离心机中球形贯入仪贯入黏土特性
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摘要
目前球形全流贯入被仪广泛应用于岩土离心试验中,以表征软弱黏土土样的抗剪性能。然而,在离心加速度作用下离心机试验中的球贯入仪比现场使用的标准球贯入仪有更大的加载杆与球的面积比a、更大的等效原型直径以及不一样的球-土摩擦系数,从而使得离心机球体会出现不一样的贯入特性,进而导致不一样的土体抗剪承载力校验系数。通过大变形有限元(large deformation finite element,简称LDFE)方法对中国常见离心机球形贯入仪贯入单层黏土进行分析,获得不同几何尺寸和摩擦系数下球形贯入仪的贯入特性。计算结果通过与有关解析解以及其他前人研究结论的对比分析,验证了有限元分析结果的合理性。通过大量参数分析表明,球摩擦系数对空腔的临界深度以及深层破坏深度的影响较小,面积比a对浅层和深层承载力系数以及达到深层破坏深度有显著的影响。根据数值模拟的结果,提出了不同面积比和摩擦系数下的极限间隙深度Hc、浅层和深层临界破坏模式深度Hd、不同摩擦系数和面积比情况下的深层承载力系数和浅层承载力校准系数的计算公式,从而能获得更精确的土体抗剪强度,为离心机中球形贯入仪的应用提供了理论依据。
Full-flow ball penetrometers have been used widely in centrifuge testing for characterizing the undrained shear strength of soil sample. However, the soil flow mechanism and bearing capacity factor of ball penetrometers in centrifuge is significantly different from that of in the field tests, which induced by that the ball-soil frictional coefficient and the ratio of larger shaft diameter and cross-area of centrifuge test is different from that of in field tests. Large deformation finite element analyses are carried out to investigate the behaviour of ball penetrating into uniform clay to quantify the bearing capacity. Prior to conduct parametrical study,the plasticity solutions present good agreement with other previously published finite element results and experimental data. The roughness of ball has little effect on the critical depth of the cavity and the critical deep failure depth. The area ratio is shown to have significant influence on the shallow and deep bearing factors, the critical cavity depth, and the critical deep failure depth. Numerous formulas are proposed to quantify those effects to interpret the undrained shear strength profile, and to provide guidance for its application of ball penetrometers in centrifuge testing.
Full-flow ball penetrometers have been used widely in centrifuge testing for characterizing the undrained shear strength of soil sample. However, the soil flow mechanism and bearing capacity factor of ball penetrometers in centrifuge is significantly different from that of in the field tests, which induced by that the ball-soil frictional coefficient and the ratio of larger shaft diameter and cross-area of centrifuge test is different from that of in field tests. Large deformation finite element analyses are carried out to investigate the behaviour of ball penetrating into uniform clay to quantify the bearing capacity. Prior to conduct parametrical study,the plasticity solutions present good agreement with other previously published finite element results and experimental data. The roughness of ball has little effect on the critical depth of the cavity and the critical deep failure depth. The area ratio is shown to have significant influence on the shallow and deep bearing factors, the critical cavity depth, and the critical deep failure depth. Numerous formulas are proposed to quantify those effects to interpret the undrained shear strength profile, and to provide guidance for its application of ball penetrometers in centrifuge testing.
引文
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[12]HU Y,RANDOLPH M F.A practical numerical approach for large deformation problems in soil[J].International Journal for Numerical and Analytical Methods in Geomechanics,1998,22(5):327-350.
[13]CARTER J P,BALAAM N P.AFENA users’manual[M].Sydeny:Centre for Geotechnical Research,1995.
[14]GHOSH S,KIKUCHI N.An arbitrary LagrangianEulerian finite element method for large deformation analysis of elastic-viscoplastic solids[J].Computer Methods in Applied Mechanics and Engineering,1991,86(2):127-188.
[15]ZHOU M,HOSSAIN M S,HU Y,et al.Installation of stiffened caissons in non-homogeneous clays[J].Journal of Geotechnical and Geoenviroment Engineering,2016,142(2):04015070.
[16]ZHOU M,LIU H,HOSSAIN M S,et al.Numerical simulation of plug formation during casing installation of PCC piles[J].Canadian Geotechnical Journal,2016,53(7):1-17.
