This study investigates the mechanical properties and damage processes of cement-consolidated soils with Pisha sandstone geopolymer under impact loading using the Hopkinson lever impact test. The mechanical properties of cement-cured soils containing Pisha sandstone geopolymer were examined at various strain rates. The relationship between strain rate and strength of the geopolymer-cemented soil was established. As the strain rate increased, the coefficient of power increase for the Pisha sandstone geopolymer cement-cured soil initially rose before gradually stabilizing. The pore structure of the crushed specimens was analyzed using Mercury intrusion porosimetry. Based on the observed pore changes under impact loading, the pore intervals of the geopolymer-cemented soil were defined. A fitting model linking strain rate and porosity was developed. As strain rate increased, the porosity of the specimens first increased and then decreased, with larger internal pores gradually transforming into smaller ones. The highest porosity was observed at a strain rate of 64.67 s- 1. Crushing characteristics of the cement-cured soils under impact loading were determined through sieving statistics of the crushed particles. The average particle size of the fragments decreased as the strain rate increased. The fractal dimension initially decreased and then increased with the rise in strain rate, reaching its lowest value at a strain rate of 64.67 s- 1. Based on the dynamic mechanical properties, microscopic porosity, and fracture characteristics, the critical strain rate and damage form for cement-consolidated soils with Pisha sandstone geopolymer under impact loading were determined. This study offers valuable insights for the practical application of Pisha sandstone geopolymer cement-cured soils in engineering.

The compaction characteristics of gravelly soil are affected by gravel hardness. To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil, heavy compaction tests and crushing tests were conducted on gravelly soils with gravels originated from hard, soft and extremely soft rocks. According to orthogonal experiments and variance analysis, it was found that hardness has a significant impact on the maximum dry density of gravelly soil, followed by gravel content, and lastly, moisture content. For gravel compositions with an average saturated uniaxial compressive strength less than 60 MPa, the order of compacted maximum dry density is soft gravels > hard gravels > extremely soft gravels. Each type of gravelly soil has a threshold for gravel content, with 60% for hard and soft gravels and 50% for extremely soft gravels. Beyond these thresholds, the compacted dry density decreases significantly. There is a certain interaction between hardness, gravel content, and moisture content. Higher hardness increases the influence of gravel content, whereas lower hardness increases the influence of moisture content. Gravelly soils with the coarse aggregate (CA) between 0.7 and 0.8 typically achieve higher dry densities after compaction. In addition, the prediction equations for the particle breakage rate and CA ratio in the Bailey method were proposed to estimate the compaction performance of gravelly soil preliminarily. The results further revealed the compaction mechanism of different gravelly soils and can provide reference for subgrade filling construction.

Soil-rock mixtures (SRM) are extensively utilized as filling materials in engineering slopes and roadbeds. A comprehensive understanding of the crushing characteristics of SRM during compaction is essential for precisely controlling its mechanical properties, particularly when dealing with SRM comprising soft rock blocks. This study conducted heavy compaction and screening tests to investigate the crushing and compaction behaviors of soil-soft rock mixture (SSRM) with varying coarse particle content (P5 content), the primary focus was primarily on analyzing the double fractal characteristics of coarse and fine particles. The research findings are as follows: with the increase of P5 content, the maximum dry density of SSRM initially rises and then declines, reaching its peak when P5 content is 70%. Soft rock blocks in SSRM exhibit extreme fragility during compaction, the crushing index of coarse particles exhibits a linear increase with the rise in P5 content, whereas the crushing index of fine particles displays a double peak characteristic. After compaction, a linear positive correlation is observed between the fractal dimension and the crushing index of coarse and fine particles. With the increase in P5 content, the slope of the relationship curve between the fractal dimension and the crushing index of coarse particles remains relatively constant, while the intercept gradually decreases. Moreover, the fractal dimension of fine particles effectively reflects the compaction characteristics of SSRM, and the relationship between the fractal dimension of fine particles and dry density aligns with the compaction curve of SSRM.