不同排水条件下软黏土蠕变特性及长期强度指标确定方法研究

Study on Creep Characteristics of Soft Clay and Determination Method for Its Long-Term Strength Indicator Under Different Drainage Conditions

摘要

在工程研究领域,软黏土的蠕变行为及其长期强度的评估是岩土工程中的关键问题．本文以天津滨海黏土为研究对象,开展了不同应力水平、围压及排水条件下的三轴蠕变试验,分析了排水条件对土体蠕变特性和长期强度的影响,并对现有土体长期强度的判定方法进行了探讨和改进,提出了一种基于应力-应变等时曲线确定长期抗剪强度指标的新方法,通过对比分析验证其有效性与合理性．研究结果表明：在相同围压条件下,蠕变量及变形稳定时间随应力水平的提高而增加；在相同应力水平下,各应力水平下蠕变量随围压的增加而降低；在不同排水条件下,蠕变变形具有显著差异；土体蠕变过程中,排水条件是影响土体抗剪强度及强度指标的重要因素．在固结不排水蠕变条件下,长期抗剪强度τ_∞约为瞬时抗剪强度τ₀的84%～93%,其中黏聚力衰减明显,长期黏聚力值c_∞约为瞬时黏聚力值c₀的37%,内摩擦角变化相对较小．在固结排水蠕变条件下,长期抗剪强度τ_∞约为瞬时抗剪强度τ₀的106%～116%,其中黏聚力降低幅度较小,而内摩擦角显著提高,长期内摩擦角φ_∞约为瞬时内摩擦角φ₀的110%. 本文研究成果可为滨海软土地区土体长期稳定性分析和工程设计提供参考．

Abstract

In the field of engineering research, the creep behavior of soft clay and the evaluation of its long-term strength are crucial issues in geotechnical engineering. In this paper, the influence of drainage conditions on the creep characteristics and long-term strength of Tianjin coastal clay were analyzed through triaxial creep tests conducted under various stress levels, confining pressures and drainage conditions. The existing methods for determining the long-term strength of soil were discussed and improved, and a novel approach based on stress-strain isochronous curves was proposed to assess the long-term shear strength indicators of the soil. The proposed method was validated through comparative analysis, demonstrating its effectiveness and rationality in practical applications. Results indicate that under the same confining pressure conditions, the creep amount and deformation stability time increase with an increase in the stress level. At the same stress level, the creep amount at each stress level decreases with an increase in the confining pressure. The creep deformation difference is significant under different drainage conditions. During the process of soil creep, the drainage condition is an important factor affecting the shear strength and strength indicators of soil. Under consolidated and undrained creep conditions, the long-term shear strength τ_∞ is about 84% to 93% of the instantaneous shear strength τ₀, among which the cohesion decreases significantly, and the long-term cohesion c_∞ is about 37% of the instantaneous cohesion c₀. Meanwhile, the internal friction angle remains relatively unchanged. Under consolidated and drained creep conditions, the long-term shear strength τ_∞ is about 106% to 116% of the instantaneous shear strength τ₀, with only a minor reduction in cohesion and a significant increase in the internal friction angle. In addition, the long-term internal friction angle φ_∞ is about 110% of the instantaneous internal friction angle φ₀. The research results can provide a reference for the long-term stability analysis and engineering design of soil in coastal soft soil areas.

关键词

软黏土 / 蠕变特性 / 长期强度 / 长期强度指标 / 等时曲线

Key words

soft clay / creep behavior / long-term strength / long-term strength indicator / isochronous curve

参考文献

[1] 殷宗泽. 土工原理[M]. 北京： 中国水利水电出版社, 2007.

[2] Yin Zongze. Principles of Earth Engineering[M]. Beijing: China Water and Power Press, 2007(in Chinese).

[3] Augustesen A, Liingaard M, Lade P V. Evaluation of time—dependent behavior of soils[J]. International Journal of Geomechanics, 2004, 4(3): 137-156.

[4] 李军世, 林咏梅. 上海淤泥质粉质黏土的 Singh—Mitchell 蠕变模型[J]. 岩土力学, 2000, 21(4): 363-366.

[5] Li Junshi, Lin Yongmei. Singh—Mitchell creep model of Shanghai very soft silt clay[J]. Rock and Soil Mechanics, 2000, 21(4): 363-366(in Chinese).

[6] 雷华阳, 贾亚芳, 李肖. 滨海软土非线性蠕变特性的试验研究[J]. 岩石力学与工程学报, 2013, 32(增1): 2806-2816.

