Soil Arching Research Articles

The Soil-Arching Effect in Pile-Supported Embankments: A Review

Pile-supported embankments are widely used in foundation treatments, owing to their safety, efficient construction, and economy. The soil-arching effect is a key load-transferring mechanism in a pile-supported embankment, and it reduces the even settlement on the embankment surface. In recent years, researchers and engineers have conducted extensive research on the soil-arching phenomenon in pile-supported embankments. This paper reviews relevant studies on the effect of soil arching in pile-supported embankments in order to better understand the mechanism and influencing factors of the distribution of the arching effect. First, the development history of the practice and theory related to pile-supported embankments is discussed. This is followed by a review of theoretical studies on the soil-arching effect, load distribution and soil deformation on pile-supported embankments (with and without geogrid reinforcement), and structures and factors influencing soil arching. The results of these studies are summarized, and finally, topics for future research are suggested, providing references for the design and maintenance of civil infrastructure.

Mechanical Difference Analysis of Single-row and Double-row Side Piles in Stations by PBA Method Based on Model Test

This study employs the pile-beam-arch (PBA) method to investigate the force-evolution law of micro-steel pipe piles during the excavation process, focusing on a Guangzhou metro-station project. Through laboratory model tests, we compared and analyzed the mechanical evolution laws of single-row and double-row side piles. Our findings revealed a significant soil arch effect in both single-row and double-row piles; with similar distribution patterns and peak-stress range. As soil excavation progresses, the soil arching effect shifts downward. Notably, the stress concentration in double-row piles is weaker than that in single-row piles, especially in the soil range of 0–50 mm after the piles. This is attributed to the looser soil between single-row piles, resulting in more evident stress release. The attenuation amplitude of the Y-direction stress of the double-row piles was considerably smaller than that of the single-row piles. The soil arching between the back-row piles in doublerow configurations exhibits shielding effects on the force of front-row piles, significantly weakening the soil pressure on them. This impact alters the force of the front-row piles, even causing the tip of the front-row piles to bend in reverse. The research results provide important insights for similar projects and can serve as a valuable reference.

Analysis of face stability for shallow shield tunnels in sand

The stability of the tunnel face is the key problem in shield tunnel construction. This paper focuses on the face stability of a shallow tunnel in sand. Numerical simulation and theoretical analysis are combined to study the limit support pressure and failure zone. Firstly, numerical simulation is employed to study the collapse of the tunnel face, obtaining the limit support pressure and collapse zone. A new failure model suitable for shallow tunnels is constructed based on these numerical simulations. Then, an analytic solution for the limit support pressure is derived using limit analysis upper bound theory. The accuracy and applicability of this proposed model are verified by comparing it with numerical results and classical analytical models. Through this research, it is found that the proposed model provides a more accurate description of situations where soil arches cannot be formed for shallow tunnels in sand, leading to higher accuracy in calculating the limit support pressure. The influence of various factors on stability of the tunnel face is analyzed, revealing mechanisms of tunnel face collapse.

Influence of cutterhead opening ratio on soil arching effect and face stability during tunnelling through non-uniform soils

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.

Numerical and theoretical analysis on soil arching effect of prefabricated piles as deep foundation pit supports

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.

Tunnel entrance crossing spoil heap deformations control by micropile combine with coupling beams

Aiming at the deformation control problem of the tunnel entrance crossing the spoil heap at the Xialao junction, this paper adopts the micropile combined with the coupling beams method to treat the spoiled layers. The results show that the excavation of the tunnel after the construction of the micropile and coupling beam will cause vertical deformation of the tunnel and the slope surface. The main reason is that the soil layer structure is loose, and the tunnel excavation causes the whole displacement of the loose body. In addition, the buried depth of the tunnel is shallow, so it cannot form an effective soil arch. The stability process after the construction of the micropile method is the process of stress redistribution, and the rock and soil are gradually compressed and compacted. That is, the construction by the micropile method changes the surrounding rock level of the tunnel and reduces the height of the soil arch. Therefore, it is suggested that the tunnel excavation should be carried out when the micropile is constructed after the soil layers are consolidated completely. The micropile method treats the loose spoiled soil at the tunnel entrance, which saves 73% of the total cost compared with the scheme of directly digging out the accumulation, and the economic benefit is very obvious.

