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This study introduces a novel geotechnical composite material comprising two types of fill material sourced from the paper industry—deinking paper sludge ash (DPSA) and deinking paper sludge (DPS). Five composites with different DPSA and DPS contents were investigated. Two composites were selected for further analyses. The technology and procedure for composite installation were implemented in field tests. The composites with 80% and 70% DPSA exhibited the elasticity required to withstand minor landslide slip deformations, in addition to achieving sufficiently high values of uniaxial compressive strength. The composites had a low maximum dry density value, which led to fewer settlements in the entire support structure. The enhanced shear characteristics can enable the construction of a thinner retaining wall. The delay between preparation and installation of the composites was further investigated. The field tests confirmed that the composites with 80% and 70% DPSA can be installed on the construction site 4 h and even 24 h after mixing. In 2018, a retaining wall structure with 70% DPSA and 30% DPS was successfully implemented near a railway line using conventional technology as followed-up research to the herein presented study. Results have been derived from work performed in the scope of the H2020 Paperchain project in which novel circular economy models centered on the valorization of the waste streams generated by the pulp and paper industry as secondary raw material for several resource-intensive sectors, including the construction sector, have been developed. Environmental benefits are savings in natural raw materials, reduction of landfill disposal as well as CO2 emission reduction. [ABSTRACT FROM AUTHOR]

The current active earth pressure calculation theory cannot take into account the influence of the foundation inverse slope. For the translational mode retaining wall in this paper, taking cohesive backfill as the research object, the clay within the crack depth range is equivalent to uniform overload, using the upper limit theory, establishing the energy conservation equation of the velocity field and force, and the analytical formula of the tensile crack depth and the slip surface of the cohesive backfill being obtained. By taking into account the soil arching effect, setting up the static equilibrium equation by horizontal layer analysis, deriving the active earth pressure calculation expression of cohesive backfill, it is possible to consider the influence of the basement inverse slope. In the case of cohesionless backfill, the formula can be reduced to the theoretical solution. By comparing the calculated results with the experimental values and relevant theories, this can verify the applicability of the formula. The result of research shows that, with the increase of the basement inverse slope angle, the development of the tensile crack will be promoted, the dip angle of the slip surface changes little, and the resultant force and overturning moment will decrease, which is conducive to the antisliding stability and antioverturning stability of the wall, reducing the project cost. The active earth pressure distribution of cohesionless backfill is independent of whether there is an inverse slope in the basement. The theoretical formula obtained in this paper can be used as reference for the design of the retaining wall. [ABSTRACT FROM AUTHOR]

The problem considered in this paper is the passive earth pressure determination under various rigid wall geometry with negative wall-soil friction. An exact solution based on statically admissible stress fields is employed to evaluate the impact of negative wall-soil friction and inclined walls on the design of retaining walls. A series of conservative solutions for the passive earth pressure coefficient in the presence of negative wall friction is obtained, shedding light on the load transfer mechanism of cohesionless backfill materials. While focusing on the passive earth pressure coefficient, the study further identifies the stress state transition zone in the backfill and the influence of wall inclination on passive earth pressure. In addition, the load transfer mechanism of cohesionless backfill material in a retaining wall is affected by various factors, including wall geometry, degree of negative wall friction, the direction of the major principal stress at the wall, and the position and orientation of the transition zone and line of stress discontinuity. It follows that comprehensive design charts involving various rigid wall geometry and negative wall-soil friction are provided for engineering practice. Overall, the study successfully characterizes the admissible stress field in the backfill of rigid retaining walls, contributing to the knowledge of retaining wall design under the effect of negative wall friction. [ABSTRACT FROM AUTHOR]

This paper focuses on the design as well as on the experimental and numerical validations of the mechanical behavior of a precast ultra-high performance fibre reinforced concrete (UHPFRC) retaining walls. The design, made in accordance with the Canadian Highway Bridge Design Code (CSA S6, 2019), led to the fabrication of a full-scale UHPFRC retaining wall with 3% fibre content which had dimensions of 3 m in height, 2 m in length, 2 m in width, with two vertical and horizontal stiffeners, and very thin vertical and horizontal panels of 40 and 65 mm, respectively. The experimental tests showed that the UHPFRC retaining wall exceeded by 42% the ultimate limit state (ULS) design factored bending moment and showed a very ductile behavior under flexural loading. At service limit state (SLS), the retaining wall had maximum crack opening between 0.15 and 0.28 mm, and a maximum lateral displacement of 4 mm. The finite-element model developed for the application captured accurately the flexural behavior of the UHPFRC retaining wall and was used later in parametric studies to optimize the design. The retaining wall optimal design includes UHPFRC with 3% fibre content and stiffeners with variable cross-section which allows volume reductions of 73% for concrete and 86% for rebars in comparison to the conventional reinforced concrete design. [ABSTRACT FROM AUTHOR]

