Coefficient Of Lateral Earth Pressure Research Articles

A method for estimating coefficient of lateral earth pressure based on cone penetration tests

The coefficient of lateral earth pressure at rest (K0) is a key state soil variable for the design of foundations and underground structures, characterizes in-situ stress state and soil condition. In this study, a method for the in-situ estimation of K0 using the cone penetration test (CPT) is proposed considering vertical and inclined cone resistances (qc). For this purpose, a series of laboratory CPTs in a soil chamber were conducted to obtain and characterize vertical and inclined qc values at various inclination angles (θ) and relative densities (DR). It was observed that the values of qc increased as θ increased, which was more pronounced at higher DR. Coupled Eulerian-Lagrangian (CEL) finite element analyses were performed to quantify the values of inclined qc at various cone penetration and soil conditions. Based on results from laboratory CPTs and CEL analyses, a CPT-based K0 correlation model was established, which was given as a function of vertical and inclined qc values. The model parameter for the proposed method was evaluated and quantified. The validity of the proposed method was confirmed from the comparison with case examples.

Deformation characteristics and creep behaviour of rigid particulates-EPS beads composites

The compression behaviour of the mixture of glass beads (representing rigid particles) and EPS beads (representing deformable particles) during the loading-unloading process is systematically examined through performing two sets of large-size oedometer experiments, including incremental step-by-step and one-step loading scenarios. At each step during the loading-unloading cycle, the void ratio (e) and the at-rest coefficient of lateral earth pressure (K0) are measured for pure rigid samples and rigid-soft particle mixtures. To consider the creep effect, the overburden pressure at the final loading step is maintained on the sample for 24 h prior to unloading. The results show that at a given overburden pressure, with the addition of soft particles to the pure rigid aggregates, the values of e and K0 decrease. Additionally, for both pure rigid samples and rigid-soft particle mixtures, with increasing the overburden pressure, e decreases whereas K0 augments. Moreover, due to the creep behaviour during the constant loading step, K0 decreases over time for both samples; a phenomenon which is observed to be more pronounced for pure rigid aggregates compared to rigid-soft particle mixtures. Finally, a well-established creep model is used to simulate the creep behaviour of pure rigid samples and rigid-soft particle composites.

Effects of Pipe Deflection and Arching on Stress Distribution and Lateral Earth Pressure Coefficient in Buried Flexible Pipes

In this study, full-scale laboratory tests were conducted on a 315 mm diameter HDPE pipe under shallow buried and localised surface loading conditions to investigate the effects of pipe deflection and arching on stress distribution and the lateral earth pressure coefficient. The tests were validated using 2D finite element software, and further analyses were carried out through parametric studies. These studies considered variations in pipe stiffness, burial depth, backfill properties and pavement stiffness to increase the reliability of the test results. For a shallowly buried HDPE pipe, a comprehensive explanation is provided regarding the evolution of the lateral earth pressure coefficient within the central soil prism. Initially set at Ko conditions, this coefficient tends to shift towards Kp with increasing arching and transitions to Ka with weakening arching. The findings suggest that stress predictions in the crown region of shallow buried flexible pipes are achievable through the application of Terzaghi’s arching theory, contingent upon an accurate estimation of the lateral earth pressure coefficient for the central soil prism. Furthermore, the horizontal deflection of the pipe at the springline results in compressive behaviour and passive effects in the surrounding backfill in this specific region. This situation demonstrates that the horizontal stresses at the springline and the lateral earth pressure coefficient can be reliably estimated by considering them as functions of the horizontal deflection of the pipe.

At-rest lateral earth pressure coefficient under narrow backfill widths: A numerical investigation

<abstract> <p>The lateral earth pressure at rest is typically considered in situations where lateral wall movements are negligible. Determining the coefficient of lateral earth pressure at rest (referred to as <italic>K</italic><sub>0</sub>) often relies on established classical equations. However, these equations often overlook the influence of the width of the backfill soil on lateral earth pressure. While this omission is generally acceptable when the backfill soil is wide enough, there are instances where a retaining wall supports backfill soils of limited width, such as basement walls between adjacent buildings. Yet, there is limited research addressing the impact of narrow backfill in such scenarios. We aimed to address this gap by investigating variations in <italic>K</italic><sub>0</sub> values under different conditions, including backfill width and soil properties. Using ABAQUS for numerical simulations, we refined and validated our model using relevant laboratory experimental data. Subsequently, the validated model was applied to various simulation scenarios. For narrow backfill widths (ranging from 0.1 to 0.7 times the retaining wall height), our findings indicated a general decrease in <italic>K</italic><sub>0</sub> values with decreasing backfill widths, often smaller than those estimated using classical equations. Additionally, along the depth of the wall, <italic>K</italic><sub>0</sub> values tended to decrease with increasing depth for narrow backfill widths. These findings contribute to our understanding of the impact of narrow backfill on <italic>K</italic><sub>0</sub>.</p> </abstract>

