Theories and methods for undrained strength and deformation of saturated soils

SONG Erxiang

doi:10.11779/CJGE20241078

Volume 47 Issue 1

Turn off MathJax

Article Contents

Abstract

References

Chinese Journal of Geotechnical Engineering > 2025 > 47(1): 1-29. > DOI: 10.11779/CJGE20241078

SONG Erxiang. Theories and methods for undrained strength and deformation of saturated soils[J]. Chinese Journal of Geotechnical Engineering, 2025, 47(1): 1-29. DOI: 10.11779/CJGE20241078

Citation:

SONG Erxiang. Theories and methods for undrained strength and deformation of saturated soils[J]. Chinese Journal of Geotechnical Engineering, 2025, 47(1): 1-29. DOI: 10.11779/CJGE20241078

Citation:

SONG Erxiang. Theories and methods for undrained strength and deformation of saturated soils[J]. Chinese Journal of Geotechnical Engineering, 2025, 47(1): 1-29. DOI: 10.11779/CJGE20241078

PDF (2842 KB)

Theories and methods for undrained strength and deformation of saturated soils

SONG Erxiang

School of Civil Engineering, Tsinghua University, Beijing 100084, China

More Information

Received Date: October 27, 2024

Graphical Abstract

Abstract

Abstract

The calculation of undrained strength and deformation of saturated soils is a complex and difficult issue in geotechnical engineering, and there are still contradictory opinions regarding its many aspects. In this study, a systematic and in-depth exploration of this topic is carried out according to the author's years of relevant studies. Firstly, the total stress method and effective stress method for undrained analysis as well as their respective limitations are discussed. The treatment of pore water pressure is explained from the basic equation of finite elements, and it is pointed out that regardless of the method used, attention should be paid to distinguishing between the two types of the pore water pressures and those of the total stresses. Then, the accuracy of Skempton-Henkel's formula for calculating the excess pore pressure under different stress paths is examined, and then it is combined with the MC strength criterion to form an undrained strength model for saturated soils. The undrained strength characteristics of saturated soils under isotropic and anisotropic consolidations are analyzed, which can provide reference for the selection of strength parameters for engineering calculations. It is suggested that the generalized Tresca strength criterion should be used for practical undrained calculations. To prevent computation errors in undrained analysis using the MC criterion together with the effective stress method, a method of using the equivalent strength parameters is proposed, which is a better alternative to the direct inputting of the undrained strength. Based on the above discussions, the shortcomings of the consolidated undrained strength index (CU index) are analyzed, and it is pointed out that only when the total stress path in the soils is the same as that in the tests for determining the CU index, this index can be directly used for calculation to give accurate results. Especially for the calculation of bearing capacity of foundations, direct use of the CU index will give serious erroneous results. The drawbacks of using the CU index for calculating the active and passive soil water pressures in excavation engineering are analyzed, and the reasonable method and corresponding formula are proposed. The issue of the inclination angle of the sliding surface when the undrained ultimate soil pressures occur, puzzled to many, is also discussed in depth. Finally, regarding the calculation of bearing capacity and short-term settlements of saturated foundation, the deficiencies of the conventional methods are analyzed, and new methods are proposed based on the deep understanding of the influencing mechanisms of the relevant factors. The proposed formula for bearing capality can more accurately calculate the bearing capacity under both drained and undrained conditions, which can thus better ensure the safety and economy of the design. The new method for settlement can effectively calculate the short-term settlement of saturated soils, and also shows good prospective for drained conditions.
- saturated clay,
- undrained strength,
- excess pore water pressure,
- consolidated undrained strength parameter,
- bearing capacity,
- foundation settlement

FullText(HTML)

References (69)