Worldwide, an increasingly huge number of end-of-life tires (ELTs) are disposed of in landfills, illegally dumped, or otherwise unaccounted for, which causes significant environmental and socioeconomic issues. Finding sustainable engineering solutions to recycle and reuse ELTs, which transform them from unwanted waste into useful resources, has become a priority. In geotechnical engineering, researchers have performed laboratory and field tests to determine the mechanical properties of innovative geomaterials that consist of soil–rubber mixtures (SRMs) [i.e., gravel–rubber mixtures (GRMs)] that are obtained using recycled ELT-derived granulated rubber aggregates. Suitable engineering properties and low installation cost encourage the use of GRMs and SRMs in many applications, such as in free-draining energy-adsorption backfill material for retaining walls, underground layers for liquefaction mitigation and geotechnical seismic isolation systems for structures and infrastructures. However, due to the heterogeneity of SRMs, their ultimate adoption as geomaterials must be supported by constitutive relationships that can accurately describe their mechanical behavior under typical field loading conditions. The aim of the paper is to evaluate the effectiveness and limits of the hardening soil model with small strain stiffness (HS-small), which is present in many finite-element (FE) codes, to model the behavior of GRMs in geotechnical engineering applications. An extensive finite-element method simulation of drained triaxial tests was performed. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized framework to estimate the seismic active earth thrust on rigid retaining walls with unsaturated backfill. A novel suction stress-dependent approach was developed to compute the horizontal and vertical seismic acceleration profiles within the backfill. The framework applies the limit equilibrium method with a log-spiral failure surface and considers the influence of suction-stress through the effective stress approach. A detailed validation of the proposed framework is conducted by comparing it with well-established solutions reported in previous studies showing a satisfactory agreement. Validation was performed for the cases of static loading with suction and seismic loading without suction because of the unavailability of the data for the combined case. The influence of suction on the seismic active earth thrust for different soil types and environmental conditions is presented together with other parameters including wall height, soil friction angle, frequency of input excitation, and horizontal and vertical seismic acceleration coefficients. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive review of soil nailing as a technique for strengthening slopes and retaining walls. It deliberates various methods and materials associated with soil nailing, while also examining the advantages and disadvantages of this approach. The review incorporates previous studies to demonstrate the extensive practical application of soil nailing. To study the influence of soil nail stiffness, both physical modelling and numerical techniques, such as Finite Element Method (FEM) and Finite Difference Method (FDM), are studied. The conclusions confirm that soil nailing is a reliable and very effective method for improving soil strength and minimising settlement. Also, the review highlights the significance of considering the bending stiffness of soil nails to optimise the effectiveness of this technique in ground improvement projects. As a result, this review paper serves as a valuable resource for engineers seeking guidance in soil nailing techniques. The primary objective of this paper is to explore fundamental concepts and state-of-the-art approaches in soil slope stability, with a particular focus on soil-nailed slopes and walls. [ABSTRACT FROM AUTHOR]

The study presents state-of-the-art requirements verification process for the prediction of the stability of the multi-staged deep excavation in submerged soft soil retained by stell sheet pile walls structures applied at the development of elasto-plastic finite element calculation method performed from Cast3M and Plaxis FE codes. Optimization numerical calculation results are proposed for retained walls design and construction on the basis of the horizontal displacement, earth and water pressures measurements. The transformation of the geometry and stiffness of the stell sheet pile walls to the retaining walls of an equivalent bending stiffness on the one hand and regular geometric shapes allowed in this paper to overcome the difficulties of modelling these stell sheet pile walls in 2D with irregular shapes. The horizontal deflection of the wall, the vertical displacement behind the walls, and the settlement of the excavation bottom are given. They have been compared by those obtained by various authors around the world. The results of this approach are satisfactory in view of the horizontal displacement curves obtained on the stell sheet pile walls compared by the measures. [ABSTRACT FROM AUTHOR]

Chiaia station is one of the art stations of Line 6 of the Naples underground network; it was constructed in a 50-m-deep excavation, a few meters from historic buildings and 4.5 m from the main façade of a sixteenth-century Basilica. The excavation, carried out partially in loose to medium dense sands overlying the soft rock formation of Neapolitan Yellow Tuff (NYT), was supported by a retaining wall made of contiguous bored piles braced with internal struts and prestressed ground anchors. The excavation sequence was quite complex due to archeological findings and to the presence of anthropic cavities used over the centuries to quarry NYT blocks. One of the key goals of the design was to limit movements around the shaft to prevent damage in the historical buildings. Long-term monitoring data obtained during nearly 9 years confirm the success of the overall construction process. A rather complex three-dimensional (3D) finite-element model with constitutive relationships for both the upper sandy layers and the soft rock is presented in the paper; this model was adopted to back-analyze the data from the monitoring and explore the influence of some of the key features of the case study. The role of the building bending and shear stiffness, of the soft rock stiffness, and of further apparently minor issues—such as the seepage and the ground anchors' prestress—were investigated and discussed with the support of the model calculations. Observed settlements at the end of the excavation were in the range 10–15 mm, and in the long term they increased by 20%–50% to as much as 20 mm. The deflection ratios were very small, in the range 0.05‰–0.15‰ , and no visible damages to the buildings were recorded. These values were reproduced by the finite-element model only after the introduction of the relevant building stiffness. [ABSTRACT FROM AUTHOR]

In this paper, the shear strain-dependent dynamic response properties of a retaining wall model made of mechanically stabilized earth (MSE) with polymeric geostrip material are investigated in a 1-g shaking table test. The values of lateral displacements and accelerations measured at different points along the MSE wall surface were used to evaluate the equivalent hysteris loops. The effect of reinforcement stiffness and backfill slope angle on the equivalent shear stiffness modulus (G e) and damping ratio (D) were investigated. The experimental results show that the variation of shear stiffness modulus and damping ratio as a function of shear strain (γ) is affected by vertical pressure (σ v), but the effect of the stiffness of the polymeric geostrip on the damping ratio is negligible. The variations of the G e , G e / σ v , G e / G max , and D as a function of γ are expressed in exponential equations with high least squares values in this study. • Shaking table tests on the physical model of polymeric geostrip reinforced MSE wall. • Analytical investigation of dynamic response parameters (D , G e) of polymeric geostrip reinforced wall. • The effect of slope angle of backfill soil and stiffness of geostrip on the shear stress-shear strain hystresis loops. • The effect of reinforced soil location on the dynamic parameters. [ABSTRACT FROM AUTHOR]

A reliable assessment of earthquake-induced permanent displacements is a fundamental step for both displacement-based and force-based methods applied to the seismic design of embedded anchored walls. Acceleration reduction factors recommended by the codes for a force-based design of these structures derive from parametric studies of the performance of gravity walls or slopes. This may lead to either conservative or unconservative results and is certainly misleading from the point of view of the physics of the problem. Based on the results of an extensive numerical study, this work clarifies the mechanisms by which anchored walls accumulate permanent displacements during earthquakes, showing that full mobilization of soil passive strength requires displacements of the order ur/H≈1%–2% , making the assumption of rigid-perfectly plastic behavior of the system unsuitable. Moreover, both the critical acceleration and the pattern of final displacements depend on the plastic mechanism effectively activated within the soil-wall-anchor system. The issue of the proper choice of performance factors to be used in a force-based design of anchored walls is also addressed, and a new method is outlined for a preliminary calculation of the permanent displacements of the wall. Finally, the paper critically reviews two methods recently proposed in the literature to compute earthquake-induced wall displacements. All three methods account for the soil-wall system nonlinearity and hardening during the earthquake. The results discussed herein, together with the complementary work presented by the same authors in a companion paper, provide a thorough conceptual framework for the performance-based seismic design of anchored walls. [ABSTRACT FROM AUTHOR]

