循环荷载作用下南京片状细砂的不排水动力性态  

Undrained cyclic behaviors of Nanjing flake-shaped fine sand under cyclic loading

作　　者：陈国兴[1] 刘雪珠[1,2] 

机构地区：[1]南京工业大学岩土工程研究所,江苏南京210009 [2]江苏省岩土工程公司,江苏南京210018

出　　处：《岩土工程学报》2009年第10期1498-1504,共7页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金重大研究计划项目(90715018);国家重点基础研究发展计划项目(2007CB714200);中国地震局地震工程与工程振动开放实验室基金项目(2007A02)

摘　　要：以南京片状细砂为研究对象,采用英国WFI动静多功能三轴仪,研究饱和南京片状细砂在循环荷载作用下静偏应力水平、循环应力水平对其不排水动力特性的影响。把振动孔压的发展与应力路径相联系,分析了循环荷载作用下不同阶段南京片状细砂所处的初始压密状态、压缩状态和膨胀状态的发生和发展过程;根据静偏应力与循环偏应力的大小,视有无偏应力反向,将南京片状细砂的破坏模式可分为循环活动性和塑性应变累积破坏;同时,针对振动孔压上升使得南京片状细砂出现动剪切模量软化现象,研究了每一次循环过程中滞回曲线的卸载段及再加载段的割线动剪切模量Gsec和最大割线模量Gmax的变化规律,发现Gsec和Gsec/Gmax与循环应变εs之间的关系可用指数函数描述。A series of dynamic behavior tests on flake-shaped Nanjing fine sand soils are performed by using the WFI cyclic triaxial apparatus made in England. The dynamic behaviors of Nanjing flake-shaped fine sand soils under different static deviator stress levels and cyclic stress ratios are studied. Through comparing the effective stress path under cyclic loading with static loading,the process of liquefaction of Nanjing saturated flake-shaped fine sand with development of vibration pore-water pressure,including the initial compact state, compression state and dilative state, is investigated. According to different combinations of static deviator stress and cyclic stress, two kinds of failure patterns with or without deviator stress reversal are observed in the samples tested in this series, including cyclic mobility and the failure of accumulation residual strain. In addition, the degradation of dynamic shear modulus is due to development of vibration pore-water pressure, and it is observed that the shear modulus reduces with the progressive number of cycles. The variation of the shear stiffness with number of cycles and cyclic strain is investigated by analyzing the secant shear modulus in each unload-reload loop of dynamic stress-strain relationship. And by means of the exponential function, the empirical equations of the relationship among the secant shear modulus Gsec, shear modulus ratio Gsec / Gmax and cyclic strain ε are established based on test results.

关 键 词：南京片状细砂 循环三轴试验 破坏模式 有效应力路径 动剪模量软化 

分 类 号：TU411.8[建筑科学—岩土工程]