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Jointed rock specimens with a natural replicated joint surface oriented at a mean dip angle of 60° were prepared, and a series of cyclic triaxial tests was performed at different confining pressures and cyclic deviatoric stress amplitudes. The samples were subjected to 10,000 loading-unloading cycles with a frequency of 8 Hz. At each level of confining pressure, the applied cyclic deviatoric stress amplitude was increased incrementally until excessive deformation of the jointed rock specimen was observed. Analysis of the test results indicated that there existed a critical cyclic deviatoric stress amplitude (i.e. critical dynamic deviatoric stress) beyond which the jointed rock specimens yielded. The measured critical dynamic deviatoric stress was less than the corresponding static deviatoric stress. At cyclic deviatoric stress amplitudes less than the critical dynamic deviatoric stress, minor cumulative residual axial strains were observed, resulting in hysteretic damping. However, for cyclic deviatoric stresses beyond the critical dynamic deviatoric stress, the plastic strains increased promptly, and the resilient moduli degraded rapidly during the initial loading cycles. Cyclic triaxial test results showed that at higher confining pressures, the ultimate residual axial strain attained by the jointed rock specimen decreased, the steady-state dissipated energy density and steady-state damping ratio per load cycle decreased, while steady-state resilient moduli increased.

Intelligent Compaction (IC) has been acquiring a growing interest in real-time quality control of compacted soil layers because of its high efficiency and full-area coverage. The current intelligent compaction technology allows the determination of the uniformity level of compaction over large areas according to the dynamic response of the roller. However, accurate real-time determination of the soil modulus during compaction based on roller acceleration has been challenging due to the multi-layered composite nature of the soil and the nonlinearities of the governing dynamic equations of motion and soil response. This study adopts a double-layered soil profile, and a three-dimensional finite element model, accounting for soil-drum interaction, is utilised for the analysis. The isotropic hardening elastoplastic hysteretic model was implemented to simulate the soil behaviour subjected to cyclic loading ranging from small to large strain amplitudes and account for stiffness degradation. The comprehensive dataset composed of the roller acceleration response and ground characteristics is then used to correlate the predicted soil modulus via an advanced machine learning approach. The adopted machine learning method incorporating Gaussian Kernel and Generalised Gegenbauer Kernel functions can reasonably predict the double-layered soil modulus during roller compaction. Additional analyses were conducted to observe the proper training size and number of iterations to achieve real-time quality control to be used by site engineers. Furthermore, the influences of the relative modulus ratio, drum length and top layer modulus on the soil surface dynamic displacement are discussed.

While design methods of deep foundations are mainly developed for homogenous soil deposits, the presence of highly cemented layers could lead to underestimation of resistance and overestimation of settlement of pile foundations. This study presents a novel approach using competent caliche layers bonded to the top and bottom of a continuous flight auger (CFA) pile as a new composite foundation system named caliche stiffened pile (CSP). The key objective is to optimize the required pile length in a cost-effective approach without ameliorating soil properties. Settlements of the CSP foundation for a high- rise building were monitored and full-scale tests were conducted to measure piles’ capacity. Finite element back analyses were performed to avoid adverse effect of sample disturbance in settlement calculations. A back calculation of a test fill embankment was performed to determine soil stiffness parameters by simulating an unscheduled imposed load to the structure. Impacts of the CSP on controlling the settlement of pile foundation and optimizing the required pile length are investigated using finite element analysis and a parametric study. The proposed CSP foundation can reduce the CFA pile settlement significantly in the presence of caliche layers with thickness equal or greater than a pile diameter at CFA pile head and toe, where the CSP is located.