References

[1]	李广信. 浅议土的复杂性[J]. 岩土工程学报, 2024, 46(5): 1085-1093. doi: 10.11779/CJGE20230188 LI Guangxin. On complexity of soil[J]. Chinese Journal of Geotechnical Engineering, 2024, 46(5): 1085-1093. (in Chinese) doi: 10.11779/CJGE20230188
[2]	建筑基坑支护技术规程: JGJ 120—2012[S]. 北京: 中国建筑工业出版社, 2012. Technical Specification for Retaining and Protection of Building Foundation Excavations: JGJ 120—2012[S]. Beijing: China Architecture & Building Press, 2012. (in Chinese)
[3]	基坑工程技术标准(上海市工程建设规范): DG/TJ 08—61—2018[S]. 上海: 同济大学出版社, 2018. Technical Code for Excavation Engineering. (Shanghai Code of Engineering Construction): DG/TJ 08—61—2018[S]. Shanghai: Tongji University Press, 2018. (in Chinese)
[4]	建筑地基基础设计规范: GB 50007—2011[S]. 北京: 中国建筑工业出版社, 2012. Code for Design of Building Foundation: GB 50007—2011[S]. Beijing: China Architecture & Building Press, 2012. (in Chinese)
[5]	SONG E X. Elasto-plastic consolidation under steady and cyclic loads[D]. Delft: Delft University of Technology, 1990.
[6]	宋二祥. 土力学理论与数值方法[M]. 北京: 中国建筑工业出版社, 2020. SONG Erxiang. Theory and Numerical Methods in Geomechanics[M]. Beijing: China Architecture & Building Press, 2020. (in Chinese)
[7]	宋二祥. 试论有效应力法与总应力法的应用[J]. 地基处理, 2001(1): 64-66. SONG Erxiang. On the application of effective stress method and total stress method[J]. Journal of Ground Improvement, 2001(1): 64-66. (in Chinese)
[8]	宋二祥, 付浩, 林世杰, 等. 饱和黏性土不排水分析中总应力强度指标的选用[J]. 土木工程学报, 2021, 54(9): 88-95. SONG Erxiang, FU Hao, LIN Shijie, et al. Discussion on the choice of strength parameters for the analysis of saturated clay under undrained conditions[J]. China Civil Engineering Journal, 2021, 54(9): 88-95. (in Chinese)
[9]	NAYLOR D J. Stresses in nearly incompressible materials by finite elements with application to the calculation of excess pore pressures[J]. International Journal for Numerical Methods in Engineering, 1974, 8(3): 443-460. doi: 10.1002/nme.1620080302
[10]	BRINKGREVE R B J, KUMARSWAMY S, SWOLFS W M. PLAXIS Manual 2016[R]. Delft: PLAXIS bv, 2016.
[11]	ROWE P W. The stress-dilatancy relation for static equilibrium of an assembly of particles in contact[J]. Proceedings of the Royal Society of London Series A, 1962, 269(1339): 500-527.
[12]	SKEMPTON A W. The pore-pressure coefficients A and B[J]. Géotechnique, 1954, 4(4): 143-147. doi: 10.1680/geot.1954.4.4.143
[13]	SKEMPTON A W. The pore-pressure coefficient in saturated soils[J]. Géotechnique, 1960, 10(4): 186-187. doi: 10.1680/geot.1960.10.4.186
[14]	HENKEL D J. The relationships between the strength, pore-water pressure, and volume-change characteristics of saturated clays[J]. Géotechnique, 1959, 9(3): 119-135. doi: 10.1680/geot.1959.9.3.119
[15]	HENKEL D J. The shear strength of saturated remolded clays[C]// Proceedings of Research Conference on Shear Strength of Cohesive Soils. Boulder, 1960.
[16]	HENKEL D J. The relationships between the effective stresses and water content in saturated clays[J]. Géotechnique, 1960, 10(2): 41-54. doi: 10.1680/geot.1960.10.2.41
