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Seismic design of water retaining structures relies heavily on the response of the retained water to shaking. The water dynamic response has been evaluated by means of analytical, numerical, and experimental approaches. In practice, it is common to use simplified code-based methods to evaluate the added demands imposed by water sloshing. Yet, such methods were developed with an inherent set of assumptions that might limit their application. Alternatively, numerical modeling methods offer a more accurate way of quantifying the water response and have been commonly validated using 1 g shake table experiments. In this study, a unique series of five centrifuge tests was conducted with the goal of investigating the hydrodynamic behavior of water by varying its height and length. Moreover, sine wave and earthquake motions were applied to examine the water response at different types and levels of excitation. Arbitrary Lagrangian-Eulerian finite element models were then developed to reproduce 1 g shake table experiments available in the literature in addition to the centrifuge tests conducted in this study. The results of the numerical simulations as well as the simplified and analytical methods were compared to the experimental measurements, in terms of free surface elevation and hydrodynamic pressures, to evaluate their applicability and limitations. The comparison showed that the numerical models were able to reasonably capture the water response of all configurations both under earthquake and sine wave motions. The analytical solutions performed well except for cases with resonance under harmonic motions. As for the simplified methods, they provided acceptable results for the peak responses under earthquake motions. However, under sine wave motions, where convective sloshing is significant, they underpredict the response. Also, beyond peak ground accelerations of 0.5 g., a mild nonlinear increase in peak dynamic pressures was measured which deviates from assumed linear response in the simplified methods. The study confirmed the reliability of numerical models in capturing water dynamic responses, demonstrating their broad applicability for use in complex problems of fluid-structure-soil interaction.

In this contribution observed median collapse frequencies and calculated median failure probabilities of retaining structures are compared. Such comparisons have already been carried out for bridges, dams, tunnels, buildings, stadiums and wind turbines. The comparison is carried out as a meta-analysis using values from the literature. Furthermore, collapse frequencies due to earthquakes were determined by the authors' own calculations. The comparison of median collapse frequencies and median failure probabilities of retaining structures shows a good agreement. The ratio of the median failure probability and the median collapse frequency is in the range of other engineering structures. However, the comparison with other engineering structures shows an above-average frequency of collapses. This seemingly accepted high frequency of collapse appears to be justified by the lower number of victims and lower damage costs when retaining structures fail. [ABSTRACT FROM AUTHOR]

In complex underground conditions, the excavation of deep foundation pits has a significant impact on the deformation of retaining structures and nearby subway stations. To investigate the influence of deep excavation on the deformation of adjacent structures, a three-dimensional numerical model of the foundation pit, existing subway station, and tunnel structure was established using FLAC 3D software, based on the Shenzhen Bay Super Headquarters C Tower foundation pit project. The study analyzed the deformation characteristics of retaining structures, adjacent subway stations, and tunnels during different stages of deep excavation, and the accuracy of the numerical simulation results was validated through field monitoring data. The results indicate that during the excavation process of the foundation pit, the lateral horizontal displacement of the retaining structure is generally small, with a typical "concave inward" lateral deformation curve; the horizontal displacement value of the contiguous wall section is less than that of the interlocking pile section. The bending moments of the retaining structure show a distribution pattern with larger values in the middle and smaller values at the top and bottom of the pit, with a relatively uniform distribution of internal support forces. The maximum displacement of the nearby subway station is 8.75 mm, and the maximum displacement of the subway tunnel is 2.29 mm. The research findings can provide references for evaluating the impact of newly built foundation pits near subway stations and contribute to the rational design and safe construction of new projects. [ABSTRACT FROM AUTHOR]