This study aims to evaluate the usability of a recycled alkaline solution, a residue from cleaning iron plates in the car manufacturing industry, to enhance the strength and stiffness of clayey soil by carrying out unconfined compressive strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity (UPV) and microstructural (SEM, XRD) tests. High- and low- calcium fly ashes with percentages of 10% to 40% and 10% to 30%, respectively, were independently introduced into the alkaline activation process to determine the proper type and content of precursors at room temperature. Two mixtures of the residual cleaning solution blended with 2 M and 4 M NaOH solutions at a weight ratio of one were also utilized to determine how efficiently binary solutions could improve the performance of the parent clay soil. These experiments revealed that all mixtures of the residual alkaline solution work better to activate high-calcium fly ash as compared to the low-calcium fly ash in terms of both mechanical strength and stiffness. The sample of high-calcium fly ash with fly ash/solid and Na/ash ratios equal to 30% and 0.037, respectively, experienced the highest improvement. A microstructural analysis showed the formation of C-(A)-S-H and N–(C)–A–S–H gels in the corresponding sample, thus providing a considerably dense structure, which in turn significantly contributed to the enhancement of the maximum strength and stiffness of the treated soil. In fact, the high-calcium precursor proved to be the best candidate for a low-range alkaline activator because it contributes more calcium to a low-alkaline environment. An environmental impact assessment was also carried out to compare the CO2 emissions of clays treated with the 4 M NaOH binary solutions tested in this study with those conventionally stabilized by cement and lime and also those treated traditionally with commercial 2, 4, and 8 M NaOH. The samples in this study treated with environmentally friendly binary solution

The rocking pile foundation system is a relatively new design concept that can be implemented in bridges to improve their seismic performance. This type of foundation prevents plastic damage at the bridge piers and the foundation system, which are difficult to repair and can lead to collapse. However, lack of adequate energy dissipation in this type of foundation can result in large deck displacements and subsequent catastrophic failures of the bridge. The present study proposes a novel foundation system that integrates post-tensioned piles with the rocking foundation to simultaneously prevent plastic hinging at the piers and reduce the deck displacements during severe earthquakes. The effectiveness of the proposed foundation system is investigated and compared against the rocking pile and conventional fixed-base foundation systems using identical bridge configurations. Three-dimensional finite element models of these bridges were developed to capture possible nonlinear behavior of the bridge as well as soil-structure interaction effects. Six strong earthquakes with both horizontal components were selected and scaled to the appropriate seismic hazard level with a return period of 2475 years. Static pushover and nonlinear time-history analyses were then performed to compare the dynamic response of the bridges, including deck displacements, pier and pile inertial forces, and other nonlinear behavior experienced by the structure. The results reveal that by integrating the post-tensioned piles with the rocking foundation, the deck displacements were reduced to an acceptable limit without subjecting the bridge to any damage. In contrast, the bridge with the fixed base foundation experienced extensive damage at the piers, and the bridge with the rocking foundation experienced substantial deck displacements that ultimately led to unseating, resulting in the collapse of both bridges. It was therefore concluded that the proposed rocking foundation system with post-tensioned

The present study provides an insight into the effect of recycled carpet fibre on the mechanical response of clean sand as backfill material subjected to monotonic loading and cyclic loading as well as post-liquefaction resistance of both unreinforced and carpet fibre reinforced soils. To achieve these goals, a series of multi-stage soil element tests under cyclic loading event resulting in liquefaction followed by undrained monotonic shearing without excess pore water pressure dissipation as well as a series of monotonic undrained shear test is conducted. All the specimens are isotropically consolidated under a constant effective confining stress of 100 kPa by considering the effect of cyclic stress ratio and carpet fibre content ranging from 0.25% to 0.75%. The obtained results revealed the efficiency of carpet fibre inclusion in increasing the secant shear modulus and ductility of clean sand under monotonic shearing without previous loading history. The impact of carpet fibre inclusion on the trend of cyclic excess pore water pressure generation and cyclic stiffness degradation was minimal. However, adding carpet fibre significantly improved both liquefaction and post-liquefaction resistances of clean sand. The liquefaction resistance of clean sand, at a constant 15 loading cycles, improved by 26.3% when the soil was reinforced with 0.75% recycled carpet fibre. In addition, the initial shear modulus of the liquefied specimen significantly increased by adding recycled carpet fibre.

This paper presents an analytical solution for free strain consolidation of a stone column-stabilised soft soil under instantly applied loading and two-dimensional plane strain conditions. Both horizontal and vertical flows of water were integrated into the mathematical model of the problem, while the total vertical stresses induced by the external load were assumed to distribute uniformly within each column and soil region. By utilising the separation of variables method, an exact series solution was obtained to predict the variation of excess pore water pressure and settlement with time for any point in the model. The achieved solution can capture the drain resistance effect due to the inclusion of permeability and size of the stone column in the mathematical model. A worked example investigating the dissipation of excess pore water pressure was conducted to exhibit the capabilities of the obtained analytical solution. The correctness of the solution was verified against a finite element modelling with good agreements. Besides, a parametric study to inspect the influence of consolidation parameters of soil on performance objectives (e.g. average degree of consolidation and average differential settlement) was also reported in this study. The results from the parametric analysis show that an increase in permeability of soil sped up considerably the consolidation and differential settlement. Furthermore, an increase in soil stiffness accelerated the consolidation and reduced the average differential settlement between stone column and soft soil significantly. Eventually, the proposed analytical solution is also feasible to predict the consolidation of soft soil with the inclusion of prefabricated vertical drains or pervious columns by adopting appropriate consolidation parameters and stress concentration ratio.