The horizontal displacement values experienced by the isolation layer of base-isolated buildings can exceed the allowable range and cause failures during the rare or very-rare earthquakes. Excessive horizontal displacements of the isolation layer may cause collisions between the building and retaining walls of the isolation ditch and even cause the collapse of the isolated building. This paper proposes a cost-effective, easy-to-build, passive bumper device, called Flexible Limit Protective Device (FLPD) in order to act as shock-absorbers. Through numerical simulations and experiments, the nonlinear behavior of the FLPD is investigated. Subsequently, through structural simulations, the effectiveness of using FLPDs is studied. The elitist non-dominated sorting genetic algorithm (NSGA-II) is used to optimize the design of FLPDs, and the response of structures equipped with optimized FLPDs are simulated numerically. The results indicate that proposed optimized FLPDs can effectively work as shock-absorbers for base-isolated structures. This paper can provide a guideline for the design of shock-absorbers. [ABSTRACT FROM AUTHOR]

Geotechnical engineers are faced with great uncertainty with regard to the stability design of soil structures such as retaining walls, foundations, and slope stability. Instead of using a deterministic approach by replacing the design parameter with a single mean number, Monte Carlo simulations could be used to provide better decisions by considering all possible outcomes under parametric uncertainty. This paper studies probabilistic failures of classical passive trapdoors in shallow depths with spatially random soils. The effects of soil strength variability are investigated for various spatial correlation lengths and trapdoor depths using the latest adaptive finite-element upper-bound limit analysis with second-order cone programming. In addition, probabilistic stability results are compared with those published in renowned literature, and a comprehensive probability of design failure (PF) charts is developed for a practical range of deterministic factors of safety. The extensive results reported in this paper would be of great interest to engineering practitioners because better decisions can be made in the design process and design confidence improved. [ABSTRACT FROM AUTHOR]

A two-stage cantilever retaining wall is composed of two single-stage cantilever retaining walls, which are stacked up and down. The structure not only has the advantages of a single-stage retaining wall, but also compensates for the shortcomings of the height limit of the single-stage retaining wall; therefore, it has been gradually applied in projects. Based on the actual project of Zhongwei-Lanzhou Passenger Dedicated Line into Lanzhou Hub, this paper studies the influence of the construction of new cantilever retaining wall and the filling of subgrade on the deformation and earth pressure of the new cantilever wall and the existing cantilever wall by means of field test and numerical simulation. The results show that with an increase in the filling height after the new cantilever wall (upper wall), the horizontal displacement of the top of the upper and lower walls increased nonlinearly. The displacement direction of the upper wall was the filling direction, and that of the lower wall was the deviation from the filling direction. The higher the filling height, the greater is the displacement. With an increase in the filling height, the earth pressure behind the upper wall increases gradually along the wall height and decreases slightly to the bottom of the wall, which is approximately a linear distribution. The earth pressure behind the existing cantilever wall first increases along the wall height and gradually decreases after reaching a certain depth, but the earth pressure of the lower wall does not increase significantly with an increase in the filling height behind the upper wall. The slope failure mode is the overall sliding failure of the retaining wall together with the fill soil. The sliding surface passed through the lower edge of the lower wall heel and was similar to an arc shape. The stability of the two-stage cantilever retaining wall was better than that of a single-stage retaining wall. Finally, a calculation method for the overall stability and earth pressure of the existing two-stage cantilever retaining wall was proposed. [ABSTRACT FROM AUTHOR]

This paper investigates the sliding surface failure characteristics, earth pressure distribution law and stability safety factor of inverted T-type retaining wall by using the finite element limit analysis software OptumG2, the effects of width of wall heel plate, width of wall toe plate, thickness of bottom plate, soil–wall interface friction angle, soil cohesion and soil internal friction angle of filling on the failure characteristics of sliding surface, the earth pressure distribution law and stability safety factor of retaining walls are analyzed, The stability safety factor of the retaining wall showed a gradually increasing trend as the width of wall heel plate and wall toe plate increased; as the bottom plate thickness increases, the stability safety factor of the retaining wall gradually increases; as the soil-wall interface element reduction coefficient rises, that is, the internal friction angle of the soil-wall gradually increases to the soil internal friction angle, the stability safety factor of the retaining wall gradually increases; as the soil cohesion and internal friction angle increase, the stability safety factor of the retaining wall progressively increases. The safety factor of retaining wall increases by 0.45 for every 0.5m increase in the width of the wall heel plate; the safety factor of the retaining wall increases by 0.29 when the width of the wall toe plate increases by 0.5m; for every 0.5m increase in the width of wall plate thickness, the safety factor of the retaining wall is increased by 0.62; for every 0.25 increase in soil-wall interface element reduction coefficient, the safety factor of the retaining wall increases by 0.29; for every increase of 5KPa in soil cohesion, the safety factor of the retaining wall increased by 1.16; for every 5° increases in soil internal friction angle, the safety factor of retaining wall increases by 0.6. The research is significant for studying the failure laws and stability of retaining walls and providing references for retaining wall design. [ABSTRACT FROM AUTHOR]

A retaining wall is generally provided to protect the unsupported soil mass. For designing the retaining walls, pseudostatic methods are well established for the computation of soil thrust and coefficients of earth pressure in seismic conditions. In the present paper, the coefficients of active earth pressure due to soil wedge and strip load present on the cohesionless backfill of the retaining wall are determined by considering the pseudostatic method for seismic conditions and using the kinematic limit approach. The proposed solution considers the presence of soil–wall friction angle, as well as the size and distance of the strip load. Closed-form solutions are provided to calculate the coefficients of active earth pressure. It can be observed that for the strip load of magnitude 30 kPa and width 1.65 m situated close to the retaining wall, the coefficient of earth pressure due to soil wedge decreases by 10.05% compared with the absence of the strip load. The proposed method has been compared with the investigations available in the literature. The influence of the magnitude of the strip load and its distance from the wall is thoroughly investigated and presented with different parameters. [ABSTRACT FROM AUTHOR]

