列车振动荷载作用下南京细砂动强度变化规律研究

Variation Rule of Dynamic Strength of Nanjing Fine Sand under Train-induced Vibration Load

以南京细砂为研究对象,采用空心圆柱扭剪仪模拟列车振动荷载作用对应的土体单元所受应力路径,考虑试样围压、加载幅值和排水条件,研究列车振动荷载作用下土体动强度的变化规律。试验结果分析表明:在模拟列车振动荷载作用对土体竖向应变的影响时,采用椭圆应力路径来代替心形应力路径是切实可行的,能克服试验仪器高频加载时无法有效模拟心形应力路径的缺点;其次,当围压和加载幅值都较小时南京细砂主要表现为在振动初期强度强化特征,当振动次数达到一定数量后强度也达到一个稳定阶段;当试验围压较大时,随振动次数增加,南京细砂的强度变化主要以强度弱化阶段为主;同时,排水条件对其强度变化的主要影响表现为对其振动前期强度强化阶段的影响,对其强度弱化阶段的影响并不明显。

Using a GDS hollow cylindrical torsional shear apparatus to model the stress path of strain-induced vibration,we investigated the dynamic strength of Nanjing fine sand under different loading conditions.To simplify the loading method,we modeled the relationship of the normal and shear stresses with an oval,rather than heart-shaped,stress path.Our results show that when the confining pressure and the amplitude of the train-induced vibration are small,the dynamic strength of the Nanjing fine sand first increases and then stays stable over time.However,when the confining pressure increases,the increasing stage of the dynamic strength of the Nanjing fine sand is very short and the dynamic strength values are also much smaller.After some vibration time,the dynamic strength of the Nanjing fine sand decreases almost linearly with increasing vibration.Also,as the amplitude of the vibration increases,the dynamic strength weakens more quickly.This also proves that the drain condition mainly affects the increasing stage of the dynamic strength and has very little influence on its weakening stage.