Soil is a cross anisotropic particulate medium with different strengths in various directions; this is primarily due to its geological deposition process and the very fact that particles always settle in their most stable positions. This study examines the influence of inherent anisotropy on the ultimate bearing capacity of eccentrically and obliquely loaded strip footings that rest on cohesionless granular soils using a two-dimensional plane strain finite element simulation in conjunction with the lower bound limit analysis method and second-order cone programming (SOCP). The inherent anisotropy, manifested in the so-called parameter of anisotropy ratio, is simulated by considering variable internal friction angles along different directions. The nonlinear form of the universal Mohr-Coulomb failure criterion is also used to optimize the lower bound formulation. The failure envelopes of shallow foundations that correspond to inclined and eccentric loadings are depicted and discussed for various anisotropy ratios of the underlying soil deposit. It is observed that the failure locus generally decreases in size as the anisotropy ratio increases. Based on the results of numerical simulations, a general equation that describes the general bearing capacity of shallow foundations resting on inherently anisotropic cohesionless granular medium subjected to combined vertical-horizontal-moment loadings is presented and discussed.

Liquefied Natural Gas (LNG) tanks seismic design is critically important considering the high consequences of failure given the hazardous nature of the stored product. The LNG tanks aspect ratio (H/D), as decided at the design stage based on several considerations, can impact its dynamic characteristic and in turn the seismic performance of the tank under the design earthquakes. In this paper, the seismic vulnerability of the inner steel LNG tanks with varying height (H) to diameter (D) aspect ratios is investigated. Dynamic fluid–structure interaction is captured using the added-mass method and tank walls are modelled using general-purpose finite element software ABAQUS considering the material and geometric nonlinearities. Adopting time-history analysis, deformation and stresses developed in the tank subjected to two large near-field earthquakes namely 1994 Northridge and 1995 Kobe earthquakes are assessed. The results demonstrate that the tank aspect ratio (H/D) plays an important role in the modes of failure, where increasing the aspect ratio (tall tanks) initiates the elephant’s foot buckling mode of failure. The selection of optimum aspect ratio can lead to a safe and economic seismic design.

Scrap tyres are used to produce tyre-derived aggregates (TDA), which can be used as fill material, backfill material, drainage layers, and vibration-damping material, among other uses. This study presents a comprehensive review of TDA applications in civil engineering with a specific focus on railway projects. A review of the existing literature reveals the lack of sufficient knowledge on the use of TDA in slab tracks. This article also analyses the adequacy of different constitutive models to properly simulate the performance of TDA while highlighting the importance of adopting the most suitable constitutive model. The variations in shear stresses and displacements with depth below ballasted and slab tracks in the presence and absence of TDA are discussed. It is shown that TDA effectively reduces the shear stresses for the subgrade layer of both track types. Moreover, the impact of TDA on stress transfer in the vertical and lateral track directions is assessed. The findings from the present analysis reveal that TDA helps in reducing the vertical and lateral stresses near its placement position in ballasted and slab tracks.

An emerging real-time ground compaction and quality control, known as intelligent compaction (IC), has been applied for efficiently optimising the full-area compaction. Although IC technology can provide real-time assessment of uniformity of the compacted area, accurate determination of the soil stiffness required for quality control and design remains challenging. In this paper, a novel and advanced numerical model simulating the interaction of vibratory drum and soil beneath is developed. The model is capable of evaluating the nonlinear behaviour of underlying soil subjected to dynamic loading by capturing the variations of damping with the cyclic shear strains and degradation of soil modulus. The interaction of the drum and the soil is simulated via the finite element method to develop a comprehensive dataset capturing the dynamic responses of the drum and the soil. Indeed, more than a thousand three-dimensional (3D) numerical models covering various soil characteristics, roller weights, vibration amplitudes and frequencies were adopted. The developed dataset is then used to train the inverse solver using an innovative machine learning approach, i.e. the extended support vector regression, to simulate the stiffness of the compacted soil by adopting drum acceleration records. Furthermore, the impacts of the amplitude and frequency of the vibration on the level of underlying soil compaction are discussed. The proposed machine learning approach is promising for real-time extraction of actual soil stiffness during compaction. Results of the study can be employed by practising engineers to interpret roller drum acceleration data to estimate the level of compaction and ground stiffness during compaction.