At-rest lateral earth pressure in compacted silica sand

ABSTRACTAt-rest lateral earth pressure is one of the major sources of disturbing force on retaining structures and provides resisting force for anchors and piles. A theoretical model is proposed, and experimentally validated, for the normally and overconsolidated at-rest lateral earth pressure coefficients in silica sand. In addition, the experiment illustrates a procedure to determine the maximum historic vertical stress equivalent to the standard and modified Proctor energies of compaction. The previous equivalent maximum historic vertical stress, which is found to be constant for the relative density reached by each energy of compaction, is then proposed as a parameter to determine the overconsolidation ratio within the backfill and its resultant at-rest lateral earth pressure distribution behind a vertical wall. The at-rest lateral earth pressure distribution incorporated with the overconsolidation ratio naturally results in a greater magnitude and is curved in contrast to the linear distribution characteristic of a normally consolidated state. A limit equilibrium analysis and a plane-strain particle-scale model of a granular media under critical state were used to derive the equations herein.

Empirical Relationship between Three Geotechnical Properties Obtained in Three Sites in Kerbala City, Iraq

The material index (Im), concentration index (Ic ), and Coefficient of Lateral earth pressure at res (Ko ) are important geotechnical properties, which are determined in seismic cross holes depending on wave velocities. These three geotechnical properties were determined in three sites in Kerbala City, Iraq. These geotechnical properties are determined depending on the cross-hole survey achieved at Al-Abbas holy shrine, the pure water p, project and the Al-Khiam hotel sites. From a comparison of of the values of these properties in the three sites, three empirical relations were found between them, these are Im = - Ko, Ic = 4 – Ko, and Ic = 4 + Im. the author believed that these relations are usfule in determine these properties. In this research, it was reached to find new equations or relationships through which these three properties can be calculated by calculating one of them, and then finding the values of the other properties ia n short time, and with high accuracy. These new equations or relations I called Al-Kafeel equaions. Im , ,Ic and Ko have been calculated for more than 2034 samples from the surface of tearthths to up 15 m. These parameters have been calculated for more than 2034 samples from the earth's surface and up to 15 m, which used seismic velocity values in calculating these properties by the international old equations. This paper used new equations which are called Al-Kafeel geotechnical equations. The results were compared using the two equations, and it was very successful, and the error rate was between 1%–2%. These simple equations or relations, Al-Kafeel Equations, have been reached and used for the first time since 2017 and have given excellent results in terms of time, and accuracy.

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.

The compression characteristics and lateral earth pressure coefficient of sand–HDPE mixtures

In recent decades, considerable attempts through geotechnical study have been made to reduce plastic waste by recycling and reuse. The aim of this study was to reuse waste plastic mixed with sand for geotechnical application. To this end, large-scale oedometer experiments were carried out to examine the compressibility of Bandar-e Anzali sands stabilised with plastic-waste-originated high-density polyethylene (HDPE). Bandar-e Anzali is a populated coastal city in the vicinity of the Caspian Sea (northern Iran). Large-scale oedometer and direct shear tests were performed to study the applicability of HDPE chips mixed with sand at various HDPE contents (0, 2, 4, 6 and 8%). Based on the experimental tests, the addition of plastic waste to the soil improved the soil's strength, significantly raised its compressibility and decreased the undrained elasticity modulus. By adding 8% HDPE, the constrained compression modulus decreased to 50% at a pressure of 300 kPa due to the elastic deformability of HDPEs. However, at higher relative density, adding HDPE by more than 4% did not affect the coefficient of lateral earth pressure at rest.