Research on Static and Dynamic Loading Performance of Geosynthetic Reinforced and Pile-Supported Embankment

Geosynthetic reinforced and pile-supported (GRPS) provide an economic and effective solution for embankments. To investigate the load-bearing mechanism of the GRPS embankment in loess, experimental and numerical studies under static and dynamic loading are carried out. The characteristics of soil arch effect and tensile membrane effect of GPRS embankment under static and dynamic loading are revealed by analyzing pile–soil stress ratio, tension of geogrid, and stress distribution of pile. The test results show that the pile–soil stress ratio under dynamic loading is reduced by 2.3 compared with static loading. In comparison to static load, the soil arching effect is attenuated under dynamic load, and the stronger the static load soil arching effect, the greater the degree of weakening under dynamic load. In addition, under dynamic loading, the tensioned membrane effect is still effective, but its enhancement is not as pronounced as under static loading. Furthermore, by using the finite element software, the numerical model is developed and validated with the experimental results. The parameter analysis of the load-bearing performance of the GRPS embankment is accomplished using the finite element model as well.

Face failure of EPB shield tunnels in dry dense sand: a model test and DEM study

This study aims at addressing the face failure of earth pressure balance (EPB) shield tunnels in dry dense sand by model tests and discrete element method (DEM) models. The model tests incorporated a miniature EPB shield which could fully reproduce the real tunnel construction of excavation and support. DEM models simulating the model tests were developed to capture the underlying face failure mechanism. Results show that both the limit support pressure obtained at chamber board and tunnel face increase with increasing C/ D ( C is tunnel cover depth, and D is tunnel diameter). The ratio of the former to the latter approximates 0.60 due to the soil retaining of cutter head panel, and it is independent of C/ D. The local face failure initializes around tunnel face and develops directly to the global failure outcropping the ground surface in one phase with C/ D ≤ 1.0, while the local failure develops to the global failure in three phases with C/ D = 2.0 due to the soil arching evolution. The soil arching gets weaker when it propagates upward, and the horizontal stress concentration in the longitudinal direction is stronger than the transverse direction due to the difference of arch foot.

Soil Arching Effect Associated with Ground Movement and Stress Transfer Adjacent to Braced Excavation in Clayey Ground

Soil Arching Effect Associated with Ground Movement and Stress Transfer Adjacent to Braced Excavation in Clayey Ground

Shaking-Table Tests for Seismic Response of Arch Foot of a Long-Span Arch Bridge on Sand-Gravel Soil Sites Considering SSI Effect

ABSTRACT The seismic performance of arch bridges is dependent on the strength of bridges and the built-on soil site types. To investigate the influence of soil-structure interaction (SSI) on the seismic response of an arch-foot arch bridge with a sand-gravel soil site, several shaking-table tests for a 1/90 downscaled arch-foot model placed on sand-gravel soil were conducted based on the engineering prototype of the third Pingnan Bridge with a long-span concrete-filled steel-tube (CFST) arch bridge. The test results showed the following: (1) The seismic acceleration response of both the sand-gravel soil site and arch foot were amplified, which is related to both the non-linear dynamic behavior of sand-gravel soil and frequency-spectrum characteristics of the input seismic waves. (2) The sliding displacement of the arch foot under strong ground motions increased accompanied with a settlement of the soil surface. However, the safety risk of the arch foot may be underestimated in seismic design. (3) The dynamic shear stress-strain loops of sand-gravel soil exhibited a high-energy dissipation capacity, and the energy-transfer mechanism at the interface between the model soil and arch foot was integrated. The results obtained are expected to provide insights into the dynamic interaction behavior of the gravel soil and arch bridge systems and the seismic design of arch bridges built on sand-gravel soil sites in practical engineering.

Evaluating Pile-Supported Embankment Considering the Soil Anisotropy Effect

It is an economical way to use the pile-supported embankment for the construction of the embankment over soft soil. The combined use of piles and reinforcement effectively reduces the differential settlement of the embankment surface. However, the previous analysis of embankment stress and settlement did not take into account the anisotropy in the embankment filler. In this paper, the UMAT subroutine is developed by using the material subroutine interface in ABAQUS 2016 finite element software. The anisotropy of soil cohesion and friction angle has been incorporated into the Mohr–Coulomb yield criterion so that it can consider the anisotropy of soil. The accuracy of the anisotropic yield criterion in this paper is verified by an ABAQUS source program and related engineering examples. It is found that the anisotropy value of soil cohesion is inversely proportional to the stress ratio on the pile–soil interface while being directly proportional to the tensile stress applied to the geogrid. The results show that the anisotropy of the friction angle decreases with the soil arching effect but increases by 23.1% with the tensile stress on the geogrid. The position of the settlement plane remains relatively constant at 2.3 m as the friction angle anisotropy coefficient increases. These research results provide valuable theoretical guidance for on-site construction design.