Jointed rock specimens with planar, sawtooth and natural replicated joint types with a dip angle of 60° were prepared, and a series of cyclic triaxial tests were performed at different confining pressures and cyclic deviatoric stress amplitudes subjected to 10,000 loading cycles to evaluate their effect on dynamic properties of the jointed rock specimen. Analysis of the test results indicated that the level of confining pressure and cyclic deviatoric stress amplitude along with the type of the joint had a significant influence on the dynamic characteristics of the jointed rock samples. With increasing confining pressure, the maximum residual axial strain attained decreased, while they increased with cyclic deviatoric stress amplitude for all the joint types. Jointed rock specimens subjected to cyclic loading responded with higher resilient moduli at higher confining pressures, while increasing cyclic deviatoric stress amplitude resulted in reduced resilient moduli. Furthermore, a higher confining pressure corresponded to a lower dissipated energy and damping ratio, while a higher cyclic deviatoric stress amplitude corresponded to a higher dissipated energy and damping ratio. With increasing number of cycles, the residual axial strains attained by the samples showed an increasing trend, especially during the initial phase of deformation. The resilient moduli illustrated a decreasing trend with number of cycles whereas dissipated energy and damping ratio showed a prompt decreasing trend within the first few cycles and then stabilised for all the joint types. Empirical relationships for the steady state resilient moduli and steady state damping ratio were developed through nonlinear regression analysis which incorporated the influence of confining pressure, applied cyclic deviatoric stress amplitude, shear strength and joint friction angle.

Intelligent compaction (IC) is an emerging technology for efficient and optimized ground compaction. IC combines the roller-integrated measurements with the Global Positioning System (GPS), which performs the real-time quality control and assurance during the compaction work. Indeed, IC technology is proven to be capable of providing a detailed control system for compaction process with real-time feedback and adjustment on full-area of compaction. Although roller manufacturers offer typical recommended settings for rollers in various soils, there are still some areas needing further improvement, particularly on the selection of vibration frequency and amplitude of the roller in soils experiencing significant nonlinearity and plasticity during compaction. In this paper, the interaction between the road subgrade and the vibrating roller is simulated, using the three-dimensional finite element method capturing the dynamic responses of the soil and the roller. The developed numerical model is able to simulate the nonlinear behavior of soil subjected to dynamic loading, particularly variations of soil stiffness and damping with the cyclic shear strain induced by the applied load. In this study, the dynamic load of the roller is explicitly applied to the simulated cylindrical roller drum. Besides, the impact of the frequency and amplitude on the level of subgrade compaction is discussed based on the detailed numerical analysis. The adopted constitutive model allows to assess the progressive settlement of ground subjected to cyclic loading. The results based on the numerical modeling reveal that the roller vibration characteristics can impact the influence depth as well as the level of soil compaction and its variations with depth. The results of this study can be used as a potential guidance by practicing engineers and construction teams on selecting the best choice of roller vibration frequency and amplitude to achieve high-quality compaction.

Use of intelligent compaction (IC) is a growing technique for compaction in the field of construction. It provides an efficient way of evaluating the soil compaction level with a higher degree of certainty than traditional quality control methods. IC involves the interpretation of measured values received through the accelerometer and other sensors attached to the roller. The key objective of this paper is to analyse the dynamic roller–soil interaction via a three-dimensional nonlinear finite element model, capturing soil nonlinear response and damping in both small and large strain ranges as a result of dynamic load applied via the vibratory roller. In particular, the impact of soil plasticity index (PI) on the response of a typical vibratory roller is assessed. Indeed, the soil plasticity impacts stiffness degradation with shear strain influencing the soil stiffness during compaction and the roller response. The numerical predictions exhibit that the soil plasticity can significantly influence the response of the roller and the ground settlement level; hence, practising engineers can consider the soil plasticity index as an influencing factor to interpret the intelligent compaction results and optimize the compaction process.

