冲击荷载作用下的路基动力反算

Subgrade dynamic backcalculation under impact loading

根据半正弦波圆形刚性垂直分布冲击荷载作用下弹性半空间表面竖向位移的动力响应解析解,通过合理提取PFWD实测的压力和位移的时程数据,建立了基于最小二乘准则的路基动力反算数学模型,并采用修正的Gauss-Newton算法提出了相应的反算方法。实际反算表明,将压力时程拟合为半正弦波可获得冲击荷载作用的角速度和不应期2个反算参数,据此通过位移时程曲线拟合可获得动模量和动密度2个路基动力参数。动静反算对比表明,PFWD实测的动、静模量基本一致,而动密度与灌砂法实测干密度和含水率之间具有良好的相关性。因此,PFWD可同时检测路基设计指标(模量)和施工指标(压实度),实现二者统一评价。

According to the analytic solutions of dynamic response of vertical displacement on the elastic half-space surface under the impact loads of semi-sine wave with circular rigid vertical distribution, the time history data of pressure and displacement tested with the PF- WD （Portable Falling Weight Deflectometer） were reasonably extracted to establish the mathematical models of subgrade dynamic backcalculation based on the least square criteri- on. The corresponding backcalculation method was proposed with the modified Gauss-New- ton algorithm. The practical backcalculations show that the time history of pressure was fit- ted as a semi-sine wave to obtain two backcalculation parameters of impact load, i.e. the an- gular velocity and the nonresponsive period. The displacement time history was fitted to ob- tain two subgrade dynamic parameters, i.e. the dynamic modulus and the dynamic density. The comparisons of dynamic backcalculation to static backcalculation show that the dynamic modulus is substantially equal to the static modulus, and there are good correlations between the dynamic density and the dry density and the moisture content measured with the poured sand method. Therefore, the PFWD can simultaneously test the design index （modulus） and the construction index （compactness） for the subgrade to achieve the both unified evaluation.