考虑初始固结状态影响的软基固结计算方法研究
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摘要
按Terzaghi一维固结理论计算的软基固结过程与实测值存在较大误差,其部分原因是该理论假定固结系数为常数,忽略了初始固结状态和固结过程对渗透系数的影响。根据达西渗透系数公式和柯森–卡门渗透系数公式以及3种固结状态土的e-lgσ关系,推导同时考虑初始固结状态和固结过程中应力状态影响的软基堆载预压过程中的渗透系数预测公式;利用室内固结–渗透试验和已有研究探究预测公式的适用性和可靠性;将预测公式代入固结系数表达式,进而获得考虑初始固结状态和固结过程中应力状态影响的修正的Terzaghi一维固结方程;借助工程应用分析探讨了修正的Terzaghi一维固结方程的合理性。研究发现,预测公式能够快捷准确地预估软基堆载预压过程中的渗透系数变化过程;当上覆荷载较小时,修正的Terzaghi一维固结方程与原方程的计算结果相近;但当上覆荷载较大时,固结过程对土体孔隙比和渗透系数的影响较大,修正后的Terzaghi一维固结方程计算的固结度明显滞后于修正前的计算结果,更符合工程实际。旨在为不同初始固结状态的软基提供一种较为准确的固结计算方法。
There sometimes exits notable difference between the consolidation process of soft soil based on Terzaghi's one-dimensional consolidation theory and the field settlement observations,which can be in a certain extent ascribed to that the theory assumes the consolidation coefficient is constant and ignores the influence of initial consolidation state and consolidation process on permeability coefficient. According to the Darcy permeability coefficient formula,Kozeny-Carman permeability coefficient formula and e-lgσ relations of three consolidation state soils,the permeability coefficient prediction formulas of soft soil in process of surcharge preloading are established considering the influence of the initial consolidation state and stress state during consolidation process. The applicability and reliability of the predictive formulas are explored by the laboratory consolidation-permeability test and reference. The prediction formulas are substituted into the consolidation coefficient expression to obtain the modified Terzaghi one-dimensional consolidation equations considering the influence of the initial consolidation state and stress state during consolidation process. And the rationality of the modified Terzaghi one-dimensional consolidation equations is discussed by engineering application analysis. The results show that the predictive formulas can quickly and accurately estimate the permeability coefficient of the soft soil in the process of surcharge preloading. When the overloading is small,the calculation results of Terzaghi one-dimensional consolidation equations and original equations are similar. However,when the overloading is large,the consolidation process has a greater impact on the porosity ratio and permeability coefficient of soil. The consolidation degree calculated by modified Terzaghi one-dimensional consolidation equations is obviously behind the pre-modified calculation result,which is greatly agree with the engineering practice. The purpose of this paper is to provide a more accurate consolidation calculation method for the soft soil of different initial consolidation state.
There sometimes exits notable difference between the consolidation process of soft soil based on Terzaghi's one-dimensional consolidation theory and the field settlement observations,which can be in a certain extent ascribed to that the theory assumes the consolidation coefficient is constant and ignores the influence of initial consolidation state and consolidation process on permeability coefficient. According to the Darcy permeability coefficient formula,Kozeny-Carman permeability coefficient formula and e-lgσ relations of three consolidation state soils,the permeability coefficient prediction formulas of soft soil in process of surcharge preloading are established considering the influence of the initial consolidation state and stress state during consolidation process. The applicability and reliability of the predictive formulas are explored by the laboratory consolidation-permeability test and reference. The prediction formulas are substituted into the consolidation coefficient expression to obtain the modified Terzaghi one-dimensional consolidation equations considering the influence of the initial consolidation state and stress state during consolidation process. And the rationality of the modified Terzaghi one-dimensional consolidation equations is discussed by engineering application analysis. The results show that the predictive formulas can quickly and accurately estimate the permeability coefficient of the soft soil in the process of surcharge preloading. When the overloading is small,the calculation results of Terzaghi one-dimensional consolidation equations and original equations are similar. However,when the overloading is large,the consolidation process has a greater impact on the porosity ratio and permeability coefficient of soil. The consolidation degree calculated by modified Terzaghi one-dimensional consolidation equations is obviously behind the pre-modified calculation result,which is greatly agree with the engineering practice. The purpose of this paper is to provide a more accurate consolidation calculation method for the soft soil of different initial consolidation state.