Assessment of seismic resilience of critical infrastructure such as liquefied natural gas (LNG) storage tanks, is essential to ensure availability and security of services during and after occurrence of large earthquakes. In many projects, it is preferred to build energy storage facilities in coastal areas for the ease of sea transportation, where weak soils such as soft clay and loose sand with liquefaction potential may be present. In this study, three-dimensional finite element model is implemented to examine the seismic response of a 160,000 m3 full containment LNG tank supported by 289 reinforced concrete piles constructed on liquefiable soil overlaying the soft clay deposit. The seismic soil-structure interaction analysis was conducted through direct method in the time domain subjected to the 1999 Chi-Chi and the 1968 Hachinohe earthquakes, scaled to Safe Shutdown Earthquake hazard level for design of LNG tanks. The analyses considered different thicknesses of the liquified soil deposit varying from zero (no liquefaction) to 15 m measured from the ground surface. The key design parameters inspected for the LNG tank include the acceleration profile for both inner and outer tanks, the axial, hoop and shear forces as well as the von Mises stresses in the inner tank wall containing the LNG, in addition to the pile response in terms of lateral displacements, shear forces and bending moments. The results show that the seismic forces generated in the superstructure decreased with increasing the liquefied soil depth. In particular, the von Mises stresses in the inner steel tank exceeded the yield stress for non-liquefied soil deposit, and the elastic–plastic buckling was initiated in the upper section of the tank where plastic deformations were detected as a result of excessive von Mises stresses. However, when soil liquefaction occurred, although von Mises stresses in the inner tank shell remained below the yield limit, localised stress concentrations were observed i

Liquefied natural gas (LNG) is cleaner and cheaper for power generation than traditional energy sources. Many tanks that store LNG are located in coastal areas with less favorable geotechnical conditions and often in seismically active regions. The seismic loads acting on LNG tanks are highly affected by the soil-foundation-structure interaction (SFSI) and evaluating this effect is quite challenging as a result of the nonlinear response of the structure and foundation interacting with the soil. This paper presents the application of a three-dimensional (3D) numerical simulation technique to study the impacts of foundation type on the seismic behavior of a large LNG tank considering the SFSI effects. Fully nonlinear dynamic analysis under the influence of the 1994 Northridge and 1995 Kobe earthquakes are performed using finite-element analysis software ABAQUS version 2018 to assess the LNG tank seismic response under different foundation types, namely, end-bearing pile foundation and pile-raft foundation with two different frictional pile lengths. The results show the importance of the SFSI effect in evaluation of the seismic response of LNG tanks built on pile foundations. Indeed, choice of the deep foundation system and composition of the foundation in terms of raft effects and pile length can significantly change the dynamic response of an LNG tank and thus seismic forces in the foundation and superstructure.

This study presents a new mathematical equation for calculating the pile group efficiency in cohesionless soil under combined axial and lateral loading conditions, considering the tapering angle effect. Based on the mathematical definition of the pile group efficiency, analytical correlations are developed. The tapering effect is considered by developing a new geometry coefficient for efficiency associated with the shaft vertical bearing component of tapered piles. In addition, a simplified mathematical equation is developed for predicting the group interaction factor as a function of pile spacing, number of piles in the group, diameter of the cylindrical reference pile, tapering angle, and pile slenderness ratio. On the other hand, an array of three-dimensional numerical analyses is performed for modeling same-volume single bored piles and pile groups with various arrangements to capture the accuracy of the proposed mathematical equation. The hardening soil constitutive model is adopted for the modeling of piles in loose sand. Subsequently, the load-displacement diagrams of single piles, as well as pile groups, are obtained. The bearing capacities of straight-sided and tapered bored piles are then calculated and compared using a definite settlement criterion. By computing the various bearing-capacity components, group efficiencies can be attained from both numerical and mathematical analyses. The results indicate an acceptable agreement between both analyses. Finally, the developed equation can predict the pile group efficiency incorporating the tapering angle and other influencing parameters as a novel and simple relationship under simultaneous axial and lateral loading conditions.

