This research examines the impact of lateral constraints on the deformation and mechanical properties of compacted loess, a prevalent material for road construction foundations. Through laboratory compression tests on samples from a specific project area, it evaluates how compactness, confining pressures, and vertical loads affect compacted loess's stress-strain behavior and lateral deformation. The study demonstrates that lateral constraints significantly influence soil deformation behavior and mechanical characteristics, particularly under complete confinement. A new formula for accurately calculating soil compression deformation in engineering practices is introduced, enhancing the prediction and management of subgrade settlement in loess regions. This work contributes to improved construction methodologies and infrastructure durability in challenging terrains by offering insights into compacted loess's compressibility under various lateral constraints.

In this paper, a dynamic model is established to investigate the dynamic behavior of train-tracksubgrade-soil (TTSS) interaction. The effects of interfacial damage of the track slab induced by soil settlement on the dynamic interaction system are considered. The model framework is established by the finite element method. The soil settlement-induced track deformation is calculated by a practical iteration algorithm, where the nonlinear interfacial damage is simulated by the cohesive zone model. The simulation model is verified by comparison with other models. In regards to the excitations of the dynamic TTSS interaction system, two types of track irregularities are considered, namely the conventional track irregularities generated by known spectrums, and the additional irregularities caused by soil settlement. In the numerical study, the dynamic performances of the TTSS interaction subjected to interfacial damage, and soil settlement are compared. Next, the short wavelength irregularity is discussed as well. From the results, the vibration enhancement can be observed in the time and frequency domain. The interfacial damage of the track enhances the vibration both in low- and high-frequency domains, while the impacts of settlement are only observed in the frequency band of 0 similar to 3 Hz. The frequency band of vibrations triggered by short wavelength irregularities is correlated with its wavelength range. Moreover, the settlement with different wavelengths and amplitudes is studied. It is shown that the increase of settlement amplitude and decrease of settlement wavelength lead to higher damage degree in amplitude and wider spatial distribution. In regards to the dynamic responses, the vehicle accelerations, wheel-rail contact forces, track displacement, and soil displacement are more sensitive to the settlement amplitudes varying from 10 to 80 mm, while the sensitive settlement wavelength is concentrated in 20 to 40 m.

Monitoring road subgrade settlement is crucial for maintaining pavement integrity, durability, and safety. It is important to understand the causes and mechanism of the settlement ahead of implementing monitoring methods, while few studies have examined the influencing factors comprehensively. On the other hand, there are many existing and emerging monitoring methods, such as In-SAR, GPR etc., each possessing different adaptability and accuracy level. There is a gap of knowledge about commons and differences among these methods in terms of working principle, data processing, precision level, as well as practicability. The objective of this paper is to provide reference of the state-of-the-art and state-of-the-practice of subgrade settlement monitoring methods for the engineers and researchers. A comprehensive literature review was conducted in the aspects of influencing factor, measurement method and advancements in monitoring subgrade settlement. A framework of joint monitoring system is proposed subsequently and suggestions for future studies are presented.