Design guidelines for geosynthetic-reinforced soil (GRS) walls in a tiered configuration are often limited to two tiers with zero batter. To facilitate rational expansion of current design, this paper extends the current top-down procedure, based on limit equilibrium analysis, from single GRS walls to multitiered walls. For a given factor of safety, the required reinforcement tension distribution and connection load are determined for each reinforcement layer. The approach considers the impact of potential compound failures. Parametric studies are conducted to investigate the influences of backfill soil, wall geometry (i.e., wall batter, number of tiers, and offset distance), and reinforcement layout. The results demonstrate quantitively that increasing the internal friction angle of backfill soil, wall batter, number of tiers, and offset distance reduce the required maximum tension. The tiered configuration in GRS walls leads to localized increase in connection load at the toe elevation of each tier. Using close reinforcement spacing could significantly reduce the connection load. The critical offset distance is realized when the reinforcement in each tier acts internally independent of others. Its value decreases with increasing the internal friction angle of backfill soil, wall batter, and number of tiers. The observations in this study are significant in the context of optimal design of multitiered GRS walls. [ABSTRACT FROM AUTHOR]

Free-standing retaining walls are usually designed for earthquake loads assuming cohesionless backfill soil and using the Mononobe-Okabe method. This simple design approach has led to satisfactory performance and is supported by laboratory testing and analytical studies. For major wall structures there are a number of refinements to the method that should be considered. In the paper methods of assessing the influence on the earthquake loads of the flexibility of the wall, soil cohesion and ground water in the backfill are presented. Equations for predicting failure plane angles to allow a better assessment of the soil properties within the failure wedge are included. Procedures for estimating the outward displacement and the influence of passive resistance and wall geometry on the sliding resistance are discussed. Design charts are presented which allow the magnitude of these refinements to be rapidly assessed. [ABSTRACT FROM AUTHOR]

This paper introduces the Goodman contact element based on the virtual element method framework. Since the virtual element method can calculate polygonal elements with any number of nodes, the limitation of mesh matching of the contact part required by the Goodman contact element is overcome by adding nodes to the contact element. Combine the virtual element method with the Goodman contact element to enable the Goodman contact element to solve practical problems in geotechnical engineering. In this paper, first, we derive the elastoplastic virtual element equations, and then, the Goodman contact stiffness matrix based on the virtual element method is calculated. Finally, several numerical examples are shown. In numerical models, the sensitivity of the virtual element method to mesh distortion is studied. We also investigate the shape sensitivity of the algorithm and the convergence of the Voronoi element through several frictionless contact examples. And then, the contact examples under friction state and elastic–plastic constitutive law are carried out. Finally, the contact force between soil and wall under the non-matching mesh in the gravity retaining wall commonly used in geotechnical engineering is presented. [ABSTRACT FROM AUTHOR]

An accurate estimation of earth pressure on retaining walls is imperative to achieving its design. This paper presents an analytical method framework that considers the effect of plant transpiration relative to the traditional calculation approaches. Specifically, a closed-form solution for one-dimensional steady unsaturated flow considering plant transpiration is incorporated into a representation of effective stress to obtain the changes in matric suction, and effective stress. The representations are used to extend Hooke's law and Rankine's earth pressure theory to determine at-rest, active, and passive earth pressures. Subsequently, the analytical method is used in a series of analysis case studies on the influence of root architecture types, transpiration rates, and soil types on earth pressure, to reveal that it can rapidly obtain the earth pressure. Notably, the effect of plant transpiration on earth pressure is significant. Furthermore, it is found that soil types and transpiration rates have a larger influence than root architecture types. Collectively, the research not only reveals the effect of plant on earth pressure for retaining wall, but also provides a theoretical basis for further exploration of the contribution of plants to the stability of retaining wall. [ABSTRACT FROM AUTHOR]

Retaining walls are a part of the geotechnical construction industry for the support of structures from soil erosion. Granular materials are conventionally used as backfill behind retaining walls. Instead of the conventional compacted granular fill, other industrial by-products are also used nowadays. The utilisation of these industrial by-products for Civil engineering applications helps to build a sustainable environment by reducing the waste depositions. In this paper, an experimental study was conducted to evaluate the properties of coal ash-based Controlled Low Strength Materials (CLSM) for backfill applications. The properties of pond ash-based CLSM mixes were studied to identify the effectiveness in utilising CLSM for backfill applications. Further, numerical analysis using PLAXIS 2D was carried out to evaluate the stresses and displacements developed in retaining walls for different backfilling materials. It was observed that CLSM mixes exhibit the properties required for utilising it as a backfill material. The stresses and deformations developed in situations where CLSM was used were found to be negligible compared to the normal compacted backfill materials. Thus, the studies on CLSM mixes showed that pond ash can be used as a replacement to natural aggregates which can be used as a backfill for retaining wall applications. [ABSTRACT FROM AUTHOR]

Soil arching that is generated and develops within the ground behind the retaining wall in a multistrutted excavation is a soil stress transfer process related to the relative movement between the well-retained soil mass and the inward-moved soil mass. The lateral earth pressure behind the wall is redistributed induced by this soil arching, which has not been deeply investigated. In this paper, the wall deflection, lateral soil movement, ground surface settlement, strut forces, total lateral earth pressure, and the water level outside the excavation were monitored in a multistrutted excavation in soft soil. The measured results indicated that the lateral earth pressure redistribution was associated with the arching effect. A lateral earth pressure model considering the soil arching effect is proposed, and was verified using measurements obtained from this study and the literature. It was found that the coefficients of the proposed model are linearly related to the ratio of the soil volume loss to the gain (RLG), which can be used to characterize the soil arching process development. This study improves the understanding of the lateral earth pressure redistribution induced by soil arching, and the proposed model can be used to calculate more-realistic lateral earth pressure. [ABSTRACT FROM AUTHOR]

An accurate estimation of earth pressure on retaining walls is imperative to achieving its design. This paper presents an analytical method framework that considers the effect of plant transpiration relative to the traditional calculation approaches. Specifically, a closed-form solution for one-dimensional steady unsaturated flow considering plant transpiration is incorporated into a representation of effective stress to obtain the changes in matric suction, and effective stress. The representations are used to extend Hooke's law and Rankine's earth pressure theory to determine at-rest, active, and passive earth pressures. Subsequently, the analytical method is used in a series of analysis case studies on the influence of root architecture types, transpiration rates, and soil types on earth pressure, to reveal that it can rapidly obtain the earth pressure. Notably, the effect of plant transpiration on earth pressure is significant. Furthermore, it is found that soil types and transpiration rates have a larger influence than root architecture types. Collectively, the research not only reveals the effect of plant on earth pressure for retaining wall, but also provides a theoretical basis for further exploration of the contribution of plants to the stability of retaining wall. [ABSTRACT FROM AUTHOR]