[7] Lei Huayang, Jia Yafang, Li Xiao. Experimental study of nonlinear creep property of soft soil in littoral area[J]. Chinese Journal of Rock Mechanics and Engineering, 2013, 32(Suppl 1): 2806-2816(in Chinese).

[8] 王元战, 黄东旭, 肖忠. 天津滨海地区两种典型软黏土蠕变特性试验研究[J]. 岩土工程学报, 2012, 34(2): 379-384.

[9] Wang Yuanzhan, Huang Dongxu, Xiao Zhong. Experimental research on creep properties of two typical soft clays in coastal region of Tianjin[J]. Chinese Journal of Geotechnical Engineering, 2012, 34(2): 379-384(in Chinese).

[10] 袁宇, 刘润, 邱长林, 等. 与应力相关的软土蠕变本构模型的建立和应用[J]. 天津大学学报(自然科学与工程技术版), 2018, 51(7): 711-719.

[11] Yuan Yu, Liu Run, Qiu Changlin, et al. Establishment and application of creep constitutive model related to stress level of soft soil[J]. Journal of Tianjin University(Science and Technology), 2018, 51(7): 711-719(in Chinese).

[12] Deng H, Dai G L, Azadi M R, et al. Drained creep test and creep model evaluation of coastal soft clay[J]. Indian Geotechnical Journal, 2021, 51(6): 1283-1298.

[13] 董卫军. 软土流变特性室内试验研究及长期强度的确定[D]. 南京： 河海大学土木工程学院, 2007.

[14] Dong Weijun. Study on the Laboratory Test of Rheological Characteristic of Soft Clay and Long—term Strength[D]. Nanjing: College of Civil Engineering, Hohai University, 2007(in Chinese).

[15] 陈宗基. 地下巷道长期稳定性的力学问题[J]. 岩石力学与工程学报, 1982, 1(1): 1-20.

[16] Tan Tjongkie. The mechanical problems for the long—term stability of underground galleries[J]. Chinese Journal of Rock Mechanics and Engineering, 1982, 1(1): 1-20(in Chinese).

[17] 刘克瑾. 天津滨海新区新近吹填软黏土的流变特性及非线性流变本构模型研究[D]. 天津： 天津大学建筑工程学院, 2010.

[18] Liu Kejin. Rheological Property and Non—linear Rheological Constitutive Model Study of Recently Reclaimed Soft Clay in Tianjin Binhai New Area[D]. Tianjin: School of Civil Engineering, Tianjin University, 2010(in Chinese).

[19] Tran T T T, Hazarika H, Indrawan I G B, et al. Prediction of time to soil failure based on creep strength reduction approach[J]. Geotechnical and Geological Engineering, 2018, 36(4): 2749-2760.

[20] 杨爱武, 张静, 肖敏. 基于不同结构强度软黏土长期强度特性研究[J]. 自然灾害学报, 2019, 28(2): 109-117.

[21] Yang Aiwu, Zhang Jing, Xiao Min. Study on the long—term strength characteristics of soft clay with different structural strength[J]. Journal of Natural Disasters, 2019, 28(2): 109-117(in Chinese).

[22] 杨爱武, 杨少坤, 梁超, 等. 吹填泥浆固化土蠕变及长期强度特性研究[J]. 自然灾害学报, 2020, 29(3): 28-35.

[23] Yang Aiwu, Yang Shaokun, Liang Chao, et al. Research on creep and long—term strength characteristics of solidified dredger mud[J]. Journal of Natural Disasters, 2020, 29(3): 28-35(in Chinese).

[24] 何仕娟, 王志良, 瞿嘉安, 等. 昆明泥炭土直剪蠕变特性及长期强度试验研究[J]. 土木工程学报, 2019, 52(增1): 16-22.

[25] He Shijuan, Wang Zhiliang, Qu Jia’an, et al. Experimental study on direct shear creep characteristics and long—term strength of peaty soil in Kunming[J]. China Civil Engineering Journal, 2019, 52(Suppl 1): 16-22(in Chinese).

[26] 吴谦. 软黏土的结合水对其次固结和长期强度的影响及机理研究[D]. 长春： 吉林大学建设工程学院, 2015.

[27] Wu Qian. Research on Influence of Bond Water on Secondary Consolidation and Long Term Strength of Soft Clay[D]. Changchun: College of Construction, Jilin University, 2015(in Chinese).