[17]MA H,ZHOU M,HU Y,et al.Interpretation of layer boundaries and shear strengths for soft-stiff-soft clays using CPT data:LDFE analyses[J],Journal of Geotechnical and Geoenviroment Engineering,2016,142(1):04015055.
[18]范庆来,奕茂田,刘占阁.软土中T型触探仪贯入阻力的数值模拟[J].岩土力学,2009,30(9):2850-2854.FAN Qing-lai,LUAN Mao-tian,LIU Zhan-ge.Numerical simulation of penetration resistance of T-bar penetrometer in soft clay[J].Rock and Soil Mechanics,2009,30(9):2850-2854.
[19]HERRMANN,LEONARD R.Finite element analysis of contact problems[J].Journal of the Engineering Mechanics Division,1978,104(5):1043-1057.
[20]MA H,ZHOU M,HU Y,et al.Effects of cone tip roughness,in-situ,stress anisotropy and strength inhomogeneity on CPT data interpretation in layered marine clays:numerical study[J].Engineering Geology,2017:S0013795217308803.
[21]ZHOU M.HOSSAIN M S,HU Y,et al.Scale issues and interpretation of ball penetration in stratified deposits in centrifuge testing[J].Journal of Geotechnical&Geoenvironmental Engineering,2016,142(5):04015103.
[22]HOSSAIN M S,HU Y,RANDOLPH M F,et al.Limiting cavity depth for spudcan foundations penetrating clay[J].Géotechnique,2005,55(55):679-690.
[23]HOSSAIN M S,RANDOLPH M F.New mechanismbased design approach for spudcan foundations on single layer clay[J].Journal of Geotechnical&Geoenvironmental Engineering,2009,135(9):1264-1274.
[24]MA H,ZHOU M,HU Y,et al.Interpretation of layer boundaries and shear strengths for soft-stiff-soft clays using CPT data:LDFE analyses[J].Journal of Geotechnical&Geoenvironmental Engineering,2016,142(1):04015055.
[25]ZHOU H,RANDOLPH M F.Resistance of full-flow penetrometers in rate-dependent and strain-softening clay[J].Géotechnique,2009,59(2):79-86.
[26]LU Q,HU Y,RANDOLPH M F.FE analysis for T-bar and spherical penetrometers in cohesive soil[C]//Proceedings of 10th International Offshore and Polar Engineering Conference.Seattle:[s.n.],2000:617-623.
[2]彭鹏,蔡国军,刘松玉,等.T型全流触探仪机制分析及海洋工程应用综述[J].岩土工程学报,2017,39(增刊1):151-156.PENG Peng,CAI Guo-jun,LIU Song-yu,et al.Review of T-bar full-flow penetration testing in offshore engineering[J].Chinese Journal of Geotechnical Engineering,2017,39(Suppl.1):151-156.
[3]郭绍曾,刘润.静力触探测试技术在海洋工程中的应用[J].岩土工程学报,2015,37(增刊1):207-211.GUO Shao-ceng,LIU Run.Application of cone penetration test in offshore engineering[J].Chinese Journal of Geotechnical Engineering,2015,37(Suppl.1):207-211.
[4]RANDOLPH M F,LEE K K,CASSIDY M J.Bearing capacity on sand overlying clay soils:experimental and finite-element investigation of potential punch-through failure[J].Geotechnique,2013,63(15):1271-1284.
[5]HOSSAIN,M S,CASSIDY M J,HU Y.T-Bar to spudcan design approach in single-layer clays and calcareous silts[J].Journal of Geotechnical&Geoenvironmental Engineering.2016,142(7):04016025.
[6]RANDOLPH M F,MARTIN C M,HU Y.Limiting resistance of a spherical penetrometer in cohesive material[J].Géotechnique,2000,50(5):573-582.
[7]EINAV I,RANDOLPH M F.Combining upper bound and strain path methods for evaluating penetration resistance[J].International Journal for Numerical Methods in Engineering,2005,63(14):1991-2016.
[8]ZHOU H,RANDOLPH M F.Effect of shaft on resistance of a ball penetrometer[J].Géotechnique,2011,61(11):973-981.
