Analysis of Soil arching effect for Blind sheet-pile wharf based on ABAQUS

Combined with practical engineering, based on the introduction of soil arching theory, we explore the impact of barrier piles in blind sheet-pile bank connecting structure. Besides, we build a plane strain model by ABAQUS sot＇cware to study the impact of cross section type, the pile spacing and soil properties on soil arching effect. We find that cross section type of the pile has a certain influence on soil stress distribution in front of the barrier piles by comparing circular cross section and rectangular cross section. We also find that clear distance between the barrier piles and cohesive force of the soil have a great influence on that impact. We can increase clear distance between the barrier piles appropriately to improve the efficiency of construction and reduce the proiect cost.

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.

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.

Analytical model of vertical load acting on jacked pipe considering soil arching effect in cohesionless soil

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.

Effect of seepage on soil arching effect in deep shield tunnel

Shield tunneling and post-tunneling steady seepage are accompanied by stress and displacement variations,which could induce and influence the soil arching effect.Although there are many studies on the tunneling-induced soil arching effect,the research about the effect of seepage on soil arching effect is extremely lacking.In this study,a numerical model is firstly established and verified by field data.Then,a series of numerical models,whose simulation method of steady seepage is verified by adopting the conformal mapping technique,are established to study the soil arching evolution of deep-buried tunneling and post-construction steady seepage.The results indicate that seepage leads to an increase in effective vertical stress,which is consistent with the existing theory.The seepage weakens the soil arching effect resulting in the height of the arch zone reducing from 2.38D(D is the tunnel diameter)to 1.25D.The seepage leads to the further development of ground consolidation settlement,but the differential displacement in the soil mass decreases.The ground reaction curve in the steady seepage condition shows a bigger value than that after excavation.It is reasonable to control the ground loss ratio in the range of 0.5–1.0%,which can minimize overburden pressure with moderate ground deformation.

Improved method for determining active earth pressure considering arching effect and actual slip surface

To determine the distribution of active earth pressure on retaining walls, a series of model tests with the horizontally translating rigid walls are designed. Particle image velocimetry is used to study the movement and shear strain during the active failure of soil with height H and friction angle φ. The test results show that there are 3 stages of soil deformation under retaining wall translation: the initial stage, the expansion stage and the stability stage. The stable sliding surface in the model tests can be considered to be composed of two parts. Within the height range of 0.82 H-1.0 H, it is a plane at an angle of π/4+φ/2 to the horizontal plane. In the height range of 0-0.82 H, it is a curve between a logarithmic spiral and a plane at an angle of π/4+φ/2 to the horizontal. A new method applicable to any sliding surface is proposed for active earth pressure with the consideration of arching effect. The active earth pressure is computed with the actual shape of the slip surface and compared with model test data and with predictions obtained by existing methods. The comparison shows that predictions from the newly proposed method are more consistent with the measured data than the predictions from the other methods.

Soil-structure interaction of unsymmetrical trench installation culvert

The computation of the design load on culverts in the current Chinese General Code for Design of Highway Bridges and Culverts （CGCDHBC）is primarily based on the linear earth pressure theory, which cannot accurately reflect the changes in vertical loads on trench installation culverts. So the changes in vertical earth pressure and soil arching effect in the backfill for an unsymmetrical trench installation culvert are studied based on a full scale experiment and finite element （FE） simulation. The variation laws of foundation pressure and settlement are also analyzed. Meanwhile, the influence of eccentric load induced by an unsymmetrical trench installation on the interaction of a soil- structure system is discussed. Results show that soil arch is formed when the backfill on the culvert reaches a certain height. It can relieve the earth pressure concentration on the crest of the culvert, but it is instable. The earth pressures obtained by full scale experiment and numerical simulation are greater than those calculated by the current CGCDHBC method. The eccentric load effect on the culvert has a significant influence on the stress states and deformation of the soil-structure system.

Earth Pressure of the Trapdoor Problem Using Three-Dimensional Discrete Element Method

Load transformation from the yielding part of the soil to the adjacent part is known as the soil arching effect,which plays an important role in the design of various geotechnical infrastructures.Terzaghi’s trapdoor test was an importantmilestone in the development of theories on soil arching.The research on earth pressure of the trapdoor problem is presented in this paper using the three-dimensional(3D)discrete element method(DEM).Five 3D trapdoor models with different heights are established by 3DDEMsoftware PFC 3D.The variation of earth pressure on the trapdoor with the downward movement of the trapdoor,the distribution of vertical earth pressure along the horizontal direction,the distribution of vertical earth pressure along the vertical direction,the distribution of lateral earth pressure coefficient along the depth direction,the magnitude and direction of contact force chain are studied,respectively.Related research results show that the earth pressure on the trapdoor decreases rapidly after the downward movement of the trapdoor,and then reaches the minimum earth pressure.After that,the earth’s pressure will rise slightly,and whether this phenomenon occurs depends on the depth ratio.For the bottom soil,due to the stress transfer caused by the soil arching effect,the ratio of earth pressure in the loose area decreases,while the ratio of earth pressure in the stable area increases.With the trapdoor moving down,the vertical earth pressure along the depth in the stable zone is basically consistent with the initial state,which shows an approximate linear distribution.After the trapdoor moves down,the distribution of earth pressure along with the depth in the loose area changes,which is far less than the theoretical value of vertical earth pressure of its self-weight.Because of the compression of the soil on both sides,the lateral earth pressure coefficient of most areas on the central axis of the loose zone is close to the passive earth pressure coefficient Kp.The existence of a‘soil arch’can be observed intuitively from the distribution diagram of the contact force chain in the loose zone.

Loosening earth pressure above shallow trapdoor in unsaturated soil with different groundwater level

The consideration of unsaturated conditions is infrequently addressed in current Terzaghi’s soil arching research.A modified analytical method for calculation of unsaturated loosening earth pressure above shallow trapdoor is proposed in this paper.By assuming the existence of a vertical slip surface above the trapdoor,the stress state of the soil in the loosening area are delineated in the extended Mohr–Coulomb circle.To account for the non-uniform distribution of vertical stress at arbitrary points along the horizontal differential soil trip,a virtual rotation circle trajectory of major principal stress is employed.Subsequently,the average vertical stress acting on the soil trip is determined through integral approach.Taking into account the influence of matric suction on soil weight and apparent cohesion,the differential equation governing the soil trip is solved analytically for cases of uniform matric suction distribution and alternatively using the finite difference method for scenarios involving non-uniform matric suction distribution.The proposed method’s validity is confirmed through comparison with published results.The parameter analysis indicates that the loosening earth pressure initially decreases and subsequently increases with the increase of the soil saturation.With the rise of groundwater level,the normalized effective loosening earth pressure shows a decreasing trend.

Analytical solutions of limit support pressure and vertical earth pressure on cutting face for tunnels

This paper focuses on theoretical analytical models to calculate the limit support pressure and vertical earth pressure on the cutting face for tunnels.The failure zone is divided into two parts:a sliding failure zone and an upper loosen zone,and the limit support pressure calculation equation is derived.To verify the rationality of the theoretical model,it was compared with the existing theory,numerical simulation,and centrifugal test,and then the parameter analysis was carried out.The results show that the results of this paper agree well with the existing theory,numerical simulation,and centrifugal test.The inclination angle of the proposed mechanism is determined based on the results of the existing centrifuge test,and the recommended inclination angle is between 52°+φ/2 and 54°+φ/2.The method is proven to be safe and accurate.It can provide a theoretical basis for similar projects.