[17]	SCHOFIELD A, WROTH P. Critical State Soil Mechanics[M]. New York: McGraw-Hill Book Company Limited, 1968.
[18]	沈珠江. 饱和黏土抗剪强度的变化规律及其在土工建筑稳定分析中的应用[J]. 土木工程学报, 1963(2): 29-36. SHEN Zhujiang. Variation law of shear strength of saturated clay and its application in stability analysis of geotechnical buildings[J]. China Civil Engineering Journal, 1963(2): 29-36. (in Chinese)
[19]	沈珠江. 软土工程特性和软土地基设计[J]. 岩土工程学报, 1998, 20(1): 100-111. http://cge.nhri.cn/article/id/10084 SHEN Zhujiang. Engineering properties of soft soils and design of soft ground[J]. Chinese Journal of Geotechnical Engineering, 1998, 20(1): 100-111. (in Chinese) http://cge.nhri.cn/article/id/10084
[20]	沈珠江. 理论土力学[M]. 北京: 中国水利水电出版社, 2000. SHEN Zhujiang. Theoretical Soil Mechanics[M]. Beijing: China Water & Power Press, 2000. (in Chinese)
[21]	李广信. 高等土力学[M]. 北京: 清华大学出版社, 2004. LI Guangxin. Advanced Soil Mechanics[M]. Beijing: Tsinghua University Press, 2004. (in Chinese)
[22]	黄茂松, 姚仰平, 尹振宇, 等. 土的基本特性及本构关系与强度理论[J]. 土木工程学报, 2016, 49(7): 9-35. HUANG Maosong, YAO Yangping, YIN Zhenyu, et al. An overview on elementary mechanical behaviors, constitutive modeling and failure criterion of soils[J]. China Civil Engineering Journal, 2016, 49(7): 9-35. (in Chinese)
[23]	KNAPPETT J, CRAIG R F. Craig's Soil Mechanics[M]. Boca Raton: CRC Press, 2019.
[24]	王立忠, 叶盛华, 沈恺伦, 等. K₀固结软土不排水抗剪强度[J]. 岩土工程学报, 2006, 28(8): 970-977. http://cge.nhri.cn/article/id/12136 WANG Lizhong, YE Shenghua, SHEN Kailun, et al. Undrained shear strength of K₀ consolidated soft clays[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(8): 970-977. (in Chinese) http://cge.nhri.cn/article/id/12136
[25]	王秋生. K₀固结软黏土的临界不排水强度研究[J]. 岩土力学, 2008, 29(12): 3179-3185. WANG Qiusheng. Research on critical undrained strength of K₀ consolidated soft clays[J]. Rock and Soil Mechanics, 2008, 29(12): 3179-3185. (in Chinese)
[26]	黄茂松, 李弈杉, 唐震, 等. 基于不排水强度的黏土基坑抗隆起稳定计算方法[J]. 岩土工程学报, 2020, 42(9): 1577-1585. doi: 10.11779/CJGE202009001 HUANG Maosong, LI Yishan, TANG Zhen, et al. Analysis method for basal stability of braced excavations in clay based on undrained shear strength[J]. Chinese Journal of Geotechnical Engineering, 2020, 42(9): 1577-1585. (in Chinese) doi: 10.11779/CJGE202009001
[27]	陈志辉, 程晓辉. 饱和黏土不排水抗剪强度各向异性的热力学本构模型研究[J]. 岩土工程学报, 2014, 36(5): 836-846. doi: 10.11779/CJGE201405005 CHEN Zhihui, CHENG Xiaohui. Thermodynamic constitutive model for anisotropic undrained shear strength of saturated clays[J]. Chinese Journal of Geotechnical Engineering, 2014, 36(5): 836-846. (in Chinese) doi: 10.11779/CJGE201405005
[28]	KRABBENHOFT K, LYAMIN A V. Generalised Tresca criterion for undrained total stress analysis[J]. Géotechnique Letters, 2015, 5(4): 313-317. doi: 10.1680/jgele.15.00120
[29]	宋二祥, 付浩, 林世杰, 等. 用MC模型实现固结不排水计算的一种巧妙方法: CN117034692A[P]. 2023-11-10. SONG Erxiang, FU Hao, LIN Shijie, et al. A Noval Method for Consolidated Undrained Calculation by Using MC Model: CN117034692A[P]. 2023-11-10. (in Chinese)
