Based on an actual excavation of a metro station in Tianjin, China, a fluid–solid coupling numerical model was developed to study the characteristics of groundwater flow and strata movement induced by dewatering and excavation considering the barrier effect of pre-existing adjacent underground structures. Two parameters were selected for the model: the distance between the excavation and the existing underground structure (D), and the buried depth of the adjacent structure (H). By comparing the distribution of groundwater drawdown and deformation modes of the retaining structure and the strata under different working conditions, the influence mechanism of adjacent structures on the movement of groundwater and strata was revealed. The results show that the pile foundations have different effects on the groundwater flow and excavation deformation. Generally, the maximum groundwater drawdown could be enlarged by considering the adjacent underground structure, while the retaining structure deflection would be reduced and the ground settlement could be either enlarged or reduced. Additionally, as D decreases and H increases, a much greater groundwater drawdown and a much smaller retaining structure deflection would appear, which together affect the ground behavior. On the one hand, greater groundwater drawdown would lead to greater ground settlement by soil consolidation, while on the other hand, a smaller retaining structure deflection would lead to smaller ground settlement. Thus, a complex development of ground settlement would appear, and a specific analysis should be performed to assess this in practice, based on a specific H and D.

In regions with abundant groundwater resources, pre-excavation dewatering on deep foundation pits often leads to the deformation of the enclosure wall and settlement of the surrounding ground. Based on a series of engineering measurements, we conducted a series of numerical simulations to investigate the behaviors of wall and soil during pre-excavation dewatering with and without the existing pile foundations and under different distances between the existing pile foundations and foundation pits (D). Numerical results indicated that when the foundation pit is adjacent to existing building pile foundations, the soil was restricted by the pile foundations (i.e., soil-blocking effect). When D ≤ 40 m, the soil-blocking effect grows stronger as D gets smaller; while when D > 40 m, the soil-blocking effect is significantly weakened and the water-blocking effect (i.e., the blockage of groundwater seepage by the building pile foundation) gradually appears, which intensifies the ground surface settlement. The maximum settlement position of the soil behind the pile foundation of the existing building is farther away from the foundation pit as the soil-blocking effect becomes stronger. The coupling effect of soil-blocking and water-blocking on the ground deformation should be considered in the design of the foundation pit project to get a more reasonable support and dewatering scheme.

Foundation pit dewatering will impact the surrounding underground environment. To mitigate the adverse effects on adjacent underground structures, groundwater recharge is commonly utilized to control groundwater drawdown outside the pit. However, under a barrier effect of underground structures, the recharge effect may be different from that without the barrier effect. Meanwhile, the results of recharging different aquifers may also be different under the barrier effect. Therefore, based on an actual foundation pit project, this paper establishes a three-dimensional finite element model to investigate the impact of recharge on the surrounding environment under the barrier effect. To be specific, the recharge simulations were conducted in aquifers at different depths, and the effects on groundwater, enclosure wall deflection, and ground settlement under each recharge condition were compared and discussed. Furthermore, the optimal recharge scheme under the barrier effect was proposed. The results show the following: (1) When recharge is conducted in an aquifer that is completely cut off by underground structures, both groundwater levels rise and enclosure deflection induced by recharge are dramatic; therefore, caution should be taken when recharging under this condition to avoid an excessive response of recharge on the surrounding environment. (2) When recharge is conducted in an aquifer that is not cut off, most of the recharged water flows far away from the foundation pit, resulting in a low recharge efficiency. (3) When recharge is conducted in an aquifer with a direct hydraulic connection between the inside and outside of the foundation pit, it can significantly raise the groundwater levels of each aquifer, and effectively control the ground settlement without obviously increasing the deflection of the enclosure; engineers could benefit from this recharge scheme to achieve a better recharge effect under the barrier effect.

This study investigates the complete process of water level elevation’s impact on structural buoyancy under varying environmental conditions (with/without surrounding barriers) using model testing. The experiments simulated the buoyancy response patterns in sandy soil layers under different hydraulic heads. Dynamic variations of structural buoyancy over time were systematically analyzed, revealing distinct differences across the working conditions. The key findings demonstrate: (1) in the presence of the barrier effect, the growth of structure buoyancy is significantly slower than that without a barrier, but the measured value of structure buoyancy in sand is basically consistent with the theoretical value of Archimedes’ law, and the reduction coefficient is between 0.78 and 0.96; (2) the influence rate of water level rise under high water head pressure on structure buoyancy is significantly higher than that under low water head pressure. Therefore, special attention should be paid to monitoring structure buoyancy when the water level rises under high water levels.

In water-rich strata, a traditional vertical barrier exhibits certain limitations when applied to deep foundation pit construction under complex geological conditions, such as it is difficult to completely cut off deep and thick aquifer, which may pose potential risks during pit dewatering. To address the above challenge, this study introduced a mixed barrier system in which the horizontal barrier (HB) was set at the bottom of the foundation pit and was combined with the enclosure wall to collectively retard groundwater seepage into the pit. Based on an actual project in Tianjin, this study established HB models with varying numbers of its layers using ABAQUS 6.14 software. It systematically investigated the effect of HB on groundwater drawdown, ground surface settlement, and enclosure deflection during foundation pit dewatering. The research shows that HB can significantly reduce the magnitude of external water level drawdown by altering groundwater seepage paths while effectively controlling soil settlement. Furthermore, it exhibits favorable overall restraining effects on wall deformation. Varying the number of horizontal barrier layers (L) exhibits an insignificant effect on water-blocking and subsidence-control performance. However, the constraint effect on the enclosure shows a correlation with L.

With the development of flexible electronic technology, lately, there has been an increase in demand for flexible electronic devices based on soft polymer-substrate metal film structures in challenging applications. These soft polymer-substrate metal film structures must tolerate bending, folding, stretching, and even deformation into any shape without failing to be used successfully. As a result, research into the fracture behavior of soft polymer-substrate metal film structures is essential. The purpose of this study was to investigate how fractures develop in Cr film attached to a polyimide (PI) substrate under biaxial stress. A fracture development model was built to determine the fracture propagation law of soft polymer-substrate metal film structures under biaxial stress. Experiments and finite element methods were applied to verify the correctness of the model. The theoretical analysis and finite element simulation results showed that fractures appeared initially at the perimeter of the film and then propagated to the center under biaxial stress. The theoretical and experimental results indicated that the crack propagation direction was related to the ratio of biaxial loading, which became progressively parallel to the direction of small loading as the biaxial loading ratio increased. The theoretical results were in line with the experiment results, which could be used as a preliminary step for further research on the fracture behavior of film-substrate structures.