引文
[1]TERZAGHI K.Theoretical soil mechanics[M].New York:John Wiley and Sons Inc.,1943:265-296.
[2]DUNCAN J M.Limitations of conventional analysis of consolidation settlement[J].Journal of Geotechnical Engineering,ASCE,1993,119(9):1 333-l 359.
[3]MESRI G,TAVENAS F.Discussion on“Permeability and consolidation of normally consolidated soils”by Huang Y H and Drenevich V P[J].Journal of Geotechnical Engineering,Division,ASCE,1983,109(GT6):873-878.
[4]孙立强,闫澍旺,邱长林.考虑新近吹填土固结系数为变量的固结理论研究[J].岩土工程学报,2013,35(增1):313-316.(SUNLiqiang,YAN Shuwang,QIU Changlin.Consolidation theory considering coefficent of consolidation of hydraulic fill as variable[J].Chinese Journal of Geotechnical Engineering,2013,35(Supp.1):313-316.(in Chinese))
[5]章为民,顾行文,王芳.Terzaghi固结系数的试验反演分析[J].岩土工程学报,2016,38(增1):99-103.(ZHANG Weimin,GUXingwen,WANG Fang.Back analysis of Terzaghi consolidation coefficient[J].Chinese Journal of Geotechnical Engineering,2016,38(Supp.1):99-103.(in Chinese))
[6]庄迎春,刘世明,谢康和.萧山软黏土一维固结系数非线性研究[J].岩石力学与工程学报,2005,24(12):4 565-4 569.(ZHUANGYingchun,LIU Shiming,XIE Kanghe.Study on nonlinearity of one-dimensional consolidation coefficient of Xiaoshan clay[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(12):4 565-4 569.(in Chinese))
[7]GIBSON R E,ENGLISH G L,HUSSEY M J L.The theory of one dimensional consolidation of saturated clays:I Finite non-linear consolidation of thin homogeneous layer[J].Geotechnique,1967,17(2):261-273.
[8]谢新宇,朱向荣,谢康和,等.饱和土体一维大变形固结理论新进展[J].岩土工程学报,1997,19(4):30-38.(XIE Xinyu,ZHUXiangrong,XIE Kanghe,et al.New developments of one-dimensional large strain consolidation theories[J].Chinese Journal of Geotechnical Engineering,1997,19(4):30-38.(in Chinese))
[9]NEWLAND P L,ALLEY B H.A study of the consolidation characteristics of a clay[J].Geotechnique,1960,10(2):62-74.
[10]詹美礼,钱家欢,陈绪禄.软土流变特性试验及流变模型[J].岩土工程学报,1993,15(3):54-62.(ZHAN Meili,QIAN Jiahuan,CHENXulu.Tests on rheological behavior of soft soil and rheologic model[J].Chinese Journal of Geotechnical Engineering,1993,15(3):54-62.(in Chinese))
[11]DAVIS E H,RAYMOND G P.A non-linear theory of consolidation[J].Geotechnique,1965,15(2):161-173.
[12]LEKHA K R,KRISHNASWAMY N R,BASAK P.Consolidation of clays for variable permeability and compressibility[J].Journal of Geotechnical and Geoenvironmental Engineering,2003,129(11):1 001-1 009.
[13]POSKITT T J.The consolidation of saturated clay with variable permeability and compressibility[J].Geotechnique,1969,19(2):234-252.