An Experimental Study on Estimation of the Lateral Earth Pressure Coefficient (K) from Shaft Friction Resistance of Model Piles under Axial Load

Estimating a pile shaft’s frictional capacity is challenging and has been a controversial subject among researchers. In this study, the shaft friction resistance of non-displacement (pre-installed) model piles under axial load was investigated. Four different model piles were used, including steel, timber, and two composite piles (FRP and PVC filled with concrete). The angle of interface friction (δ) between test sand, and pile materials was determined using an interface shear test (IST) at four relative densities. Axial pile load experiments were implemented in a soil tank and piles were embedded into loose to very dense sand. Model pile load tests were performed in such a way that there was no end (point) bearing capacity (only friction was generated), and lateral friction resistance between the pile material and the soil along the pile shaft formed the complete bearing capacity of the model pile. According to experimental results, it was observed that, with increasing sand relative density and surface roughness of the pile material, the shaft friction resistance of the model pile increases. A back-calculation analysis was also performed to find the values of lateral earth pressure coefficient (K) using Burland’s (1973) equation with the help of measured shaft friction capacity of the model pile load test. By performing multivariate regression analysis, an equation was obtained between the back-calculated lateral earth pressure coefficient (K) and other parameters. The obtained equation was used to calculate the K values given in other studies in the literature. It was determined that the obtained equation was in good agreement with the data in other studies. This equation can be beneficial in practice and can be advantageous for further study in the future.

Numerical Investigation of Uplift Failure Mode and Capacity Estimation for Deep Helical Anchors in Sand

The uplift capacity of helical anchors is generally taken as the control condition for design in different applications, including transmission tower foundations and offshore structures. However, it is difficult to identify the failure surface for a deep helical anchor, which may result in an incorrect assessment of uplift capability. This research proposes a new unified method to estimate the uplift capacity of deep single-helix and multi-helix anchors based on the investigation of failure mechanisms. The deep failure mode was identified by FEM analysis using a modified Mohr–Coulomb model considering the strain softening of sand, along with the coupled Eulerian–Lagrangian technique. Thereby, a simplified rupture surface is proposed, and the equations estimating the uplift capacity are presented by the limit equilibrium method. Two important factors—the lateral earth pressure coefficient and the average internal friction angle included in the equations—are discussed and determined. The comparisons with centrifugal tests verify the reasonability of the proposed method.

Large scale land reclamation and the effects on hydro-mechanical behavior in loess and loess-derived fill

To discover the complex hydro-mechanical evolution on Loess Plateau that accompany large-scale land reclamation project, we tracked changes of moisture, matric suction, anisotropic displacements and stresses in geological interfaces of natural loess and deep man-made fill during a comprehensive process of construction and the subsequent three years rest period. Results indicate that vertical stress increases during emplacement of thick fill, while the lateral earth pressure first increases and then gradually decreases with elapsed time. There was a non-linear increase in lateral earth pressure with depth of infill during construction. Whereas lateral earth pressure decreased with depth in lengthy rest period. The fill vertically compressesed and laterally extended during construction, while the geological interface of fill and loess laterally rebounded during construction pause. The primary vertical displacement occurred at the contact zone between the original loess slope and fill. The lateral earth pressure coefficient of infill is influenced by lateral compression and extension of contact zone during land reclamation process. It mirrors the observation that variations in lateral earth pressure with depth are dependent on deformation of natural slope materials. Interestingly, vertical stress and lateral earth pressure periodically fluctuated during rest period, correlating to creeping and shrinkage in loess influenced by moisture content change under different environmental relative humidity. The volumetric moisture contents in fill and contact zone significantly increased during construction. The moisture content of contact zone is 10% higher than the overlying higher density fill after construction, which is attribute to the process of matric suction equilibrium. Considering a constant moisture content, the ratio of historical mean principal stress to deviatoric stress in fill and interface are under the principal stress failure line during construction. However, water diffusion potentially threats the stability of this man-made geological structure.

A parametric study on the dynamic lateral earth forces on retaining walls according to European and Turkish Building Earthquake Codes

In the earthquake regulations of many countries, Mononobe-Okabe method was used to determine the seismic lateral earth forces and earth pressure coefficients for the design of retaining structures. However, there are various interpretation differences of this method between earthquake regulations of different countries. In this study, effect of different seismic acceleration coefficients (S_DS) and different soil friction angles(ϕ_d^,) on the seismic earth forces acting on a high retaining structure were investigated through a parametric study based on the methods described in 2018 Turkish Building Earthquake Code (TBEC-2018) and EuroCode-8 (EC-8). For this purpose, approximately 120 analyzes were carried out by using different parameters and the analysis results were shown in tables and figures. Analyses were performed for yielding rigid retaining walls and anchored walls for the principles defined in the mentioned earthquake codes. It was observed that the seismic lateral force estimations made with TBEC-2018 are higher compared to values calculated according to EuroCode-8. In the calculation of dynamic thrust, unexpected results may occur at some critical values of θ angle which is dependent on the lateral acceleration coefficient.

