黄土和泥岩的动力学特性及微观损伤效应

为了系统研究天水地区黄土和泥岩的动力学特性和微细观损伤机制,采用循环荷载试验、反复剪试验和SEM电镜扫描技术,获取岩土体的动力学行为特征和微观参量。研究结果表明:黄土和泥岩的动弹性模量随围压的增加逐渐增大,呈非线性关系,而动弹性模量与阻尼比呈反比关系;动剪应力比大于某阈值时,岩土体在相应周期动应力下发生破坏;地震强度以及岩土体自身材料对其动力学强度影响较大;反复剪切次数增加,岩土体的抗剪强度降低,最终达到残余强度,但随围压的增大,岩土体咬合程度增强,抗剪强度增加;静力剪切使土颗粒变细,属颗粒剪切磨碎模式,土颗粒排列更平整,定向性好,颗粒间孔隙变密实;循环动荷载作用下,随着剪切幅值的增加,颗粒剪切磨碎,排列更平整,孔隙明显减少,剪切面表现为"板结"。泥岩微观孔隙的定量化分析与定性研究一致性较好。研究结果对黄土高原地区工程灾害的预测和控制具重要的理论意义和实用价值。

Dynamic characteristics and microcosmic damage effect of loess and mudstone

The cyclic loading test，repeated shear test and scanning electron microscope(SEM) technology were used to study the dynamic characteristics and microcosmic damage mechanism of loess and mudstone in Tianshui area. The dynamic elasticity moduli of loess and mudstone increase nonlinearly with the increasing of confining pressure and are inversely proportional to the damping ratio. When the dynamic shear stress ratio is larger than a certain value，the soil sample fails after the loading cycles reaching a certain number. With the increasing of shearing cycles，the shear strength decreases and finally achieves the residual strength. But with the increasing of confining pressure，the soil occlusion and shear strength increase. The static shear which makes the particles finer belongs to the particle shear trituration mode. The soil particles arranges more smoothly with regular orientation and the inter-particle pores become tight. Under the cyclic dynamic loading，the particles experience the shearing-grinding with the increasing of shear amplitude. The soil particles arranged more smoothly，and the inter-particle pores decreased obviously. The shear plane is shown to be hardened and impervious.