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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。
In order to systematically study the dynamic characteristics and microscopic damage mechanism of loess and mudstone in Tianshui area, cyclic loading test, repeated shear test and SEM scanning technology were used to obtain the dynamic behavior and microscopic parameters of rock and soil. The results show that the dynamic elastic modulus of loess and mudstone increases with the increase of confining pressure, which shows a nonlinear relationship, while the dynamic elastic modulus is inversely proportional to the damping ratio. When the dynamic shear stress ratio is greater than a certain threshold, The damage occurred under the corresponding cyclic dynamic stress. The seismic intensity and the material of the rock mass itself have a great influence on its dynamic strength. The number of repeated shearing increases, the shear strength of the rock mass decreases, and eventually reaches the residual strength. However, , The degree of rock-soil bite increases and the shear strength increases. The static shear makes the soil particles thinner and belongs to the grain shear graining mode. The soil particles are arranged more smoothly and with good directivity and the pores between the particles become denser. Under the action of cyclic dynamic load, with the increase of the shear amplitude, the particles are sheared and grinded, the arrangement is more even, the porosity is obviously reduced, and the shear surface shows “compaction ”. The quantitative analysis and qualitative study of the microscopic pores in mudstone are in good agreement. The research results have important theoretical and practical values for predicting and controlling engineering disasters in the Loess Plateau.