昆明泥炭土直剪蠕变特性及长期强度试验研究
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摘要
昆明泥炭土的蠕变特性影响着该地区各类建(构)筑物的长期稳定性和结构安全。采用改进的应力控制式直剪仪,以分级加载方式开展一系列的直剪蠕变试验,研究不同固结压力下剪应变随剪应力与时间的变化规律,以及长期强度与短期强度间的关系。结果表明:昆明泥炭土具有显著的非线性蠕变特性,当剪应力较低时,直剪蠕变曲线表现为衰减稳定蠕变;随着剪应力增大,蠕变曲线会同时出现衰减稳定蠕变和非稳定等速蠕变;当剪应力较大时,则会呈现出加速蠕变现象,并快速发生破坏。在施加水平剪应力的瞬间,泥炭土即产生较大的剪切应变,且瞬时应变随着剪应力的增加而加大,而瞬时应变占总应变的比例逐渐降低,表明泥炭土在高剪应力水平下,蠕变现象加剧。与短期强度相比,泥炭土长期强度的黏聚力和内摩擦角均有一定程度的下降。当固结压力为50～400kPa时,长期强度约为短期强度的57%～70%。
Creep characteristics of peaty soil in Kunming affect the long-term stability and structure safety. By the improved stress-controlled direct shear apparatus, a series of direct shear creep tests are carried out with the multi-stage loading method. The variation of shear stress and strain with time and the relationship between long-term and short-term strength are studied under different consolidation pressures. The results show that the peaty soil in Kunming has obvious nonlinear creep characteristics. When the shear stress is low, the direct shear creep curve of peaty soil shows decay creep. With the increase of shear stress, both decay creep and unstable equal velocity creep appear in the creep curve. When the shear stress is high, peaty soil exhibits acceleration creep phenomenon, and is destroyed quickly. The large shear strain occurs at the moment of applying horizontal shear stress, the instantaneous strain increases with the increase of shear stress, while the proportion of instantaneous strain to total strain decreases gradually, which indicates that the creep deformation is aggravated under high shear stress. Compared with short-term strength, the cohesion and friction angle of long-term strength is smaller for peaty soil, and the long-term strength is about 57%～70% of the short-term strength when the consolidation pressure is 50-400 kPa.
Creep characteristics of peaty soil in Kunming affect the long-term stability and structure safety. By the improved stress-controlled direct shear apparatus, a series of direct shear creep tests are carried out with the multi-stage loading method. The variation of shear stress and strain with time and the relationship between long-term and short-term strength are studied under different consolidation pressures. The results show that the peaty soil in Kunming has obvious nonlinear creep characteristics. When the shear stress is low, the direct shear creep curve of peaty soil shows decay creep. With the increase of shear stress, both decay creep and unstable equal velocity creep appear in the creep curve. When the shear stress is high, peaty soil exhibits acceleration creep phenomenon, and is destroyed quickly. The large shear strain occurs at the moment of applying horizontal shear stress, the instantaneous strain increases with the increase of shear stress, while the proportion of instantaneous strain to total strain decreases gradually, which indicates that the creep deformation is aggravated under high shear stress. Compared with short-term strength, the cohesion and friction angle of long-term strength is smaller for peaty soil, and the long-term strength is about 57%～70% of the short-term strength when the consolidation pressure is 50-400 kPa.
引文
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[15]许豪,肖宏彬,滕珂.南宁膨胀土直剪蠕变特性及长期强度试验研究[J].公路工程,2011,36(1):31-35(Xu Hao,Xiao Hongbin,Teng Ke.Experimental study on direct shear creep characteristics and long-term strength for Nanning expensive soil[J].Highway Engineering,2011,36(1):31-35(in Chinese))
[16]卢萍珍,曾静,盛谦.软黏土蠕变试验及其经验模型研究[J].岩土力学,2008,29(4):1041-1044(Lu Pingzhen,Zeng Jing,Sheng Qian.Creep tests of soft clay and its empirical models[J].Rock and Soil Mechanics,2008,29(4):1041-1044(in Chinese))
[17]朱鸿鹄.软土固结-蠕变耦合效应的试验研究及有限元分析[D].广州:暨南大学,2005(Zhu Honghu.Experimental investigation and finite element analysis of consolidation-creep effect of soft soil[D].Guangzhou:Jinan University,2005(in Chinese))
