甘肃科学学报

黄土是一种具有大孔隙和弱胶结结构的岩土体,具有独特的水敏性和结构性。强震区黄土灾害频发,认识强震区黄土结构演变对宏观力学性质的影响是揭示强震区黄土滑坡、泥石流等灾害内在机制的关键,也是寻找科学有效防治措施的重要保障。研究采用预震试验处理原状黄土,结果表明预震引起黄土试样轴向应变发生变化,当初始含水量为5%～15%时,震后轴向应变减小0.032%～6.665%,近塑限含水量时的变形是天然含水量时的4～12倍,表明水敏性对黄土的变形特征影响显著,同时基于压汞试验测定震后黄土内部孔隙结构的变化,低含水量黄土预震前后大孔隙数量增加,中孔隙和微孔隙变化较小,高含水量黄土预震前后大孔隙数量减小。地震引起的黄土微结构演变是其变形及后期力学性质出现差异的重要原因。

Loess is a kind of geotechnical body with large pores and weak cementation structure,which has unique water sensitivity and structural properties.Loess disasters occur frequently in the strong earthquake area.Recognizing the influence of the structural evolution of loess in the strong earthquake area on the macro-mechanical properties is the key to revealing the intrinsic mechanism of loess landslides,mudflows and other disasters in the strong earthquake area,as well as an important guarantee for finding scientific and effective preventive and control measures.Through the pre-seismic test to simulate the impact of historical earthquakes on loess in the strong earthquake zone,the results show that the pre-seismic caused changes in the axial strain of loess specimens,and the axial strain after the earthquake decreased by 0.032%～6.665%when the initial water content was 5%～15%,and the deformation of near-plastic-limit water content was4～12 times of the deformation of natural water content,which indicated that the water sensitivity has a significant effect on the deformation characteristic of loess,and the deformation of loess was significantly affected by water-sensitive properties.Meanwhile,the changes of internal pore structure of loess after the earthquake were determined based on the pressure mercury test,the number of macropores increased before and after the pre-seismic earthquake in low water content loess,and the changes of meso-pores and micropores were small;and the number of macropores decreased before and after the pre-seismic earthquake in high water content loess which was small.Therefore,the evolution of the microstructure of loess induced by the earthquake was an important reason for the variability of the deformation and the mechanical properties of the loess at the later stage of the earthquake.