Rocking foundations can be used in bridges to reduce the seismic demand of the structure and prevent inelastic behaviour from developing at the piers during large earthquake events. Several studies have proven that rocking is an effective seismic isolation technique under lateral earthquake loading. However, limited research has been conducted on the effect of the vertical component of earthquakes on the rocking behaviour of bridge piers. This paper aims to numerically investigate the effect of the vertical component of near-fault earthquakes on the seismic performance of bridges with rocking pile foundations. Two identical bridge configurations with different foundation systems (conventional fixed base foundation and rocking foundation) are subjected to two loading cases: (1) horizontal ground motions only, (2) combined horizontal and vertical ground motions. Three-dimensional models of the bridges are developed with the appropriate material models to capture possible inelastic behaviour, as well as to model the soil–structure interaction. Four near-fault ground motions with three components are selected and scaled to the appropriate seismic hazard and applied to the bridges using nonlinear dynamic time history analyses. The dynamic responses of the bridges are compared in terms of deck displacements, deck bending moments, and pier axial and bending moments. The results show that the vertical component of ground motions can considerably increase the dynamic response of the bridge with the rocking foundation when compared to the fixed base foundation, leading to increased deck displacements and inertial actions on the bridge structure.

This paper presents the interaction mechanism of a 12-story building sitting on a piled raft foundation with a strike-slip fault rupture. The mechanical response of foundation including both structural and geotechnical response of the foundation are evaluated through three-dimensional numerical modelling using ABAQUS. The obtained results showed that the raft significantly suffers from rotation about the vertical axpipelinis and horizontal displacement. Both bending moment and shear forces in piles due to fault rupture exceeded the capacity values of piles. The maximum bending moment and shear forces within piles took place at the connection of piles to the raft and exceeded allowable values when the fault slipped more than 0.3 m.

This paper presents the study in the machine learning aided stochastic slope stability analysis through the finite element method. The probability of failure of a dam with cohesive slope has been investigated. The numerical model has been built by the finite element method. An advanced machine learning algorithm called Extreme Learning Machine (ELM) is adopted to establish the regression model. The applicability and effectiveness of the presented approach are compared by the Monte-Carlo simulation method.

This paper proposes an analytical solution in terms of Green's function formulations for axisymmetric consolidation of a stone column improved soft soil deposit subjected to time-dependent loading under free strain condition. The mathematical derivations incorporate the pore water flows in radial and vertical directions in stone column and soft soil synchronously. The capabilities of the proposed analytical solution are evaluated via worked examples investigating the influences of three common time-dependent external surcharges (namely step, ramp and sinusoidal loadings) on consolidation response of the composite ground. The examples show that a faster increase of load from an initial surcharge to an expected loading might generate more significant excess pore water pressure to be dissipated during the early stages of consolidation, but the dissipation rate in soft soil would speed up significantly afterwards. The column and soil settlements along with the differential settlement between them also proceed faster corresponding to the acceleration of loading – unloading processes. Finally, the proposed analytical solution is employed to evaluate the excess pore water pressure dissipation rate at an investigation point in soft clay of a case history foundation. The calculation results exhibit a reasonable agreement with field measurement data when various constant values of stress concentration ratio are substituted into the solution to reflect the increase of stress concentration ratio with consolidation time in real practice.

In the present study, the interaction mechanism of a 10-story moment-resisting building frame sitting on the conventional piled raft foundation with a strike-slip fault rupture with a dip angle of 90̊ is studied via three-dimensional finite element numerical simulation using ABAQUS. In addition, an alternative composite foundation system with geosynthetics reinforced interposed layer between piles and raft is proposed to improve the safety and performance of foundation under strike-slip fault ruptures. The interposed layer is reinforced with two high tensile strength of the geotextile layer. The inelastic behaviour of piles under large ground deformations is simulated using moment-curvature relationships of the real reinforced concrete section of piles and ductility concepts. The performance of both composite and conventional piled raft foundations are evaluated in terms of the geotechnical and structural responses of foundations including rotational and translational displacements and shear forces of the raft, as well as shear forces and ductility capacity of piles. The obtained results show the superior performance of composite foundation with geotextile reinforced interposed layer in terms of a significant reduction in shear forces in the raft and piles, as well as ductility demand in the piles.