[18]SL 264-2001水利水电工程岩石试验规程[S].北京:中国水利水电出版社,2001(SL 264-2001Specializations for rock tests in water conservancy and hydroelectric engineering[S].Beijing:China Water&Power Press,2001(in Chinese))
[2]丁祖德,黄娟,袁铁映,等.昆明泥炭质土动剪切模量与阻尼比的试验研究[J].岩土力学,2017,38(12):3627-3634(Ding Zude,Huang Juan,Yuan Tieying,et al.Experimental study of dynamic shear modulus and damping ratio of peaty soil in Kunming[J].Rock and Soil Mechanics,2017,38(12):3627-3634(in Chinese))
[3]陈成,周正明,张先伟,等.循环荷载作用下泥炭质土动力累积特性试验研究[J].岩石力学与工程学报,2017,36(5):1247-1255(Chen Cheng,Zhou Zhengming,Zhang Xianwei,et al.Experimental study on accumulative behaviour of peaty soil under cyclic loading[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(5):1247-1255(in Chinese))
[4]阮永芬,刘岳东,王东,等.昆明泥炭与泥炭质土对建筑地基的影响[J].昆明理工大学学报:理工版,2003,28(3):121-124(Ruan Yongfen,Liu Yuedong,Wang Dong,et al.Effect of Kunming's peaty and peaty soil on the building foundation[J].Journal of Kunming University of Science and Technology:Science and Technology,2003,28(3):121-124(in Chinese))
[5]柳雁玲.草炭土路基沉降与变形特性研究[D].长春:吉林大学,2006(Liu Yanling.Research on settlement and deformation characteristics of peat soil roadbed[D].Changchun:Jilin University,2006(in Chinese))
[6]Hendry M T,Martin C D,Barbour S L.Measurement of cyclic response of railway enbankments and underlying soft foundations to heavy axle loads[J].Canadian Geotechnical Journal,2013,50(5):467-480
[7]Hendry M T,Sharma J S,Martin C D,et al.Effect of fibre content and structure on anisotropic elastic stiffness and shear strength of peat[J].Canadian Geotechnical Journal,2012,49(4):403-415
[8]周秋娟,陈晓平.软土蠕变特性试验研究[J].岩土工程学报,2006,28(5):626-630(Zhou Qiujuan,Chen Xiaoping.Experimental study on creep properties of soft soil[J].Chinese Journal of Geotechnical Engineering,2006,28(5):626-630(in Chinese))
[9]陈晓平,朱鸿鹄,张芳枝,等.软土变形时效特性的试验研究[J].岩石力学与工程学报,2005,24(12):2142-2148(Chen Xiaoping,Zhu Honghu,Zhang Fangzhi,et al.Experimental study on aging characteristics of soft soil deformation[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(12):2142-2148(in Chinese))
[10]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(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))
[11]王松鹤,骆亚生,董晓宏,等.黄土剪切蠕变特性试验研究[J].岩石力学与工程学报,2010,29(增1):3088-3092(Wang Songhe,Luo Yasheng,Dong Xiaohong,et al.Experimental study on shear creep properties of loess[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(S1):3088-3092(in Chinese))
[12]王常明,王清,张淑华.滨海软土蠕变特性及蠕变模型[J].岩石力学与工程学报,2004,23(2):227-230(Wang Changming,Wang Qing,Zhang Shuhua.Creep characteristics and creep model of marine soft soils[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(2):227-230(in Chinese))
[13]杨爱武,张艳.不同初始固结度吹填土蠕变特性研究[J].岩土工程学报,2013,35(增1):222-226(Yang Aiwu,Zhang Yan.Study on creep characteristics of filling soil with different initial consolidation degrees[J].Chinese Journal of Geotechnical Engineering,2013,35(S1):222-226(in Chinese))
[14]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,2013,31(增1):2806-2816(Lei Huayang,Jia Yafang,Li Xiao.Experimental study on nonlinear creep properties of coastal soft soil[J].Chinese Journal of Rock Mechanics and Engineering,2013,31(S1):2806-2816(in Chinese))
[15]许豪,肖宏彬,滕珂.南宁膨胀土直剪蠕变特性及长期强度试验研究[J].公路工程,2011,36(1):31-35(Xu Hao,Xiao Hongbin,Teng Ke.Experimental study on direct shear creep characteristics and long-term strength for Nanning expensive soil[J].Highway Engineering,2011,36(1):31-35(in Chinese))
[16]卢萍珍,曾静,盛谦.软黏土蠕变试验及其经验模型研究[J].岩土力学,2008,29(4):1041-1044(Lu Pingzhen,Zeng Jing,Sheng Qian.Creep tests of soft clay and its empirical models[J].Rock and Soil Mechanics,2008,29(4):1041-1044(in Chinese))
[17]朱鸿鹄.软土固结-蠕变耦合效应的试验研究及有限元分析[D].广州:暨南大学,2005(Zhu Honghu.Experimental investigation and finite element analysis of consolidation-creep effect of soft soil[D].Guangzhou:Jinan University,2005(in Chinese))
[18]SL 264-2001水利水电工程岩石试验规程[S].北京:中国水利水电出版社,2001(SL 264-2001Specializations for rock tests in water conservancy and hydroelectric engineering[S].Beijing:China Water&Power Press,2001(in Chinese))
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