The performance of a retaining wall is dependent on multiple factors including lateral earth pressure, which results from backfill soils and adjacent footings located behind a retaining wall. The prediction of a retaining wall's performance in a footing–soil–wall system (FSPS) must incorporate the influences caused by the movement of a retaining wall. This study examines the performance of a retaining wall formed by driven, precast, concrete piles located adjacent to a concrete footing using two- and three-dimensional finite element analysis (2D and 3D FEA) by ANSYS 13.0 software. Both soil and concrete are assumed to behave as non-linear, elastic-perfectly plastic and rate-independent materials in compliance with the upper-bound model of Drucker–Prager yield criterion. Three backfill and foundation soils are considered: kaolin, silty clay, and kaolin–sand. Various conditions of soil type, footing shape ratio, pile width, and footing–pile distance through 180 FEA runs are investigated. The effects of 2D and 3D FEA on the behavior of the pile–wall system are compared. The lateral deflection and pressure distribution profiles along the pile–wall are studied and presented. Two empirical equations predicting lateral deflections at the pile toe and pile head and useful for pile structural design are developed under the ultimate pressure of the adjacent footing. [ABSTRACT FROM AUTHOR]

In excavation engineering, most of the retaining structures are subjected to asymmetrical loads, including in asymmetrical excavation and asymmetrical overloading. However, a theoretical solution to, and deformation-controlling method for, this problem has remained elusive to date. In this work, a semianalytical solution for determining the deformation of retaining structures subjected to asymmetrical loads was derived based on the principle of minimum potential energy. The retaining structures were viewed as flexible, and the overall deformation of the retaining system was evaluated by our proposed theoretical model. This model was verified by comparing it with practical monitoring data. Subsequently, the theoretical solution was applied to analyze the stress and deformation characteristics under the conditions of asymmetrical excavation and asymmetrical overloading, which can be controlled to ensure the safety of a project. Finally, because of the requirement for a small amount of deformation in the foundation pit retaining piles, the earth pressure on the retaining piles is close to the static earth pressure. Reducing the length of the retaining pile on one side had a greater influence on the deformation on that side, but less of an influence on the other side. Thus, the proposed model can be used for optimizing the asymmetrical design of a retaining structure in order to balance the economy and safety of a project. Our design theory can be applied to a variety of engineering projects. A typical case is the Guangzhou Baiyun District Comprehensive Transportation Hub Project in China. The method was used to analyze the status of the subway foundation pit, offering a new design scheme to reduce the design length of the retaining piles, which resulted in great economic benefits in its practical application. The findings provided in this paper can be applied to the engineering of any long, narrow foundation pit that can be simplified into a two-dimensional plane–strain calculation model, being used to realize more accurate deformation control over the foundation pit envelope. The core of this calculation method is that it can accurately describe the magnitude of the earth pressure. The distribution of the earth pressure is worthy of further study. [ABSTRACT FROM AUTHOR]

On October 30, 2020 14:51 (UTC), a moment magnitude (Mw) of 7.0 (USGS, EMSC) earthquake occurred in the Aegean Sea north of the island of Samos, Greece. Turkish and Hellenic geotechnical reconnaissance teams were deployed immediately after the event and their findings are documented herein. The predominantly observed failure mechanism was that of earthquake-induced liquefaction and its associated impacts. Such failures are presented and discussed together with a preliminary assessment of the performance of building foundations, slopes and deep excavations, retaining structures and quay walls. On the Anatolian side (Turkey), and with the exception of the Izmir-Bayrakli region where significant site effects were observed, no major geotechnical effects were observed in the form of foundation failures, surface manifestation of liquefaction and lateral soil spreading, rock falls/landslides, failures of deep excavations, retaining structures, quay walls, and subway tunnels. In Samos (Greece), evidence of liquefaction, lateral spreading and damage to quay walls in ports were observed on the northern side of the island. Despite the proximity to the fault (about 10 km), the amplitude and the duration of shaking, the associated liquefaction phenomena were not pervasive. It is further unclear whether the damage to quay walls was due to liquefaction of the underlying soil, or merely due to the inertia of those structures, in conjunction with the presence of soft (yet not necessarily liquefied) foundation soil. A number of rockfalls/landslides were observed but the relevant phenomena were not particularly severe. Similar to the Anatolian side, no failures of engineered retaining structures and major infrastructure such as dams, bridges, viaducts, tunnels were observed in the island of Samos which can be mostly attributed to the lack of such infrastructure.

