Explore the vast range of titles available.

•A new analytical model considering the soil arching effect was established.•The calculation method of load transfer of parabolic soil arch is proposed.•Formula of horizontal pressure coefficient was deduced in the failure zone.•Formula for predicting the height of shear bands was proposed. For the project of pipe jacking in cohesionless soil, it is key to determine the vertical load on jacked pipe so as to predict the jacking force accurately. In this paper, a new parabolic soil arching model was proposed to calculate the vertical load on jacked pipe. This proposed analytical model was composed of parabolic soil arching zone, parabola-typed collapse zone and friction arch zone. Combined with existing literature, the key parameters (i.e., height of parabolic soil arching, horizontal pressure coefficient and width and height of friction arch) were determined. In addition, considering that the trajectory of major stress is parabola, the formula of horizontal pressure coefficient was deduced in the friction arch. The parabolic soil arching zone is assumed as a three-hinged arch with reasonable arch axis, and the formula of load transfer was derived considering the transition effect of parabolic soil arching. The results of experiment, theoretical models and numerical model were adopted to verify the proposed analytical model. Finally, the influence of the key parameters on the vertical load on jacked pipe were also discussed in detail. This work provides a meaningful reference for evaluating the vertical load on jacked pipe for design of pipe jacking.

Tunnelling has increasingly become an essential tool in the exploration of underground space. A typical construction problem is the face instability during tunnelling, posing a great threat to associated infrastructures. Tunnel face instability often occurs with the soil arching collapse. This study investigates the combined effect of cutterhead opening ratio and soil non-uniformity on soil arching effect and face stability, via conducting random finite-element analysis coupled with Monte–Carlo simulations. The results underscore that the face stability is strongly associated with the evolution of stress arch. The obtained stability factors in the uniform soils can serve as a reference for the design of support pressure in practical tunnelling engineering. In addition, non-uniform soils exhibit a lower stability factor than uniform soils, which implies that the latter likely yields an underestimated probability of face failure. The tunnel face is found to have a probability of failure more than 50% if the spatial non-uniformity of soil is ignored. In the end, a practical framework is established to determine factor of safety (FOS) corresponding to different levels of probability of face failure considering various opening ratios in non-uniform soils. The required FOS is 1.70 to limit the probability of face instability no more than 0.1%. Our findings can facilitate the prediction of probability of instability in the conventionally deterministic design of face pressure.

This study presents a detailed investigation into the soil arching effects within deep foundation pits (DFPs), focusing on their mechanical behavior and implications for structural design. Through rigorous 3D finite element modeling and parameter sensitivity analyses, the research explores the formation, geometric characteristics, and spatial distribution of soil arching phenomena. The investigation encompasses the influence of key parameters such as elastic modulus, cohesion, and internal friction angle on the soil arching effect. The findings reveal that soil arching within DFPs exhibits distinct spatial characteristics, with the prominent arch axis shifting as excavation depth progresses. Optimal soil arching is observed when the pile spacing approximates three times the pile diameter, enhancing soil retention and minimizing deformation risks. Sensitivity analyses highlight the significant impact of soil parameters on soil arching behavior, underscoring the critical role of cohesive forces and internal friction angles in shaping arching characteristics. By elucidating the interplay between soil parameters and soil arching effects, the research provides insights for optimizing pile spacing and structural stability.