This study presents a new simple equation for prediction of pile group efficiency considering the effect of tapering angle in cohesionless soil under vertical loading. Firstly, a simple analytical relationship based on the mathematical definition of the pile group efficiency is developed. However, the effect of tapering angle is captured by defining a new geometry efficiency coefficient associated with the shaft vertical bearing component of tapered piles. Thereafter, a mathematical equation is developed by taking into account the shaft vertical bearing ratio and the new geometry efficiency coefficient. On the other hand, a numerical analysis is performed for modelling a single bored cylindrical pile and a tapered pile with the same volume as well as bored tapered pile groups to validate the proposed mathematical equation. The UBC sand constitutive model is adopted for the modelling of piles in loose Cambria sand. Subsequently, the load-displacement diagrams of single and group of piles are obtained. Then, the bearing capacities of cylindrical and tapered bored piles both as single and group are computed and compared, using a specific settlement criterion. Besides, the friction resistance ratio and the shaft vertical bearing ratio are separated, applying numerical methods. Having calculated the ratios of various components of bearing capacity, pile group efficiencies can be obtained from both numerical and mathematical models. The results show that the proposed equation can predict the pile group efficiency incorporating the tapering angle as well as other influencing parameters as a simple and novel relationship.

This paper provides an analytical solution to predict the free strain consolidation of a stone column supported soft soil under plane strain configuration. The external load on the ground surface was assumed to be applied instantly, which results in time-independent but space-dependent total stresses in the composite ground. A rigorous analytical solution to evaluate the changes of excess pore water pressure with time at any point in the model was derived as a double series, using the method of separation of variables. The obtained solution can capture any distribution patterns of total stresses caused by the external load, where the total stresses are described as separable functions against spatial coordinates. The validation of the proposed solution was exhibited through an example evaluating the effect of change patterns of the total stresses with depth on consolidation of the composite ground. The calculation results were presented graphically in terms of average degree of consolidation for column and for soft soil, and average differential settlement between the column and soil regions. The more diminution of the total stresses with depth led to accelerated consolidation of the composite ground and more significant reduction in the average differential settlement between the column and the soil.

In order to obtain a better understanding of the load transfer mechanism of open-ended tubular piles driven into weak rocks, numerical analysis is conducted to study the internal and external shaft frictions, base resistance and the stress distribution pattern in the surrounding rock mass. Meanwhile, since pile shoes are often applied when driving to the rock layer, a common inner pile shoe attached to the open-ended tubular pile was analysis and compared with the pile without a shoe. In this study, the discrete element method (DEM), which can mimic rock grains and the interaction between grains, is adopted due to its ability to simulate large deformation problems such as pile penetration process. The flat-joint model that allows partial damage at the contact interface was employed to replicate the discrete nature of the rock mass. The rock behaviour was calibrated against triaxial test results for a pyroclastic weak rock, and then the calibrated rock was employed for the simulation of pile penetration. A 30° segment of the true-scale model was simulated using the DEM with a height of 3 m and a radius of 1.5 m, which was composed of about 557,000 particles. Initial stresses were applied at the boundary of the testing chamber, while the side of the chamber was discretised into several sections with increasing horizontal stresses with depth to establish the at rest condition. Numerical results for penetration of an open-ended tubular pile show that the external shaft resistance of the pile with inner pile shoe increased approximately linearly as the pile penetrated deeper. In addition, the internal shaft friction was notably less than the external shaft friction for both piles with and without a shoe. Plugging was observed for both piles with and without a driving shoe. The inner pile shoe allowed the pile partial plugging to occur at shallower penetration depth. This study sheds a light on the load transfer mechanism of the open-ended tubular piles and the effect of

This paper presents the effect of burial depth on the response of conventional buried pipelines under strike-slip fault rupture and also proposes a mitigation method using geofoam blocks to safeguard buried pipelines. The performance of the buried pipelines is assessed using three-dimensional numerical simulation using ABAQUS. The configuration of geofoam blocks for protection consists of two blocks at each side of the pipeline and one block on the top of pipeline. The results shows that although the conventional buried pipeline failed due to fault rupture as a result of excessive compressive strain as well as local buckling within the pipe wall, geofoam blocks could successfully reduce the compressive and tensile strains along the pipeline satisfying the design requirements.