In complex underground conditions, the excavation of deep foundation pits has a significant impact on the deformation of retaining structures and nearby subway stations. To investigate the influence of deep excavation on the deformation of adjacent structures, a three-dimensional numerical model of the foundation pit, existing subway station, and tunnel structure was established using FLAC 3D software, based on the Shenzhen Bay Super Headquarters C Tower foundation pit project. The study analyzed the deformation characteristics of retaining structures, adjacent subway stations, and tunnels during different stages of deep excavation, and the accuracy of the numerical simulation results was validated through field monitoring data. The results indicate that during the excavation process of the foundation pit, the lateral horizontal displacement of the retaining structure is generally small, with a typical “concave inward” lateral deformation curve; the horizontal displacement value of the contiguous wall section is less than that of the interlocking pile section. The bending moments of the retaining structure show a distribution pattern with larger values in the middle and smaller values at the top and bottom of the pit, with a relatively uniform distribution of internal support forces. The maximum displacement of the nearby subway station is 8.75 mm, and the maximum displacement of the subway tunnel is 2.29 mm. The research findings can provide references for evaluating the impact of newly built foundation pits near subway stations and contribute to the rational design and safe construction of new projects.

The interaction between groundwater and civil engineering works is a key aspect in geotechnical design. In the case of excavations confined in sheet pile walls, steel sheeting, diaphragm walls, cut-off walls, or cofferdams, this design requires the estimation, among other soil mechanics properties, of the groundwater flowing into the excavation (seepage) caused by piezometry depletion. Numerical methods, graphical solutions, and analytical procedures are the methodologies traditionally used to solve this issue, solutions of which require an understanding of basic soil mechanical properties, hydraulic conditions and structure geometry. In this work, the discriminated non-dimensionalization technique is applied to obtain, for the first time, the dimensionless groups that govern the seepage, in anisotropic conditions, in large-scale scenarios where groundwater flow is not conditioned by impervious bedrock or the length of the back of the wall: π1=ab,π2=kxb2kyc2 and, π3=T/b. Numerical simulations are carried out to check the validity of dimensionless groups and to develop three sets of type curves that relate to these groups. Once the physical and geometrical data are known, the seepage (Q), the characteristic depth (T*) and the characteristic horizontal extension (L*) can be directly and easily calculated from these abacuses. The influence of anisotropy on the characteristic lengths is also addressed.

The second generation of Eurocode 7 includes both soil and rock. In addition to the current practice of ground engineering, this document aims at incorporating rock engineering, improving the ease of use, the harmonization of regulations and covering new developments. This paper provides an overview of some of the significant changes to Eurocode 7 in rock engineering design, taking into consideration limit state design, robustness, durability, and reliability. It focuses on the design of slopes, spread foundations, and retaining structures. The clauses focus on soil mechanics, but also include special rock mechanical issues such as the influence of discontinuities and strength anisotropy on the limit states. Many matters associated to verification of rock mechanical design are linked to the use of prescriptive rules and shall be given in National Annexes. For geotechnical structures in rock, it is mentioned that geotechnical mapping and documentation is important to verify the limit states. However, the basic issues with partial factor methods for verification of the ground‐structure interaction of reinforced slopes and retaining structures are not fully resolved. This has caused some difficulties in setting up partial factors and obtaining a sufficient overview of the application of partial factor method, especially in rock engineering. The design of slopes, spread foundations and retaining structures must likewise consider other clauses in the Eurocode. Rock support for slopes and retaining structures is described in Clause 13 "Rock Bolts and Surface Support". Groundwater‐related issues are described in clause 12 "Ground water control" which influence the design and limit states for the actual geotechnical structure. Dams and levees are featured in Clause 4 "Slopes, Cuttings and Embankments". [ABSTRACT FROM AUTHOR]

