中国南海钙质砂蠕变-应力-时间四参数数学模型
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摘要
钙质砂是一种海洋生物沉积形成的具有特殊结构和力学性质的岩土材料,是我国南海岛礁吹填工程的物源材料。为进一步了解其蠕变特性,采用三轴流变仪对取自中国南海某岛礁的钙质砂进行不同围压条件下的长期蠕变试验研究。试验结果表明,在小于其破坏强度的恒定应力作用下,饱和钙质砂发生衰减蠕变,随时间增加,变形不断增加,但变形速率不断减小,直至变形稳定,所受应力越大则达到变形稳定所需时间越长,且蠕变变形量与所受偏应力正相关、与有效围压反相关。应力-应变与应变-时间均为非线性关系。试验研究发现,可采用幂函数对钙质砂蠕变应变-时间进行数学描述,基于试验结果,提出了一种蠕变应变与时间、偏应力和有效围压相关的四参数新的蠕变模型,可以对钙质砂的蠕变过程进行较好的数学描述;与经典的Mesri蠕变模型相比,所提出的数学蠕变模型不需要开展常规三轴压缩试验确定破坏时的峰值偏应力,减少了试验工作,具有一定的优势。
Calcareous sand, a type of geo-material with special structure and mechanical properties formed due to the marine biological deposition process, is the material used in the dredger filling engineering of South China Sea. To further understand its creep properties, a series of long-term creep tests under different confining pressures were carried out using triaxial rheological apparatus on calcareous sand sampled from a coral reef island located at South China Sea. Experimental results show that the damping creep of saturated calcareous sand occurs under constant pressure load that is less than the failure strength. The deformation increases with time, while the deformation rate decreases until the deformation becomes stable. The larger the applied stress is, the longer the deformation becomes stable. The creep deformation is positively correlated with the deviatoric stress, while it is inversely correlated with the effective confining pressure. The relationships of strain-stress and strain-time are nonlinear. It is found that the strain-time relationship of calcareous sand can be described by power function. A new creep model of calcareous sand, considering the relationships of four parameters(i.e. creep strain, time, deviatoric stress and effective confining pressure), is proposed in this paper.Compared with the traditional empirical Mesri creep model, it is unnecessary to perform the conventional triaxial test to determine the peak failure strength in the proposed new model. Less experimental work is required and thus it is much easier to be used.
Calcareous sand, a type of geo-material with special structure and mechanical properties formed due to the marine biological deposition process, is the material used in the dredger filling engineering of South China Sea. To further understand its creep properties, a series of long-term creep tests under different confining pressures were carried out using triaxial rheological apparatus on calcareous sand sampled from a coral reef island located at South China Sea. Experimental results show that the damping creep of saturated calcareous sand occurs under constant pressure load that is less than the failure strength. The deformation increases with time, while the deformation rate decreases until the deformation becomes stable. The larger the applied stress is, the longer the deformation becomes stable. The creep deformation is positively correlated with the deviatoric stress, while it is inversely correlated with the effective confining pressure. The relationships of strain-stress and strain-time are nonlinear. It is found that the strain-time relationship of calcareous sand can be described by power function. A new creep model of calcareous sand, considering the relationships of four parameters(i.e. creep strain, time, deviatoric stress and effective confining pressure), is proposed in this paper.Compared with the traditional empirical Mesri creep model, it is unnecessary to perform the conventional triaxial test to determine the peak failure strength in the proposed new model. Less experimental work is required and thus it is much easier to be used.
引文
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[5]王新志,王星,刘海峰,等.珊瑚礁地基工程特性现场试验研究[J].岩土力学,2017,38(7):2065-2070.WANG Xin-zhi,WANG Xing,LIU Hai-feng,et al.Field test study of engineering behaviors of coral reef foundation[J].Rock and Soil Mechanics,2017,38(7):2065-2070.
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[7]LADE P V,CARL D,LIGGIO J R,et al.Strain rate,creep,and stress drop-creep experiments on crushed coral sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2009,135(7):941-953.
