重复循环荷载作用下原状黄土动力特性试验研究

Experimental Study on Dynamic Characteristics of Intact Loess under Repeated Cyclic Loading

摘要:

为探究重复循环荷载作用下含水率、固结压力对原状黄土动力特性、变形性状的影响规律，利用英国GDS双向动态三轴试验系统模拟交通荷载，对海东地区原状黄土进行动三轴试验研究。试验结果表明：单一重复循环动荷载作用下，在加载初期，海东地区原状黄土的轴向动应变随着循环次数的增大急剧增加，后期缓慢增加至趋于稳定，即发生应变硬化现象。在加载初期，含水率、固结压力对原状黄土的轴向动应变无明显影响，当循环次数N>400时，原状黄土的轴向动应变随含水率的升高而增加，随固结压力的增大而减小。动剪切模量随循环次数的增加出现先减小后增加再减小的变化，随含水率的升高有较大幅度的降低。动阻尼比随循环次数的增加先增加后减小，随含水率的升高而增大。表明海东地区原状黄土所具有的大孔隙架空结构使其在重复循环荷载作用下易发生振动变形。

Abstract:

This study investigated the effects of moisture content and consolidation pressure on the dynamic properties and deformation behavior of intact loess under repeated cyclic loads. The British GDS bidirectional dynamic triaxial test system was used to simulate traffic loads, and a dynamic triaxial test was carried out on intact loess in Haidong area, Qinghai Province. The test results showed that under a single cyclic dynamic load, in the initial loading stage, the axial dynamic strain of intact loess significantly increased with an increase in the number of cycles; the increase rate gradually reduced, and the strain eventually became stable in the late loading stage. The moisture content and consolidation pressure had no significant impact on the axial dynamic strain of intact loess in the initial loading stage. However, when cycle number N exceeded 400, the axial dynamic strain of intact loess increased with an increase in moisture content and decreased with an increase in the consolidation pressure. With increasing number of cycles, the dynamic shear modulus of intact loess first decreased, then increased, and finally decreased; moreover, it significantly decreased with increasing moisture content. The dynamic damping ratio of intact loess first increased and then decreased with the increase in the number of cycles, and it increased with increasing moisture content. The test results showed that intact loess in Haidong area can easily undergo vibration deformation because of its large-void overhead structure.