浅表层软黏土不排水强度的原位测试方法
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摘要
提出了一种新的条形探头,该探头不仅具有全流动探头的优点,并缩小了已有的全流动探头的端部效应,可较好地测定浅表层软黏土的不排水强度。开展了条形探头浅层贯入室内模型试验,分析了探头贯入过程中土体的运动规律。应用数值方法进一步研究了探头贯入过程中的土体破坏模式,建立了深、浅破坏模式转换深度的下限解。依据试验结果和土体破坏形态,提出了条形探头在浅层软土中贯入时的虚拟应力场和机动场,基于极限分析理论求解了土体贯入阻力与土体强度关系的上下限解。根据试验得到的贯入阻力计算出土体强度的上下限值,十字板强度均位于极限分析上下限解之间,证明了条形探头探测浅表层软土强度的适用性。
A new type penetrometer named strip penetrometer is proposed.The strip penetrometer has the same advantages of other full-flow penetrometers with less end effect,and it is also applicable to detecting undrained strength of shallow soil.The shallow penetration test results of strip penetrometer are introduced.The motion modes of soils in the tests are analyzed.The lower bound solution at the shallow-deep transforming depth is established based on the numerical simulation.The virtual stress fields and kinematically admissible velocities are proposed as the penetrometer penetrates shallowly,and the lower and upper bounds are solved.The upper and lower limit strengths of soil test are compared with the vane shear strength.The results of the strip penetrometer fit well with the test ones.
A new type penetrometer named strip penetrometer is proposed.The strip penetrometer has the same advantages of other full-flow penetrometers with less end effect,and it is also applicable to detecting undrained strength of shallow soil.The shallow penetration test results of strip penetrometer are introduced.The motion modes of soils in the tests are analyzed.The lower bound solution at the shallow-deep transforming depth is established based on the numerical simulation.The virtual stress fields and kinematically admissible velocities are proposed as the penetrometer penetrates shallowly,and the lower and upper bounds are solved.The upper and lower limit strengths of soil test are compared with the vane shear strength.The results of the strip penetrometer fit well with the test ones.
引文
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[15]郭绍曾,刘润,洪兆徽,等.插桩过程对临近平台桩基础的影响研究[J].地震工程学报,2015,37(2):446-452.(GUO Shao-zeng,LIU Run,HONG Zhao-hui.Influence of spudcan penetration on pile foundations near a platform[J].China Earthquake Engineering Journal,2015,37(2):446-452.(in Chinese))
[16]周龙,刘润,郭绍曾,等.桩靴连续贯入过程的动态模拟方法研究[J].地震工程学报,2015,37(2):460-466.(ZHOU Long,LIU Run,GUO Shao-zeng et al.A Dynamic simulation method for continuous spudcan penetration[J].China Earthquake Engineering Journal,2015,37(2):460-466.(in Chinese))
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[2]RANDOLPH M F,HOULSBY G T.The limiting pressure on a circular pile loaded laterally in cohesive soil[J].Géotechnique,1984,36(36):457-457
[3]RANDOLPH M F,MARTIN C M,HU Y.Limiting resistance of a spherical penetrometer in cohesive material[J].Géotechnique,2000,50(5):573-582.
[4]STEWART D P,RANDOLPH M F.A New site investigation tool for the centrifuge[C]//Proceedings of the International Conference Centrifuge.Rotterdam,1991:531-531.
[5]STEWART D P,RANDOLPH M F.T-Bar penetration testing in soft clay[J].Journal of Geotechnical Engineering,1994,120(12):2230-2235.
[6]DEJONG J T,YAFRATE N J,DEGROOT D J.Evaluation of undrained shear strength using full-flow penetrometers[J].Journal of Geotechnical and Geoenvironmental Engineering,2010,137(1):14-26.
[7]YAFRATE N J,DEJONG J T.Considerations in evaluating the remoulded undrained shear strength from full-flow penetrometer cycling[C]//Proceedings of the 1st International Symposium on Frontiers in Offshore Geotechnics.Rotterdam:Taylor&Francis,2005:991-997.
[8]LUNNE T,RANDOLPH M F,CHUNG S F.Comparison of cone and T-bar factors in two onshore and one offshore clay sediments[C]//Proceedings of the International Symposium on Frontiers in Offshore Geotechnics.Balkema,2005:981-989.
[9]LOW H E,MAYNARD M L,RANDOLPH M F,et al.Geotechnical characterisation and engineering properties of Burswood clay[J].Géotechnique,2011,61(7):575-591.
[10]范庆来,栾茂田,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.(FANQing-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.(in Chinese))
[11]蔡国军,张涛,刘松玉,等.江苏海相黏土电阻率与岩土特性参数间相关性研究[J].岩土工程学报,2013,35(8):1470-1477.(CAI Guo-jun,ZHANG Tao,LIU Song-yu,et al.Relationship between electrical resistivity and geotechnical characteristic parameters for Jiangsu marine clay[J].Chinese Journal of Geotechnical Engineering,2013,35(8):1470-1477.(in Chinese))
[12]蔡国军,刘松玉,ANAND J P,等.基于CPTU测试的桩基承载力可靠性分析[J].岩土工程学报,2011,33(3):404-412.(CAI Guo-jun,LIU Song-yu,ANAND J P,et al.Reliability assessment of bearing capacity of pile foundation based on CPTU data[J].Chinese Journal of Geotechnical Engineering,2011,33(3):404-412.(in Chinese))
[13]蔡国军,刘松玉,童立元,等.基于聚类分析理论的CPTU土分类方法研究[J].岩土工程学报,2009,31(3):416-424.(CAI Guo-jun,LIU Song-yu,TONG Li-yuan,et al.Soil classification using CPTU data based upon cluster analysis theory[J].Chinese Journal of Geotechnical Engineering,2009,31(3):416-424.(in Chinese))
[14]WHITE D J,GAUDIN C,BOYLAN N,et al.Interpretation of T-bar penetrometer tests at shallow embedment and in very soft soils[J].Canadian Geotechnical Journal,2008,47(2):218-229.
[15]郭绍曾,刘润,洪兆徽,等.插桩过程对临近平台桩基础的影响研究[J].地震工程学报,2015,37(2):446-452.(GUO Shao-zeng,LIU Run,HONG Zhao-hui.Influence of spudcan penetration on pile foundations near a platform[J].China Earthquake Engineering Journal,2015,37(2):446-452.(in Chinese))
[16]周龙,刘润,郭绍曾,等.桩靴连续贯入过程的动态模拟方法研究[J].地震工程学报,2015,37(2):460-466.(ZHOU Long,LIU Run,GUO Shao-zeng et al.A Dynamic simulation method for continuous spudcan penetration[J].China Earthquake Engineering Journal,2015,37(2):460-466.(in Chinese))
[17]黄传志.土体极限分析理论与应用[M].北京:人民交通出版社,2007.(HUANG Chuan-zhi.Theory and application of soil limit analysis[M].Beijing:China Communications Press,2007.(in Chinese))