强夯置换中碎石运动机制和成墩过程的数值模拟

Numerical simulation of forming of replacement piers during a dynamic replacement process

关于强夯置换碎石墩形成机理(特别是碎石运动和动态成墩过程)的数值模拟研究较少。之前的数值模拟研究往往将碎石垫层视为均匀的连续介质进行分析,偏离了碎石体的物理实质。将碎石分为个体分散接触进行了建模,对单次夯击和连续多次夯击过程中碎石体的变形成墩过程进行了数值模拟。分析结果表明:将碎石垫层视为分离的碎石个体进行模拟可展现强夯置换中碎石墩的形成过程及其变形机制;强夯置换过程按时间顺序可分为夯锤与碎石的能量传递和碎石垫层之间的应力波传播过程、碎石垫层接触软土后的整体变形、夯锤二次冲击碎石结构重分布、稳定结构的碎石与夯锤共同运动4个阶段,并分别阐述了各阶段的具体原因和作用;从铅垂方向排列碎石的水平运动分析了整体成墩的原因。通过对连续夯击过程的数值模拟,获得了夯锤运动状态、能量释放时间变化规律,数值模拟得到的夯锤运动位移、速度、加速度与试验观测结果比较吻合。

Numerical studies on the forming mechanism of replacement piers are scarce, particularly on the kinetic movement of the reinforcement （the stones） and the deformation of the gravel layers. Previous studies tend to treat the stone layer as a continuum, which does not conform to the reality. The numerical simulation is conducted to study the movement of many stones in the soils during the dynamic replacement process. The deformation and forming process of the reinforcement are modeled as the frictionally contacting circular granules. The dynamic replacement process is also simulated under repeated impacts. The numerical results show the forming process of the reinforcement pier. The movement and the distribution of the stones within the soils can be divided into 4 stages. The numerical simulated of repeating tampings agrees reasonably well with the experimental results in terms of hammer velocity, displacement and acceleration.