A measuring method for layered compactness of loess subgrade based on hydraulic compaction

Abstract

Subgrade compactness is a key factor determining subgrade quality. However, defects exist in the traditional methods for subgrade compactness measurement. Based on the theoretical analysis of dynamic impact and vibration wave, the hydraulic compaction method was used to measure the layered compactness of loess subgrade in this paper. A full-scale test was then carried out to observe the variation of soil parameters after hydraulic compaction. The results show that the layered interface settlement (LIS) of subgrade has the characteristic of stage change bounded by 0.9m of depth and 6-9 blow times respectively. The compaction effect is not obvious when the depth exceeds 1.2m, and thus the improvement depth (ID) was introduced. The settlement curve has the characteristic of Boltzmann function. The relationship between layered compacted compactness (LCC) and LIS was obtained by regression method. Finally, based on the theory of layered compaction, a measuring method for layered compactness of loess subgrade based on hydraulic compaction was presented. The field application demonstrate that the results of hydraulic compaction method correspond well with that of sand filling method.