循环荷载作用下原状花岗岩残积土动力特性

Dynamic Characteristics of Undisturbed Granite Residual Soil under Cyclic Loading

研究目的:东南沿海地区高速公路、铁路和地铁迅速发展,深入研究该地区广泛分布的花岗岩残积土的动力特性尤为重要。本文对福州原状花岗岩残积土进行动三轴试验,揭示循环荷载作用下花岗岩残积土的动应力应变关系、动强度、动剪切模量和阻尼比等动力特性。研究结论:(1)循环荷载作用下原状花岗岩残积土的动应变与振次的关系表现为稳定型、破坏型和临界型三种典型类型;(2)随着振次增加,原状花岗岩残积土的动强度值降低,动强度与振次的关系曲线呈半对数函数关系;(3)长期循环荷载作用后,花岗岩残积土的动黏聚力和动内摩擦角将产生大幅下降;(4)原状花岗岩残积土的动剪切模量随着振次及动剪切应变的增加而降低;动剪切模量与动应力幅值的相关关系可用线性模型来描述;(5)循环荷载作用下,原状花岗岩残积土的阻尼比随振次的发展表现出稳定型、临界型和破坏型三种典型类型;(6)本研究成果对认识花岗岩残积土的动力特性以及合理选择土的动强度指标具有一定参考价值。

Research purposes:With the rapid development of expressways,railways and subways in southeast coastal areas,it is particularly important to study the dynamic characteristics of undisturbed granite residual soil under long-term cyclic loading in this area.A series of dynamic triaxial tests were carried out on undisturbed granite residual soil in Fuzhou,and the dynamic stress and strain relation,dynamic strength,dynamic shear modulus and damping ratio characteristics of undisturbed granite residual soil under cyclic loading were studied.Research conclusions:(1)The relationship between dynamic strain and vibration number of undisturbed granite residual soil under cyclic loading shows three typical types:stable,destructive and critical.(2)The dynamic strength value of undisturbed granite residual soil decreases with the increase of vibration number,and the relationship between dynamic strength and vibration number is a semi logarithmic function.(3)The dynamic cohesion and the dynamic internal friction angle of granite residual soil both decrease greatly after long-term cyclic loading.(4)The dynamic shear modulus of undisturbed granite residual soil decreases with the increase of vibration number or dynamic shear strain,and the correlation between dynamic shear modulus and dynamic stress amplitude can be described by linear model.(5)With the development of vibration number,the damping ratio of undisturbed granite residual soil under cyclic loading shows three typical types:stable,critical and destructive.(6)The research results have certain reference value for understanding the dynamic characteristics of granite residual soil and selecting the dynamic strength index of soil reasonably.