土工袋减振隔振机制分析及试验研究

Mechanism analysis and experimental study of vibration reduction and isolation effect of geotextile bag

设置于地基中的土工袋不仅可以提高地基承载力,而且具有减振隔振效果。通过水平循环剪切试验研究了土工袋的动力特性,验证了土工袋具有可变的水平刚度和较大的阻尼比,表明土工袋是一种良好的基础减振隔振材料。土工袋的等效阻尼比随着竖向压力的增大而减小,随着最大剪应变的增大而增大。同时,采用离散单元法进行了土工袋在动力荷载作用下的数值模拟计算,土颗粒间采用弹簧-阻尼器接触模型;而土工袋被看成具有张力的小颗粒薄层,这些小颗粒间的接触与袋内土颗粒间的接触模型相同,但仅设置法向的接触而无切向接触,且只受拉不受压。结果表明,土工袋的减振消能效果主要来自于袋内材料的摩擦耗能、黏滞耗能以及袋子张力引起的耗能。另外,还进行了土工袋沟槽的原位振动测试,验证了土工袋的减振隔振效果。

Geotextile bag buried in subgrade can improve the bearing capacity of subgrade and also reduce or isolate vibrations. A series of horizontal cyclic shear tests are carded out to investigate the dynamic characters of piled geotextile bag. The test results indicate that geotextile bag is excellent materials for base vibration reduction and isolation as it has variable horizontal stiffiness and large damping ratio. The damping ratio of geotextile bag decreases with increasing of vertical pressure, and increases with the increasing of maximum shear strain. Besides, the discrete element analysis is carried out on a geotextile bag under cyclic loading. The contact between soil particles in geotextile bag is modeled as a spring-dashpot system. The geotextile bag is modeled as coating of small particles with tension. The contact between the small particles in coating is also spring-dashpot system which has no tangential contact but only normal contact, and can only carry tension stress. The simulation results illustrate that the vibration reduction ofgeotextile bag is due to the energy dissipation mainly resulting from frictional and viscous forces among soil particles and the tension of bag. Moreover, in-situ tests are performed on a trench built with geotextile bag to validate the vibration reduction and isolation effect of geotextile bag.