A New Analytical Model for Trapdoor Tests Considering Effect of Incomplete Soil Arching and Principal Stress Deflection

A New Analytical Model for Trapdoor Tests Considering Effect of Incomplete Soil Arching and Principal Stress Deflection

Investigation of the soil arching evolution in the ground with or without a tunnel

The soil arching effect has been widely observed in geotechnical engineering. Despite extensive studies on this topic, there is still a lack of research on the effect of an existing tunnel on the evolution of the soil arching effect, which is investigated in this study via trapdoor tests. Digital image correlation was used to visualize the displacement and shear information of the sand. The effect of the backfill burial depth was considered. The results showed that the same load–displacement curve characteristics can be obtained with four stages (initial arching, maximum arching, load recovery, and ultimate stages), whether an existing tunnel is present or not. The ultimate soil arching ratio is degraded in ground with a tunnel, and most evident with H/B = 4.0, compared to the results without structures. A shield region was generated above the existing tunnel. A double-groove-shaped displacement was formed in the sand above it in the presence of an existing tunnel; it was symmetrical along the central axis of the trapdoor. The shear band gradually expanded from the inside to the outside as the trapdoor slid downward. New shear bands formed at the tunnel shoulder when the shear band exceeded the trapdoor width range. Two deformation patterns, parallel flow over a tunnel and cross-flow over a tunnel, were identified based on development of shear bands in the sand within the existing tunnel.

Suggested method of utilizing soil arching for optimizing the design of strutted excavations

An expression was derived for the soil arching effect behind foundation pits by considering the natural static equilibrium. An optimization strategy for super-large deep foundation pits was proposed based on the arching-related stress transformation and the limit span of soil arching. Steel–concrete composite piles that act as arching feet to formulate the soil arching are introduced. The proposed arching-effect methodology is supported using numerical modelling that reveals the stress arching in the principal stress contours. Once the interval between piles is less than the analyzed limit span of the soil arch, introducing steel–concrete composite piles can cause a sharp decline (by one third) in the wall deflection. It is essential that the steel struts are moved to the diaphragm wall where the steel–concrete composite piles form the arching feet and that the total number of steel supports remains unchanged. The formation of an arching foot can also significantly reduce the lateral wall deflection, enhancing the stability of the deep foundation pit during construction. Grouping the piles efficiently is a reliable tool for stabilizing deep foundation pits from the point of view of multi-arching action. Furthermore, the maximum principal stress contours reveal the arched trajectory between adjacent piles.

Experimental study on stress distribution characteristics of a shield tunnel under passive failure

Urban rail transit construction will inevitably encounter tunnel working conditions with extremely complex surrounding environment and buried deep shield tunnel, and the stability of the tunnel surface cannot be ignored. A series of passive instability geotechnical model tests were carried out on the tunnel faces at different burial depths. The earth pressure, lateral earth pressure coefficient and soil arch area evolution law caused by passive instability of the tunnel face in sandy cobble stratum were studied. Once the preset position is reached, the rotation is stopped using the cutterhead and the screw excavator and the shield machine continues the jack, simulating passive instability of the tunnel face. The results show that the soil pressure in the horizontal earth pressure is significantly more affected by the passive instability of the tunnel face than the vertical direction. The soil in front of the excavation caused by the ejection of the shield machine is squeezed and moved forward, resulting in a decrease in horizontal earth pressure perpendicular to the direction of shield tunnel excavation. The results of the passive instability region obtained by numerical simulation are larger than those obtained by model experiments, because the numerical simulation method fails to consider the compacting effect caused by the extrusion of sandy cobble formations. It can be found that the uplift value of C/D = 1.0 is significantly greater than that of C/D = 1.5, which also confirms the conclusion that the instability area with a relatively small burial depth is larger and develops farther to the front of excavation.