As urbanization accelerates, the demand for efficient underground infrastructure has grown, with rectangular tunnels gaining prominence due to their enhanced space utilization and construction efficiency. However, ensuring the stability of shallow rectangular tunnel faces in undrained clays presents significant challenges due to complex soil behaviors, including anisotropy and non-homogeneity. This study addresses these challenges by developing a novel failure mechanism within the kinematic approach of limit analysis, integrating soil arching effects alongside anisotropic and non-homogeneous undrained shear strength. The mechanism's analytical solutions are rigorously validated against finite element simulations using PLAXIS 3D and existing models, demonstrating superior accuracy. Key findings show that the proposed model improves predictive performance for critical support pressure, with relative differences as low as 5% for wide rectangular tunnels compared to numerical simulations. Results reveal that limit support pressure decreases with increasing non-homogeneity ratios and rises with higher anisotropy factors. However, both effects diminish in wider tunnels, where increasing width in soils with high non-homogeneity and low anisotropy factors significantly enhances stability. Practical implications of this study are substantial, offering design formulas and dimensionless coefficients for estimating critical face pressures in shallow rectangular tunnels. These tools enable engineers to account for soil anisotropy and non-homogeneity, optimizing design and ensuring safety in urban environments. Furthermore, the proposed model’s applicability extends to circular tunnels, where it offers comparable accuracy. This study bridges a critical gap in understanding the stability of rectangular tunnels, providing a robust framework for tackling the challenges of modern urban construction.

The passive soil arching effect exists in many soil–grille interaction systems. Increasing mental grillage foundations are used for transmission lines in aeolian sand areas; thus, exploring the evolution mechanism of passive soil arching is crucial. This study investigates the evolution and influencing factors of passive soil arching through a series of tests using a trapdoor device and particle image velocimetry (PIV). The test results show that the evolution of the arching structure causes the aeolian sand deformation to gradually extend to the backfill surface and stationary zone, generating two triangular arching surfaces between the movable beams and sliding surface at the junction of the active and stationary zones. Cracks in the arching and sliding surfaces were connected to form a W-shaped shear band. The development of the soil pressure was divided into four arching structure stages. The different stages of the inner and outer arches of the bearing characteristics had strong differences. Taking the appearance of the first arch surface as the time point, the soil pressure changes abruptly and the inner and outer arches alternate to bear the as a major role. The beam spacing significantly affected the arching evolution. A smaller beam spacing formed an initial bending configuration with an inconspicuous arching structure and incomplete shear band. As the beam spacing increased, the arching shape changed from triangular to parabolic, sudden changes in the soil pressure were more pronounced, and the arch height increased. The relative density and water content had little impact on the arch shape and shear zone but significantly affected the arching strength, soil pressure transfer, and arching height. The medium and high relative densities and low water contents resulted in a stronger arching structure and greater arching height, while low relative densities and high water contents weakened the soil pressure transfer. The range values for the optimum beam spacing, relative density, and water contents are given based on the variation characteristics of the evaluated parameters (E, n) under different conditions.

Leakage in underground structures, especially tunnels, may cause seepage erosion in the surrounding soil, which in turn leads to ground subsidence, posing a great threat to urban safety. The current literature mainly focuses on seepage erosion in the sand but lacks a systematic study on the development process of seepage erosion induced by tunnel leakage in different strata. To investigate the different seepage erosion modes induced by tunnel leakage in different stratum types, a series of reduced-scale model tests were carried out. A coupled fluid–solid numerical model was further established to analyze the fine-scale characteristics of different seepage erosion modes. The results show that (1) the soil seepage erosion modes can be divided into three categories: no soil cave, unstable soil cave, and stable soil cave; (2) the adopted coupled fluid–solid numerical model based on DEM, which takes into account the degradation of clay during seepage erosion, can effectively simulate the erosion process of soil with different seepage erosion modes; (3) the phenomena of the three erosion modes are different in the process of erosion development; and (4) the micro-mechanisms of the three seepage erosion modes are different, which are manifested in the erosion range, soil arching effect, and displacement.