Prediction of Reinforcement Connection Loads in Geosynthetic Reinforced Segmental Retaining Walls Using Response Surface Method

This paper presents an improved earth pressure method that considers the capacity of a wall toe to carry an earth load to predict the connection loads of GRS segmental walls constructed with cohesionless backfills on competent foundations. In this method, a response surface model (RSM) of the lateral earth pressure coefficient replaces the Coulomb active earth pressure coefficient. The parameters of the RSM were determined from numerical studies on the impacts of toe restraint, wall geometry, and backfill properties on the distribution of earth loads between the toe and reinforcement layers. The unknown coefficients of the RSM were obtained through a regression analysis of 705 reinforcement load values from 65 simulated walls. The proposed method was compared to the earth pressure method and the stiffness method using measured connection loads from field and centrifuge GRS segmental walls. The results show that the predictions of the proposed RSM method are in better agreement with the measurements than those of the stiffness method and the earth pressure method, whether under a typical or poor toe restraint condition.

Influence of input motion and surface layer properties on seismic site response: A stochastic simulation method–based MLR model

AbstractSeismic site response analyses are simulations in which the effects of geological conditions on seismic waves are examined. The uncertainties that make these analyses crucial are defined as the source of motion, the travel path of seismic waves, and geological conditions. In this study, a series of non‐linear seismic response analyses were performed using data from site investigation studies. The results of non‐linear analyses performed under earthquakes with different characteristics based on real soil data were investigated in terms of acceleration time histories and response spectra. The relationship between site response with the surface layer properties and input motion properties used in the simulations was examined in a parametrical manner. Based on the results obtained, Monte Carlo simulation, which is a stochastic data simulation method, was performed. Additionally, multiple regression and variance analysis (ANOVA) was performed on the dataset created by both site response analysis and stochastic simulations. The MLR model displayed highly accurate results with a coefficient of determination, R2 of 0.9763, and a standard error of 0.109. The efficiency level of the independent variables used as input parameters in the simulations on the dependent variable, AF was examined. It was revealed that the coefficient of lateral earth pressure at rest (Ko), earthquake motion (i.e., PGA of input motion) and surface layer thickness (dsurface) from the soil properties had the highest effect on the amplification factor.

Effects of Geogrid Reinforcement on the Backfill of Integral Bridge Abutments

The construction of integral bridges is one of the most effective methods to reduce bridges’ construction and in-service costs. However, there are associated geotechnical problems with their abutments backfill due to the integrated abutments. The main goal of this study is to evaluate and quantify the benefits of geogrid reinforcement for reducing the backfill’s geotechnical problems. For this purpose, using small-scale physical modeling, the benefits of geogrid reinforcing of the backfill of an integral abutment bridge subjected to cyclic movements are evaluated. The results are then compared with a previous study performed on unreinforced backfill and two types of geocells. In this study, 120 loading cycles are applied to geogrid-reinforced soil to simulate the cyclic loadings on integral abutment backfill due to seasonal abutment displacement. The horizontal reaction load at the top of the wall, changes in pressure behind the wall, and deformation in backfill soil are measured during the test. Then the results are discussed in terms of equivalent peak lateral soil coefficient (Kpeak), lateral earth pressure coefficient (K*), and normalized settlement behind the wall (Sg/H). The derived lateral soil coefficients and settlement behind the abutment show that geogrid substantially reduces pressure and settlements after 120 cyclic loads. Based on the results, Kpeak and K* of the geogrid-reinforced backfill decrease by up to 36%, and Sg/H behind the wall decreases by 62%. In addition, the comparison of the results for geogrid with two geocell types shows that geogrid is more efficient in terms of lateral soil coefficients.

