Numerical simulation of horizontal displacement at the top of support piles for ultra-deep foundation pits in silty formations.

Lagged settlement is a typical accident induced by shield construction in sandy cobble strata. This paper analyzed the process and mechanism of lagged settlement, results show that all phases are in accord with the characteristics of ellipsoid theory of particle flows. Based on this theory, a method for calculating coefficient of lateral earth pressure and loosened earth pressure is proposed in this research. For the coefficient of lateral earth pressure, the boundary of loosened ellipsoid is divided into two parts, the arch zone and the excavation zone, and the lateral pressure coefficients are derived respectively according to the stress state. For loosened earth pressure on tunnel, the Terzaghi earth pressure theory and Protodyakonov earth pressure theory are adapted in different conditions according to the state of loosened cobble soil. Theories developed in this study can be applied on determination of shield excavation parameters, as well as calculation of loosened earth pressure and control of tunnel support.

Lateral earth pressure on retaining walls is a widely researched classical problem in geotechnical engineering. This study investigates the active lateral earth pressure on a circular retaining wall using the stress characteristics method in the presence of soil-wall adhesion and friction. A computer code was developed for determining the lateral pressure of soil on the wall as well as the lateral pressure coefficients upon receiving the required input parameters. The principle of superposition was implemented to determine the lateral earth pressure coefficients. The effects of the soil-wall adhesion and friction angle on the lateral earth pressure were studied under active conditions. Moreover, the effects of these parameters on the characteristics network and failure region were demonstrated. The results showed that the coefficient of lateral earth pressure due to cohesion increased with increasing adhesion at the soil-wall boundary.

The effect of initial particle fabric on the one-dimensional compression response of Fraser River sand was investigated. One-dimensional compression with lateral stress measurement was carried out on reconstituted Fraser River sand specimens using an instrumented oedometer. Laboratory specimens were reconstituted by air pluviation, tamping, and vibration and were prepared with an initial relative density ranging from medium loose to very dense. For Fraser River sand in one-dimensional compression, air-pluviated specimens yielded the highest values for the coefficient of lateral earth pressure at rest (Ko), tamped specimens produced the lowest Kovalues, and vibrated specimens produced intermediate Kovalues. The results from the present study demonstrate that specimens resulting from different laboratory reconstitution methods (i.e., different initial particle fabrics) exhibit different one-dimensional compression responses and produce different Kovalues. A “fabric factor” was introduced to account for the effect of the initial particle fabric on the measured coefficient of lateral earth pressure at rest. Using the fabric factor, the constant volume friction angle, and the specimen relative density, a new empirical equation defining the coefficient of lateral earth pressure at rest during normally consolidated loading is proposed.

Scour significantly reduces the lateral load capacity of rigid piles, threatening the stability of offshore wind turbines. During scour, the lower soil around the foundation may be changed from a normally consolidated state to an overconsolidated state due to the removal of the upper soil, altering soil parameters such as friction angle, overconsolidation ratio, relative density, void ratio, and lateral earth pressure coefficient. While these changes have been extensively studied theoretically, they have not been fully incorporated into numerical studies. Ignoring these variations can lead to overly conservative designs. This article focuses on the increased lateral earth pressure coefficient due to scour and its impact on numerical simulations. Using the Boussinesq solution and considering the shading effect of the pile foundation, the vertical effective stress of the remaining soil around the pile was adjusted, resulting in a theoretical formula for the lateral earth pressure coefficient after scour. Based on numerical simulation and model tests, an empirical formula is obtained. Finally, a semiempirical and semitheoretical formula is proposed to calculate the increased lateral earth pressure coefficient postscour. This study provides a reference for determining the appropriate lateral earth pressure coefficient in numerical studies.

Taking into consideration both stress dispersion effect and shear strength of crust layer, based on Flamant formula of polar coordinates representation and Mohr-Coulomb strength criterion, this paper deduces a new formula of critical edge pressure of natural soft foundation considering the realistic coefficient of lateral earth pressure. A calculation method of critical embankment height on natural soft foundation is proposed. The limit value of the result calculated by the new method is also put forward, which can ensure the reliability of the method applied. Additionally, critical embankment height at different thickness of crust layer h2, width of embankment loading B, soft layer soil coefficient of lateral earth pressure K0, crust layer soil coefficient of lateral earth pressure K1 is studied. Researches discover that the change of h2, B and K0 has significant influences on critical embankment height; a calculation result of critical embankment height is significantly partially high when the coefficient of lateral earth pressure is equal to 1 under this assumption.

Assessing the state of stress in soil in the free field, as defined by the vertical and lateral earth pressures, is important in some geotechnical problems such as the design of underground structures and estimation of soil liquefaction potential. Unlike the vertical earth pressure, several factors can influence the lateral earth pressure, particularly overconsolidation. This is typically accounted for by relating the coefficient of lateral earth pressure at rest, K0, with the estimated overconsolidation ratio (OCR). The corresponding relations available in the literature are related to the K0 occurring for a given OCR during unloading, and do not take into account the unloading–reloading effect that may be present in centrifuge tests. In this paper, the relationship between the coefficient of lateral earth pressure at rest, K0, and overconsolidation ratio, OCR, is investigated for the whole loading–unloading–reloading condition. Four centrifuge model experiments were conducted on Ottawa F#55 sand. Two of the models were tested using a tactile pressure sensor to measure K0 and the other two models were tested using a miniature cone penetration test (CPT) system. The paper concludes with recommendations for centrifuge operation when testing overconsolidated sand in the centrifuge.

