Scouring can reduce the strength and rigidity of the pile–soil system and become one of the major causes for the failure of the structure of the partially-embedded single pile. The stratification of the soil fields has a significant influence on the internal force and deformation of laterally-loaded piles. A dynamic model of the laterally-loaded single pile in layered soil is established employing Hamilton’s principle based on the modified Vlasov foundation model. Then, the finite difference method is used to obtain the numerical matrix containing the control equations of the single pile to achieve accurate modeling of the soil–structure interaction (SSI) system affected by scouring, so as to solve the natural frequencies of the single pile. Green’s function method obtains the analytical solution of the forced vibration of the single pile. The effects of scouring and the layered soil on the dynamic response of the single pile are studied by numerical calculation and parameter analysis. It is shown that the dynamic model of the partially-embedded single pile in layered soil based on the modified Vlasov foundation model can accurately predict the dynamic characteristics of pile foundation affected by scouring. As the scouring degree intensifies, the first-order natural frequencies of the single pile in layered soil decrease significantly. The subgrade reaction coefficient of each layer of soil in the modified Vlasov foundation model decreases, and the shear coefficient increases. The first-order natural frequencies of the single pile at each scour level increase with the increase in the thickness of the underlying soil. When the elastic modulus of the first layer of soil is increased by one time, the first-order natural frequencies of the single pile are increased by about 20%.

This paper presents a new method to evaluate the piping risk of unconfined sandy cobble aquifers during the dewatering of deep foundation pits. Firstly, the possibility of piping is judged according to the particle size distribution and pore diameter of the sandy cobble stratum. Secondly, the critical hydraulic gradients of particles with different sizes are calculated according to the pipe flow model. Thirdly, the hydraulic gradient around the foundation pit during the dewatering process is calculated by numerical method. Then, combined with the distribution of hydraulic gradient around the foundation pit and the critical hydraulic gradients of particles with different sizes, the range of moveable particles with different sizes in the surrounding stratum is evaluated. Finally, according to the sandy cobble aquifers conditions and the influence of particle movement on the stratum, the level of piping risk is determined. This method was successfully applied to evaluate the piping risk of Tawan Station in Luoyang Metro Line No.1, and according to the risk evaluation the pensile curtain was recommended for the retaining structure in this case. From the satisfied applications, this method is a reference for the evaluation of piping risk and selection of retaining structure when considering the impact of the dewatering in deep foundation pit with unconfined aquifers on the surrounding stratum.

The scouring effect is widely acknowledged as a primary contributor to the weakening in the bearing performance of offshore piles; it often results in asymmetric scour patterns around the pile. To meticulously examine the impact of three-dimensional asymmetric local scour on the lateral bearing performance of a single pile, the Boussinesq solution is employed to determine the effective stress within the soil encompassing the pile, considering the presence of a three-dimensional asymmetric local scour hole. Utilizing the strain wedge model, the calculation method for the lateral bearing performance of a single pile under the condition of three-dimensional asymmetric local scour is established. The validity of this approach is established, and parameter analysis unveils the effect of varying sizes of three-dimensional asymmetric scour holes on the mechanical properties and displacement performance of a single pile. The analysis reveals that, as scouring dimensions around the pile escalate, the impact of scouring on single-pile lateral displacement and internal forces intensifies, leading to a decrease in the lateral bearing performance of a single pile. At a constant scour depth, the bottom area of the upstream scour hole significantly influences the displacement performance of a single pile. When the bottom length S_wb1 of the upstream scour hole grows by 1 time, 4 times, and 8 times, the lateral displacement of a single pile at a buried depth of 6 m is augmented by approximately 0.41%, 1.65%, and 2.06%, respectively. The simplified model obtained via the modified strain wedge model and Boussinesq solution can provide a theoretical basis for the preliminary design of a single pile under asymmetric scour hole conditions.

