加筋建筑垃圾土大型动三轴试验及加筋机制探讨

Large dynamic triaxial test study on reinforcement mechanisms of reinforced construction waste

以建筑垃圾土为主要研究对象,开展一系列大型动三轴试验,分析砂土、建筑垃圾土轴向累积变形及不同加筋形式下建筑垃圾土超静孔隙水压力发展规律、动应力–动应变和动弹性模量,并对轮胎加筋建筑垃圾土作用机制进行探讨。结果表明:(1)循环次数和动应力幅值对填料动力性能影响明显,轴向累积变形试验结果符合安定理论,且在相同安定范围内,建筑垃圾土承载能力高于砂土;(2)加筋建筑垃圾土轴向累积变形预估模型在10个循环次数内,符合双曲线模型;10个循环次数外,符合修正Monismith模型;(3)当动应力幅值高于临界动应力时,超静孔隙水压力波动较大,且越靠近临界动应力现象越明显;(4)随循环次数增大,滞回圈面积逐渐缩小,土体动弹性模量逐渐增大;(5)轮胎提供的侧壁约束力与摩阻力可以增大土体颗粒间的咬合作用,限制裂缝的横向与竖向发展;建筑垃圾土顶部加筋效果优于底部加筋,双向土工格栅加筋效果不如轮胎加筋。

A series of large dynamic triaxial tests are performed mainly on construction waste. The accumulative axial deformation of construction waste and sand,excess pore water pressure,dynamic stress-strain and dynamic elastic modulus with different types of reinforcement are investigated,and the reinforcement mechanism of construction waste reinforced with tires is analyzed. The experimental results demonstrate that cycle number and dynamic stress have a significant effect on dynamic behaviors of the filler. The accumulative axial deformation obtained in the tests is in line with the shakedown theory,and the load capacity of construction waste is higher than that of sand in the same shakedown range. Within 10 cycles,the accumulative axial deformation of construction waste is suitable for the hyperbolic model,while it is suitable for the modified Monismith model after 10 cycles. When the dynamic stress is higher than the critical dynamic stress,the excess pore water pressure has violent fluctuations. The closer the dynamic stress to the critical dynamic stress,the more obvious the fluctuation phenomenon is. As the cycle number increases,the hysteresis loop area gradually decreases while the dynamic elastic modulus of construction waste gradually increases. The hoop stress and friction resistance provided by the tire sidewall can enhance the particle-tire-particle interaction,which can reduce the horizontal and vertical developments of cracks. It is also revealed that the reinforcement effect of construction waste with the top tire is better than that of the bottom tire,and the effect of biaxial geogrid is not better than that of waste tire.