加载频率对饱和珊瑚砂剪切模量硬化和衰退特性的影响  

Effect of loading frequency on the stiffening and decline characteristics of shear modulus of saturated coral sand

作　　者：杨铮涛 秦悠 吴琪[1] 陈国兴[1] Yang Zhengtao;Qin You;Wu Qi;Chen Guoxing(Nanjing University of Technology,Nanjing 211816,China)

机构地区：[1]南京工业大学,江苏南京211816

出　　处：《土木工程学报》2024年第5期99-106,共8页China Civil Engineering Journal

基　　金：国家自然科学基金(52278503)。

摘　　要：为探究循环加载频率f对珊瑚砂动剪切模量硬化和衰退特性的影响,采用不同f(0.01Hz、0.05Hz、0.1Hz、0.5Hz、1Hz)的分级和单级加载模式,开展中密、均等固结、应力控制的饱和珊瑚砂不排水循环剪切试验。珊瑚砂的孔压门槛剪应变(低于该应变不会产生超静孔压)和模量门槛剪应变(低于该应变不会产生剪切模量衰退)的大小基本相同,可统一称为门槛剪应变γ_(th),且γ_(th)值的大小不受f的影响。低应变(≤γ_(th))时,动剪切模量G随循环剪应变幅值γ_(a)的增大而增大,与施加的循环应力比(CSR)呈二次多项式关系,模量硬化指数δ_(s)最大可达1.2;高应变(>γ_(th))时,G-γ_(a)关系曲线不受f的影响,模量衰退指数δ_(d)可表示为γ_(a)的负幂函数;G随循环次数N增大而衰退的速率随f的增大而减小,与f相关的δ_(d)可表示N的显式表达式。To investigate the effect of loading frequency f on the stiffening and decline characteristics of dynamic shear modulus of saturated coral sand,a series of multi⁃stage and single⁃stage stress⁃controlled undrained cyclic shear tests were performed on medium dense saturated specimens under isotropically consolidated condition in various f(0.01 Hz,0.05 Hz,0.1 Hz,0.5 Hz,and 1 Hz).The excess pore water pressure threshold shear strain(below which there is no excess pore pressure buildup)and the modulus threshold shear strain(below there is no shear modulus decline)of the coral sand were basically the same and they could be uniformly termed as the threshold shear strainγ_(th),whose value is not influenced by f.Forγ_(a)≤γ_(th)(low strain level),the dynamic shear modulus G increases with the cyclic shear strain amplitudeγa,and can be expressed as a quadratic polynomial function of the applied cyclic stress ratio CSR.The maximum value of modulus stiffening indexδs can reach 1.2.Forγ_(a)>γ_(th)(high strain level),the shape of G⁃γ_(a)curves is independent of f,the modulus decline indexδd decreases in a negative power function form asγa increases;meanwhile,the decline rate of G with the number of cycles N decreases as f increases,and frequency⁃dependentδd can be expressed as an explicit function of N.

关 键 词：珊瑚砂 动剪切模量 加载频率 门槛剪应变 模量硬化 模量衰退 

分 类 号：TU435[建筑科学—岩土工程]