CIRCULAR TUNNEL STRUCTURAL ANALYSIS IN SOFT GROUND

Analytical bedded-beam spring model is most commonly adopted in the tunnel engineering practice due to its simplicity and promising outputs. Despite many well documented literatures exist concerning about the theories and fundamentals of various methods, there is a dearth of information on the modelling framework of a bedded-beam spring and many details are often overlooked in the modelling process. The main aim of this paper is to produce the modelling framework of the bedded-beam spring model in soft ground, for both direct and indirect approaches in considering the effects of segmental joints. Particular emphasis is devoted to the modelling techniques of each components of the structural model which in turn, is able to facilitate the modelling quality and process for the practicing engineers. Reviews on the technical papers of tunneling variables as well as parameters identification for the structural analysis have been first performed followed by the comparison of the consideration adopted in the modelling techniques. Analyses have been carried out to evaluate the structural forces on the tunnel lining and the obtained results are discussed in a comparison with the field measurements and design values of the actual tunneling projects. The results suggested that the direct approach always yields greater bending moments up to i) 26% for 6+1 ring configuration and ii) 21% for 5+1 ring configuration compared to that of the indirect approach. With the presence of more number of radial joints, the differences between the approaches have the tendency to be greater. With the validated models, parametric studies including tunnel lining flexibility ratio, compressibility ratio and the soil lateral earth pressure coefficient have been performed to provide better insight on the relative importance of each of the parameters. The results of the studies suggested that with the increase in flexibility ratio, the difference between the direct and indirect approach has shown to increase from 10% to 28%. However, insignificant influence has been observed on the axial forces regardless of the joint consideration approach a well as the compressibility ratio.

Experimental Studies on Some Clays Leading to Instability

The landslide problem in the city of Constantine (Algeria) is mostly due to clayey soil, which is covering the whole area. Therefore, all the structures and foundations built over such soil are quite vulnerable. The sensitivity of this soil increases during the rainfall season, which might reach an extreme magnitude and cause damage to the structures. To understand some aspects of the failure of the mentioned soil and its mechanism, a large campaign of geotechnical characterization was undertaken using samples from the area. The specific gravity, Atterberg limits, and coefficient of lateral earth pressure at rest were determined. Samples were tested in triaxial stress path cells over a range of stresses, with the test being either stress- or strain-controlled, leading to sliding phenomena under different stress levels. The clays can be classified as over-consolidated soils. The test program and the characterization study indicated that Kois directly related to the stress history of the soil and also dependent upon the state of the sample before the test (i.e., undisturbed or disturbed). The clay minerals in the Mio-Pliocene landslide zones in Constantine are mostly montmorillonite and kaolinite, which have the lowest frictional resistance. As the montmorillonite content increases, the angle of internal friction decreases. The present study focuses on the critical state analysis since all the behavior problems of these tested samples show a peak shear strength, which is characteristic of over-consolidation materials that could lead to instability in this area. Doi: 10.28991/CEJ-2023-09-02-012 Full Text: PDF

The laterally confined consolidation of initially compacted and wetted swelling clay

This paper describes the laterally confined consolidation of an Israeli clay following compaction and swelling on wetting, including the measurement of lateral stresses. The results of the tests are compared to those obtained during consolidation of the clay from an initially slurried condition. In comparing the compression and expansion indices relative to vertical, lateral and mean stress, it was found that they varied, depending on the initial, preparation conditions; the values approached the slurried values with decreasing initial dry density. During unloading, the expansion indices were found to be independent of initial conditions, and essentially the same as those of the slurried soil. The coefficient of lateral earth pressure at rest during loading, K0, of the compacted and then wetted specimens was found to be reasonably constant regardless of initial soil conditions, but significantly higher than the value of the slurried soil. However, during unloading, the relationship between the normalized coefficients of lateral earth pressure at rest, K0'/K0, and the overconsolidation ratio, OCR, was found to be essentially the same as that obtained for the slurried soil.

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 important milestone 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 3D DEM software 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.

Hyperbolic stress-strain behaviour of sandy soil under plane strain unloading condition and its application on predicting displacement-dependent active earth pressure

This study investigates the displacement-dependent lateral earth pressure of sandy soil in active state. 3D DEM numerical simulations of plane strain unloading test (unloading in the minor principal stress direction) are carried out firstly to acquire the hyperbolic stress–strain relationship of sandy soil. The initial modulus of sandy soil is observed to increase with the increasing of major principal stress, initial lateral earth pressure coefficient and relative density, while the failure ratio is little influenced by these factors. A simplified hyperbolic model calibrated by the DEM results are then developed to calculate the displacement-dependent active lateral earth pressure of sandy soil. It was found that the hyperbolic model can well predict the variation of lateral earth pressure distribution at intermediate active state of T- (Translation) and RB- (Rotate about the base) mode of retaining structure movement. But it can hardly capture the lateral earth pressure distribution on retaining structure under RT- (Rotate about the top) mode due to significant rotation of principal stress direction. According to the theoretical analysis, the required retaining structure displacement leading to the limiting active state is varied along the retaining structure, and it also dependents on the initial stress state as well as the relative density.