the penetration depth reached 1 times of the diameter of bucket, and the incremental filling ratio of soil plug is about 0.7 after penetration. The penetration resistance and the inner earth pressure of bucket increase linearly with the penetration depth during the penetration, then exponentially grow when the penetration depth reaches half times of the height of bucket shirt. The soil plug is more effective with 10 cm in diameter of bucket, and the height of soil plug is 15 cm. There is a soil arching effect inside the bucket, a passive soil arch is formed first at the end of bucket, then destroyed as the penetration depth increase, and the active soil arch form.
引文
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[22]RANDOLPH M F.Science and empiricism in pile foundation design[J].Géotechnique,2003,53(10):847-875.
[23]贾海莉,王成华,李江洪.关于土拱效应的几个问题[J].西南交通大学学报,2003,38(4):398-402.JIA Hai-li,WANG Cheng-hua,LI Jiang-hong.Discussion on some issues in theory of soil arch[J].Journal of Southwest Jiaotong University,2003,38(4):398-402.
[2]WU K,FAN Q,ZHENG J.Effect of strength anisotropy on failure envelope of offshore shallow foundations under combined loading[J].Journal of Coastal Research,2015,73:521-526.
[3]GOURVENEC S.Effect of embedment on the undrained capacity of shallow foundations under general loading[J].Géotechnique,2008,58(3):177-185.
[4]BIENEN B,HOULSBY G T,CASSIDY M J,et al.Investigating six-degree-of-freedom loading of shallow foundations on sand[J].Géotechnique,2006,56(6):367-379.
[5]罗强,冯娜,贾虎,等.竖向偏心荷载作用下吸力桶荷载-变形特性非共轴本构数值分析[J].大连理工大学学报,2018,58(1):72-78.LUO Qiang,FENG Na,JIA Hu,et al.Non-coaxial constitutive numerical analysis of load-deformation behavior of suction buckets with vertical eccentric loading[J].Journal of Dalian University of Technology,2018,58(1):72-78.
[6]ZHU BIN,KONG DEQIONG,CHEN RENPENG,et al.Installation and lateral loading tests of suction caissons in silt[J].Canadian Geotechnical Journal,2011,48(7):1070-1084.
[7]ZHU B,ZHANG W L,YING P P,et al.Deflection-based bearing capacity of suction caisson foundations of offshore wind turbines[J].Journal of Geotechnical&Geoenvironmental Engineering,2014,140(5):04014013.
[8]朱斌,应盼盼,邢月龙.软土中吸力式桶形基础倾覆承载性能离心模型试验[J].岩土力学,2015,36(增刊1):247-252.ZHU Bin,YING Pan-pan,XING Yue-long.Centrifuge model test on suction caisson foundation in soft clay subjected to lateral loads[J].Rock and Soil Mechanics,2015,36(Supp.1):247-252.
[9]VULPE C.Design method for the undrained capacity of skirted circular foundations under combined loading:effect of deformable soil plug[J].Géotechnique,2015,65(8):669-683.
[10]XIAO Z,TIAN Y,GOURVENEC S.A practical method to evaluate failure envelopes of shallow foundations considering soil strain softening and rate effects[J].Applied Ocean Research,2016,59:395-407.
[11]李大勇,吴宇旗,张雨坤,等.砂土中桶形基础吸力值的设定范围[J].岩土力学,2017,38(4):985-992.LI Da-yong,WU Yu-qi,ZHANG Yu-kun,et al.Determination of suction range for penetration of suction caissons in sand[J].Rock and Soil Mechanics,2017,38(4):985-992.
[12]ANDERSEN K H,JOSTAD H P,DYVIK R.Penetration resistance of offshore skirted foundations and anchors in dense sand[J].Journal of Geotechnical&Geoenvironmental Engineering,2008,134(1):106-116.
[13]CAO J,PHILLIPS R,POPESCU R,et al.Penetration resistance of suction caissons in clay[J].Frontiers in Immunology,2002,2(5):72-72.
[14]陈飞.砂土中海上风机筒型基础沉放过程筒-土作用研究[D].天津:天津大学,2014.CHEN Fei.Research on the soil-skirt interaction of suction buckets for wind turbines during installation in sand[D].Tianjin:Tianjin University,2014.
[15]刘润,祁越,练继建.无黏性土中筒型基础静压下沉模型试验研究[J].水利学报,2016,47(12):1473-1483.LIU Run,QI Yue,LIAN Ji-jian.Experimental study on static pressure penetration of bucket foundation in cohesionless soil[J].Journal of Hydraulic Engineering,2016,47(12):1473-1483.
[16]闫澍旺,林澍,霍知亮,等.桶形基础液压下沉过程的耦合欧拉-拉格朗日有限元法分析[J].岩土力学,2017,38(1):247-252.YAN Shu-wang,LIN Shu,HUO Zhi-liang,et al.Coupled Eulerian-Lagrangian finite element analysis of suction caisson penetration process under hydraulic pressure[J].Rock and Soil Mechanics,2017,38(1):247-252.
[17]李大勇,吴宇旗,张雨坤.砂土中吸力式桶形基础竖向承载性状研究[J].山东科技大学学报(自然科学版),2016,35(3):33-39.LI Da-yong,WU Yu-qi,ZHANG Yu-kun.Vertical bearing capacity of suction caisson foundation in sand[J].Journal of Shandong University of Science and Technology(Natural Science),2016,35(3):33-39.
[18]练继建,马煜祥,王海军,等.筒型基础在粉质黏土中的静压沉放试验研究[J].岩土力学,2017,38(7):1856-1162.LIAN Ji-jian,MA Yu-xiang,WANG Hai-jun,et al.Experimental study on static pressure sedimentation for bucket foundation in silty clay[J].Rock and Soil Mechanics,2017,38(7):1856-1162.
[19]詹永祥,姚海林,董启朋,等.砂土中开口管桩沉桩过程的颗粒流模拟研究[J].岩土力学,2013,34(1):283-289.ZHAN Yong-xiang,YAO Hai-lin,DONG Qi-peng,et al.Study of process of open-ended pipe pile driven into sand soil by particle flow simulation[J].Rock and Soil Mechanics,2013,34(1):283-289.
[20]黄生根,冯英涛,徐学连,等.考虑土塞效应时开口管桩的挤土效应分析[J].沈阳工业大学学报,2015,37(5):582-587.HUANG Sheng-gen,FENG Ying-tao,XU Xue-lian,et al.Analysis on squeezing effect of open-ended pipe pile with considering plugging effect[J].Journal of Shenyang University of Technology,2015,37(5):582-587.
[21]吴子树,张利民,胡定.土拱的形成机理及存在条件的探讨[J].成都科技大学学报,1995(2):15-19.WU Zi-shu,ZHANG Li-min,HU Ding.Studies on the mechanism of arching action in loess[J].Journal of Chengdu University of Science and Technology,1995(2):15-19.
[22]RANDOLPH M F.Science and empiricism in pile foundation design[J].Géotechnique,2003,53(10):847-875.
[23]贾海莉,王成华,李江洪.关于土拱效应的几个问题[J].西南交通大学学报,2003,38(4):398-402.JIA Hai-li,WANG Cheng-hua,LI Jiang-hong.Discussion on some issues in theory of soil arch[J].Journal of Southwest Jiaotong University,2003,38(4):398-402.