[9]ZHOU M,HU Y,HOSSIAN M S,et al.Behaviour of ball penetrometer in uniform single-and double-layer clays[J].Géotechnique,2013,63(8):682-694.
[10]张霆,刘汉龙,胡玉霞,等.鼓式土工离心机技术及其工程应用研究[J].岩土力学,2009,30(4):1191-1196.ZHANG Ting,LIU Han-long,HU Yu-xia,et al.Geotechnical drum centrifuge technique and its engineering application[J].Rock and Soil Mechanics,2009,30(4):1191-1196.
[11]李刚,张金利,杨庆,等.人工岛沉降的离心机模型试验与数值分析[J].岩土力学,2015,36(8):2249-2254.LI Gang,ZHANG Jin-li,YANG Qing,et al.Centrifuge modeling and numerical analysis of the settlement of an artificial island[J].Rock and Soil Mechanics,2015,36(8):2249-2254.
[12]HU Y,RANDOLPH M F.A practical numerical approach for large deformation problems in soil[J].International Journal for Numerical and Analytical Methods in Geomechanics,1998,22(5):327-350.
[13]CARTER J P,BALAAM N P.AFENA users’manual[M].Sydeny:Centre for Geotechnical Research,1995.
[14]GHOSH S,KIKUCHI N.An arbitrary LagrangianEulerian finite element method for large deformation analysis of elastic-viscoplastic solids[J].Computer Methods in Applied Mechanics and Engineering,1991,86(2):127-188.
[15]ZHOU M,HOSSAIN M S,HU Y,et al.Installation of stiffened caissons in non-homogeneous clays[J].Journal of Geotechnical and Geoenviroment Engineering,2016,142(2):04015070.
[16]ZHOU M,LIU H,HOSSAIN M S,et al.Numerical simulation of plug formation during casing installation of PCC piles[J].Canadian Geotechnical Journal,2016,53(7):1-17.
[17]MA H,ZHOU M,HU Y,et al.Interpretation of layer boundaries and shear strengths for soft-stiff-soft clays using CPT data:LDFE analyses[J],Journal of Geotechnical and Geoenviroment Engineering,2016,142(1):04015055.
[18]范庆来,奕茂田,刘占阁.软土中T型触探仪贯入阻力的数值模拟[J].岩土力学,2009,30(9):2850-2854.FAN Qing-lai,LUAN Mao-tian,LIU Zhan-ge.Numerical simulation of penetration resistance of T-bar penetrometer in soft clay[J].Rock and Soil Mechanics,2009,30(9):2850-2854.
[19]HERRMANN,LEONARD R.Finite element analysis of contact problems[J].Journal of the Engineering Mechanics Division,1978,104(5):1043-1057.
[20]MA H,ZHOU M,HU Y,et al.Effects of cone tip roughness,in-situ,stress anisotropy and strength inhomogeneity on CPT data interpretation in layered marine clays:numerical study[J].Engineering Geology,2017:S0013795217308803.
[21]ZHOU M.HOSSAIN M S,HU Y,et al.Scale issues and interpretation of ball penetration in stratified deposits in centrifuge testing[J].Journal of Geotechnical&Geoenvironmental Engineering,2016,142(5):04015103.
[22]HOSSAIN M S,HU Y,RANDOLPH M F,et al.Limiting cavity depth for spudcan foundations penetrating clay[J].Géotechnique,2005,55(55):679-690.
[23]HOSSAIN M S,RANDOLPH M F.New mechanismbased design approach for spudcan foundations on single layer clay[J].Journal of Geotechnical&Geoenvironmental Engineering,2009,135(9):1264-1274.
[24]MA H,ZHOU M,HU Y,et al.Interpretation of layer boundaries and shear strengths for soft-stiff-soft clays using CPT data:LDFE analyses[J].Journal of Geotechnical&Geoenvironmental Engineering,2016,142(1):04015055.
[25]ZHOU H,RANDOLPH M F.Resistance of full-flow penetrometers in rate-dependent and strain-softening clay[J].Géotechnique,2009,59(2):79-86.
[26]LU Q,HU Y,RANDOLPH M F.FE analysis for T-bar and spherical penetrometers in cohesive soil[C]//Proceedings of 10th International Offshore and Polar Engineering Conference.Seattle:[s.n.],2000:617-623.
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