Ground movements induced by deep excavations may cause damages on neighboring existing buildings. Finite element simulations generally give acceptable estimates of the horizontal displacements of the retaining wall, but results are less satisfactory for the vertical displacements of the ground surface behind the structure. A possible explanation is that most constitutive models describe volumetric strains in a simplified way. This paper proposes an elastoplastic constitutive model aimed at improving the prediction of vertical displacements behind retaining walls. The model comprises a single plastic mechanism with isotropic strain hardening, but has a specific flow rule that allows to generate contractive plastic strains. Identification of the parameters based on triaxial tests is explained and illustrated by an example of calibration. A numerical analysis of a well-documented sheet pile wall in sand in Hochstetten (Germany) is presented. The results given by the model are compared with the measurements and with those obtained using the Hardening Soil Model. The potential advantages of the proposed model are then discussed. [ABSTRACT FROM AUTHOR]

Deep excavations in soft clays often demand heavy shoring supports. Closely spaced struts are known to impede construction within an excavation, resulting in longer construction time. This paper presents a novel strut-free retaining wall constructed by deep cement mixing (DCM). A new U-shaped DCM system (UDCM) was developed to support a 6.5-m-deep, 16-m-wide excavation in newly reclaimed land. Field measurements involving inclinometers and surface movement markers were interpreted using a fully coupled three-dimensional finite-element model. Results indicated a rotational deformation mechanism in the DCM wall. The mechanism was triggered by stress relief and basal heave. Due to the rigidity of the UDCM, the occurrence of basal heave caused the DCM walls to deflect outward toward the retained side. Such a mechanism is not typical in conventional retaining wall systems in which lateral props are installed after certain depths of excavation. The present UDCM possesses a distinctive characteristic, which is the capability to implement and activate props prior to excavation. It also is unique in that basal heave is used to regulate the rotation of the wall, thereby limiting lateral displacements during an excavation. This study includes a design chart developed for the prediction of lateral displacements with varying treatment geometries. [ABSTRACT FROM AUTHOR]

Design approach against failure of the earth support using the finite element method The application of the finite element method (FEM) in geotechnical engineering has been established in the last decades for the prediction of deformations in the serviceability limit state (SLS). In practice, stability analyses in the ultimate limit state (ULS) are only partially performed using the FEM and are currently still state of the art. The next generation of Eurocode 7 is intended to regulate numerical methods with regard to their application in the ULS. However, the handling of the additionally required analysis of the German National Annex and DIN 1054 is still unsolved. In this paper, an approach for the numerical analysis of the earth support is presented. Following the well‐established strength reduction method, the weight of the soil γ and the cohesion c' ${{c}^{{ {\prime}}}}$ on the earth resistance side are reduced until failure occurs. On the basis of this, the analysis in ULS is carried out by defining a safety factor for the existing embedment depth of the retaining wall. This is followed by a comparison with the analytical free earth support method, identifying system reserves using the FEM. [ABSTRACT FROM AUTHOR]

This paper reports numerical modeling of the prototype geosynthetic reinforced soil (GRS) walls corresponding to four centrifuge models that have different toe restraint conditions. The development of the interface stresses and displacements at wall toe during wall construction is investigated to understand how the toe carries load in the GRS walls with a practical toe structure. The numerical results show good agreement with the data from the centrifuge modeling. For the GRS walls with a leveling pad embedded in foundation soil, the shear resistance at the facing block-leveling pad interface acts as the toe resistance to counterbalance a portion of horizontal earth load, while the leveling pad-foundation soil interface play no role in wall performance because the soil passive resistance in front of the leveling pad inhibits the development of the shear stress and displacement on this interface. For the GRS walls with an exposed leveling pad, it is the leveling pad-foundation soil interface that works for carrying the earth load because the wall is more likely to slide along this weaker interface. The contribution of the toe to load capacity depends on the shear strength of the effective toe interface that contributes to the resistance against the earth load. • Paper reports numerical modeling of four prototype GRS walls corresponding to the centrifuge models at a specific centrifugal acceleration. • The effect of toe restraint conditions on the development of interface stresses and displacements at wall toe during wall construction was investigated. • How the toe carries load in the GRS walls with a practical toe structure was analyzed. [ABSTRACT FROM AUTHOR]

Back analysis is the most common method to study landslide movements after the event, and it allows us to understand how a landslide evolved along the slope. This paper presents the back-analysis of the Pomarico landslide (Basilicata, Italy) that occurred on January 25th, 2019, on the southwestern slope of the Pomarico hill. The landslide, of rotational clayey retrogressive type—planar sliding, evolved in different phases until it caused a paroxysmal movement in the early afternoon on January 29th, 2019. The landslide caused the collapse of a bulkhead (built at the end of the twentieth century) and of some buildings along the village's main road. In this paper, a multi-layer back-analysis study is presented, based on the limit equilibrium model (LEM), applying the solution proposed by Morgenstern and Price in Geotechnique 15(1):79–93zh, (1965) and implemented in the freeware software SSAP 2010. The analysis allowed the reconstruction of the entire landslide evolution, using geotechnical parameters obtained from both laboratory and in situ tests, and data from the literature. The application of multilayer back-analysis made it possible to avoid the homogenisation of the layers, modelling the event according to the real conditions present on the slope. The use of the SSAP software made it possible to curb the problem related to the theoretical limitation of the shape of the rupture surfaces, by evaluating independently the friction angle locally and by discarding all those surfaces, which, due to this problem, presented a non-reliable factor of safety (FS) value. The modelling revealed a slope that is highly unstable as the height of the water table changes. The FS calculated under water table conditions close to ground level was less than 1 (FS = 0.98), simulating the first landslide movement (November 2018). The subsequent model reconstructed the critical surface responsible for the January 2019 movement and calculated the FS present on the slope (FS = 1.01). Eventually, the paroxysmal event on January 29th, 2019, was modelled, returning an FS of 0.83, and a sliding surface that sets below the bulkhead, causing its failure. Furthermore, the modelling of the slope in the presence of adequate retaining structures demonstrated the (non-) effectiveness of the retaining wall system represented by the bulkhead. The proposed method of analysis suggests further applications in similar complex multi-layer soil-structure interaction scenarios. [ABSTRACT FROM AUTHOR]

