Experimental investigation of stress field evolution in soil under roller compaction

The article examines the problem of the absence of a deterministic model linking the evolution of the stress field in the soil with the kinetics of density gain during multi-pass roller compaction, which is relevant for optimizing the construction of forest roads. The purpose of the work is to determine the quantitative patterns of this process to develop criteria for selecting technological parameters. To achieve this purpose, an integrated field experiment methodology was developed, based on the synchronous registration of integral characteristics (sediment, density) and the stress-strain state component using tensometric sensors and the chalk beacon method. Studies were conducted on sandy loam, loam, and gravel, varying the thickness of the layer, the speed of movement, and the number of passes. As a result, three stages of stress state evolution were experimentally identified, reflecting the transition from plastic deformations to elastic ones. The universal damped hyperbolic nature of the dependence of the maximum normal stress on the number of passages, described by the model σmax = N / (a + bN), has been revealed. The two-humped form of the tangential stresses diagram was discovered, and a significant anisotropy of residual stress relaxation was revealed: horizontal stresses disappear within 18-20 hours, while vertical stresses relax almost instantaneously. The obtained results deepen the theory of contact interaction and provide practical criteria for determining the optimal number of passes and the timing of compaction quality control.