This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs around the soil friction angle of 40° and 45°. Also, the effect of K0 on side resistance is approximately constant by increasing the soil unit weight. Finally, a correction factor for coefficient of lateral earth pressure is determined.

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.

In this paper, the active lateral earth pressure is evaluated using the stress characteristics or slip line method. The lateral earth pressure is expressed as the lateral earth pressure coefficients due to the surcharge, the unit weight and cohesion of the backfill soil. Seismic horizontal and vertical pseudo-static coefficients are used to consider the seismic effects. The equilibrium equations along the characteristics lines are solved by the finite difference method. The slope of the ground surface, the wall angle and the adhesion and friction angle of the soil-wall interface are also considered in the analysis. A computer code is provided for the analysis. The code is capable of solving the characteristics network, determining active lateral earth pressure distribution and calculating active lateral earth pressure coefficients. Closed-form solutions are provided for the lateral earth pressure coefficients due to the surcharge and cohesion. The results of this study have a good agreement with other reported results. The effects of the geometry of the retaining wall, the soil and soil-wall interface parameters are evaluated. Non-dimensional graphs are presented for the active lateral earth pressure coefficients.

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.

The relationship between temperature and earth pressure acting on a rigidly framed earth-retaining structure (RFERS) subject to wide temperature variation was explored. A distressed RFERS open concrete garage that retains 11 m (36 ft) of soil was instrumented. After some repairs, movement of the building was monitored and recorded hourly for a period of four and a half years. The monitoring revealed complex temperature-dependent soil–structure interactions. The measured displacements were used to calculate the earth pressure coefficient using closed form equations that were developed by treating the structure as an equivalent cantilever beam, and calibrating the expression using a total of 42,000 FEM models. The data indicated that the coefficient of earth pressure behind the monitored RFERS had a strong linear correlation with temperature. During the cold season the building contracted, and the retained soil followed. During the hot season, the building was unable to overcome the earth pressure, thus it expanded away from the soil, resulting in a cumulative annual displacement. The coefficient of lateral earth pressure changed by approximately 0.005/°C, varying in the range of 1.25–1.5, depending on the season. The study also reveals that thermal cycles, rather than lateral earth pressure, caused some of the structural elements to fail.

Traditional earth pressure theories are based on the assumption of semi-infinite space. The existence of intermediate principal stress and soil arching effects is ignored, which will cause significant errors in the application of finite width soil. This study introduced the intermediate principal stress based on the twin-shear unified strength theory; the stress deflection caused by soil arching and the uniform surcharge on the retained soil surface were also considered. An improved calculation method for cohesive soil’s lateral earth pressure coefficient, an analytical solution for active earth pressure of finite width soil, the resultant force, and its action point were proposed. The lateral earth pressure distribution of finite width cohesive soil was studied by calculation examples. In addition, relevant parameters were also analyzed. The results indicate that due to the influence of the intermediate principal stress and soil arching effects, the resultant active earth pressure is lower than the traditional method. The lateral earth pressure coefficient gradually increases with the depth, but it is always lower than the traditional one. As the soil width increases, the resultant force action point presents a nonlinear trend that first decreases, then rises, and stabilizes. The proposed method was compared with the previous studies and got better results; it can provide a new idea for estimating the active earth pressure of finite width soil.

In past decade, the application of lightweight composite materials has received great attention in geotechnical engineering discipline. This paper evaluates the effect of expanded polystyrene (EPS) beads on the compressibility and lateral earth pressure of completely rounded particulates presented by virtual steel pellets. EPS beads were added to steel pellets at 0%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight. A series of tall oedometer tests have been carried out to investigate the compressibility and “at rest” lateral earth pressure. Tests were conducted under five different overburden pressure (100 kPa, 150 kPa, 200 kPa, 250 kPa and 300 kPa). As well, a series of passive earth pressure tests have been conducted using a physical modelling of retaining wall in laboratory scale. The test results revealed that for a given overburden pressure, the volume compressibility and “at rest” lateral earth pressure coefficient increase as the EPS content increases. However, the internal friction angle and passive lateral earth pressure coefficient exhibited reduction by an increase of the EPS beads content.

Tire derived aggregates have recently been in wide use both in industry and engineering applications depending on the size and the application sought. Five different contents of tire derived aggregates (TDA) were mixed with sand thoroughly to ensure homogeneity. A series of large scale oedometer experiments were conducted to investigate the compressibility properties of the mixtures. Tire shreds content, TDA aspect ratio, skeletal relative density and overburden pressure are studied parameters. Constrained deformation modulus and coefficient of earth pressure at rest are measured parameters. All tests were conducted at seven overburden pressure levels. It was concluded that deformability of TDA-sand mixture increases with soft inclusion. Overburden pressure and skeletal relative density are also important parameters which render more rigidity and less lateral earth pressure coefficient accordingly. TDA size or aspect ratio was shown to have minor effect at least for the constrained strain conditions encountered in current study. An EPR-based parametric study and also sensitivity analyses based on cosine amplitude method revealed quantitative evaluation of the relative importance of each input parameter in varying deformation and lateral earth pressure coefficient as the outputs.

Accurate measurement of lateral earth pressure coefficient, k , is a key step in any geotechnical investigation. Since conventional approaches for obtaining this value leads to high risk of uncertainty in the results, this paper introduces a new experimental approach for measuring the value of k , particularly in unsaturated soils. Details of the new instrument designed for this purpose is provided in the manuscript, which is capable of obtaining k value of unsaturated soils in a range of matrix suction or degree of saturation. Finally, some test results are presented that examine the accuracy of the novel apparatus in order to measure the coefficient of lateral earth pressure in unsaturated soils.