Evaluation of lightweight aggregate to reduce vertical stresses and improve load transfer in pile-supported embankments

Lightweight aggregate has unique characteristics of light self-weight, high friction angle, and good interaction with geosynthetics, and may be used as a fill material in load transfer platforms (LTP) over piles to support embankments on soft soils. This study included five plane-strain trapdoor tests to evaluate the use of lightweight aggregate to improve the performance of load transfer platforms over piled beams to support embankments on soft soils. These model tests consisted of trapdoor downward movement (settlement) and surface loading to investigate the mobilization and degradation of soil arching above the trapdoor. The surface loading was applied locally using a hydraulic jack through a footing. The vertical stresses on the trapdoor and the stationary supports were measured using earth pressure cells and the settlement of the footing was measured using a displacement transducer. Test results showed that soil arching mobilized with the settlement of the trapdoor and degraded with the footing loading. The geosynthetic reinforcement hindered the degradation of soil arching and increased the bearing capacity of the embankment under footing loading. Overall, the lightweight aggregate had favorable soil arching behavior with low vertical stresses on the trapdoor and the stationary supports as compared with the river dand. Lightweight aggregate is proven to be a good alternative material for load transfer platforms in pile-supported embankments.

Soil Arching–Induced Lateral Earth Pressure Redistribution on the Retaining Wall in a Multistrutted Excavation in Soft Soil

Soil Arching–Induced Lateral Earth Pressure Redistribution on the Retaining Wall in a Multistrutted Excavation in Soft Soil

Deformation Analysis of a New Subway Transfer Channel Closely Undercrossing an Existing Station

Disturbances that occur due to the construction of new subway transfer channels in cities pose a significant threat to the safe operation and structural stability of existing subway stations. Due to the construction of the new Jin-Fu Station of Chengdu Rail Transit Line 27, the transfer channel of the new Jin-Fu Station closely underpasses the station of the existing Metro Line 6. First, based on the random medium theory, the curved integral boundaries of the rectangular section are improved and simplified by the numerical simulation. Second, the mechanical response of the underpass construction to the existing subway station is analyzed by Pasternak foundation model theory. Finally, the accuracy of the theoretical calculation is verified by the three-dimensional numerical calculation and the measured data, and the sensitivity of its parameters is analyzed. The results show that maintaining a certain net distance d (that is, increasing the thickness of the interlayer soil) is conducive to forming the soil arch effect and reducing the deformation of the existing station above. The settlement of the existing station can be reduced by increasing the height-to-width ratio of the excavated section, but the maximum bending moment of the floor will increase slightly. With the increase in the foundation reaction coefficient k, the interaction between the soil mass and the existing station is enhanced, and the deformation, bending moment, and shear force on the floor of the existing station increase significantly. When the foundation reaction coefficient increases to 10k, there is an obvious uplift phenomenon outside the settlement trough of the existing station floor.

Numerical multi‐span segmented trapdoor test with viscoelastic boundary for soil arching within pile‐supported embankment under cyclic loading

AbstractDynamic wave reflections would interfere with the laboratory observation of the soil arching under cyclic loading when a traditional trapdoor model with rigid boundaries was used. This problem would be prominent when investigating the soil arching in pile‐supported embankments where the stationary support (pile) would be small, making the rigid boundary close to the domain of interest affected by dynamic loads. To avoid dynamic wave reflections and narrow the calculation domain, soil arching within a pile‐supported embankment under cyclic loading is numerically investigated in a multi‐span segmented trapdoor model with flexible boundaries by the particle flow code (PFC). In addition, a pavement structure is included and the springs supporting the trapdoor follow a bi‐linear constitutive model. The energy‐absorbing flexible boundary at the bottom weakens the dynamic wave reflections and is in favor of passing vertical dynamic waves to compact the fill and weaken the influence of cyclic loading on the soil arching effect during the loading stage. Lateral flexible boundaries would facilitate realistically reproducing the effect of cyclic loading on the soil arching because they could consider the weakening of the plugging effect that occurs during the lateral expansion. The development of soil arches of mid‐span and side‐span are different when the load applied at the mid‐span is laterally transferred to adjacent spans by the arching effect.

Passive Soil Arching Effect in Aeolian Sand Backfills for Grillage Foundation.

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.