循环荷载下饱和南京细砂的孔压增量模型  

Pore water pressure increment model for saturated Nanjing fine sand subjected to cyclic loading

作　　者：王炳辉[1] 陈国兴[1] 

机构地区：[1]南京工业大学岩土工程研究所,江苏南京210009

出　　处：《岩土工程学报》2011年第2期188-194,共7页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目重大研究计划(90715018);国家重点基础研究发展计划项目(2007CB714200);国家公益性行业(地震)科研专项(200808022)

摘　　要：等幅循环荷载的不排水三轴试验的结果表明,饱和南京细砂孔压比曲线的形状随循环周数比增大而发生规律性的变化。引入孔压增量比的概念,并定义有效动剪应力比和有效应力对数衰减率,发现孔压增量比的发展过程可分为下降段、平稳段和上升段;在平稳段和上升段,孔压增量比的累积量与有效动剪应力比的自然对数具有很好的线性关系,并推导出第N周的孔压增量比与第N-1周的有效应力比对数衰减率成正比,而与动应力幅值无关。据此建立的饱和南京细砂孔压增量模型,能够较好地描述等幅循环荷载作用引起的孔压比随循环周数的增大而增长的发展趋势。Undrained triaxial tests are carried out for saturated Nanjing fine sand subjected to uniform cyclic loading.The curve shapes of the excess pore water pressure（EPWP） ratio regularly change with the increase of the ratio of number of cycles.The concept of EPWP increment ratio is introduced.Two new concepts of the effective dynamic shear stress ratio and the log decrement of effective stress are defined.It is found that the development of the EPWP increment ratio can be divided into three stages： descending stage,stable stage and ascending stage.At the stable and ascending stages,a satisfactory linear relationship is obtained between the accumulative EPWP increment ratio and the natural logarithm of the effective dynamic shear stress ratio.Accordingly it is deduced that the EPWP increment ratio at the number of cycle N is in direct proportion to the log decrement of the effective stress at the number of cycle N-1,but is independent of the cyclic stress amplitude.Based on the above analysis,a new EPWP increment model is developed,and it fits the test results for better prediction of the curves of EPWP generation.

关 键 词：循环荷载 南京细砂 孔压增量模型 孔压增量比 有效动剪应力比 有效应力对数衰减率 

分 类 号：TU411[建筑科学—岩土工程]