[14]谢康和,郑辉,LEO C J.软黏土一维非线性大应变固结解析理论[J].岩土工程学报,2002,24(6):680-684.(XIE Kanghe,ZHENGHui,LEO C J.An analytical theory for 1-D nonlinear large strain consolidation of soft clay[J].Chinese Journal of Geotechnical Engineering,2002,24(6):680-684.(in Chinese))
[15]李传勋,徐超,谢康和.考虑非达西渗流和应力历史的土体非线性固结研究[J].岩土力学,2017,38(1):91-100.(LI Chuanxun,XU Chao,XIE Kanghe.Nonlinear consolidation of clayed soil considering non-Darcy flow and stress history[J].Rock and Soil Mechanics,2017,38(1):91-100.(in Chinese))
[16]李传勋,谢康和.基于非达西渗流的软土一维非线性固结半解析解[J].岩土力学,2013,34(8):2 181-2 188.(LI Chuanxun,XIEKanghe.Semi-analytical solution of one-dimensional nonlinear consolidation with non-Darcian flow[J].Rock and Soil Mechanics,2013,34(8):2 181-2 188.(in Chinese))
[17]刘忠玉,孙丽云,乐金朝,等.基于非Darcy渗流的饱和黏土一维固结理论[J].岩石力学与工程学报,2009,28(5):973-979.(LIUZhongyu,SUN Liyun,YUE Jinchao,et al.One-dimensional consolidation theory of saturated clay based on non-Darcy flow[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(5):973-979.(in Chinese))
[18]林鹏,许镇鸿,徐鹏,等.软土压缩过程中固结系数的研究[J].岩土力学,2003,24(1):106-108.(LIN Peng,XU Zhenhong,XUPeng,et al.Research on coefficient of consolidation of soft clay under compression[J].Rock and Soil Mechanics,2003,24(1):106-108.(in Chinese))
[19]CASAGRANDE A.The determination of the pre-consolidation load and its practical significance[C]//Proceedings of the 1st International Conference on Soil Mechanics.Harvard:[s.n.],1936:60-64.
[20]中华人民共和国行业标准编写组.SL 237-1999土工试验规程[S].北京:中国水利水电出版社,1999.(The Professional Standards Compilation Group of People?s Republic of China.SL 237-1999Specification of soil test[S].Beijing:China Water Power Press,1999.(in Chinese))
[2]DUNCAN J M.Limitations of conventional analysis of consolidation settlement[J].Journal of Geotechnical Engineering,ASCE,1993,119(9):1 333-l 359.
[3]MESRI G,TAVENAS F.Discussion on“Permeability and consolidation of normally consolidated soils”by Huang Y H and Drenevich V P[J].Journal of Geotechnical Engineering,Division,ASCE,1983,109(GT6):873-878.
[4]孙立强,闫澍旺,邱长林.考虑新近吹填土固结系数为变量的固结理论研究[J].岩土工程学报,2013,35(增1):313-316.(SUNLiqiang,YAN Shuwang,QIU Changlin.Consolidation theory considering coefficent of consolidation of hydraulic fill as variable[J].Chinese Journal of Geotechnical Engineering,2013,35(Supp.1):313-316.(in Chinese))
[5]章为民,顾行文,王芳.Terzaghi固结系数的试验反演分析[J].岩土工程学报,2016,38(增1):99-103.(ZHANG Weimin,GUXingwen,WANG Fang.Back analysis of Terzaghi consolidation coefficient[J].Chinese Journal of Geotechnical Engineering,2016,38(Supp.1):99-103.(in Chinese))
[6]庄迎春,刘世明,谢康和.萧山软黏土一维固结系数非线性研究[J].岩石力学与工程学报,2005,24(12):4 565-4 569.(ZHUANGYingchun,LIU Shiming,XIE Kanghe.Study on nonlinearity of one-dimensional consolidation coefficient of Xiaoshan clay[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(12):4 565-4 569.(in Chinese))
[7]GIBSON R E,ENGLISH G L,HUSSEY M J L.The theory of one dimensional consolidation of saturated clays:I Finite non-linear consolidation of thin homogeneous layer[J].Geotechnique,1967,17(2):261-273.
