The excavation of the foundation pit impacts the safety, stability, and normal operational functionality of adjacent existing tunnels. With the increasing urban building density, it is becoming more common to conduct foundation pit excavation in close proximity to existing tunnels, which may result in deformation and damage to the tunnels. The impact of foundation pit excavation on adjacent existing tunnels was investigated using a transparent soil scale model and Particle Image Velocimetry technology. The horizontal and vertical distances between the foundation pit and tunnel, as well as the soil consolidation pressure, were individually examined to analyze their respective trends and magnitudes of impact on the maximum vertical deformation of adjacent existing tunnels. The findings suggest that as the excavation depth increases, the deformation of existing tunnels is increasingly impacted by the excavation of foundation pit. However, this impact decreases with greater horizontal or vertical distance between the foundation pit and tunnel. Furthermore, the impact of vertical distance between the tunnel and foundation pit on tunnel deformation is more significant. The pre-consolidation strength of the soil mass significantly impacts the deformation of the existing tunnel. In order to minimize tunnel deformation in practical engineering, constructive recommendations were proposed.

Ground settlement resulting from consolidation may lead to tilted buildings, cracks in the pavement, damage to underground utilities, etc. Therefore, it is crucial to understand the consolidation behaviors (including primary consolidation and secondary compression) of the soil of the subgrade. There is a large amount of soft clay deposited in Nanjing, located in the Yangtze River Basin. The consolidation behavior of Nanjing soft clay can significantly affect foundation design and the cost of construction. In this study, experimental measurements of the consolidation behavior of Nanjing soft clay were conducted, and parameters (such as pre-consolidation pressure, secondary consolidation index and secondary consolidation ratio) related to consolidation were assessed. The concept of simulated over-consolidation ratio (OCRs) was proposed, and the close relationship between primary consolidation and secondary compression settlement and the OCRs of Nanjing clay was investigated.

Despite several parameters having been identified as having an impact on the undrained monotonic response of granular soils, the impact of the overconsolidation ratio (OCR) is still a contentious issue. One of the significant reasons for the inconsistencies in the undrained behavior is the method by which the stresses are applied--specifically, the effective preconsolidation and confining pressures. To address this, two separate series of triaxial compression tests were realized in order to examine and compare the influence of the OCR (OCR = 1, 2, 4, and 8) on the mechanical response of Chlef River (Algeria) sand, considering the way the stress state was applied. During the first series, the OCR was accomplished by consolidating the specimens to an effective preconsolidation pressure (sigma p ' = 100, 200, 400, and 800 kPa) and subsequently unloading them to a constant desired effective confining pressure of 100 kPa. In the second series, all specimens were consolidated to a maximum effective preconsolidation pressure of sigma p ' = 800 kPa (constant effective preconsolidation pressure) and then unloaded to different effective confining pressures (sigma c ' = 800, 400, 200, and 100 kPa), using two different sample preparation techniques--dry funnel pluviation and moist tamping. The test results revealed a suitable increase in the shear strength with an increase in OCR in the first series, with the opposite trend observed in the pore water pressure. For the second series, an increase in the OCR parameter resulted in a minimized shear strength and pore water pressure (although the trend in pore water pressure evolution did not really reflect the behavior of the deviator stress for this series). In addition, certain parameters, such as normalized behaviors, the brittleness index, ratio of excess pore water pressure to deviator stress at the critical state, and flow potential, appear to be reliable predictors for clarifying and, consequently, explaining the studied behaviors.

The structural strength of the Loess-Paleosol Sequence (LPS) and the presence of paleosols within the LPS have significant implications for tillage and understanding past climate conditions. This research investigation sought to examine the structural strengths of the Luochuan (LC) LPS via both triaxial shear and oedometer tests, with the microstructure being further characterized through scanning electron microscopy. Results indicate that the LPS's structural strength tends to increase as burial depth increases. Additionally, the loess layer's structural strength is typically lower than that of the adjacent paleosol layer. The LPS's microstructure experiences considerable transformations with increased burial depth, particularly regarding changes in particle contact relationship, degree of cementation, and pore volume. This shift is characterized by a transition from an overhead structure to a matrix structure. These findings suggest that the loess layers' structural strength is associated with weaker pedogenic weathering occurring under cold and dry climatic conditions, whereas the paleosol layer exhibits a higher structural strength due to intense weathering during a warm and humid climate. Overall, this study establishes a link between paleoclimate and mechanical properties, using microstructure as a mediating factor, and provides a theoretical basis for tillage on the Loess Plateau.