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冻土的动力学参数是工程设计的重要依据之一,也是数值模拟时不可或缺的因素,动力学参数的正确与否直接影响了工程设计和数值模拟的正确性。通过分析其他学者做过的冻土动荷载三轴试验,以及参考普通直剪仪器的构造,北京交通大学冻土室研制了一种新型的冻土动荷载直剪仪,该仪器将传统直剪仪的水平静载部分改造为能够提供动荷载作动器,可以提供一个0.1~6 Hz、20kN以内的动荷载,用于测定冻土的动力学参数。介绍了动荷载直剪仪的结构组成、动力系统、测控系统等,并详细分析了仪器框架、直剪盒、动荷载作动器等的参数选取方法。最后使用该仪器进行了一组验证试验,试验结果表明,动荷载直剪仪能够完成其设计目的,可以测量出冻土在动荷载下的应力-应变曲线,从而求出动弹性模量、动阻尼比等,为冻土的动力学参数测定开辟了一条新的道路。
The dynamic parameters of frozen soil are one of the important bases of engineering design and also an indispensable factor in numerical simulation. Whether the dynamic parameters are correct or not has a direct impact on the correctness of engineering design and numerical simulation. By analyzing the triaxial tests of frozen earth moving loads made by other scholars and referring to the structure of ordinary direct shear instruments, a new type of dynamic shear load direct shear tester for frozen soil was developed in the permafrost chamber of Beijing Jiaotong University. The instrument combines traditional direct shear The instrument’s horizontal static load is partially modified to provide a dynamic load actuator that provides a dynamic load of 0.1-6 Hz and less than 20 kN for the determination of the kinetic parameters of the frozen soil. The structure, dynamical system, measurement and control system of dynamic load shears are introduced, and the parameter selection methods of instrument frame, straight shear box and dynamic load actuator are analyzed in detail. Finally, a set of verification tests were carried out by using the instrument. The experimental results show that the dynamic load shears can accomplish its design purpose and can measure the stress-strain curve of frozen soil under dynamic load so as to obtain the dynamic elastic modulus. Damping ratio, etc., for the determination of kinetic parameters of frozen soil has opened up a new road.