[30]	DAS B M. Advanced Soil Mechanics[M]. 5th ed. Boca Raton: Taylor & Francis, 2019.
[31]	BURLAND J B, CHAPMAN T. ICE Manual of Geotechnical Engineering[M]. London: ICE, 2012.
[32]	KRABBENHOFT K. OPTUM G2: Theory[M]. Copenhagen NV Denmark: Optum Computational Engineering, 2019.
[33]	李广信, 张丙印, 于玉贞. 土力学[M]. 2版. 北京: 清华大学出版社, 2013. LI Guangxin, ZHANG Bingyin, YU Yuzhen. Soil Mechanics[M]. 2nd ed. Beijing: Tsinghua University Press, 2013. (in Chinese)
[34]	罗嗣海, 龚晓南, 史光金. 固结应力和应力路径对黏性土固结不排水剪总应力强度指标的影响[J]. 工程勘察, 1998, 26(6): 5-8. LUO Sihai, GONG Xiaonan, SHI Guangjin. Influence of consolidation stress and stress path on total stress intensity index of cohesive soil with consolidated undrained shear[J]. Geotechnical Investigation & Surveying, 1998, 26(6): 5-8. (in Chinese)
[35]	LADD C C. Stability evaluation during staged construction[J]. Journal of Geotechnical Engineering, 1991, 117(4): 540-615. doi: 10.1061/(ASCE)0733-9410(1991)117:4(540)
[36]	沈珠江. 基于有效固结应力理论的黏土土压力公式[J]. 岩土工程学报, 2000, 22(3): 353-356. http://cge.nhri.cn/article/id/10517 SHEN Zhujiang. Earth pressure of clay based on effective consolidation stress theory[J]. Chinese Journal of Geotechnical Engineering, 2000, 22(3): 353-356. (in Chinese) http://cge.nhri.cn/article/id/10517
[37]	陈祖煜. 深基坑稳定分析中几个问题的讨论[J]. 岩土工程学报, 2010, 32(S1): 1-8. http://qikan.cqvip.com/Qikan/Article/Detail?id=3000037122 CHEN Zuyu. Discussion on several problems in deep foundation pit engineering[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(S1): 1-8. (in Chinese) http://qikan.cqvip.com/Qikan/Article/Detail?id=3000037122
[38]	黄茂松. 土体稳定与承载特性的分析方法[J]. 岩土工程学报, 2016, 38(1): 1-34. doi: 10.11779/CJGE201601001 HUANG Maosong. Analysis methods for stability and bearing capacity of soils[J]. Chinese Journal of Geotechnical Engineering, 2016, 38(1): 1-34. (in Chinese) doi: 10.11779/CJGE201601001
[39]	李广信. 有效自重压力下预固结的三轴不排水试验[J]. 工程勘察, 2010, 38(12): 1-4. LI Guangxin. Undrained triaxial tests with pre-consolidation under effective overburden pressures[J]. Geotechnical Investigation & Surveying, 2010, 38(12): 1-4. (in Chinese)
[40]	魏汝龙, 张凌. 稳定分析中的强度指标问题[J]. 岩土工程学报, 1993, 15(5): 24-30. http://cge.nhri.cn/article/id/9705 WEI Rulong, ZHANG Ling. Strength parameters in stability analysis[J]. Chinese Journal of Geotechnical Engineering, 1993, 15(5): 24-30. (in Chinese) http://cge.nhri.cn/article/id/9705
[41]	张在明. 关于地基承载力问题的分析[J]. 工程勘察, 1995, 23(2): 1-7. ZHANG Zaiming. Analysis of foundation bearing capacity[J]. Geotechnical Investigation & Surveying, 1995, 23(2): 1-7. (in Chinese)
[42]	北京地区建筑地基基础勘察设计规范(2016版): DBJ 11-501-2009[S]. 中国计划出版社, 2017. Code for Geotechnical Investigation and Design of Building Foundations in Beijing area: DBJ 11-501-2009[S]. Beijing: China Planning Press, 2017. (in Chinese)
[43]	天津市岩土工程技术规范: DB/T 29-20-2017[S]. 北京: 中国建材工业出版社, 2017. Tianjin Technical code for geotechnical engineering (Tianjin Code of Engineering Construction): DB/T 29-20-2017[S]. Beijing: China Building Materials Press, 2017 (in Chinese)
