筋—土界面循环剪切刚度和阻尼比的试验研究

Experimental research on reinforcement-soil interface stiffness and damping ratio under cyclic shearing

为了研究筋—土界面在遭受动力作用时的表现,利用大型直剪仪对土工格栅、土工编织布、土工无纺布和砂土界面进行了一系列循环剪切试验,得到了不同工况下界面的剪切刚度和阻尼比,并探究了循环次数与剪切刚度和阻尼比之间的规律。研究结果表明,同一循环次数时格栅—土界面的循环剪切刚度最大,土工编织布—土界面的阻尼比最大;剪切位移幅值为3 mm时3种竖向应力下界面都呈现出循环剪切硬化的特征,随着循环次数的增加,各竖向应力下的界面阻尼比有趋于某一值的趋势;砂土密实度越大,同一循环次数对应的剪切刚度越大,阻尼比越小,且随着循环次数的增加3种砂土密实度的界面阻尼比有趋于同一值的趋势;循环剪切位移幅值为5 mm的界面发生循环剪切软化现象,剪切位移幅值越大,界面同一循环次数的阻尼比也越大。

In order to investigate the behavior of reinforcement-soil interface under dynamic load, a series of cyclic direct shear tests focused on geogrid,woven geotextile,non-woven geotextile with sand interface are performed through large-scale direct shear device. The shear stiffness and damping ratio of the interface in different conditions are gained; and then the relationship between cycle number and shear stiffness or damping ratio are analyzed. Results show that, in the same cycle number, the geogrid-sand interface has the largest value of shear stiffness; and the woven getextile-sand interface has the largest value of damping ratio. The interface exhibit cyclic shear hardening in the three values of normal stress with the cyclic shear amplitude of 3 mm. The damping ratio of the interface in different normal stresses tends to a same stable value with the increase of cycle number. The interface shear stiffness is increased and damping ratio is decreased with sand relative density, and with the increase of cycle number the damping ratio of the interface in different sand relative densities tends to a same stable value. Cyclic shear degradation is observed in the interface suffering cyclic direct shear with shear amplitude of 5 mm; the interface with a larger shear amplitude in cyclic direct shear has larger value of stiffness.