振动单剪仪的研制和调试

在我所1964年制成的静力单剪仪的基础上,研制了一种振动单剪仪。此仪器由剪切盒、静力加荷系统、电磁式激振器和电子测量系统组成。剪切盒由多个圆环迭成,圆环内有橡皮膜,在其中安装试样.垂直和水平荷重是用气压施加的,并且分别由两个调压阀控制。利用水平加荷设备,可以使试样在各种不同的初始剪应力下振动.激振力是由超低频讯号发生器发出的讯号,通过功率放大器放大,再输入激振器而产生的。最大激振力为120kg,常用的频率为每秒2周。利用这种仪器,可以测量不排水试样在各种振动过程中的动剪应力、孔隙压力和位移,并确定其动剪切模量、阻尼比或液化强度等。经过初步试验,证明其性能尚佳.此仪器结构简单,加工容易,电子仪器设备可用国内产品配套,进行试验时制备试样和操作都比较方便,是目前一种比较实用的研究土的动力性质的仪器.

A Cyclic Simple Shear Test Apparatus

A cyclic simple shear test apparatus, based on a static simple shear test apparatus which has been developed in Nanjing Hydraulic Research Institute since 1964, is constructed. This apparatus is composed of a simple shear box, an electro-magnetic exciter, the static loading system and the electronic recording system. A sample with diameter of 7cm and height of 2cm is enclosed inside a rubber membrane which is in turn confined by steel rings and is attached rigidly to the end plates. By means of the horizontal loading system the initial shear stress is applied to the sample. The vertical and horizontal loads are applied pneumatically and are controlled seperately by two regulating valves.The base of the simple shear box is connected with the excitor which applies the cyclic shear stress to the sample. The amplitude and the frequency of excitation is controlled by the extra-low frequency signal generator, and the signal generated by the latter is amplified and input to the excitor. The max. exciting force is 120kg, and the frequency generally used is 2~3 Hz. During the test the variation of dynamic shear stress, pore pressure and displacement are measured by the transducers and are recorded by the oscilloscope.This apparatus has been now tested, adjusted, and used to investigate the characteristics of liquefaction of some saturated sand samples. It is shown that this apparatus works fairly well. Furthermore, its construction is simple, and it can be operated easily. Therefore it is concluded that this apparatus may be used to study the dynamic behaviour of the soil either for the practical engineering project or for the research purpose.