This study presents the results of consolidated drained triaxial tests conducted to investigate the influence of various parameters on the volumetric change behavior of cemented sand reinforced with polyvinyl alcohol (PVA) fibers. The primary objective is to explore the interaction between fiber weight ratio, cement weight ratio, confining pressure, and relative density on the dilatation behavior of cemented sand reinforced with PVA fibers. PVA fibers were incorporated into dry sand-cement mixtures at weight ratios of 0.0%, 0.3%, and 0.6%. The specimens were prepared with cement content of 0%, 2%, and 4% by weight of dry sand and cured for 7 days. Two relative densities were used in specimen preparation, and triaxial compression tests were conducted under different confining pressures. The results reveal that decreasing relative density, increasing cement content, and adding fibers all contribute to a reduction in sample dilatation. Specifically, the peak dilation rate increases with higher relative density and cement content, while it decreases with higher fiber content and confining pressure. A notable aspect of this study is its investigation of how these parameters interact when combined, offering a deeper understanding of their collective effects on soil behavior.

Chemical stabilization is among the methods utilized to improve the shear strength properties and volumetric changes of problematic soils. This research assesses the possibility of using sludge ash from a wood and paper mill (SAWP) as an industrial sludge to improve the fat clay engineering characteristics. Thus, unconsolidated-undrained triaxial, direct shear, one-dimensional swelling, and consolidation tests were conducted. Results showed that shear strength parameters (both in short and long-term) increase with increasing SAWP contents and curing period due to the production of sufficient cementitious components and the formation of strong bonds between the particles. Investigating the direct shear test results indicated that the failure envelope in stabilized samples with high SAWP contents was slightly curved. Stabilized samples with high amounts of SAWP at low vertical stresses show brittle failure, while the type of failure observed for these samples at high vertical stresses is more ductile. Moreover, the magnitude of free swell gradually decreased with increasing SAWP contents. The replacement of clay particles with SAWP and flocculation and/or agglomeration of clay particles were the main reasons for this issue. Finally, the compression index, swell index, and coefficient of volume compressibility decrease with increasing SAWP content for the applied load increment, indicating the effect of stabilization in reducing the consolidation settlement of the layers. The test results revealed that the sludge ash used in this study can be used to enhance the engineering properties of fat clay.

In artificial freezing engineering, the freezing temperature is an important factor affecting soil frost heave deformation, and studying its impact is of great significance. The frost heave ratio of soil is a crucial factor for designing and predicting soil frost heave. However, it only considers vertical deformation while neglecting radial deformation. This paper introduces a simple unidirectional freezing apparatus specifically designed for three-dimensional x-ray computed tomography (CT) scanning, which allows for the investigation of internal structural changes in clay during freezing at four different freezing temperatures (i.e., -3 degrees C, -5 degrees C, -7 degrees C, and -9 degrees C). Freeze-necking of the soil was observed during freezing. An image processing method was proposed to segment the soil samples, and parameters such as length, equivalent diameter, and volume were measured to assess changes during freezing. The observed variations in necking depth and equivalent diameter indicate that freeze-necking is uniform. As the freezing temperature decreased, the necking depth reduced from 72.4 mm to 38.1 mm, and within this necking depth, the equivalent diameter decreased progressively from the bottom to the top. Moisture content increased near the cold end of the soil and decreased near the warm end, suggesting that freeze-necking is due to moisture migration within the soil. Considering freeze-necking, the volumetric frost heave ratio was defined to characterize soil frost heave deformation. This ratio also decreases as the freezing temperature decreases, and the values are smaller than those of the traditional frost heave ratio. The discrepancies become more pronounced at higher freezing temperatures, reaching up to 1.8% at -3 degrees C. The results indicate that lower freezing temperatures can reduce frost heave deformation, and freeze-necking requires greater attention in engineering at higher freezing temperature.