The interaction between groundwater and civil engineering works is a key aspect in geotechnical design. In the case of excavations confined in sheet pile walls, steel sheeting, diaphragm walls, cut-off walls, or cofferdams, this design requires the estimation, among other soil mechanics properties, of the groundwater flowing into the excavation (seepage) caused by piezometry depletion. Numerical methods, graphical solutions, and analytical procedures are the methodologies traditionally used to solve this issue, solutions of which require an understanding of basic soil mechanical properties, hydraulic conditions and structure geometry. In this work, the discriminated non-dimensionalization technique is applied to obtain, for the first time, the dimensionless groups that govern the seepage, in anisotropic conditions, in large-scale scenarios where groundwater flow is not conditioned by impervious bedrock or the length of the back of the wall: π 1 = a b , π 2 = k x b 2 k y c 2   and, π 3 = T / b . Numerical simulations are carried out to check the validity of dimensionless groups and to develop three sets of type curves that relate to these groups. Once the physical and geometrical data are known, the seepage (Q), the characteristic depth (T*) and the characteristic horizontal extension (L*) can be directly and easily calculated from these abacuses. The influence of anisotropy on the characteristic lengths is also addressed. [ABSTRACT FROM AUTHOR]

The performance of a retaining wall is dependent on multiple factors including lateral earth pressure, which results from backfill soils and adjacent footings located behind a retaining wall. The prediction of a retaining wall’s performance in a footing–soil–wall system (FSPS) must incorporate the influences caused by the movement of a retaining wall. This study examines the performance of a retaining wall formed by driven, precast, concrete piles located adjacent to a concrete footing using two- and three-dimensional finite element analysis (2D and 3D FEA) by ANSYS 13.0 software. Both soil and concrete are assumed to behave as non-linear, elastic-perfectly plastic and rate-independent materials in compliance with the upper-bound model of Drucker–Prager yield criterion. Three backfill and foundation soils are considered: kaolin, silty clay, and kaolin–sand. Various conditions of soil type, footing shape ratio, pile width, and footing–pile distance through 180 FEA runs are investigated. The effects of 2D and 3D FEA on the behavior of the pile–wall system are compared. The lateral deflection and pressure distribution profiles along the pile–wall are studied and presented. Two empirical equations predicting lateral deflections at the pile toe and pile head and useful for pile structural design are developed under the ultimate pressure of the adjacent footing.

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

This paper introduces novel analysis procedures for the structural assessment of masonry earth retaining structures subjected to traffic loading. Given their substantial presence, particularly in transportation networks of historical cities, and the challenges posed by ageing, deterioration, and exposure to loads beyond their original design considerations, this research highlights the necessity of accounting for potential load redistribution mechanisms during their assessment. This can prevent overly conservative interventions that may not be necessary and also contravene sustainability and heritage preservation principles. Four distinct analysis procedures – 2D monotonic, 3D monotonic, 3D static moving load and 3D dynamic moving load – are developed, each progressively more refined than its predecessor in capturing potential load redistribution mechanisms in masonry earth retaining structures. These mechanisms may develop due to the dynamic loading conditions of the vehicular passage, the 3D structural configuration of retaining structures, and non-linear material behaviour. By comparing the structural capacity evaluated using the four procedures, contributions from different sources of load redistribution can be separately quantified, aiding in the reduction of conservatism inherent in less refined assessment procedures. The application of the developed procedures and consequent quantification of load redistribution is demonstrated through a case study of an existing masonry retaining structure in Amsterdam, the Netherlands. • Analysis procedures for masonry earth retaining structures under traffic loading. • 2D monotonic, 3D monotonic, 3D static and 3D dynamic moving load procedures. • Load redistribution is due to dynamic loading and 3D structural configuration. • Demonstrated application to a case study in Amsterdam, the Netherlands. [ABSTRACT FROM AUTHOR]