[28] GB/T 50123—2019 土工试验方法标准[S]. 北京： 中国计划出版社, 2019.

[29] GB/T 50123—2019 Standard for Geotechnical Testing Method[S]. Beijing: China Planning Press, 2019(in Chinese).

[30] 陈宗基, 康文法. 岩石的封闭应力、蠕变和扩容及本构方程[J]. 岩石力学与工程学报, 1991, 10(4): 299-312.

[31] Tan Tjongkie, Kang Wenfan. On the locked in stress, creep and dilatation of rocks, and the constitutive equations[J]. Chinese Journal of Rock Mechanics and Engineering, 1991, 10(4): 299-312(in Chinese).

[32] 杨果岳, 徐运龙, 李良吉, 等. 压实红黏土三轴蠕变特性试验及模型研究[J]. 地下空间与工程学报, 2019, 15(3): 727-735.

[33] Yang Guoyue, Xu Yunlong, Li Liangji, et al. Research on triaxial creep characteristics test and models of compacted red clay[J]. Chinese Journal of Underground Space and Engineering, 2019, 15(3): 727-735(in Chinese).

[34] 张浴阳, 巨能攀, 周新. 倾倒变形边坡层间破碎带土体三轴蠕变试验研究[J]. 科学技术与工程, 2016, 16(1): 232-236.

[35] Zhang Yuyang, Ju Nengpan, Zhou Xin. Study of triaxial creep tests of soil from fracture zone between the slope layer in toppling rock slope[J]. Science Technology and Engineering, 2016, 16(1): 232-236(in Chinese).

[36] 陈昌富, 朱世民, 毛凤山, 等. 红黏土固结—蠕变特性及其耦合模型[J]. 工程地质学报, 2019, 27(4): 723-728.

[37] Chen Changfu, Zhu Shimin, Mao Fengshan, et al. Characterization and modelling of coupled consolidation—creep behavior of red clay[J]. Journal of Engineering Geology, 2019, 27(4): 723-728(in Chinese).

[38] 孙淼军, 唐辉明, 王潇弘, 等. 蠕动型滑坡滑带土蠕变特性研究[J]. 岩土力学, 2017, 38(2): 385—391, 399.

[39] Sun Miaojun, Tang Huiming, Wang Xiaohong, et al. Creep propertiess of sliding—zone soil from a creeping landslide[J]. Rock and Soil Mechanics, 2017, 38(2): 385—391, 399(in Chinese).

[40] SL/T 264—2020 水利水电工程岩石试验规程[S]. 北京： 中国水利水电出版社, 2020.

[41] SL/T 264—2020 Code for Rock Tests in Water and Hydropower Projects[S]. Beijing: China Water and Power Press, 2020(in Chinese).

[42] 董建国, 袁聚云. 基坑设计考虑黏性土变形局部化的探讨[J]. 岩土工程学报, 2006, 28(增1): 1383-1386.

[43] Dong Jianguo, Yuan Juyun. Studies on design method of excavation considering clay localization[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(Suppl 1): 1383-1386(in Chinese).

[44] 朱鸿鹄, 陈晓平, 程小俊, 等. 考虑排水条件的软土蠕变特性及模型研究[J]. 岩土力学, 2006, 27(5): 694-698.

[45] Zhu Honghu, Chen Xiaoping, Cheng Xiaojun, et al. Study on creep characteristics and model of soft soil considering drainage conditions[J]. Rock and Soil Mechanics, 2006, 27(5): 694-698(in Chinese).

[46] 杨超, 戴国亮, 龚维明, 等. 望江地区典型淤泥质粉质黏土蠕变特性试验研究[J]. 土木工程学报, 2015, 48(增2): 47-52.

[47] Yang Chao, Dai Guoliang, Gong Weiming, et al. Experimental research on creep properties of typical mucky silty in region of Wangjiang[J]. China Civil Engineering Journal, 2015, 48(Suppl 2): 47-52(in Chinese).

[48] JTS 147—2017 水运工程地基设计规范[S]. 北京： 人民交通出版社, 2018.

[49] JTS 147—2017 Code for Foundation Design on Port and Waterway Engineering[S]. Beijing: China Communication Press, 2018(in Chinese).

[50] ISO/DIS 19901—4 Petroleum and Natural Gas Industries—Specific Requirements for Offshore Structures—Part 4: Geotechnical Design Considerations[S]. Geneva: ISO, 2022.

基金资助

国家重点研发计划资助项目(2022YFB2603000)