© 2019 American Society of Civil Engineers. For a foundation to perform safely, the ultimate strength of each pile must satisfy the structural and geotechnical requirements. Pile load testing is considered to be a direct method for determining the ultimate geotechnical capacity of piles. In this paper the dynamic and static response of a driven steel pipe pile monitored as part of a highway bridge construction project in New South Wales, Australia, has been simulated and then numerically analyzed using the finite-element method. A continuum numerical model has been established to simulate the dynamic load testing of steel pipe piles with unplugged behavior in which adopting measured soil properties resulted in a reasonable match between the measured and predicted results and without needing random signal matching in an iterative process. Settlement at the head and toe of the pile was then calculated when a static load represented by a dead load plus a heavy platform load of a bridge was applied over the pile head. During the dynamic and static load testing simulation, a hardening soil model with small strain stiffness was used to obtain the best correlation between the large and small strains, which occurred while the pile was under static load and being driven. The numerical predictions obtained using continuum finite-element simulations were then compared with the corresponding predictions obtained from the Case Western Reserve University (CASE) method and CASE Pile Wave Analysis Program (CAPWAP) to evaluate the predictions. The results show that the hardening soil model with small strain stiffness exhibits a reasonable correlation with the field measurements during static and dynamic loading. Moreover, parametric studies have been carried out in the established continuum numerical model to evaluate how the interface properties between the pile and soil and the reference shear strain define the backbone on the velocity at the head of the pile and traces of its dis

© 2020 Elsevier Ltd This study aims to investigate the influence of cementation on the stress-strain and strength characteristics of soil during cavity expansion in lightly cemented sand deposit using three-dimensional discrete element simulations. Contact models, simulating the cementation effects of bonded clumps and capturing the interlocking effects between discrete sand particles, are incorporated to mimic the cemented sands with various cement contents. The microscopic parameters are calibrated and validated against existing experimental results. Real scale cylindrical cavity expansion models starting from zero initial cavity radius with different levels of cementation are developed, and each proposed model consists of 150,000 particles with boundary conditions carefully selected to reproduce the realistic scenario. The embedded scripting is utilised to precisely measure both the local and global stress–strain variations, and record and analyse the cementation bond breakage during the cavity expansion process. The results confirm that the cementation enhances the material strength through the increase in cohesion and tensile strength at the contacting interfaces, whereas the friction angle is not altered notably. Hence, the failure envelope of the cemented sand gradually merges with the critical state line due to the cementation degradation, particularly at a high confining pressure. It was found that the failure mode of the lightly cemented sand adopted in this study, was mainly controlled by the shear rather than tensile strength at the contacting interfaces. Referring to the numerical predictions it is evident that the zone with significant cementation degradation due to the cavity expansion extends as far as 4af for all cemented specimens (af being the final cavity radius). In addition, specimens with higher cement content experience a more pronounced dilation at the internal cavity wall, while an inverse trend is captured at a greater radial distance. Fur

© 2020 Elsevier Ltd The construction of railway embankment on soft soil is a challenging task for practitioners. In the past, several approaches have been employed in practice to overcome this problem. Pile foundation is considered one of the reliable solutions for soft ground. In a pile-supported railway embankment, soil arching plays a vital role in the efficient load transfer to the piles. In this study, the soil arching phenomenon in a granular embankment subjected to train induced loading is demonstrated based on the two-dimensional (2D) finite element modeling approach. A 2D plane strain idealization is used to convert a real three-dimensional (3D) case into 2D. The effects of the piled railway embankment properties on soil arching are investigated. It is found that pile modulus, embankment modulus and friction angle affect the arching mechanism significantly. Pile spacing (s) variation affects soil arching (i.e., the arching zone can be increased by reducing s). In addition, the height and shape of arching are studied. A comparison with the available analytical design methods for embankments is presented which indicates inconsistencies in the previously published results.

© 2019 Elsevier Ltd This paper proposes using geofoam blocks to improve the safety of buried steel pipelines under permanent ground deformation due to strike-slip fault rupture. Since these geofoam blocks are deformable, they can compress during fault rupture and thus reduce the pressure imposed on the pipeline by the surrounding soil. This means that the pipe can sustain a higher level of tectonic deformations. For the pipeline system adopted in this study, the geofoam blocks consist of two 1 m thick blocks at each side and another on the top of the pipeline. The effectiveness of this configuration is then assessed in comparison to the conventional buried pipeline by three dimensional numerical simulations that consider the interaction between soil and structure and the impact of critical parameters such as the pipeline-fault trace crossing angle, geofoam blocks thickness and the internal pressure of the pipeline. The results indicated that the geofoam blocks reduced the axial tensile strain of non-pressurised pipeline from the unacceptable 4.16% to the safe level of 0.75% when the crossing angle was 135°. In addition, geofoam blocks successfully decreased the maximum ovalisation parameter and compressive strain of the non-pressurised pipeline from 0.237 and −25.8% to 0.065 and −0.47%, respectively when the crossing angle was 65°.