模拟干湿循环及含低围压条件的膨胀土三轴试验
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摘要
针对膨胀土边坡坍滑多呈浅层性,取广西百色膨胀土为对象,设计并开展经干湿循环作用含低围压条件的重塑土饱和三轴固结排水试验,着重分析橡皮膜约束对围压的影响并做出校正,对比分析校正前、后的实测抗剪强度参数,探究不同干湿循环次数及试验围压下的强度及应力-应变关系。结果表明:经干湿循环作用,各级围压下试件的应力-应变均呈应变硬化特征;围压越大,初始模量越大,主应力差也越大;干湿循环作用下,橡皮膜约束等效围压σ_(3e)均随试验围压σ_3增大而减小;0次干湿循环下,σ_3由5 kPa增至200 kPa时,σ_(3e)从9.1 kPa减少至6.7 kPa,σ_(3e)/σ_3由181.8%减少至3.4%,橡皮膜约束对低围压的测试结果影响显著,须进行校正;干湿循环由0次增至6次,校正前低、高和全围压段的黏聚力分别衰减34.7%、27.7%和28.3%,校正后衰减达77.1%、31.9%和35.6%,但摩擦角变化小;橡皮膜约束影响后,经6次干湿循环作用,低围压段的黏聚力仅为0.8 kPa,趋于0,摩擦角为18.5°;膨胀土边坡稳定性分析时,宜采用低、高围压两段拟合校正围压应力圆的强度参数,以获得与实际坍滑破坏较吻合的计算结果。
According to the occurrence of shallow failure of most expansive soil slopes, consolidated drained triaxial compression tests on saturated Baise remolded expansive soil were carried out, considering the wet-dry cycles and low confining pressures. The influence of rubber membrane confinement on the confining pressure was analyzed and correction was made. The shear strength parameters measured before and after correction were compared. The strength and stress-strain relationship under different wet-dry cycles and experimental confining pressure were investigated. The results show that stress-strain relationships at all levels of confining pressures due to wet-dry cycles have a strain hardening characteristic. The greater the confining pressure, the greater the initial modulus and principal stress difference. Under the action of wet-dry cycle, the equivalent confining pressure of the rubber membrane σ_(3 e) decreases with the increase in experimental confining pressure σ_3. In the zero wet-dry cycle, when σ_3 increases from 5 kPa to 200 kPa, the σ_(3 e) decreases from 9.1 kPa to 6.7 kPa, and σ_(3 e)/σ_3 decreases from 181.8% to 3.4%. The rubber membrane constraints significantly influence the low confining pressure test results, and correction should be made. When the wet-dry cycle increases from zero times to six times, the cohesion values of low, high, and all confining pressure segments without correction attenuate by 34.7%, 27.7% and 28.3%, while those after correction attenuate by 77.1%, 31.9% and 35.6%, respectively. However, the change in friction angle is small. Considering the influence of the rubber membrane constraint under the action of six dry-wet cycles, the corrected cohesive force value of the low confining pressure segment is only 0.8 kPa tending to zero, and the value of friction angle is 18.5. When analyzing the stability of expansive soil slope, the strength parameters obtained from the confining pressure stress circle fitted by two segments of low and high confining pressure should be used to obtain the calculation results in consistent with the actual collapse failure.
