压实土体试件动力学参数室内测试

Laboratory test of kinetic parameters of compacted soil specimen

为了获得压实土体试件的无阻尼固有频率、阻尼比及刚度系数等动力学参数,给现场施工压实质量控制和碾压工艺改进提供技术参考,依据振动理论,将试件简化为依靠自身重力固定在振动台台面的有阻尼单自由度系统,首先基于台面位移振幅恒定时基础振动引起的试件系统运动微分方程,给出了利用位移、速度和加速度共振条件求解试件动力学参数的基础思路。其次,针对试验用振动台台面振幅随振动频率增大而减小的特点,依据台面振幅不变时的位移共振条件,形成了台面位移变幅情况下试件系统的位移幅值和速度有效值的理论表达式;根据试验过程中频率共振区试件发生偏移的状况,采用手持式测振仪测得的非共振区试件的位移峰峰值和速度有效值,通过最小二乘原理,建立了压实试件动力学参数识别方法。结果表明:基于位移峰峰值得到的压实度为94%时,土体试件的无阻尼固有频率为45.9 Hz,阻尼比为0.9881,刚度系数为382860.5 N/m,黏性阻尼系数为2625.7 N·s/m,幅值不变的基础振动引起的位移共振频率为32.6 Hz。

In order to obtain the kinetic parameters such as undamped natural frequency,damping ratio and stiffness coefficient of compacted soil specimen,and to provide technical support for the quality control of compaction and the improvement of rolling process in the field construction,according to the vibration theory,the specimen was simplified as a damped single-degree-of-freedom system fixed on the surface of the shaking table by its own gravity.Firstly,based on the differential equation of motion of the specimen system caused by the foundation vibration when the displacement amplitude of the mesa was constant,the basic idea of solving the dynamic parameters of the specimen by the resonance conditions of displacement,velocity and acceleration was given.Secondly,according to the characteristics that the amplitude of the vibration table decreases with the increase of the vibration frequency,and according to the displacement resonance condition when the amplitude of the vibration table was constant,the theoretical expressions of the displacement amplitude and the effective value of the velocity of the test specimen system,under the condition that the displacement amplitude of the vibration table changes were respectively formed.In view of the deviation of the specimen in the frequency resonance region during the test,the displacement peak-peak value and the effective value of velocity of the specimen in the non-resonance region measured by the hand-held vibrometer were adopted,and the identification method of the vibration mechanics parameters of the compacted specimen was established by the least square principle.The results show that for the compacted specimen with 94%compactness the undamped natural frequency,damping ratio,stiffness coefficient and viscous damping coefficient are respectively 45.9 Hz,0.9881,382860.5 N/m and 2625.7 N·s/m,according to the peak-peak displacement.The displacement induced by the base vibration with constant amplitude has a resonance frequency of 32.6 Hz.1 tab,6 figs,20 refs.