With the rapid development of key projects in China, such as West-to-East Gas Transmission and South-to-North Water Diversion, buried pipelines will inevitably pass through the mountainous area and are affected by regional topography and landforms. However, the interaction mechanism between slope and pipelines is still relatively unclear. In this study, the model tests on sandy slope-pipe interaction under loading are carried out in laboratory based on distributed strain sensing (DSS) and particle image velocimetry (PIV) technologies. The factors influencing the bearing capacity of the foundation are investigated. The failure characteristics of the slope and the structural responses of the buried pipeline are also explored. The research results show that: (1) The slope foundation has undergone three stages: elastic compaction, local shear and overall destruction. The foundation shows asymmetrical wedge-shaped failure pattern. (2) With the increase in slope angle, the ultimate bearing capacity of the foundation decreases. Under the same slope angle, the presence of pipeline reduces the ultimate bearing capacity of the slope foundation. (3) With the increase in slope angle, the influence of the pipeline on the slope failure mechanism increases. (4) Under the loading of the slope, the circumferential strain in the cross-section of the buried pipe is “elliptically” distributed, and an ellipticity calculation formula and a simplified calculation model of the soil resistance around the pipe circumference are proposed. This study can provide a reference for the deformation control and structural design of buried pipelines in sandy slopes.

The deformation of foundation soil caused by freeze-thaw cycles is a typical geological disaster in engineering construction in permafrost areas. Fiber optic sensing technology provides an important technical means for accurate and distributed real-time monitoring of frozen soil deformation. To explore the feasibility of distributed fiber optic strain sensing in monitoring frozen soil deformation, this study utilized a self-developed optical cable-frozen soil interface mechanical characteristics tester to investigate the failure mechanism of the cable-soil interface in frozen soil samples with different dry densities and initial water contents. The experimental results indicate that the fiber optic strain monitoring results accurately reflect the progressive failure characteristics of the cable-soil interface, and the strain softening model can better describe the mechanical properties of the interface. During the freezing process, the liquid water in the soil becomes ice, causing the movement of the freezing front and water migration, and resulting in significant differences in the mechanical properties of the interface. The evolution process of the shear stress at the cable-soil interface at different depths reflects the deformation coordination state with the frozen soil during the cable pullout process, indicating that the measurement range of the cable and the coupling of the interface are closely related to the dry density and initial water content of the soil. This study provides a reference for the application of optical fiber sensing technology in deformation monitoring of frozen soil foundation in cold regions.

Geogrid reinforcements can effectively improve the pullout capacity of anchor plates, but the failure mechanism and influencing factors during the uplift process need to be further investigated. In this paper, a series of uplift tests was carried out on horizontal anchor plates in sand to investigate their pullout characteristics, and the influence of various factors was analyzed, including sand density, anchor embedment depth, and number of geogrids and their locations. The particle image velocimetry (PIV) technology was used to explore the deformation and failure mechanism of the sand around anchor plates. The results show that for the pullout capacity of an anchor plate is significantly enhanced by one layer of contact-type geogrid, and the reinforcing effect is better than that with non-contact geogrid. This phenomenon is associated with mobilized friction of the geogrid and the increased weight of sand within the failure surface. When two layers of geogrids are installed, the lower geogrid plays a dominant role in restricting the lateral soil deformation and homogenizing the stress distribution, and the contribution of the upper geogrid is relatively low. Whether geogrids are applied or not will alter the deformation mechanism at the anchor-sand interface. With geogrid reinforcement, the failure surface converges inward, and the shear strain distribution is more uniform.