This paper presents a unified semi-analytical solution to investigate the passive earth resistance of unsaturated soils retained by a rigid wall in the framework of limit-equilibrium approach based on a rotational log-spiral failure mechanism. Coupled influences of unit weight and suction stress changes in unsaturated soils under different steady vertical flow conditions have been considered to provide a more realistic solution. The impact of different parameters such as effective internal friction angle soil, inclination of backfill surface and wall back face, surcharge pressure, height of wall, location of water table, and soil–wall interface friction has been explored by performing a parametric study. It has been found that the changes in the suction stress and unit weight of unsaturated soils under different input parameters have a greater effect on modifying the critical slip surface, and magnitude and point of application of passive earth resistance on the retaining walls. The results obtained from the present study compare reasonably well with the solutions in the literature. [ABSTRACT FROM AUTHOR]

Based on the salp swarm algorithm (SSA), this paper proposes an efficient metaheuristic algorithm for solving global optimization problems and optimizing two commonly encountered geotechnical engineering structures: reinforced concrete cantilever retaining walls and shallow spread foundations. Two new equations for the leader- and followers-position-updating procedures were introduced in the proposed adaptive salp swarm optimization (ASSA). This change improved the algorithm's exploration capabilities while preventing it from converging prematurely. Benchmark test functions were used to confirm the proposed algorithm's performance, and the results were compared to the SSA and other effective optimization algorithms. A Wilcoxon's rank sum test was performed to evaluate the pairwise statistical performances of the algorithms, and it indicated the significant superiority of the ASSA. The new algorithm can also be used to optimize low-cost retaining walls and foundations. In the analysis and design procedures, both geotechnical and structural limit states were used. Two case studies of retaining walls and spread foundations were solved using the proposed methodology. According to the simulation results, ASSA outperforms alternative models and demonstrates the ability to produce better optimal solutions. [ABSTRACT FROM AUTHOR]

The importance of the retaining structures is crucial in geotechnical engineering and the accurate determination of static and seismic earth pressures and natural frequency is important for study the dynamic behavior of these structures. Usually analytical formulas which do not consider the earth pressures behind retaining structure are used. An analytical model for predicting the natural frequency of retaining structures including the earth pressures by failure wedges is proposed in the present analysis. The model considers the effect of Coulomb and Mononobe Okabe failure wedges. Backfill material is considered in the analysis as cohesionless. The failure wedge is an important factor which should be considered in determining the natural frequency of retaining structures. As the weight of failure wedge increases the natural frequency decreases significantly. The current model is validated using several analytical models reported in the literature of the earlier researcher.

The article discusses the safety requirements specified in pertinent standards and recommendations for designing civil engineering objects, with particular emphasis on earth structures intended for vehicle traffic. The focus was on the following issues: the essence of reliability and durability of the structure and ensuring safety at the stage of designing vehicle traffic embankments with a slope supported with the use of a retaining wall and embankments placed on a substrate characterized by insufficient bearing capacity. The procedure for designing traffic embankments on weak ground, reinforcing weak ground and designing retaining structures (on the example of a reinforced soil massif) was carried out in accordance with the calculations pertaining to the field of geo-engineering, applying general analytical dependencies.