[44]	魏汝龙. 总应力法计算土压力的几个问题[J]. 岩土工程学报, 1995, 17(6): 120-125. http://cge.nhri.cn/article/id/9923 WEI Rulong. Some problems of tolal stress method for calculating earth pressures[J]. Chinese Journal of Geotechnical Engineering, 1995, 17(6): 120-125. (in Chinese) http://cge.nhri.cn/article/id/9923
[45]	李广信. 基坑支护结构上水土压力的分算与合算[J]. 岩土工程学报, 2000, 22(3): 348-352. http://cge.nhri.cn/article/id/10516 LI Guangxin. Estimating the water and earth pressures on the supporting structure around a foundation pit separately and together[J]. Chinese Journal of Geotechnical Engineering, 2000, 22(3): 348-352. (in Chinese) http://cge.nhri.cn/article/id/10516
[46]	李广信. 对与基坑工程有关的一些规范的讨论(3)[J]. 工程勘察, 2013, 41(11): 1-4. LI Guangxin. Discussion on some codes concerned with building foundation pit (Part 3)[J]. Geotechnical Investigation & Surveying, 2013, 41(11): 1-4. (in Chinese)
[47]	杨晓军, 龚晓南. 基坑开挖中考虑水压力的土压力计算[J]. 土木工程学报, 1997, 30(4): 58-62. YANG Xiaojun, GONG Xiaonan. Calculation of earth pressure on excavation considering pore water pressure[J]. China Civil Engineering Journal, 1997, 30(4): 58-62. (in Chinese)
[48]	魏汝龙. 开挖卸载与被动土压力计算[J]. 岩土工程学报, 1997, 19(6): 88-92. http://cge.nhri.cn/article/id/10048 WEI Rulong. Unloading and passive earch pressure calculation during excavation[J]. Chinese Journal of Geotechnical Engineering, 1997, 19(6): 88-92. (in Chinese) http://cge.nhri.cn/article/id/10048
[49]	英国土木工程师学会. 岩土工程手册[M]. 高文生, 译. 北京: 中国建筑工业出版社, 2023. ICE. Manual of Geotechnical[M]. GAO Wensheng, trans. Beijing: China Architecture and Building Press, 2023. (in Chinese)
[50]	宋二祥, 付浩, 李贤杰. 基坑坑底抗隆起稳定安全系数计算方法改进研究[J]. 土木工程学报, 2021, 54(3): 109-118. SONG Erxiang, FU Hao, LI Xianjie. Improvement of calculation method for safety factor of basal heave stability of deep excavation[J]. China Civil Engineering Journal, 2021, 54(3): 109-118. (in Chinese)
[51]	宋二祥, 付浩, 李贤杰, 等. 饱和黏性地层中基坑坑底抗隆起稳定验算方法[J]. 土木工程学报, 2021, 54(10): 97-105. SONG Erxiang, FU Hao, LI Xianjie, et al. Checking method for basal heave stability of deep excavation in saturated cohesive soil[J]. China Civil Engineering Journal, 2021, 54(10): 97-105. (in Chinese)
[52]	DAVIS E H, BOOKER J R. The effect of increasing strength with depth on the bearing capacity of clays[J]. Géotechnique, 1973, 23(4): 551-563.
[53]	郑颖人, 龚晓南. 岩土塑性力学基础[M]. 北京: 中国建筑工业出版社, 1989. ZHENG Yingren, GONG Xiaonan. Foundations of Geotechnical Mechanics[M]. Beijing: China Architecture & Building Press, 1989. (in Chinese)
[54]	谭凡, 黄斌, 饶锡保, 等. 关于三轴试验破裂角的试验论证与探讨[J]. 西北地震学报, 2011, 33(增刊): 181-184. TAN Fan, HUANG Bin, RAO Xibao, et al. Experimental proof and discussion on rupture angle of triaxial test[J]. Northwestern Seismological Journal, 2011, 33(S0): 181-184. (in Chinese)
[55]	APOLLONIA G. Advanced Laboratory Characterisation of London Clay[D]. London, UK: Imperial College London, 2005.
