Mechanical behavior and microstructural variation of loess under dynamic compaction

The laboratory dynamic compaction test was used to study the effects of dyn amic impact loads on the shear strength characteristics of loess. Loess spe cimens were compacted by different numbers of blows and their shear strengt hs measured. The experimental results revealed that the shear strength vari es in stages with the number of blows. During the initial stage, the shear strength increases with the number of blows. It reaches a peak value acid t hen decreases with the number of blows. To reveal the relationship between this alternation in shear strength and microstructural variation, quantitat ive microstructural analyses were performed on some tested specimens at dif ferent stages of strength evolution. This microstructural study demonstrate d that the variation of shear strength is directly related to the alteratio n of microstructure. It is concluded that the shear strength of loess is ba sically controlled by its microstructural stale. Growing particle size hete rogeneity, varying particle orientations and increasing microstructural dam age are the main causes of the alternation of shear strength. (C) 2001 Else vier Science B.V. All rights reserved.