Featured Application: A potential application of the study is the use of the technology described in the construction of bridges, in particular for the construction of retaining structures within abutments. This study considered the possibility of using steel gabion baskets made of welded mesh for a soil-strengthening function. Examples of such applications are known for meshes made of wires with diameters from 6.3 to 12.7 mm and mesh openings from 125 to 225 mm. In the case of a welded grid, the pulling resistance of fine-grained soil consists of two factors: frictional resistance and bearing resistance. Therefore, for the purposes of this issue, a simplified laboratory pullout test was carried out with four types of welded steel grid (common in Europe) embedded in the fine sand. The geometry of the grid (opening size: 76.2 × 76.2 mm), the type of steel (low carbon steel, tensile strength from 500 to 700 MPa), the diameter of the wire (2.7–4.5 mm) and its cover (ZN + PVC or ZnAl) were taken into account during the analysis. It was unequivocally stated that as the stiffness of the steel grid itself increases, its strength increases during the pullout test, which is not so obvious in the case of popular steel woven meshes. In addition, it has been shown that steel welded meshes with wire diameters less than 6 mm are suitable for soil reinforcement in structures with gabion facing, and the determined apparent friction coefficient (μk = 0.39–1.47) takes values similar to the friction coefficient given in references for welded meshes of larger diameters. This is a positive premise for starting further research on the use of wires of smaller diameters for welded mesh production used as soil reinforcement. [ABSTRACT FROM AUTHOR]

Comparison of collapse frequency and failure probability of retaining structures In this contribution observed collapse frequencies and calculated failure probabilities of retaining structures are compared. Such comparisons are so far only available for bridges, dams and tunnels. The comparison is mainly based on values from the literature. These were recorded in the context of a literature search. Furthermore, collapse frequencies for earthquake impacts were determined by own calculations. The comparison of collapse frequencies and failure probabilities of retaining structures shows a good agreement. However, the comparison of the values with other types of structures shows an above‐average frequency of collapses. This seemingly accepted high frequency of collapse is justified by the lower number of victims and damage costs when retaining structures fail. [ABSTRACT FROM AUTHOR]

One of the major challenges for a numerical modeler/practitioner designing a sheet-pile retaining structure shoring waterfront regions under dynamic loading is to reasonably capture its seismic response solely on appropriate soil constitutive model calibration. This is particularly important as the numerical modelers usually do not have access to the dynamic centrifuge testing or large-scale 1G experimental facilities for the purpose of full-scale FE model validation based on the in-situ conditions. This paper emphasizes the significance of the consideration of initial static shear during the model calibration phase on the blind numerical predictions involving a sheet-pile wall retaining a submerged backfill. For this purpose, a strain space multiple mechanism model was initially calibrated against cyclic direct simple shear (CDSS) tests performed on the Ottawa F-65 sand under different initial states. The strain space multiple mechanism model was able to replicate the essential features in the cyclic soil response under the presence of initial static shear such as the non-occurrence of liquefaction and mobilization of shear strain limited to the compression side. The calibrated soil constitutive model employed within the FLIP-ROSE FE program was reasonably able to blind-predict the measured response from the centrifuge experiments. In particular, the measured seismic lateral displacements experienced by the retaining wall were excellently captured. Finally, this study signifies the role of the stress reversal and non-stress reversal cyclic loading scenarios in the elemental calibration on the extent of permanent deformation experienced by a sheet-pile wall under earthquake excitations having different characteristics. Overall, it is observed that calibration of a soil constitutive model by incorporating the essential features of the stress reversal and non-stress reversal unsymmetrical cyclic loading may result in the appropriate FE predictions for the sheet-pile wall deformation mechanism when subjected to earthquake excitations with different characteristics. • Strain space multiple mechanism model is used to assess the influence of initial static shear on the cyclic shear mechanism. • The model was able to replicate the essential features under the symmetrical and unsymmetrical cyclic loading conditions. • The developed FE model was reasonably able to blind-predict the seismic response of a sheet-pile wall. • Significance of the consideration of stress reversal and non-stress reversal cyclic loading in model calibration is shown. [ABSTRACT FROM AUTHOR]

