预剪应力作用下原状黄土动力特性试验研究
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摘要
以陕西武功地区原状黄土为对象,在不同含水率与不同初始平均主应力下进行动扭剪三轴试验,研究了预剪应力作用下原状黄土动剪切模量与阻尼比的变化规律。结果表明:原状黄土动剪切模量随动剪应变变化的整体趋势并未因存在预剪应力作用而发生改变;存在预剪应力作用时,含水率与初始平均主应力对原状黄土动剪切模量的影响程度降低;含水率与初始平均主应力对预剪应力作用下原状黄土的初始动剪切模量具有显著的影响;存在预剪应力作用时原状黄土的阻尼比随动剪应变的增大先减小而后缓慢增大,其值总体上在0.20～0.35之间;现有的半对数坐标进行直线方程拟合的方法已不再适用于存在预剪应力作用时原状黄土阻尼比的计算;含水率对原状黄土阻尼比随动剪应变变化规律的影响呈现出含水率越大、阻尼比越大的趋势;初始平均主应力对原状黄土阻尼比随动剪应变变化的影响规律不明显。
The dynamic torsional shear triaxial tests are carried out on undisturbed loess of Wugong(Shaanxi province) under different water contents and different initial average principal stresses conditions;and the changing laws of dynamic shear modulus and damping ratio of undisturbed loess under pre-shearing stresses are obtained.Results show that the general trend of the changing law of dynamic shear modulus of undisturbed loess does not change with the changing of the dynamic shear strains under the condition of pre-shearing stresses.The degrees of effects of water content w and initial average principal stress pm0 on the dynamic shear modulus of undisturbed loess reduce under the condition of pre-shearing stresses.Water content w and initial average principal stress pm0 have significant influences on the initial dynamic shear modulus of undisturbed loess under the condition of pre-shearing stresses.Damping ratio λ of undisturbed loess under the condition of pre-shearing stress first decreases with the increase of the dynamic shear strain,and then increases gradually.In general,the values of the damping ratios are between 0.2 and 0.35.The existing method of using semilogarithmic coordinates to fit the line equation is no longer applicable to the calculation of the damping ratios of undisturbed loess under the condition of pre-shearing stresses.The effects of w on λ-γd relations of undisturbed loess show a trend that the higher w,the larger λ.The laws of effects of pm0 on λ-γd relations of loess are not obvious.
The dynamic torsional shear triaxial tests are carried out on undisturbed loess of Wugong(Shaanxi province) under different water contents and different initial average principal stresses conditions;and the changing laws of dynamic shear modulus and damping ratio of undisturbed loess under pre-shearing stresses are obtained.Results show that the general trend of the changing law of dynamic shear modulus of undisturbed loess does not change with the changing of the dynamic shear strains under the condition of pre-shearing stresses.The degrees of effects of water content w and initial average principal stress pm0 on the dynamic shear modulus of undisturbed loess reduce under the condition of pre-shearing stresses.Water content w and initial average principal stress pm0 have significant influences on the initial dynamic shear modulus of undisturbed loess under the condition of pre-shearing stresses.Damping ratio λ of undisturbed loess under the condition of pre-shearing stress first decreases with the increase of the dynamic shear strain,and then increases gradually.In general,the values of the damping ratios are between 0.2 and 0.35.The existing method of using semilogarithmic coordinates to fit the line equation is no longer applicable to the calculation of the damping ratios of undisturbed loess under the condition of pre-shearing stresses.The effects of w on λ-γd relations of undisturbed loess show a trend that the higher w,the larger λ.The laws of effects of pm0 on λ-γd relations of loess are not obvious.
引文
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[2]张振中.黄土地震灾害预测[M].北京:地震出版社,1999.
[3]崔文鉴,孙远茹.陕西东坡地区原状黄土动剪模量及阻尼比的试验研究[J].西北地震学报,1990,12(4):60-68.CUI Wen-jian,SUN Yuan-ru.An experimental researchon dynamic shear modulus and damping ratio of loess inDongpo area,Shaanxi Province[J].NorthwestSeismological Journal,1990,12(4):60-68.
[4]骆亚生,田堪良.非饱和黄土的动剪模量与阻尼比[J].水利学报,2005,36(7):830-834.LUO Ya-sheng,TIAN Kan-liang.Dynamic shear modulusand damping ratio of unsaturated loess[J].Journal ofHydraulic Engineering,2005,36(7):830-834.
[5]陈存礼,何军芳,高鹏.不同含水量下原状黄土的动力变形特性[J].西安理工大学学报,2006,22(4):390-394.CHEN Cun-li,HE Jun-fang,GAO Peng.Dynamicdeformation characteristics of intact loess under differentwater content[J].Journal of Xi’an University ofTechnology,2006,22(4):390-394.
[6]王志杰,骆亚生,王瑞瑞,等.不同地区原状黄土动剪切模量与阻尼比试验研究[J].岩土工程学报,2010,32(9):1464-1469.WANG Zhi-jie,LUO Ya-sheng,WANG Rui-rui,et al.Experimental study on dynamic shear modulus anddamping ratio of undisturbed loess in different regions[J].Chinese Journal of Geotechnical Engineering,2010,32(9):1464-1469.
[7]柳伟,王军,蔡袁强.初始剪应力对软土场地震反应的影响[J].岩土力学,2011,32(6):1731-1735.LIU Wei,WANG Jun,CAI Yuan-qiang.Effect of initialshear stress on earthquake response for soft clay site[J].Rock and Soil Mechanics,2011,32(6):1731-1735.
[8]杨利国.复杂初始应力条件下压实黄土动力特性的试验研究[硕士学位论文D].杨凌:西北农林科技大学,2010.
[9]付磊,王洪瑾,周景星.主应力偏转角对砂砾料动力特性影响的试验研究[J].岩土工程学报,2000,22(4):435-440.FU Lei,WANG Hong-jin,ZHOU Jing-xing.Effect of theinitial rotation angle of principal stress on the dynamicproperties of soil[J].Chinese Journal of GeotechnicalEngineering,2000,22(4):435-440.
[10]HARDIN B O,DRNEVICH V P.Shear modulus anddamping in soils:design equation and curves[J].Journalof Soil Mechanics and Foundation Division,ASCE,1972,98(7):667-692.
[11]谢定义.土动力学[M].西安:西安交通大学出版社,1988.
[12]王志杰.复杂初始应力状态下黄土动剪切模量与阻尼比特性试验研究[硕士学位论文D].杨凌:西北农林科技大学,2010.
[13]胡仲有,骆亚生,李焱.不同地区黄土阻尼比变化特性试验研究[J].地震工程与工程振动,2010,30(2):167-172.HU Zhong-you,LUO Ya-sheng,LI Yan.Experimentalstudy on damping ratio variation characteristics of loessin different areas[J].Journal of Earthquake En-gineering and Engineering Vibration,2010,30(2):167-172.
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