循环荷载下硅藻土应变和孔压特性
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摘要
针对嵊州硅藻土的高结构性及地基应力场的复杂多变,应用GDS动三轴仪进行不同围压和不同循环应力比下的不排水循环加载试验,分析应力-应变滞回曲线演化、应变累积特性、回弹特性及孔压特性.研究表明:循环应力比及围压对原状硅藻土应变和孔压的发展规律影响明显,随着循环应力比的增加,滞回曲线由线性状态转变为非线性状态,且逐渐向x轴倾斜,累计应变和回弹应变都随着循环应力比的增加而略微增加,但总应变基本小于2%;残余孔压比随循环应力比增大而增大,范围为0.1～0.5.并且存在一个临界循环应力比,其值随有效围压的增大而减小,范围为0.8～2.2,当循环应力比大于该值时,试样内部产生一个破裂面迅速发生破坏.在相同循环应力比下,试样的应变随着有效围压的增大而增大.
In view of the high structural and complex stress field of the diatomite in Shengzhou, the undrained cyclic loading test under different confining pressures and different cyclic stress ratios was carried out by GDS dynamic triaxial apparatus to analyze the evolution law of the stress-strain hysteresis curve, strain accumulation and rebound characteristics. The research shows that the cyclic stress ratio and confining pressure have obvious influence on the development of strain and pore pressure of undisturbed diatomite. With the increase of cyclic stress ratio, the hysteresis curve changes from linear state to nonlinear state, and gradually tilts to the x-axis. Both the cumulative strain and the rebound strain increase slightly with the increase of the cyclic stress ratio, but the total strain is less than 2%; the residual pore pressure ratio increases with the increase of the cyclic stress ratio, and the range is0.1～0.5. And there is a critical cyclic stress ratio, the value of which decreases with the increase of the effective confining pressure,the range is 0.8～2.2. When the cyclic stress ratio is greater than this value, a crack surface is generated inside the sample and rapidly breaks. At the same cyclic stress ratio, the strain of the sample increases as the effective confining pressure increases.
In view of the high structural and complex stress field of the diatomite in Shengzhou, the undrained cyclic loading test under different confining pressures and different cyclic stress ratios was carried out by GDS dynamic triaxial apparatus to analyze the evolution law of the stress-strain hysteresis curve, strain accumulation and rebound characteristics. The research shows that the cyclic stress ratio and confining pressure have obvious influence on the development of strain and pore pressure of undisturbed diatomite. With the increase of cyclic stress ratio, the hysteresis curve changes from linear state to nonlinear state, and gradually tilts to the x-axis. Both the cumulative strain and the rebound strain increase slightly with the increase of the cyclic stress ratio, but the total strain is less than 2%; the residual pore pressure ratio increases with the increase of the cyclic stress ratio, and the range is0.1～0.5. And there is a critical cyclic stress ratio, the value of which decreases with the increase of the effective confining pressure,the range is 0.8～2.2. When the cyclic stress ratio is greater than this value, a crack surface is generated inside the sample and rapidly breaks. At the same cyclic stress ratio, the strain of the sample increases as the effective confining pressure increases.
引文
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[3]刘功勋,栾茂田,郭莹,等.复杂应力条件下长江口原状饱和软黏土门槛循环应力比试验研究[J].岩土力学,2010,31(4):1123-1129.
[4]周建,李剑强.循环荷载作用下饱和软粘土特性试验研究[J].工业建筑,2000,30(11):43-47.
[5]李家广.北部湾吹填场地海积软土动力与强度特性试验研究[D].南宁:广西大学,2017.
[6]柳伟.各向异性固结饱和软粘土动力特性研究[D].杭州:浙江大学,2007.
[7]王军.单、双向激振循环荷载作用下饱和软粘土动力特性研究[D].杭州:浙江大学,2007.
[8]张向东,刘家顺,张虎伟.循环荷载作用下软土动力特性试验研究[J].公路交通科技,2014,31(5):1-7.
[9]莫小霞.循环荷载作用下海积软土动力特性及细观结构试验研究[D].南宁:广西大学,2017.
[10]郑晓,刘胜群,海钧.振动频率对饱和软粘土动力特性影响试验研究[J].路基工程,2009,6:84-85.
[11]周健,简琦薇.循环荷载下老黏土的动力特性试验研究[J].地下空间与工程学报,2013,9(6):1248-1256.
[12]郭林.复杂应力路径下饱和软粘土静动力特性试验研究[D].杭州:浙江大学,2013.
[13]郭林,蔡袁强,谷川,等.循环荷载下软黏土回弹和累积变形特性[J].浙江大学学报:工学版,2013,47(12):2111-2117.
[14]唐葭,邓宗伟,高乾丰,等.湖相软土动力特性影响因素敏感性分析[J].重庆大学学报,2014,37(8):59-66.
[15]田兆阳,李平,郑志华,等.软土动力特性动三轴试验研究[J].地震工程学报,2017,39(1):95-99.
[16]COOP M R,GASPARRE A,NISHIMURA S,et al.The influence of structure on the behaviour of London Clay[J].Géotechnique,2007,57:19-31.
[17]NISHIMURA S.Laboratory study on anisotropy of natural London clay[D].London:University of London,2006.
[18]NISHIMURA S,JARDINE R J,MINH N A.Shear strength anisotropy of natural London Clay[J].Géotechnique,2007,57(1):49-62.
[19]GASPARRE A,COOP M.Techniques for performing small-strain probes in the triaxialapparatus[J].Géotechnique,2006,56(56):491-495.
[20]ZHOU J,GONG X.Strain degradation of saturated clay under cyclic loading[J].Revue Canadienne De Géotechnique,2001,38(1):208-212.