The transfer process of vertical stress of strata is affected by local soil arching effect, to address the limitation of differential soil layer method in overestimating the transferred stress, a method for calculating average vertical stress based on stress transfer ratio was proposed. This approach integrates numerical simulation results on the relationship between the rotation angle of principal stress and the average vertical compressive and shear stresses. Additionally, the shear stress distribution and the transmission behavior of vertical stress in both the equal settlement zone and the arching zone were verified. The results indicate that the stress transfer ratio can be used to define the boundary between the equal settlement plane and the soil arching zone of the tunnel. As the final stress transfer ratio increases, the path of principle stress gradually evolves into a closed arch trace, the proportion of transition section before the peak of the average vertical stress curve decreases, while both the inflection point of the stress curve and the boundary of the equal settlement zone shift upward, and the transferred stress of strata with unit thickness increases accordingly. The transferred stress increases with gradual rotation of the principal stress, once the principal stress path forms a closed arch, the stress transfer function exhibits a sharp rise. The rate of change of the stress transfer ratio also increases in tandem with the rotation angle of the principal stress. These findings reveal the vertical stress transfer mechanism in the local soil arching zone and clarify the influence of the principal stress path on this process.

Combining field test research with finite element numerical analysis, this paper studies the mechanical behavior of pile-supported reinforced embankments in soft soil areas. We analyze and compare the variation law of load transfer efficacy at the subgrade center, the right side of the centerline, and the road shoulder; the variations of the load sharing ratios of the soil arching effect and the load sharing ratios of the membrane effect; and the load variation law of wide subgrade cross-sections. Then, the model calculation results are compared with the calculation results of the five theoretical methods and the applicability of the various methods is evaluated. The results show that: increasing the pile length, pile cap width, and embankment height and reducing the pile spacing will increase the pile load transfer efficacy; pile cap width has the greatest influence on the load transfer efficacy; regarding the variation law of the load sharing ratios of subgrade cross-sections, the load-sharing ratio of the soil arch effect at the shoulder is smaller than that at the center of the subgrade, indicating that the deformation of the geogrid at the shoulder is large and the membrane effect is significant; and, regarding the load variation law of subgrade cross-sections, from the subgrade center to the shoulder direction, the pile load transfer efficacy decreases gradually and the load transfer efficacy at the shoulder decreases significantly.

The downslope movement of sliding soils usually leads to a nonlinear distribution of lateral forces on stabilizing piles in a row. Precise prediction of the lateral forces is of significance to assess the stability of pile-reinforced soil slopes. A simplified pressure-based method is presented for estimating the lateral force distribution on piles embedded in a semi-infinite c–φ inclined soil slope. The soil arching theory was incorporated to calculate the driving forces transferred onto piles after determining the active lateral earth pressure between adjacent piles through the horizontal slice method. Several published experimental and numerical studies were selected to examine the applicability of the proposed method. It is demonstrated that the predicted result is in good agreement with the observed data in terms of both the shape and the magnitude of the distribution of lateral forces. The parametric study further indicates that the distribution of lateral forces along the depth changes from nonlinear to planar as slope angle increases, whereas the other parameters, such as friction angle, soil cohesion, pile spacing and depth of unstable soil layer, mainly influence its magnitude. The proposed method could be employed in the preliminary prediction of response of piles with scarce design parameters.

Soil arching effect, which relates to the load transfer and stress redistribution in a soil mass, exists commonly in various geotechnical situations. Many researchers have conducted trapdoor tests and theoretical analyses to study the soil arching and its development in recent years. However, little attention has been paid to the interaction between soil arching and seepage flow, both occurring during the tunnelling of a seabed tunnel. To study the influence of the seepage flow on soil arching, a series of two-dimensional trapdoor tests were carried out considering different fill heights and water level heights. Two subvertical slip surfaces were observed during the tests using the PIV technique. It was found that seepage flow increased the displacement of the particles and the effective vertical stress acting at the top of the trapdoor. However, there was little difference in the development of slip surfaces between the seepage condition and the saturated/no-seepage condition. In addition, a nonuniform distribution of vertical stresses at the top of the trapdoor was observed. The effective earth pressure measured along the centreline of the trapdoor was larger than that on the two edges of the trapdoor. But this nonuniformity decreased with an increasing water level height in the test chamber.