In order to investigate the frost-heaving characteristics of wintering foundation pits in the seasonal frozen ground area, an outdoor in-situ test of wintering foundation pits was carried out to study the changing rules of horizontal frost heave forces, vertical frost heave forces, vertical displacement, and horizontal displacement of the tops of the supporting piles under the effect of groundwater and natural winterization. Based on the monitoring condition data of the in-situ test and the data, a coupled numerical model integrating hydrothermal and mechanical interactions of the foundation pit, considering the groundwater level and phase change, was established and verified by numerical simulation. The research results show that in the silty clay-sandy soil strata with water replenishment conditions and the all-silty clay strata without water replenishment conditions, the horizontal frost heave force presents a distribution feature of being larger in the middle and smaller on both sides in the early stage of overwintering. With the extension of freezing time, the horizontal frost heave force distribution of silty clay-sand strata gradually changes from the initial form to the Z shape, while the all-silty clay strata maintain the original distribution characteristics unchanged. Meanwhile, the peak point of the horizontal frost heave force in the all-silty clay stratum will gradually shift downward during the overwintering process. This phenomenon corresponds to the stage when the horizontal displacement of the pile top enters a stable and fluctuating phase. Based on the monitoring conditions of the in-situ test, a numerical model of the hydro-thermo-mechanical coupling in the overwintering foundation pit was established, considering the effects of the groundwater level and ice-water phase change. The accuracy and reliability of the model were verified by comparison with the monitoring data of the in-situ test using FLAC3D finite element analysis software. The evolution of the horizontal frost heaving force of the overwintering foundation pit and the change rule of its distribution pattern under different groundwater level conditions are revealed. This research can provide a reference for the prevention of frost heave damage and safety design of foundation pit engineering in seasonal frozen soil areas.

This study undertakes a comprehensive examination of the characteristics of the argillaceous, hard soil/soft rock (HSSR) lithology of the Unterangerberg formation in Tyrol, Austria, focusing on its swelling properties and anisotropic material behavior. The objective is to achieve an extensive material characterization to be able to calibrate material models accurately. This is to be achieved by means of an in-situ test campaign within the Angath adit tunnel construction site and accompanying laboratory tests. The geotechnical monitoring concept in a designated test gallery includes a chain inclinometer, extensometers, geodetic targets, shotcrete strain meters, photogrammetric observations, and a long-term irrigation test field, with a of the invert left exposed intentionally. The in-situ tests yield valuable insights into the intricate behavior of the HSSR lithology, offering a comprehensive description of material variability, and recommendations for characterization. Results indicate that despite the high swellable clay mineral content, significant swelling occurred only to a small extent during the observation period to date. The study concludes that the in-situ behavior of such formations significantly contributes to a better understanding of their characteristics, leading to a substantial reduction in critical load cases for future planning phases.

Background Loess is prone to large deformation and flow slide due to natural and artificial interfaces inside. The strength of these interfaces controls the mechanical properties of loess. Obtaining their mechanical parameters through in-situ testing is essential for evaluating the mechanical stability in loess engineering with interfaces. Methods By developing a borehole micro static cone penetration system and creating various types of loess with interfaces, extensive borehole penetration model tests were conducted to observe changes in cone tip resistance during penetration. The response surface method was used to analyze the impact of various test conditions on the calculated resistance. A three-dimensional surface fitting method was employed to establish the relationship between penetration parameters and shear strength parameters, which was validated through in-situ testing. Results The developed borehole micro static cone penetration system achieves overall miniaturization while providing significant penetration power and ensuring an effective penetration distance. Cone tip resistance development during penetration can be divided into three stages: initial, rapid increase, and slow increase. The transition times between these stages vary for different soils. Calculated resistance is positively correlated with dry density and normal stress and negatively correlated with water content. A quadratic positive correlation was established between calculated resistance and shear strength parameters during penetration. In composite soils, the interaction between water content and normal stress is strong. Compared to intact soil samples, the shear strength parameters of composite soils are more prominently influenced by water content. Conclusion A system for testing interface mechanical parameters was innovatively developed, fulfilling the need to obtain interface shear strength parameters for deep soil. This study can provide support for ensuring the long-term stability of the loess slope or subgrade with interfaces.

Due to its distinct characteristics of instantaneity and abruptness, the stress variation characteristics of unsaturated soil under impact loads significantly differ from those under static and conventional dynamic loads. To investigate the spatial stress state under impact loads, in-situ testing was conducted on an unsaturated soil roadbed using three-dimensional stress testing technology. The three-dimensional soil pressure cells were set at depths of 0.3 m and 0.6 m below the ground surface. Continuous vertical impact loads were applied at the ground projection of the buried points. Stress testing data was collected in real time, and stress transformation methods were applied to obtain the corresponding three-dimensional stress, principal stresses, and the evolution of principal directions. Based on this, a comparison was made with existing one-dimensional stress testing methods and results, further illustrating the rationality and scientific validity of three-dimensional stress testing. The testing data revealed that under impact loads, the stress component in the impact direction (i.e., the z-axis direction) shows a notable instantaneous increase with a positive increment, whereas the increment of positive stress in the y-direction is negative. The principal stress direction angles alpha, beta, and gamma undergo considerable deviations during the impact. Specifically, alpha varies within a 90 degrees range, while beta and gamma rapidly decrease from their initial values to their supplements. Moreover, all three directional angles experience multiple reciprocating changes within a single impact duration. This research has theoretical significance in deepening the understanding of stress response and evolution processes in unsaturated soils under impact loads, providing valuable references for constitutive models, engineering design, and construction research related to seismic or other impact loadings.

Multi-row grouting can be used to repeatedly mitigate the deformation of critical structures such as tunnels. Nevertheless, no comprehensive investigation into the development patterns of soil deformation and excess pore water pressure, induced by multi-row grouting in soft soil, has been conducted to date. To address this gap, this study carried out a field test of multi-row grouting, systematically exploring the evolution and accumulation of soil horizontal displacement (SHD) and excess pore water pressure (EPWP) resulting from multi-row grouting. The findings demonstrated that the grouting process during multi-row grouting exerted reaction and shielding effects on the subsequent grouting for the behavior of soil surrounding the grouting area. The reaction and shielding effects increased proportionally with the number of grouted rows. To predict the SHD induced by multi-row grouting, considering the reaction and shielding effects, this study provided a theoretical calculation method based on cavity expansion theory and the concept of upper and lower bounds and proposed an optimal grouting scheme.

Carbon fiber reinforced polymer (CFRP) cable anchors, possessing exceptional mechanical properties and corrosion resistance, are increasingly serving as alternatives to traditional steel strands in coastal excavation support engineering. This study draws upon in -situ tests of deep excavation near the sea to examine the stress characteristics of CFRP cable anchors throughout their service period at various positions within the excavation plane. Moreover, the parameters of these cable anchors are optimized and analyzed through numerical simulations. The study revealed that the planar position, backfilling of the excavation and the time effect significantly affected the service performance of the CFRP cable anchors. As the days increase, the overall axial force and shear stress in the CFRP cable anchors undergo five stages of changes. Compared to steel strands, CFRP cable anchors demonstrated superior supporting effects on the adjacent soil. Given similar engineering geological conditions, the advisable range for inclination angle for CFRP cable anchors ranges between 20(degrees) and 30(degrees), and cable anchor lengths is 10% shorter than the test length up to the test length itself. Within the scope of this study, the optimal support strategy recommends a 30 inclination angle and a length that is 10% shorter than that of the test length.