The distribution characteristics of a seepage field generated by precipitation affects the deformation damage of the geological body and engineering geological stability, especially a seepage field with a water-rich ultra-thick sand and gravel layer. In order to study the seepage field distribution characteristics of a water-rich ultra-thick sand and gravel layer, taking Luoyang Metro Line 1 as the engineering background, combined with the actual monitoring data of on-site precipitation, numerical simulation was used to study the seepage characteristics of the pit project precipitation with a suspended water-stop curtain. Through the study, the distribution characteristics of the seepage field under different precipitation depths and aquifer thicknesses were obtained, and the changes in pore water pressure characteristics, flow velocity and water inflow, depending on the precipitation depth and aquifer thickness, were analyzed. The research results show that, when comparing the calculated and measured results of the water level drop in the foundation pit, the average value of the error of the water level drop value in the pit and the descending well is 11.7%, which indicates that the calculation model meets the needs for its use in calculation and analysis. Under the conditions of a suspended water-stop curtain and precipitation, for the pore water pressure characteristics, the variation amplitude of the pore water pressure inside the pit increases with the precipitation depth and aquifer thickness. For the maximum flow velocity, all characteristics are present at the bottom of the suspended water-stop curtain, near the inside of the pit. The maximum flow velocity increases linearly with the precipitation depth and there is a threshold when the aquifer thickness is five times the precipitation depth. For water inflow, it increases with the increase in the precipitation depth and aquifer thickness, but, with a continuous increase in the aquifer thickness, the magnitude of water inflow growth decreases.

This paper investigates the influence of soil with finite depth on the vibrational behavior of a multi-span continuous beam resting on an elastic foundation. The simplified model of the Timoshenko beam supported on soil with finite depth is established, introducing the foundation displacement decay function. The numerical solution of the continuous beam’s vibration response on the elastic foundation is obtained by using the transfer matrix method (TMM) and fourth-order Runge-Kutta method (RK4). Taking a two-span continuous beam as an illustrative example, the validity of the calculation theory is validated by comparing it with the outcomes obtained from the finite element method (FEM). Utilizing numerical computation and parametric analysis, the vibration response of continuous beams is evaluated in terms of its influence by various factors such as soil thickness, viscous damping coefficient of the soil, subgrade reaction coefficient, and span ratio. The findings indicate that the inertial motion of the soil with a finite depth significantly reduces the continuous beam’s inherent frequency and enhances the structure’s resonance effect. The rise of the subgrade response coefficient increases the system’s resonant frequency while decreasing the displacement response amplitude. The ratio between the adjacent spans determines the effect of beam span vibration energy transfer to adjacent spans. In addition, compared with the span directly excited by a concentrated harmonic load, the impact of soil thickness, subgrade reaction coefficient, and viscous damping, the coefficient of the soil is more significant on the indirect influence span of a continuous beam.

The movement of particles caused by erosion is one of the main reasons for the destruction of projects, such as dams, tunnels, and foundation pits. This study highlights a theoretical model to assess the occurrence of erosion in gap-graded, sand-gravel soils under variable seepage direction based on the critical hydraulic conditions of particle initiation. The model introduced the effects of relative exposure degree, relative hidden degree, and seepage direction by considering the difference in particle initiation conditions. On the basis of the variable-section capillary tube model formed by the skeletal pores, the mechanical analysis of the movable particles in the pores was performed, and the formulas for the critical hydraulic conditions were obtained according to the moment balance equation. Subsequently, the coupled CFD-DEM method and the available experimental data were used for validation. The comparison revealed a deviation of 0.0268 for the mean of the ratio between the calculated and simulated values compared to 1, with a covariance (COV) of 0.0344. Further, the mean value of the ratio between the calculated and test values compared to 1 had a maximum deviation of 0.095 and a covariance (COV) of 0.0143. The high degree of agreement between the data proved that the theoretical model can assess the occurrence of erosion more accurately. Finally, based on the theoretical model, the study further explored the effects of seepage direction and relative particle position on the variability in particle initiation conditions, thus finding that, unlike in other studies, the effect of seepage direction was not linear.