[8]谢新宇,朱向荣,谢康和,等.饱和土体一维大变形固结理论新进展[J].岩土工程学报,1997,19(4):30-38.(XIE Xinyu,ZHUXiangrong,XIE Kanghe,et al.New developments of one-dimensional large strain consolidation theories[J].Chinese Journal of Geotechnical Engineering,1997,19(4):30-38.(in Chinese))
[9]NEWLAND P L,ALLEY B H.A study of the consolidation characteristics of a clay[J].Geotechnique,1960,10(2):62-74.
[10]詹美礼,钱家欢,陈绪禄.软土流变特性试验及流变模型[J].岩土工程学报,1993,15(3):54-62.(ZHAN Meili,QIAN Jiahuan,CHENXulu.Tests on rheological behavior of soft soil and rheologic model[J].Chinese Journal of Geotechnical Engineering,1993,15(3):54-62.(in Chinese))
[11]DAVIS E H,RAYMOND G P.A non-linear theory of consolidation[J].Geotechnique,1965,15(2):161-173.
[12]LEKHA K R,KRISHNASWAMY N R,BASAK P.Consolidation of clays for variable permeability and compressibility[J].Journal of Geotechnical and Geoenvironmental Engineering,2003,129(11):1 001-1 009.
[13]POSKITT T J.The consolidation of saturated clay with variable permeability and compressibility[J].Geotechnique,1969,19(2):234-252.
[14]谢康和,郑辉,LEO C J.软黏土一维非线性大应变固结解析理论[J].岩土工程学报,2002,24(6):680-684.(XIE Kanghe,ZHENGHui,LEO C J.An analytical theory for 1-D nonlinear large strain consolidation of soft clay[J].Chinese Journal of Geotechnical Engineering,2002,24(6):680-684.(in Chinese))
[15]李传勋,徐超,谢康和.考虑非达西渗流和应力历史的土体非线性固结研究[J].岩土力学,2017,38(1):91-100.(LI Chuanxun,XU Chao,XIE Kanghe.Nonlinear consolidation of clayed soil considering non-Darcy flow and stress history[J].Rock and Soil Mechanics,2017,38(1):91-100.(in Chinese))
[16]李传勋,谢康和.基于非达西渗流的软土一维非线性固结半解析解[J].岩土力学,2013,34(8):2 181-2 188.(LI Chuanxun,XIEKanghe.Semi-analytical solution of one-dimensional nonlinear consolidation with non-Darcian flow[J].Rock and Soil Mechanics,2013,34(8):2 181-2 188.(in Chinese))
[17]刘忠玉,孙丽云,乐金朝,等.基于非Darcy渗流的饱和黏土一维固结理论[J].岩石力学与工程学报,2009,28(5):973-979.(LIUZhongyu,SUN Liyun,YUE Jinchao,et al.One-dimensional consolidation theory of saturated clay based on non-Darcy flow[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(5):973-979.(in Chinese))
[18]林鹏,许镇鸿,徐鹏,等.软土压缩过程中固结系数的研究[J].岩土力学,2003,24(1):106-108.(LIN Peng,XU Zhenhong,XUPeng,et al.Research on coefficient of consolidation of soft clay under compression[J].Rock and Soil Mechanics,2003,24(1):106-108.(in Chinese))
[19]CASAGRANDE A.The determination of the pre-consolidation load and its practical significance[C]//Proceedings of the 1st International Conference on Soil Mechanics.Harvard:[s.n.],1936:60-64.
[20]中华人民共和国行业标准编写组.SL 237-1999土工试验规程[S].北京:中国水利水电出版社,1999.(The Professional Standards Compilation Group of People?s Republic of China.SL 237-1999Specification of soil test[S].Beijing:China Water Power Press,1999.(in Chinese))