基于球形全流动触探仪的软土地基不排水强度确定
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摘要
球形全流动触探仪在软弱土体中具有测试数据稳定且无须修正的特点,因而在近海工程中有着较好的适用性。对球形探头贯入阻力及确定土体不排水剪切强度的方法进行介绍,并讨论了贯入阻力系数取值范围。在此基础上,通过开展离心模型试验,分析比较球形全流动触探和传统锥形静力触探的贯入阻力,以及确定的软土不排水剪切强度。研究结果表明,利用孔压修正后的锥形探头较球形全流动触探探头的贯入阻力大;而基于球形触探结果确定的软土不排水剪切强度值较传统静探方法确定的更为稳定,且与K_0固结条件下强度值较为接近。本研究将为球形全流动触探仪在近海工程中的应用提供依据。
The piezoball test is suitable for the thick deposits of soft clay in offshore engineering,since the data measured from which is steady and no need to correct.The penetration resistance of the piezoball and the corresponding methods for undrained shear strength determination are firstly introduced,and then the value ranges of the resistance coefficient are discussed.Furthermore,the centrifuge tests are conducted to analyze the penetration resistances measured by piezoball and piezocone tests,respectively.Meanwhile,the undrained shear strengths determined by two types of penetrometors are also compared.The results show that the cone penetration resistance corrected with pore water pressure is larger than that measured by the piezoball.In addition,the undrained strength profiles against the depths determined by piezoball are steadier than that from piezocone,which is closed to the strength under K_0 consolidation condition.The studies of this paper will provide reference for the application of full flow penetrometers in the offshore engineering.
The piezoball test is suitable for the thick deposits of soft clay in offshore engineering,since the data measured from which is steady and no need to correct.The penetration resistance of the piezoball and the corresponding methods for undrained shear strength determination are firstly introduced,and then the value ranges of the resistance coefficient are discussed.Furthermore,the centrifuge tests are conducted to analyze the penetration resistances measured by piezoball and piezocone tests,respectively.Meanwhile,the undrained shear strengths determined by two types of penetrometors are also compared.The results show that the cone penetration resistance corrected with pore water pressure is larger than that measured by the piezoball.In addition,the undrained strength profiles against the depths determined by piezoball are steadier than that from piezocone,which is closed to the strength under K_0 consolidation condition.The studies of this paper will provide reference for the application of full flow penetrometers in the offshore engineering.
引文
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[13] House A R,Oliveira J R M S,Randolph M F.Evaluating the coefficient of consolidation using penetration tests[J].Int.J.Phys.Modelling Geotech,2001,1(3):17-25.
[2] 邓长茂,李镜培.合肥膨胀土基坑工程事故分析与预防[J].结构工程师,2011,27(1):105-109.Deng Changmao,Li Jingpei.Analysis and prevention of Foundation pit accidents in Hefei district[J].Structural Engineerings,2011,27(1):105-109.(in Chinese)
[3] 杨岩,刘松玉,蔡国军,等.球型全流触探仪的机理研究及工程应用综述[J].工程地质学报,2017,25(6):1604-1609.Yang Yan,Liu Songyu,Cai guojun,et al.Review on penetration mechanism and application of ball penetrometer in offshore engineering[J].Journal of Enginerring Geology,2017,25(6):1604-1609.(in Chinese)
[4] Cai G J,Liu S Y,Tong L Y,et al.Field evaluation of undrained shear strength from piezocone penetration tests in soft marine clay[J].Mar.Georesources Geotechnol,2010,28:143-153.
[5] Zhang Y G,Li J P,Liang F Y,et al.A modified approach to evaluation of undrained shear strength from piezocone tests in soft clays[J].Marine Georesources & Geotechnology,2017,35(1):80-88.
[6] Einav I,Randolph M F.Combining upper bound and strain path methods for evaluating penetration resistance[J].International Journal for Numerical and Analytical Methods in Geomechanics,2005,63:1991-2016.
[7] DeJong J I,Yafrate N J,DeGroot D J.Evaluation of undrained shear strength using full-flow penetrometers[J].Journal of Geotechnical and Geoenvironmental Engnieering,2011,137(1):14-26.
[8] Colreavy C,O’Loughlin C D,Long M,et al.Field experience of the piezoball in soft clay[C].Proceedings of the 2nd International Symposium on Cone Penetration Testing.California:Polytechnic University:2010,2& 3:1-15.
[9] Chung S F,Randolph M F.Penetration resistance in soft clay for different shaped penetrometers[C].Proc.ISC-2 on Geotechnical and Geophysical Site Characterization,Viana da Fonseca A and Mayne PW,eds.Millpress,Rotterdam,2004:671-677.
[10] Stewart D P,Randolph M F.T-bar penetration testing in soft clay[J].Journal of Geotechnical Engineering,1994,120(12):2230-2235.
[11] Low H E,Lunne T,Andersen K H,et al.Estimation of intact and remoulded undrained shear strengths from penetration tests in soft clays[J].Geotechnique,2010,60(11):843-859.
[12] Chow S H,Airey D W.Free-falling penetrometers:a laboratory investigation in clay[J].Journal of Geotechnical and Geoenvironmental Engnieering,2014,140:201-214.
[13] House A R,Oliveira J R M S,Randolph M F.Evaluating the coefficient of consolidation using penetration tests[J].Int.J.Phys.Modelling Geotech,2001,1(3):17-25.