泡沫混凝土隧道减震层减震机制

基于泡沫混凝土隧道减震材料，通过室内试验研究了不同密度、围压、应变率条件下泡沫混凝土材料的力学特性。试验结果表明：随着密度的增加，试样的单轴破坏形态由骨架坍塌破坏逐渐转化为劈裂剪切破坏，峰后应变软化与材料脆性增强；随着围压的增加，材料强度增加且延性增强，峰后由应变软化逐渐转换为应变硬化。在中等应变率范围内（10?5/s ～10?3/s），随着应变率的增加，泡沫混凝土材料的强度近似呈指数增长，同时峰后残余应力增长明显，且塑性应变越大，应变率对峰后应力的影响越大。基于上述试验结果初步建立了泡沫混凝土材料的本构模型。依托嘎隆拉隧道，采用数值方法研究了减震层剪切模量、厚度及减震层-衬砌界面特性3个因素对减震效果的影响规律，相关研究成果可为高烈度区隧道工程减震层的设计提供参考。

Isolation effect of foamed concrete layer on the seismic responses of tunnel

Owing to the excellent shock absorption property of the foamed concrete, it can be used as a seismic isolation material for tunnels. In this study, a series of compression tests was conducted to study the effects of density, confining pressure and strain rate on mechanical properties of the foamed concrete. As the density increased, the failure mode of foamed concrete gradually changed from cell wall buckling to shear failure under the uniaxial compression condition. Besides, the strain-softening and material brittleness became more apparent after the peak. In addition, the strength and ductility of the foamed concrete increased with increasing confining pressure. Moreover, the property of foamed concrete transformed from a strain-softening to strain-hardening material. When strain rate increased in the range of medium strain rate (10?5/s～10?3/s), the strength of foamed concrete showed an exponential growth, and the residual stress in plastic range increased obviously. It was found that the effect of strain rate on the residual stress was greater with the increase of plastic strain. Based on the testing results, a new constitutive model was initially proposed for the foamed concrete. Then the numerical method was performed to investigate the effects of the shear modulus of isolation material, the thickness of isolation layer, and the properties of isolation interface on the isolation of Galongla tunnel. Therefore, the results can provide a helpful reference for the design of the related cushioning layer in tunnels with high intensity.