Combining bridge row piles with energy piles to create energy row piles can harness shallow geothermal energy for bridge deck deicing in winter and cooling in summer, respectively, while also supporting the mechanical loads of the bridge deck. This study investigates the thermo-mechanical response of energy row piles under heating-cooling cycles through field tests, and analyzes the interactions among energy row piles, slab, and unheated piles. An interface model considering the cyclic shear characteristics of the pile-soil interface is developed in a finite element software, and thermo-mechanical coupling numerical models of energy row piles are established to further explore the changes and mechanisms of long-term settlement of energy row pile under the combined effect of mechanical loads and heating-cooling cycles. The findings reveal that interactions among the energy row pile, slab, and unheated piles can result in load redistribution, leading to high thermally induced stresses of approximately 80% of the maximum thermally induced stress of the energy row pile (i.e. 1.1 MPa) at the top of the energy row piles due to strong restraining effects. Meanwhile, the slab experiences tensile stress exceeding the tensile strength of C30 concrete, reaching 3.75 MPa. Moreover, when the mechanical load is large, energy row piles progressively develop long-term settlement with an increasing number of thermal cycles, exhibiting a negative exponential growth pattern. This phenomenon is attributed to the mechanical load driving the pile-soil interface toward its limiting state, where cyclic shear at the interface readily induces plastic shear displacements, ultimately resulting in the long-term settlement of the energy row piles.

The microbially induced calcite precipitation (MICP) technique can effectively enhance the mechanical properties of coral sand. To investigate the small-strain dynamic characteristics of MICP-treated coral sand, resonant column tests were conducted on specimens with varying biocementation cycles N_b and effective confining pressures and the development laws of dynamic shear modulus G and damping ratio λ were comparatively analyzed. The test results reveal that: at small strains, the dynamic shear modulus G increases significantly with both N_b and . The maximum dynamic shear modulus G_max exhibits a linear correlation with N_b and a power-law correlation with . A significant power-law relationship exists between G_max and unconfined compressive strength (q_ucs). As N_b increases, the reference strain γ₀ decreases gradually while the G/G_max-γ_d curves shift downward, indicating enhanced nonlinearity. Both minimum and maximum damping ratios increase, with the λ-γ_d curve moving upward and characterized by greater energy dissipation. In contrast, increasing produces opposite trends in both G/G_max-γ_d and λ-γ_d curves, exhibiting reduced nonlinearity and energy dissipation. Empirical relationships are established to quantify the nonlinear dynamic behavior and energy dissipation characteristics of MICP-treated coral sand. Scanning electron microscope (SEM) observations reveal that stiffness improvement primarily results from three mechanisms: contact cementation between sand grains, grain coating by calcite precipitates, and matrix supporting through pore filling.

A widely distributed salinized silt in Northwest China exhibits the physical characteristics of both low-liquid-limit silt and saline soil, yet its long-term deformation behavior remains insufficiently understood. A series of uniaxial creep tests were conducted to investigate its creep properties under varying conditions of salt content, dry density, moisture content, and overburden stress. Test results indicate that, compared to salt-free soil, the creep rate of salinized silt accelerates significantly with increasing salt content, demonstrating more pronounced nonlinear creep characteristics. The final strain of the salt-washed soil was 10%, which increased to 14% at a salt content of 6.4%. To more accurately characterize the soil's creep behavior, the classical creep models were modified, leading to the proposal of two new models: an integer-order model and a fractional-order model. Comparative analysis between the experimental data and the improved models shows that both proposed models describe the actual deformation characteristics more accurately than the classical creep model. However, the integer-order model lacks refinement in describing the decay creep stage, whereas the fractional-order model demonstrates superior accuracy in capturing the detailed features of all creep stages and is therefore recommended for effectively predicting the creep behavior of salinized silt.

