法向应力对接触面循环单剪力学特性的影响研究

法向应力对土与结构接触面循环单剪力学特性的影响研究具有重要意义。运用80 t大型三维接触面试验机,进行了不同法向应力下粗粒土与结构接触面单剪试验,分析了法向应力对接触面循环单剪力学特性的影响规律。试验结果表明,法向应力对接触面变形位移、滑动位移、切向应力、可逆性剪切体变和不可逆性剪切体变以及抗剪强度等接触面性能参量的数值有显著影响,但对参量间关系形式影响较小。法向应力越大,接触面变形位移在初始几个循环内越大,随循环剪切的进行,其减小速率越快,最终稳定值越小;切向刚度越大,切向应力稳定值也越大,初始几个循环内切向刚度系数越小;不可逆性剪切体变越大,可逆性剪切体变峰值和稳定值越小,相变位移和相变应力比越小;抗剪强度越大,其异向程度则先增大后减小。不同法向应力下,接触面循环抗剪强度与法向应力符合摩尔-库仑准则;切向应力比-切向位移关系、不可逆性剪切体变和剪切功密度关系均具有良好一致性,基本不受法向应力影响,可用双曲线模型描述,这将大大简化接触面本构描述。

Effect of normal stress on cyclic simple-shear behavior of gravel-structure interface

The cyclic simple-shear behavior of soil-structure interfaces under different normal stresses is of great significance in theoretical analysis and engineering practices. A series of interface tests between gravel and steel was conducted under different normal stresses using a 3D large-scale simple-shear apparatus, and the influence of normal stress on the cyclic simple-shear behavior of the interface was explored in detail. The normal stress plays a crucial role in the magnitudes of the shear behavior of the interface, including deforming and sliding displacements, shear stress, reversible and irreversible normal displacement, and cyclic shear strength, while it has slight influence on the relationship pattern of shear behavior. Increased normal stress leads to increased deforming displacement at the first few shear cycles, accelerated reduction and decreased stabilized amplitude of deforming displacement. Enhanced normal stress also results in increased shear modulus, decreased shear modulus coefficient at the first few shear cycles, increased stabilized shear stress and cyclic shear strength of the interface. In addition, larger normal stress results in larger irreversible normal displacement, smaller peak reversible normal displacement, smaller transition tangential displacement and transition stress ratio of the interface. The cyclic shear strength behaves well in accordance with Mohr-Coulomb criteria, regardless of normal stress. Perfect consistency exists in the stress ratio versus tangential displacement response and irreversible normal displacement versus shear work density response, independent of normal stress, and can be described using hyperbolic models. These consistency characteristics will significantly simplify the constitutive modelling of soil-structure interfaces.