[56]	KARL T. Theoretical Soil Mechanics[M]. New York: Wiley, 1943.
[57]	HANSEN J B. A general formula for bearing capacity[J]. Danish Geotechnical Institute, 1961(11): 38-46.
[58]	宋二祥, 付浩, 李贤杰. 地基承载力机理及新计算方法[J]. 岩土工程学报, 2022, 44(1): 37-44. doi: 10.11779/CJGE202201002 SONG Erxiang, FU Hao, LI Xianjie. Mechanism and new calculation method for bearing capacity of foundations[J]. Chinese Journal of Geotechnical Engineering, 2022, 44(1): 37-44. (in Chinese) doi: 10.11779/CJGE202201002
[59]	宋二祥, 付浩, 李贤杰. 饱和黏性土地基不排水条件下承载力计算方法[J]. 岩土力学, 2021, 42(11): 2919-2924, 2952. SONG Erxiang, FU Hao, LI Xianjie. A calculation method for the bearing capacity of saturated soil under undrained conditions[J]. Rock and Soil Mechanics, 2021, 42(11): 2919-2924, 2952. (in Chinese)
[60]	MEYERHOF G G. Some recent research on the bearing capacity of foundations[J]. Canadian Geotechnical Journal, 1963, 1(1): 16-26.
[61]	宋二祥, 陈星屹, 林世杰. 关于偏心荷载下地基承载力的验算方法[J]. 岩土力学, 2022, 43(7): 1925-1932. SONG Erxiang, CHEN Xingyi, LIN Shijie. On the checking methods for bearing capacity of foundation under eccentric loading[J]. Rock and Soil Mechanics, 2022, 43(7): 1925-1932. (in Chinese)
[62]	建筑地基处理技术规范: JGJ 79—2012[S]. 北京: 中国建筑工业出版社, 2013. Technical Code for Ground Treatment of Buildings: JGJ 79—2012[S]. Beijing: China Architecture & Building Press, 2013. (in Chinese)
[63]	黄熙龄. 地基基础的设计与计算[M]. 北京: 中国建筑工业出版社, 1981. HUANG Xiling. Design and Calculation of Foundations[M]. Beijing: China Architecture & Building Press, 1981. (in Chinese)
[64]	郭忠, 宋二祥, 林世杰, 等. 大型设备吊装换填地基承载特性的数值分析[J]. 工业建筑, 2022, 52(7): 137-144, 214. GUO Zhong, SONG Erxiang, LIN Shijie, et al. Numerical analysis for bearing characteristics of large-equipment hoisting foundation[J]. Industrial Construction, 2022, 52(7): 137-144, 214. (in Chinese)
[65]	地基基础设计标准(上海市工程建设规范): DGJ 08-11-2018[S]. 上海: 同济大学出版社, 2019. Foundation Design Code: DGJ 08-11-2018[S]. Shanghai: Tongji University Press, 2018. (in Chinese)
[66]	杨光华. 现代地基设计理论的创新与发展[J]. 岩土工程学报, 2021, 43(1): 1-18. doi: 10.11779/CJGE202101001 YANG Guanghua. Innovation and development of modern theories for foundation design[J]. Chinese Journal of Geotechnical Engineering, 2021, 43(1): 1-18. (in Chinese) doi: 10.11779/CJGE202101001
[67]	刘光磊, 宋二祥. 饱和无限地基数值模拟的黏弹性传输边界[J]. 岩土工程学报, 2006, 28(12): 2128-2133. http://cge.nhri.cn/article/id/12250 LIU Guanglei, SONG Erxiang. Visco-elastic transmitting boundary for numerical analysis of infinite saturated soil foundation[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(12): 2128-2133. (in Chinese) http://cge.nhri.cn/article/id/12250
[68]	POULOS H G, DAVIS E H. Elastic Solution for Soil and Rock Mechanics[M]. Center for Geotechnical Research, University of Sydney, 1991.
[69]	顾晓强, 吴瑞拓, 梁发云, 等. 上海土体小应变硬化模型整套参数取值方法及工程验证[J]. 岩土力学, 2021, 42(3): 833-845. GU Xiaoqiang, WU Ruituo, LIANG Fayun, et al. On HSS model parameters for Shanghai soils with engineering verification[J]. Rock and Soil Mechanics, 2021, 42(3): 833-845. (in Chinese)