In the natural environment and engineering scenarios, there are not only bare unsaturated soils but also unsaturated soils covered by vegetation (i.e., unsaturated vegetated soils). For the unsaturated vegetated soil with a uniform root architecture, on the basis of considering the effects of roots on the hydrological properties, the linearized governing equations for one-dimensional transient seepage of water are acquired by some simplifying assumptions and variable substitution. The analytical solution for one-dimensional transient seepage of water in the unsaturated vegetated soil is obtained through the methods of separation of variable and series transformation. Subsequently, the computational results of this analytical solution have been compared with those of the existing analytical solution and the corresponding finite-difference solution to verify its reasonableness. Finally, a simple vegetated cover is taken as an example to analyze the influences of root-related parameters on its effectiveness in blocking rainwater infiltration. The results show that the cumulative leakage CQ_b at the bottom zone of a vegetated cover under the same rainfall scenario is smaller than that of a single cover without vegetation, and an increase in the rooted soil thickness l_g enhances the effectiveness of the vegetated cover in blocking rainwater leakage. The increase of the transpiration rate T_p significantly reduces the leakage rate at the bottom zone of the vegetated cover under the rainfall scenario, and the cumulative leakage CQ_b tends to decrease linearly with an increase in T_p. Compared with the extreme case where the root volume ratio R_v is zero and the effects of roots on the hydrological properties of soil are ignored, the effectiveness of the vegetated cover in blocking rainwater leakage is enhanced when the saturated permeability coefficient of the rooted soil decreases due to the value R_v, and conversely, it is weakened. Overall, this study could provide scientific guidance for engineering practices related to water infiltration in unsaturated vegetated soils.

To study the wetting deformation characteristics of undisturbed loess under true triaxial force-water path, the true triaxial apparatus with rigid-flexible-flexible loading boundary was used to carry out the true triaxial single-line humidification test of undisturbed loess in Xi'an under different spherical stresses, intermediate principal stress parameters and stress ratios. The influence of true triaxial force-water path on the humidification deformation characteristics of undisturbed loess was comprehensively analyzed. The test results show that the relationship curve between the wetting volumetric (deviatoric) strain and the spherical stress presents a three-stage of slow-steep-slow. When the spherical stress is in the second stage, the wetting collapsibility of the soil is the largest, and a large wetting deformation can occur. At a certain stress ratio, the wetting volumetric strain gradually increases with the spherical stress, and the increase of the wetting volumetric strain decreases when the spherical stress exceeds 200 kPa. Finally, the variation law between the intermediate principal stress and each humidification strain is analyzed, and the calculation expression of loess collapsible deformation considering the intermediate principal stress is given according to the test results.

In rock-lined caverns with compressed air energy storage (CAES), the hoop tensile strength of rock is an important parameter for calculating the ultimate bearing capacity and long-term stability of the cavern. The existing methods for measuring the tensile strength of rock are direct tensile tests or indirect tensile tests, such as Brazilian splitting and point load bending tests, which cannot truly reflect the circumferential stress of rock under high internal air pressure. Based on this, a new measurement method is proposed. By injecting high-pressure air into the drilled rock sample, the rock burst pressure is obtained. Then a calculation formula for the rock tensile strength is proposed considering the rock pore stress. In the experiments, the inflation rate and the temperature are changed, and it is found that the rock burst pressure is negatively correlated with the inflation rate and positively correlated with the temperature. It is found that when the number of cycles is relatively small (n≤100), the rock burst pressure is positively correlated with the number of cycles. The results can guide the design and calculation of rock-lined caverns for CAES, which is conducive to the promotion and application of CAES technology and has important engineering application value.

The accumulation of excess pore water pressure (EPWP) under cyclic loading may induce partial or complete liquefaction of saturated coral sands, posing significant threats to the safety of structures and foundations. In numerical simulations and analyses, accurate prediction of EPWP development is essential, with the determination of threshold strain serving as a critical step. A novel method has been developed to determine the threshold strains (pore pressure threshold strain γ_tp, stiffness degradation threshold strain γ_td, and flow threshold strain γ_tf) for the EPWP generation and stiffness degradation in saturated coral sands under complex stress paths. This was achieved isotopically consolidated, undrained single-stage and multistage cyclic shear tests, including 90° jumps and continuous rotations of principal stress. The findings indicate that while γ_tp, γ_td, and γ_tf are relatively insensitive to the cyclic stress, they are significantly influenced by the initial relative density (D_r). Additionally, the gap between γ_tp and γ_td widens as D_r increases. Under varying cyclic loading conditions and initial physical states, γ_tf corresponds to the EPWP ratio of approximately 0.9, with a corresponding stiffness index of around 0.10. The proposed method for determining γ_tp, γ_td, and γ_tf can effectively reduce the number of required cyclic tests, making it suitable for use as input values in numerical calculations or analytical methods, and for characterizing soil behavior under stress and strain conditions.