According to the occurrence of shallow failure of most expansive soil slopes, consolidated drained triaxial compression tests on saturated Baise remolded expansive soil were carried out, considering the wet-dry cycles and low confining pressures. The influence of rubber membrane confinement on the confining pressure was analyzed and correction was made. The shear strength parameters measured before and after correction were compared. The strength and stress-strain relationship under different wet-dry cycles and experimental confining pressure were investigated. The results show that stress-strain relationships at all levels of confining pressures due to wet-dry cycles have a strain hardening characteristic. The greater the confining pressure, the greater the initial modulus and principal stress difference. Under the action of wet-dry cycle, the equivalent confining pressure of the rubber membrane σ_(3 e) decreases with the increase in experimental confining pressure σ_3. In the zero wet-dry cycle, when σ_3 increases from 5 kPa to 200 kPa, the σ_(3 e) decreases from 9.1 kPa to 6.7 kPa, and σ_(3 e)/σ_3 decreases from 181.8% to 3.4%. The rubber membrane constraints significantly influence the low confining pressure test results, and correction should be made. When the wet-dry cycle increases from zero times to six times, the cohesion values of low, high, and all confining pressure segments without correction attenuate by 34.7%, 27.7% and 28.3%, while those after correction attenuate by 77.1%, 31.9% and 35.6%, respectively. However, the change in friction angle is small. Considering the influence of the rubber membrane constraint under the action of six dry-wet cycles, the corrected cohesive force value of the low confining pressure segment is only 0.8 kPa tending to zero, and the value of friction angle is 18.5. When analyzing the stability of expansive soil slope, the strength parameters obtained from the confining pressure stress circle fitted by two segments of low and high confining pressure should be used to obtain the calculation results in consistent with the actual collapse failure.
引文
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[11] 刘华强,殷宗泽.裂缝对膨胀土抗剪强度指标影响的试验研究[J].岩土力学,2010,31(3):727-731. LIU Hua-qiang, YIN Zong-ze. Test Study of Influence of Crack Evolution on Strength Parameters of Expansive Soil [J]. Rock and Soil Mechanics, 2010, 31 (3): 727-731.
[12] 赵鑫,阳云华,朱瑛洁,等.裂隙面对强膨胀土抗剪强度影响分析[J].岩土力学,2014,35(1):130-133. ZHAO Xin, YANG Yun-hua, ZHU Ying-jie, et al. Analysis of Impact of Crack Surface on Shear Strength of Strong Expansive Soil [J]. Rock and Soil Mechanics, 2014, 35 (1): 130-133.
[13] 程展林,龚壁卫,胡波.膨胀土的强度及其测试方法[J].岩土工程学报,2015,37(增1):11-15. CHENG Zhan-lin, GONG Bi-wei, HU Bo. Shear Strength of Expansive Soil and Its Test Method [J]. Chinese Journal of Geotechnical Engineering, 2015, 37 (S1): 11-15.
[14] 程展林,李青云,郭熙灵,等.膨胀土边坡稳定性研究[J].长江科学院院报,2011,28(10):102-111. CHENG Zhan-lin, LI Qing-yun, GUO Xi-ling, et al. Study on the Stability of Expansive Soil Slope [J]. Journal of Yangtze River Scientific Research Institute, 2011, 28 (10): 102-111.
[15] 邹维列,陈轮,谢鹏,等.重塑膨胀土非线性强度特性及一维固结浸水膨胀应力-应变关系[J].岩土力学,2012,33(增2):59-64. ZOU Wei-lie, CHEN Lun, XIE Peng, et al. Nonlinear Strength Property of Remolded Expansive Soil and Its Stress-strain Relationship for Soaking After One-dimensional Consolidation [J]. Rock and Soil Mechanics, 2012, 33 (S2): 59-64.
[16] 肖杰,杨和平,李晗峰,等.低应力条件不同密度的南宁膨胀土抗剪强度试验[J].中国公路学报,2013,26(6):15-21,37. XIAO Jie, YANG He-ping, LI Han-feng, et al. Shear Strength Test of Nanning Expansive Soil with Various Dry Densities and Low Stresses [J]. China Journal of Highway and Transport, 2013, 26 (6): 15-21, 37.
[17] 肖杰,杨和平,王兴正,等.南宁外环膨胀土抗剪强度非线性特征及影响因素分析[J].中国公路学报,2014,27(10):1-7. XIAO Jie, YANG He-ping, WANG Xing-zheng, et al. Analysis of Nonlinear Characteristics of Shear Strength of Nanning Expansive Soil and Its Influencing Factors [J]. China Journal of Highway and Transport, 2014, 27 (10): 1-7.
[18] 朱思哲,刘虔,包承纲.三轴试验原理与应用技术[M].西安:中国电力出版社,2003. ZHU Si-zhe, LIU Qian, BAO Cheng-gang. Triaxial Test Principal and Application Technology [M]. Xi'an: China Electric Power Press, 2003.
