复杂应力条件下松砂振动孔隙水压力与体变特性的试验研究
摘要
利用新研制的土工静力-动力液压三轴-扭转多功能剪切仪,在5种初始主应力方向角与5种中主应力系数相组合的初始固结条件下,对饱和松砂进行了不排水循环扭剪试验。讨论了初始固结条件对不排水条件下饱和松砂孔隙水压力变化规律及对剪胀、剪缩、卸荷体缩等体积变化过程的影响。试验研究表明:(1)分别以稳定残余孔隙水压力和破坏时循环次数归一化后的残余孔隙水压力比和循环次数比之间的关系可以用双曲线模式表达。其参数主要依赖于初始主应力方向,中主应力系数对参数的影响并不显著。归一化后的孔隙水压力比与广义剪应变之间的关系也可以用双曲线模式表达,其中的2个待定参数依赖于初始主应力方向,与中主应力系数无关;(2)在三向非均等固结条件下的不排水循环扭剪试验中,饱和松砂表现出卸荷体缩特性,不同初始主应力方向时,饱和松砂剪缩、剪胀、卸荷体缩呈现出不同的交替变化模式。
The soil static and dynamic universal triaxial and torsional shear apparatus is employed to perform undrained cyclic torsional shear experimental tests of saturated loose sand with a relative density of 30% under three-directional anisotropic initial consolidation conditions with different initial orientations of principal stress and coefficient of intermediate principal stress.The effect of initial consolidation conditions on the development pattern of cyclic pore water pressure of undrained saturated loose sand and the complex volumetric changes behaviour including dilatancy,contraction and contraction during unloading is examined on the basis of comparative experimental tests.It is shown that the ratio of residual pore water pressure to the residual pore pressure at failure state can be expressed as an empirical hyperbola function with respect to either the ratio of the cyclic number to the cyclic number required at the failure state or generalized shear strain.The two parameters involved in the hyperbola function to be defined by experimental tests are closely dependent on the initial orientation of principal stress and seem to be independent on the coefficient of intermediate principal stress.It is also shown the volumecontraction during unloading is a common phenomenon displayed commonly in undrained loose sands subjected to cyclic shearing under three-directional anisotropic consolidation condition.Furthermore the type of volumetric change behavior is closely associated with the initial orientation of principal stress.
The soil static and dynamic universal triaxial and torsional shear apparatus is employed to perform undrained cyclic torsional shear experimental tests of saturated loose sand with a relative density of 30% under three-directional anisotropic initial consolidation conditions with different initial orientations of principal stress and coefficient of intermediate principal stress.The effect of initial consolidation conditions on the development pattern of cyclic pore water pressure of undrained saturated loose sand and the complex volumetric changes behaviour including dilatancy,contraction and contraction during unloading is examined on the basis of comparative experimental tests.It is shown that the ratio of residual pore water pressure to the residual pore pressure at failure state can be expressed as an empirical hyperbola function with respect to either the ratio of the cyclic number to the cyclic number required at the failure state or generalized shear strain.The two parameters involved in the hyperbola function to be defined by experimental tests are closely dependent on the initial orientation of principal stress and seem to be independent on the coefficient of intermediate principal stress.It is also shown the volumecontraction during unloading is a common phenomenon displayed commonly in undrained loose sands subjected to cyclic shearing under three-directional anisotropic consolidation condition.Furthermore the type of volumetric change behavior is closely associated with the initial orientation of principal stress.
引文
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[3]Chang C S,Kuo C L,Selig E T.Pore pressure developm ent during cyclic load ing[J].Journal of Geotechn ical Engineering D ivision,ASCE,1983,109(1):103~107.
[4]沈瑞福,王洪瑾,周景星.动主应力轴连续旋转下砂土的动强度[J].水利学报,1996,(1):27~33.
[5]Shamoto Y,Zhang JM,Goto S.M echan ism of large post-liquefaction deformation in saturated sand[J].Soils and Foundations,1997,37(2):71~80.
[6]张建民.砂土的可逆性和不可逆性剪胀规律[J].岩土工程学报,2000,22(1):12~17.
[7]李广信,武世锋.土的卸载体缩的试验研究及其机理探讨[J].岩土工程学报,2002,24(1):47~50.
[8]沈珠江.复杂荷载条件下砂土液化变形的结构性模型[A].土动力学理论与实践.第五届全国土动力学学术会议论文集[C].大连:大连理工大学出版社,1998.1~10.
[9]谢定义,张建民.饱和砂土瞬态动力学特性与机理分析[M].西安:陕西科学技术出版社,1995.
[10]邵生俊.砂土的物态本构模型及应用[M].西安:陕西科学技术出版社,2001.23~30.
[11]郭莹,栾茂田,何杨,等.复杂应力条件下饱和松砂孔隙水压力增长特性的试验研究[J].地震工程与工程振动,2004,24(3):139~144.
[12]栾茂田,郭莹,李木国,等.土工静力-动力液压三轴-扭转多功能剪切仪研发与应用[J].大连理工大学学报,2003,43(5):670~675.
[13]汪闻韶.土的动力强度和液化特性[M].北京:中国电力出版社,1997.90~105.
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