[8]LADE P V.Creep,stress relaxation and rate effects in sand[C]//Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering.Alexandria:IOS Press,2009.
[9]LV Y R,LI F,LIU Y W,et al.Comparative study of coral sand and silica sand in creep under general stress states[J].Canadian Geotechnical Journal,2017,54(11):1601-1611.
[10]温亚楠,朱鸿鹄,张诚成,等.砂土蠕变特性研究现状及展望[J].工程地质学报,2015,23(增刊):284-291.WEN Ya-nan,ZHU Hong-hu,ZHANG Cheng-cheng,et al.Current stature and trends on the study of sand creep[J].Journal of Engineering Geology,2015,23(Suppl.):284-291.
[11]SINGH A,MITCHELL J K.General stress-strain-time function for soils[J].Journal of Soil Mechanics and Foundation Division,ASCE,1968,94(1):21-46.
[12]MESRI G,FEBRES-CORDERO E,SHIELDS D R,et al.Shear stress-strain-time behavior of clays[J].Geotechnique,1981,31(4):537-552.
[13]KONDNER R L.Hyperbolic stress-strain response:cohesive soils[J].Journal of the Soil Mechanics and Foundations Division,1963,89(1):115-144.
[14]FEDA J.Creep of soils and related phenomena[M].[S.l.]:Elsevier Science,1992.
[15]张云,薛禹群,施小清,等.饱和砂性土非线性蠕变模型试验研究[J].岩土力学,2005,26(12):1869-1873.ZHANG Yun,XUE Yu-qun,SHI Xiao-qing,et al.Study on nonlinear creep model for saturated sand[J].Rock and Soil Mechanics,2005,26(12):1869-1873.
[16]张云,薛禹群,吴吉春,等.上海砂土蠕变变形特征的试验研究[J].岩土力学,2009,30(5):1226-1231.ZHANG Yun,XUE Yu-qun,WU Ji-chun,et al.Experimental research on creep of Shanghai sands[J].Rock and Soil Mechanics,2009,30(5):1226-1231.
[17]孙晓涵.西安地面沉降与砂土蠕变关系初探[D].西安:长安大学,2010.SUN Xiao-han.The relationship between sand creep characteristic and land subsidence of Xi’an[D].Xi’an:Chang’an University,2010.
[18]刘业科,邓志斌,曹平,等.软黏土的三轴蠕变试验与修正的Singh-Mitchell蠕变模型[J].中南大学学报(自然科学版),2012,43(4):1440-1446.LIU Ye-ke,DENG Zhi-bin,CAO Ping,et al.Triaxial creep test and modified Singh-Mitchell creep model of soft clay[J].Journal of Central South University(Science and Technology),2012,43(4):1440-1446.
[19]张先伟,王常明.饱和软土的经验型蠕变模型[J].中南大学学报(自然科学版),2011,42(3):791-796.ZHANG Xian-wei,WANG Chang-ming.Empirical creep model for saturated soft soil[J].Journal of Central South University(Science and Technology),2011,42(3):791-796.
[2]黄宏翔,陈育民,王建平,等.钙质砂抗剪强度特性的环剪试验[J].岩土力学,2018,39(6):2082-2088.HUANG Hong-xiang,CHEN Yu-min,WANG Jian-ping,et al.Ring shear tests on shear strength of calcareous sand[J].Rock and Soil Mechanics,2018,39(6):2082-2088.
[3]朱长岐,陈海洋,孟庆山,等.钙质砂颗粒内孔隙结构特征成分分析[J].岩土力学,2014,35(7):1831-1836.ZHU Chang-qi,CHEN Hai-yang,MENG Qing-shan,et al.Microscopic characterization of intra-pore structures of calcareous sands[J].Rock and Soil Mechanics,2014,35(7):1831-1836.