[19] 郭爱国,茜平一.三轴压缩试验中橡皮膜约束影响的校正[J].岩土力学,2002,23(4):442-445. GUO Ai-guo, QIAN Ping-yi. Corrections for Influence of Membrane Restraint in Triaxial Test [J]. Rock and Soil Mechanics, 2002, 23 (4): 442-445.
[20] JTG E40—2007,公路土工试验规程 [S]. JTG E40—2007, Test Methods of Soil for Highway Engineering [S].
[21] 卢再华,陈正汉,孙树国.南阳膨胀土变形与强度特性的三轴试验研究[J].岩石力学与工程学报,2002,21(5):717-723. LU Zai-hua, CHEN Zheng-han, SUN Shu-guo. Study of Deformation and Strength Characteristic of Expansive Soil with Triaxial Tests [J]. Chinese Journal of Rock Mechanics and Engineering, 2002, 21 (5): 717-723.
[2] 刘特洪.工程建设中的膨胀土问题[M].北京:中国建筑工业出版社,1997. LIU Te-hong. Problems Related to Expansive Soil in Engineering Constructions [M]. Beijing: China Architecture and Building Press, 1997.
[3] 张锐,刘正楠,郑健龙,等.膨胀土侧向膨胀力及其对重力式挡墙的作用[J].中国公路学报,2018,31(2):171-180. ZHANG Rui, LIU Zheng-nan, ZHENG Jian-long, et al. Lateral Swelling Pressure of Expansive Soil and Its Effect on Gravity Retaining Wall [J]. China Journal of Highway and Transport, 2018, 31 (2): 171-180.
[4] KHEMISSA M, MEKKI L, MAHAMEDI A. Laboratory Investigation on the Behaviour of an Overconsolidated Expansive Clay in Intact and Compacted States [J]. Transportation Geotechnics, 2017, 14: 157-168.
[5] NOWAMOOZ H, JAHANGIR E, MASROURI F, et al. Effective Stress in Swelling Soils During Wetting Drying Cycles [J]. Engineering Geology, 2016, 210: 33-44.
[6] XIAO J, YANG H P, ZHANG J H, et al. Surficial Failure of Expansive Soil Cutting Slope and Its Flexible Support Treatment Technology [J]. Advances in Civil Engineering, 2018, 2018: 1-13.
[7] 杨和平,王兴正,肖杰.干湿循环效应对南宁外环膨胀土抗剪强度的影响[J].岩土工程学报,2014,36(5):949-954. YANG He-ping, WANG Xing-zheng, XIAO Jie. Influence of Wetting-drying Cycles on Strength Characteristic of Nanning Expansive Soils [J]. Chinese Journal of Geotechnical Engineering, 2014, 36 (5): 949-954.
[8] 崔溦,张志耕,闫澍旺.膨胀土的干湿循环性状及其在边坡稳定性分析中的应用[J].水利与建筑工程学报,2010,8(5):24-27. CUI Wei, ZHANG Zhi-geng, YAN Shu-wang. Cyclic Behavior of Expansive Soils and Its Application in Slope Stability Analysis [J]. Journal of Water Resources and Architectural Engineering, 2010, 8 (5): 24-27.
[9] 吕海波,曾召田,赵艳林,等.膨胀土强度干湿循环试验研究[J].岩土力学,2009,30(12):3797-3802. LU Hai-bo, ZENG Zhao-tian, ZHAO Yan-lin, et al. Experimental Studies of Strength of Expansive Soil in Drying and Wetting Cycles [J]. Rock and Soil Mechanics, 2009, 30 (12): 3797-3802.
[10] 徐彬,殷宗泽,刘述丽.膨胀土强度影响因素与规律的试验研究[J].岩土力学,2011,32(1):44-50. XU Bin, YIN Zong-ze, LIU Shu-li. Experimental Study of Factors Influencing Expansive Soil Strength [J]. Rock and Soil Mechanics, 2011, 32 (1): 44-50.
