Recently, granular anchor piles (GAPs) have emerged as a sustainable alternative for resisting uplift forces on foundations. The aim of this study is to design and analyze the behavior of GAP using finite element-based software PLAXIS 3D. The influences of the pile length, axial capacity of the anchor rod, concrete layer placement, and relative density of the granular material were analyzed. The results demonstrated that the pull-out force for GAP significantly increased when the axial capacity of the anchor rod increased, but improved negligibly beyond 250 MN. The inclusion of a concrete layer increased the value of the pull-out force for GAP. Additionally, the designed GAP was compared with other uplift-resisting piles: underreamed and helical piles. The anchorage diameter of all three pile types was held constant for comparison and the effect of the number of anchorages in the pile was analyzed. For all cases, the response of GAP ranged between those of underreamed and helical piles. However, the pull-out capacity of GAP was closer to that of underreamed piles at L/d = 5 and L/d = 10 for single and double arrangements of anchorage, respectively.
A novel technology designed to enhance the reliability and stability of post-grouting at the bottom of bridge-pile foundations is proposed in this paper. Based on a pile-foundation construction project, static load tests are conducted under distinct operational conditions: composite post-grouting and non-grouting. The investigation examines the dynamic variations in grouting parameters during the grouting process and validates the efficacy of composite post-grouting through an examination of bearing-capacity improvement. The findings reveal that the pile-bottom composite post-grouting technology can effectively improve the reliability and stability of pile grouting, eliminate sediments, form an expanded head at the bottom of the pile, and improve the bearing capacity of the pile foundation, with a noteworthy 29.5
An improved stability analysis method for embankments supported by the piles in cement-improved soil is proposed in this paper. Based on the bending moments and distribution of tension damage in inner piles at the sliding moment, it is inferred that the failure modes of the piles in cement-improved soil are substantially different from those of flexible piles. The most likely failure modes are divided into two types according to the pile locations, bending failure inside the slope foot and soil sliding upward which results in excessive deformation outside the slope foot. Thicker cement soil helps to delay inner pile cracking under bending. An analysis method for the safety factor is proposed after the determination of the resistance contribution of piles in different failure modes. Safety factors calculated by this method are the most accurate according to the numerical simulation results.
Earthquakes represent a significant risk of derailment to high-speed trains in service. Therefore, investigating the vibration behavior of the subgrade under the combined effects of seismic activity and train movement is critical. Accordingly, in this study, a three-dimensional finite element model of a track-subgrade-base system subjected to seismic and moving train loads was developed. Moreover, comparative analyses were performed to investigate the similarities and differences in vibration propagation and attenuation for trains traveling at different speeds on a saturated subgrade. Additionally, the vibration responses of elastic and saturated subgrades were compared. Notably, the results show that the vertical displacement of the saturated subgrade is primarily influenced by seismic loads, and the impact of moving train load is minimal. By contrast, the acceleration frequency spectrum is primarily influenced by the moving train load. When compared with the elastic subgrade, the saturated subgrade exhibits a higher vertical vibration displacement and lower vibration acceleration. Moreover, for a train speed of 50 m/s, a resonance phenomenon is observed in the saturated subgrade, and the vertical displacement and acceleration reach their peak values. This peak response is attributed to the alignment of the vibration frequency of the train with the dominant frequency of the earthquake.
The article was prepared based on the materials of the report at the International Scientific and Practical Conference GEOMOS26 (Gersevanov Research Institute of Bases and Underground Structures, Moscow, March 2026). Soil arching is mobilized when relative displacement occurs within the fill material owing to differential stiffness, differential settlement, or a complete loss of support. In conventional piled-raft foundation systems, dynamic forces acting at the pile–raft connection can induce considerable shear stresses and bending moments, particularly in seismically active regions. The incorporation of a cushion layer in an unconnected piled-raft foundation system subjected to seismic loading can promote the development of soil arching. Accordingly, this study investigates in detail the initiation, propagation, and degradation of soil arching within a sand cushion layer placed between the raft and piles through a series of shaking table experiments. The results indicate that, in an unreinforced cushion layer, raft settlement increases with increasing cushion-layer thickness and pile spacing. In contrast, when the cushion layer is reinforced, settlement decreases as the strength of the cushion layer increases. The vertical pressure distribution on and between the piles, in both vertical and horizontal directions, clearly shows that stresses at the pile heads (supporting zone) increase from their initial values under seismic loading, whereas stresses between the piles (yielding zone) decrease relative to the initial condition slightly in the dry state but significantly in the saturated state. Furthermore, lateral displacement decreases with increasing cushion-layer thickness, regardless of whether reinforcement is used, whereas reinforcement of the cushion layer provides more effective mitigation of horizontal displacement.