Geosynthetics have been commonly used for the construction of civil engineering structures such as retaining wall, road and railways, coastal protection, soft ground improvement work, and landfill systems since the 1960s. In the past 40 years, the development of polymer materials has helped to prolong the life of geosynthetics. In terms of the practical use of geosynthetics, engineers must understand their appropriate application. The first part of this paper provides a basic description of geosynthetics, including their types, components, and functions. The second part deals with the geosynthetics used as filters. This part briefly presents the mechanism of filtration, the factors affecting the durability of geotextile filters, design concepts, laboratory tests, and case studies. The third part of the study covers the use of geosynthetics for stabilisation. Its mechanism was explained separately for geogrids and for geocells. Several examples of applications with geosynthetics intended for the stabilisation function are described in the last part of this paper. [ABSTRACT FROM AUTHOR]

The foundation pit of a suspension bridge project in the Three Gorges Reservoir area is investigated in this paper. The pit is located under an unstable rock mass and landslide body; its base lithology is mudstone. The bridge foundation pit project mainly adopts blasting excavation to accelerate construction progress. However, as a hazardous technique to engineering safety, the explosion vibration easily causes deterioration of the surrounding strata, thereby inducing slope instability and rock mass collapse. Besides, three major challenges should be considered: complex terrain conditions, difficulties in the blasting excavation of anchors, and the extremely high risk of construction. Therefore, comprehensive risk control measures using the methods of hierarchical excavation and minimum charge blasting are put forward. After the measures were verified to be feasible through finite element simulation, it was successfully applied to actual construction. In addition, this paper proposes using fiber concrete to reinforce slope retaining walls, and simulates the reinforced effect based on the research above. The results indicate that the risk control scheme is reasonable, which not only ensures the construction process but also guarantees the stability of the slope and unstable rock body. At the same time, the slope is reinforced with fiber concrete, which effectively decreases the protection wall thickness. Finally, the article can provide a valuable reference for similar engineering projects around the world. [ABSTRACT FROM AUTHOR]

This work is mainly intended to investigate the flysch landslide reinforcement measures used in the Smokovac-Mateševo section of the North-South Expressway project in Montenegro. Bentley's Plaxis software is used for a numerical analysis of sliding surface parameters of flysch strata in the limit equilibrium state. This study analyzes the slope safety factor for rreinforcement measures such as rock bolts, retaining walls, anti-sliding piles, slope unloading and bolt anchoring and obtains an optimal combination of reinforcement application for the flysch landslide. The effects of seismic action on complex stress and the discontinuous stress boundary conditions arising from various reinforcement measures on landslide stability are also examined. The measures applied in this paper can be used as a reference for flysch landslide reinforcement or other similar slope engineering measures. [ABSTRACT FROM AUTHOR]

We investigate the behavior of subaqueous barchans reaching dune‐size obstacles by carrying out experiments where we varied the obstacle shape and size, the flow strength, and the grains' properties. We found that a subaqueous barchan can pass over or bypass a dune‐size obstacle, or even be blocked, with some intermediate situations. In the bypass cases, the original barchan can split in two or more bedforms, redistributing sand in space. Finally, we propose a classification map in which the barchan behavior depends basically on two dimensionless parameters. Our results represent a step toward understanding how barchans behave in the presence of large obstacles, such as retaining walls, tubes and bridge pillars. Plain Language Summary: This paper is devoted to crescent‐shaped dunes, known as barchans, that are found on Earth, Mars and other celestial bodies, with roughly the same morphology but different scales. In some cases, barchans can approach an obstacle of comparable size, such as houses and buildings in the aeolian case, and bridge pillars and submarine structures in the aquatic case. In order to investigate that, we carried out experiments in a water channel where granular heaps developed into barchans that approached obstacles of different shape and size. We found that barchans can be blocked, bypass or pass over dune‐size obstacles, and that bypassing barchans can split in two or more bedforms, which means a significant redistribution of sand in space. Based on the experiments, we propose a classification map in which the barchan behavior depends on two dimensionless parameters. Our results shed light on how barchans behave in the presence of large obstacles, helping us to predict the outcomes of dunes interacting with objects in other environments, and design safer and eco‐friendly structures. Key Points: We show that subaqueous barchans can be blocked, bypass, or pass over dune‐size obstaclesIn some cases, barchans can split in two or more bedformsWe propose that the barchan behavior depends basically on two dimensionless parameters [ABSTRACT FROM AUTHOR]

An approximate analytical method is developed in this paper to calculate at-rest lateral earth pressure on a retaining wall subject to Coulomb's Retaining Conditions with positive backslope and non-zero interface friction angle. The solutions were verified using a numerical approach. The procedure presents advantages over current practice using either the Danish Geotechnical Code method or the U. S. Army Corps of Engineers Strength Mobilization Factor method and may provide a lower bound for an empirical estimate of wall interface friction angle used in active earth pressure calculations based on the Coulomb theory for retaining walls. [ABSTRACT FROM AUTHOR]

For an excavation project, the existence of adjacent composite foundations influences the earth pressure on the retaining wall, which will have a significant implication for the design and construction of the excavation project. In this paper, a simplified method is proposed to assess the influence of an adjacent single pile composite foundation in the calculation of earth pressures on a retaining wall, in which the pile-soil interaction within the composite foundation is considered. Comparison was made between the proposed method and the existing methods where the pile-soil interaction is ignored, which shows that the existing methods can overestimate or underestimate the earth pressure to a large extent. For the excavation project considered in this research, when the pile-excavation distance exceeds seven times the pile diameter, the influence of the composite foundation can be reasonably ignored. [ABSTRACT FROM AUTHOR]

