考虑剪切硬化的砂土临界状态本构模型

Critical state constitutive model of sand with shear hardening

基于临界状态土力学框架,建立了一个剑桥类砂土本构模型,适用于单调静力荷载,加入了剪切硬化、依赖状态的剪胀的概念。屈服面采用倒子弹头型,硬化规律不是采用剑桥模型的体变硬化,而是借鉴Hashiguchi次加载面模型的思想,推导出与Norsand砂模型相同的增量形式的塑性剪应变硬化表达式。流动法则采用加入状态参数概念的修正的Rowe应力剪胀关系,该模型能考虑砂土变形特性对密度和固结压力的双重依赖型,只用一组材料参数就能模拟不同密度和固结压力下的应力应变响应,可反映材料的软化。通过与常规三轴试验、等p路径三轴试验等结果的对比,表明该模型是合理的、有效的。

Based on the framework of critical state soil mechanics, a new Cam-type sand model, being applicable to monotonic loading, is proposed. The model combines the concept of state-dependent dilatancy and shear strain hardening rule. Reverse bullet-shaped yielding surface is adopted. Not the volumetic strain hardening in Cam-clay model, but the shear strain hardening rule is used and a new hardening equation is given. The state parameter concept is incorporated in Rowe＇s stress dilatancy equation. The model accounts for the dependence of dilatancy on the stress state and the material internal state. A single set of model constants, once calibrated, can simulate stress-strain response under different initial void ratios and different confining pressures. The model is validated by comparing the predicted results with triaxial test results.