同一试样上的多级加载动弹模量和阻尼比试验

动弹模量和阻尼比是土动力分析中最重要的参数,利用动三轴仪器对重塑黏土进行试验,研究了一个试样改变试验围压、固结比进行多级试验的方法,考虑先期应力大小,提出了2种试验方法,并与常规方法进行比较。结果表明:方法 1得到的动弹模量、阻尼比与常规方法相差很小,但方法 2得到的动弹模量较常规方法大,采用方法1代替常规方法可有效节省试样数量;根据黏性元件理论分析了振动频率对动弹模量的影响,并通过试验得到了频率对黏土动力特性的影响,最后研究了一个试样进行多级频率试验的方法,得出先期较大频率动荷载对后期较小频率试验影响很小,但先期较小频率动荷载会影响后期较大频率的试验,引起动弹模量衰减,同时造成最大阻尼比减小;一个试样进行多级频率试验时,先进行大频率试验,后进行小频率试验,试验成果与常规试验一致。研究成果有利于提高土动力测试技术,对动力特性研究有积极作用。

Multi-stage Loading Test on One Single Sample to Obtain Dynamic Modulus and Damping Ratio

Dynamic elastic modulus and damping ratio are two of the most important parameters in soil dynamic analysis.In this paper,we studied the methods of multi-stage test on remolded clay with varying confining pressure and consolidation ratio by using dynamic triaxial instrument.In consideration of pre-consolidation pressure,we put forward two test methods and obtained the dynamic elastic modulus and damping ratio and then compared them with those from conventional method.We found that the dynamic elastic modulus and damping ratio obtained by method 1 differed slightly from those by conventional method,while the dynamic elastic modulus by method 2 was larger than that by conventional method.Therefore method 1 could effectively save the number of samples compared with conventional method.Furthermore,we analyzed the influence of vibration frequency on the dynamic elastic modulus based on the theory of viscous element,and obtained the effect of frequency on the dynamic characteristics of clay through the tests.Finally,we studied a multi-stage frequency test method on one single sample and propose that the dynamic load test with large frequency has little effect on the subsequent test with small frequency;but the dynamic load test with small frequency would have impact on the following test with large frequency,resulting in attenuation of dynamic elastic modulus and decrease in maximum damping ratio.The results of multi-stage frequency test following the sequence of large frequency and then small frequency are consistent with those of conventional test.The research results are helpful to improving the soil dynamic test technology and have positive effect on dynamic characteristics research.