Hydraulic hysteresis and mechanical behavior [i.e., void ratio (e) dependency] are fundamental in unsaturated soil behaviors. Applications of the upper bound theorem to account for these aspects in unsaturated soil mechanics have never been reported in geotechnical problems, such as bearing capacity, to the best of the author's knowledge. Therefore, this paper presented modifications to and the development of a computational limit analysis method [discontinuity layout optimization (DLO)], which considered the influence of hydraulic hysteresis, mechanical behavior, and changes in soil fabric on strength. The modified approach unsaturated DLO (UNSAT-DLO) was utilized to carry out a parametric study for a bearing capacity problem, where the numerical results were compared with 1g physical modeling tests that were conducted for a surface strip footing that was placed on sandy soil. The comparison demonstrated that the UNSAT-DLO approach could capture the nonlinearity of the experimental results within a small range of suction (s) profiles. In addition, the bearing capacity scatter-induced hydraulic hysteresis, mechanical behavior, and soil fabric changes, even at approximately the same applied s, were reasonably well defined by the UNSAT-DLO approach, because the parameters were carefully assigned. In addition, differences in the failure mechanisms due to the hysteresis were investigated to provide insights into distinct changes in the failure modes due to the hydraulic hysteresis and mechanical behaviors. The conventional design of shallow foundations was based on dry or saturated states, according to the saturation conditions, which led to a conservative design. Due to the drying and wetting cycles, soils are frequently found in unsaturated conditions. The additional strength that was imparted to soils, which was attributed to the effect of partial saturation, led to more stable geotechnical structures. The literature confirmed that suction (s) had a significant effect, and a ≤10-fold increase in bearing capacity was obtained when unsaturated cases were compared with the fully saturated conditions. Further evidence of this was the stability of vertical cuts (trenches), embankments, retaining walls, and railways. With a better understanding of the mechanics of unsaturated soils, the design of the geotechnical structures could impart additional strength due to partial saturation. The utilized (UNSAT-DLO) approach, which accounted for the effect of s and saturation, exhibited good agreement with the experimental data. In addition, it considered hydraulic and mechanical hysteresis. Therefore, the approach was a robust tool that could help with safe structures and more economical designs. [ABSTRACT FROM AUTHOR]

The present paper describes and provides an analytical solution to the problem of the stress state of a limited-thickness soil basis resting on an incompressible soil base, under the action of two distributed loads of different intensities near the retaining wall of an excavation pit. It is proposed that the method for identifying components of the stress statement within the framework of the engineering problem in question is improved, and the solution is based on the trigonometric Ribiere–Fileon series. The results obtained by the authors allow for an evaluation of the supplementary effect on a retaining wall produced by loads from heavy machinery and materials stored near this retaining wall. These findings are useful for the design of underground constructions of buildings and structures. Theoretical results are provided together with those of numerical experiments to validate the research reliability. [ABSTRACT FROM AUTHOR]

The motivation of this study stems from a retaining wall made of waste tires. The wall did not suffer any earthquake or tsunami-induced damage during the 2011 Off the Pacific Coast of Tohoku Earthquake, Japan. This paper deals with a case study on this tire retaining wall. Results from a series of field and laboratory investigations are first described. A numerical simulation is also described in which whole tires were used as protective layers in an embankment. The results show that confining effect of each tire, friction between the tires, ductility, and damping inherent in tires contribute towards the excellent performance of the retaining wall during the earthquake loading. The case study also reveals that it is the isolation mechanism due to the vibration absorption capability of rubber particles in tires, which could protect tire retaining structure during the earthquake. [ABSTRACT FROM AUTHOR]

This paper develops predictive models for optimal dimensions that minimize the construction cost associated with reinforced concrete retaining walls. Random Forest, Extreme Gradient Boosting (XGBoost), Categorical Gradient Boosting (CatBoost), and Light Gradient Boosting Machine (LightGBM) algorithms were applied to obtain the predictive models. Predictive models were trained using a comprehensive dataset, which was generated using the Harmony Search (HS) algorithm. Each data sample in this database consists of a unique combination of the soil density, friction angle, ultimate bearing pressure, surcharge, the unit cost of concrete, and six different dimensions that describe an optimal retaining wall geometry. The influence of these design features on the optimal dimensioning and their interdependence are explained and visualized using the SHapley Additive exPlanations (SHAP) algorithm. The prediction accuracy of the used ensemble learning methods is evaluated with different metrics of accuracy such as the coefficient of determination, root mean square error, and mean absolute error. Comparing predicted and actual optimal dimensions on a test set showed that an R 2 score of 0.99 could be achieved. In terms of computational speed, the LightGBM algorithm was found to be the fastest, with an average execution speed of 6.17 s for the training and testing of the model. On the other hand, the highest accuracy could be achieved by the CatBoost algorithm. The availability of open-source machine learning algorithms and high-quality datasets makes it possible for designers to supplement traditional design procedures with newly developed machine learning techniques. The novel methodology proposed in this paper aims at producing larger datasets, thereby increasing the applicability and accuracy of machine learning algorithms in relation to optimal dimensioning of structures. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present a landslide's remediation conducted on the basis of research and testing of samples, and list those measures that will help to remediate the landslide or partially mitigate its further effects. These measures include: closing cracks, collecting and draining surface water from landslides, terrain planning, making supports from stone materials, drainage trenches, draining water from traffic areas, repairing water supply and sewerage systems, and establishing monitoring. The paper analyzes the phenomenon of instability and its causes, and presents the results of research at site in question before and after the remediation of instability. The geological profile and remediation methods will be determined after the presentation of the results. [ABSTRACT FROM AUTHOR]

Excessive cracking due to restraint of thermal and shrinkage strains is a widespread problem in the concrete construction industry. In design, restraint induced cracking is managed by the provision of reinforcement intended to distribute internal strains in such a way as to control the cracking pattern and limit crack widths. The area of secondary (horizontal) reinforcement required in members such as retaining walls and water tanks is often governed by the need to control early age thermal cracking. This paper presents results from four edge restrained walls tested at Imperial College London and the University of Leeds as part of an Engineering and Physical Sciences Research Council funded project into restraint induced cracking. The paper describes the development of volumetric strain and cracking in the tested walls. The cracking performance is assessed by comparing the restrained strain with the tensile strain capacity of concrete. [ABSTRACT FROM AUTHOR]