[4]汪轶群,洪义,国振,等.南海钙质砂宏细观破碎力学特性[J].岩土力学,2018,39(1):199-206.WANG Yi-qun,HONG Yi,GUO Zhen,et al.Micro-and macro-mechanical behavior of crushable calcareous sand in South China Sea[J].Rock and Soil Mechanics,2018,39(1):199-206.
[5]王新志,王星,刘海峰,等.珊瑚礁地基工程特性现场试验研究[J].岩土力学,2017,38(7):2065-2070.WANG Xin-zhi,WANG Xing,LIU Hai-feng,et al.Field test study of engineering behaviors of coral reef foundation[J].Rock and Soil Mechanics,2017,38(7):2065-2070.
[6]SHAHNAZARI H,REZVANI R.Effective parameters for the particle breakage of calcareous sand:an experimental study[J].Engineering Geology,2013,159:98-105.
[7]LADE P V,CARL D,LIGGIO J R,et al.Strain rate,creep,and stress drop-creep experiments on crushed coral sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2009,135(7):941-953.
[8]LADE P V.Creep,stress relaxation and rate effects in sand[C]//Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering.Alexandria:IOS Press,2009.
[9]LV Y R,LI F,LIU Y W,et al.Comparative study of coral sand and silica sand in creep under general stress states[J].Canadian Geotechnical Journal,2017,54(11):1601-1611.
[10]温亚楠,朱鸿鹄,张诚成,等.砂土蠕变特性研究现状及展望[J].工程地质学报,2015,23(增刊):284-291.WEN Ya-nan,ZHU Hong-hu,ZHANG Cheng-cheng,et al.Current stature and trends on the study of sand creep[J].Journal of Engineering Geology,2015,23(Suppl.):284-291.
[11]SINGH A,MITCHELL J K.General stress-strain-time function for soils[J].Journal of Soil Mechanics and Foundation Division,ASCE,1968,94(1):21-46.
[12]MESRI G,FEBRES-CORDERO E,SHIELDS D R,et al.Shear stress-strain-time behavior of clays[J].Geotechnique,1981,31(4):537-552.
[13]KONDNER R L.Hyperbolic stress-strain response:cohesive soils[J].Journal of the Soil Mechanics and Foundations Division,1963,89(1):115-144.
[14]FEDA J.Creep of soils and related phenomena[M].[S.l.]:Elsevier Science,1992.
[15]张云,薛禹群,施小清,等.饱和砂性土非线性蠕变模型试验研究[J].岩土力学,2005,26(12):1869-1873.ZHANG Yun,XUE Yu-qun,SHI Xiao-qing,et al.Study on nonlinear creep model for saturated sand[J].Rock and Soil Mechanics,2005,26(12):1869-1873.
[16]张云,薛禹群,吴吉春,等.上海砂土蠕变变形特征的试验研究[J].岩土力学,2009,30(5):1226-1231.ZHANG Yun,XUE Yu-qun,WU Ji-chun,et al.Experimental research on creep of Shanghai sands[J].Rock and Soil Mechanics,2009,30(5):1226-1231.
[17]孙晓涵.西安地面沉降与砂土蠕变关系初探[D].西安:长安大学,2010.SUN Xiao-han.The relationship between sand creep characteristic and land subsidence of Xi’an[D].Xi’an:Chang’an University,2010.
[18]刘业科,邓志斌,曹平,等.软黏土的三轴蠕变试验与修正的Singh-Mitchell蠕变模型[J].中南大学学报(自然科学版),2012,43(4):1440-1446.LIU Ye-ke,DENG Zhi-bin,CAO Ping,et al.Triaxial creep test and modified Singh-Mitchell creep model of soft clay[J].Journal of Central South University(Science and Technology),2012,43(4):1440-1446.
[19]张先伟,王常明.饱和软土的经验型蠕变模型[J].中南大学学报(自然科学版),2011,42(3):791-796.ZHANG Xian-wei,WANG Chang-ming.Empirical creep model for saturated soft soil[J].Journal of Central South University(Science and Technology),2011,42(3):791-796.