[11] 刘华强,殷宗泽.裂缝对膨胀土抗剪强度指标影响的试验研究[J].岩土力学,2010,31(3):727-731. LIU Hua-qiang, YIN Zong-ze. Test Study of Influence of Crack Evolution on Strength Parameters of Expansive Soil [J]. Rock and Soil Mechanics, 2010, 31 (3): 727-731.
[12] 赵鑫,阳云华,朱瑛洁,等.裂隙面对强膨胀土抗剪强度影响分析[J].岩土力学,2014,35(1):130-133. ZHAO Xin, YANG Yun-hua, ZHU Ying-jie, et al. Analysis of Impact of Crack Surface on Shear Strength of Strong Expansive Soil [J]. Rock and Soil Mechanics, 2014, 35 (1): 130-133.
[13] 程展林,龚壁卫,胡波.膨胀土的强度及其测试方法[J].岩土工程学报,2015,37(增1):11-15. CHENG Zhan-lin, GONG Bi-wei, HU Bo. Shear Strength of Expansive Soil and Its Test Method [J]. Chinese Journal of Geotechnical Engineering, 2015, 37 (S1): 11-15.
[14] 程展林,李青云,郭熙灵,等.膨胀土边坡稳定性研究[J].长江科学院院报,2011,28(10):102-111. CHENG Zhan-lin, LI Qing-yun, GUO Xi-ling, et al. Study on the Stability of Expansive Soil Slope [J]. Journal of Yangtze River Scientific Research Institute, 2011, 28 (10): 102-111.
[15] 邹维列,陈轮,谢鹏,等.重塑膨胀土非线性强度特性及一维固结浸水膨胀应力-应变关系[J].岩土力学,2012,33(增2):59-64. ZOU Wei-lie, CHEN Lun, XIE Peng, et al. Nonlinear Strength Property of Remolded Expansive Soil and Its Stress-strain Relationship for Soaking After One-dimensional Consolidation [J]. Rock and Soil Mechanics, 2012, 33 (S2): 59-64.
[16] 肖杰,杨和平,李晗峰,等.低应力条件不同密度的南宁膨胀土抗剪强度试验[J].中国公路学报,2013,26(6):15-21,37. XIAO Jie, YANG He-ping, LI Han-feng, et al. Shear Strength Test of Nanning Expansive Soil with Various Dry Densities and Low Stresses [J]. China Journal of Highway and Transport, 2013, 26 (6): 15-21, 37.
[17] 肖杰,杨和平,王兴正,等.南宁外环膨胀土抗剪强度非线性特征及影响因素分析[J].中国公路学报,2014,27(10):1-7. XIAO Jie, YANG He-ping, WANG Xing-zheng, et al. Analysis of Nonlinear Characteristics of Shear Strength of Nanning Expansive Soil and Its Influencing Factors [J]. China Journal of Highway and Transport, 2014, 27 (10): 1-7.
[18] 朱思哲,刘虔,包承纲.三轴试验原理与应用技术[M].西安:中国电力出版社,2003. ZHU Si-zhe, LIU Qian, BAO Cheng-gang. Triaxial Test Principal and Application Technology [M]. Xi'an: China Electric Power Press, 2003.
[19] 郭爱国,茜平一.三轴压缩试验中橡皮膜约束影响的校正[J].岩土力学,2002,23(4):442-445. GUO Ai-guo, QIAN Ping-yi. Corrections for Influence of Membrane Restraint in Triaxial Test [J]. Rock and Soil Mechanics, 2002, 23 (4): 442-445.
[20] JTG E40—2007,公路土工试验规程 [S]. JTG E40—2007, Test Methods of Soil for Highway Engineering [S].
[21] 卢再华,陈正汉,孙树国.南阳膨胀土变形与强度特性的三轴试验研究[J].岩石力学与工程学报,2002,21(5):717-723. LU Zai-hua, CHEN Zheng-han, SUN Shu-guo. Study of Deformation and Strength Characteristic of Expansive Soil with Triaxial Tests [J]. Chinese Journal of Rock Mechanics and Engineering, 2002, 21 (5): 717-723.