Collapse hazards occur frequently in mountainous areas. Geosynthetics-reinforced soil (GRS) wall, combing the damping characteristics of soil and the tensile properties of reinforcement materials, can effectively resist rockfall impact through its flexible deformation. However, excessive deformation is easy to occur near the impact point of reinforced soil retaining wall subjected to impact loading, resulting in instantaneous instability and long repair time as well as high repair cost of the structure. Therefore, the prestressed GRS wall with buffer layer was proposed in this paper. Four retaining walls with different types and the impactor consist of pendulum device and solid steel ball was designed to study the impact resistance and dynamic stability of the retaining wall. The results show that the cumulative deformation of the wall panel experiences acceleration phase, deceleration phase and stable stage subjected to the impact loading. The application of buffer layer and prestress member can effectively improve the impact resistance and dynamic stability of retaining wall, and further control the deformation of retaining wall under the impact loading, in comparison with ordinary reinforced retaining wall. The peak impact stress of the retaining wall and the responsive strain of the reinforcement increase gradually as the distance between the measure point and the impact point decreases. The research results can provide reference for the design and the application of prestressed GRS wall under the impact of rockfall. [ABSTRACT FROM AUTHOR]

An uneconomical design of embedded cantilever retaining (ECR) walls unnecessarily restricts the lateral wall movement, whereas unwarranted wall displacement induced ground settlement can jeopardize the functionality of neighboring structures. Thus, correct estimation of the wall displacement under working conditions is imperative for a safe and economical design. This paper presents an analytical method for the displacement-controlled analysis of ECR walls in cohesionless soils, which can be used to calculate the required embedment depth for a prescribed wall displacement and retaining heights. Alternatively, when the retaining height and the embedment depth of an ECR wall are given, the lateral wall displacement can also be calculated. A displacement-dependent earth pressure mobilization model is proposed to derive the mobilized soil stresses along the wall height. The required embedment depth of the wall is determined by assuming rigid rotation of the wall about a point near the toe and satisfying the horizontal force and moment equilibriums. Analytical formulations are provided to determine the bending moment distribution and the ground settlement. The effect of construction by excavation is also taken into the analysis. The results show that the required embedment depth and the maximum bending moment increase exponentially with decreasing wall displacement. The depth of the pivot point is located at around 0.9 times the embedment depth. The validity of the proposed method is demonstrated by comparing the calculated results with those of the available numerical and experimental studies. The proposed method can provide first-hand design solutions of ECR walls without performing rigorous numerical and experimental studies. [ABSTRACT FROM AUTHOR]

This paper investigates the active earth pressure of inverted T-type retaining walls under rotational mode using a slip-line method for the typical failure mechanism simulated with adaptive finite element software. Considering the influence of the heel bottom plate, the slip-line field calculation models for the inverted T-type retaining wall with long and short heels were established, respectively. The limit equilibrium method and the finite difference method were used to solve the stress state of each point. The earth pressure acting on the stem and the imaginary wall can be obtained by converting the boundary conditions. The proposed method was verified by comparison with results from the finite element method and some existing theoretical solutions. In addition, several extensive parametric studies have been conducted to investigate the effects of heel length and interface strength. The results show that increasing the heel length and interface strength is beneficial for maintaining backfill integrity and reducing earth pressure against the stem and imaginary wall. [ABSTRACT FROM AUTHOR]

Practicing geoengineers and researchers generally consider the load sharing behavior in multi-type pile composite foundation as an important design aspect. On the other hand, due to urbanization, such foundation system in cities will inevitably appear next to supported excavation. This paper discusses the result from relatively largescale indoor experiment conducted to investigate the load sharing behavior of loaded long-short CFG pile composite foundation behind a neighboring rigid retaining wall undergoing rotation around the bottom. It was found that with progression of wall movement, the hidden load from soil displacement was borne by the piles with marked reduction in soil load sharing. At the end of wall rotation, the percentage of long piles’ head load increment needed to arrive at a new static equilibrium was about 12.57~32.22% while the end bearing increased by more than 97%. The consequences on the short piles, however, were manifested with an increasing pile head (13.42%) and toe (28.9%) load for the pile far from the wall whereas the closest one experienced a certain increment up to 15×10-4rad wall rotation and finally the head load and end bearing decreased to 8.28% and 12.63%, respectively. The 3D numerical back analysis conducted using FE software ABAQUS yielded the pile – soil stress ratio lower than the value obtained from the experiment but provided great insight into pile settlement characteristics during wall rotation. [ABSTRACT FROM AUTHOR]

This paper proposes a prediction model based on the mobilizable strength design method with an equilibrium model to predict the deflection of an embedded cantilever retaining wall in sand. The variation in the location of the pivot point within the retaining wall and the sand dilation are considered. Based on the stress–strain relationships obtained by triaxial tests, the designer can determine a specific shear strain and corresponding mobilized earth pressure for the retaining wall to achieve a global equilibrium. Then, the wall deflection, including rotation and flexure, can be derived. The locations of the pivot points obtained by this method are compared with the results predicted by the minimization approach. Finally, the prediction precision is validated via centrifuge tests and numerical model data published in prior investigations. [ABSTRACT FROM AUTHOR]

Owing to the complexity of the sheet pile wall with a relieving platform, there are a large number of factors that affect the mechanical and deformation characteristics of the wall structure. Moreover, studying the influencing factors on the deformation of the retaining wall is beneficial in the selection of design parameters and deformation control. 28 groups of test models of the retaining wall structure are designed to analyze the effect on the deformation of rib pillars and determine the reasonable width and buried depth of the unloading board in this paper. The tests are conducted with and without the unloading board, and different widths and buried depths of the unloading board are also considered. The findings show that, without the external load, the reasonable board width and buried depth are 0.70 times and 0.53 times the wall height. With the external load, the reasonable board width is 0.35 times the wall height, and the large board width cannot effectively reduce the deformation of rib pillars, and the reasonable board width is 0.60 times the wall height. When both the external load and board width are relatively small, the reasonable buried depth is 0.53 times the wall height. However, when the external load is large, the reasonable buried depth is 0.70 times the wall height. The results also show that the setting of the unloading board effectively suppresses the deformation of rib pillars and controls the maximum deformation within an allowable range of the specification. [ABSTRACT FROM AUTHOR]