Deep excavation problems are frequently encountered today. In case of construction works requiring deep excavation, a retaining system should be used to prevent damage to existing buildings around the excavation area. Steel sheet pile walls which are one of the retaining systems used for this purpose, are relatively preferred due to their resistance to high driving stresses, lightweight, long service life and the ability to use them repeatedly compared to other types of wall. One of the tasks of a geotechnical engineering who will design the required retaining structure is to create a safe and economical design. Although there are enough studies in the literature about the design of anchored pile systems, optimization studies are insufficient. For this reason, in this study, an optimization calculation has been made on cost of sheet pile system by changing lateral and vertical spacing of anchors and angles of anchor in sheet pile system which is driven into medium dense sand soil. As a result, 11296 different geometry conditions have been examined and cost functions have been established for each. Finally it has been observed that the lowest costs usually occur when the angle of anchor is 150 and horizontal distance between the anchors is 3 m.

Based on the salp swarm algorithm (SSA), this paper proposes an efficient metaheuristic algorithm for solving global optimization problems and optimizing two commonly encountered geotechnical engineering structures: reinforced concrete cantilever retaining walls and shallow spread foundations. Two new equations for the leader- and followers-position-updating procedures were introduced in the proposed adaptive salp swarm optimization (ASSA). This change improved the algorithm’s exploration capabilities while preventing it from converging prematurely. Benchmark test functions were used to confirm the proposed algorithm’s performance, and the results were compared to the SSA and other effective optimization algorithms. A Wilcoxon’s rank sum test was performed to evaluate the pairwise statistical performances of the algorithms, and it indicated the significant superiority of the ASSA. The new algorithm can also be used to optimize low-cost retaining walls and foundations. In the analysis and design procedures, both geotechnical and structural limit states were used. Two case studies of retaining walls and spread foundations were solved using the proposed methodology. According to the simulation results, ASSA outperforms alternative models and demonstrates the ability to produce better optimal solutions.

This paper illustrates an original and simple method to predict earthquake-induced deformations of geotechnical systems. The method is an extension of static non-linear analysis, and is conceived to predict the behaviour of geotechnical systems, like supported and unsupported excavations, that during the seismic motion accumulate displacements in a single direction. The seismic capacity of the system is described by its capacity curve, obtained either from a numerical push-over analysis or through a simplified procedure. The corresponding seismic demand is described by a combination of the elastic response spectrum, including basic information on the maximum amplitudes of the seismic motion, and a cyclic demand spectrum, that provides additional information about the equivalent number of cycles that contribute to the accumulation of displacements. In the paper, the method is described in detail and is validated through different procedures, namely: comparisons with experimental results obtained in the geotechnical centrifuge; comparison with results of advanced numerical analyses; extensive comparison, using a large database of seismic records, with the results of non-linear time-domain analyses. In its final part, the paper provides guidance for the practical use of the method for design. [ABSTRACT FROM AUTHOR]

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The deflections of retaining structures during deep excavation should be controlled below a predefined threshold in an attempt to mitigate the deformation-posed damage to the surrounding buildings and infrastructure facilities. In this paper, a new approach is presented to conducting deformation reliability assessments of retaining structures. The method is based on an extension of the classical first-passage reliability problem and is applied on the spatial scale of the retaining structures. With the proposed method, the in situ monitoring data and the associated measurement error can be easily incorporated, which accordingly improves the assessment accuracy. Moreover, the proposed method has a closed-form solution, which is beneficial for the computation efficiency and its practical application. The method was applied to assess the retaining structure reliability in a foundation excavation of a subway station in Fuzhou, China. The accuracy of the analytical results was verified through a comparison with those of Monte Carlo simulation. It was shown that the proposed method can represent well, the deformation-based safety level of retaining structures. [ABSTRACT FROM AUTHOR]

This research involved analysis and field testing of numerous foundation support components for highway bridges. Two classes of components were tested - cast-in-drilled-hole (CIDH) reinforced concrete piles (drilled shafts) and an abutment backwall. The emphasis of this document (Part II of the full report) is abutment backwall elements.The backwall test specimen was backfilled to a height of 5.5 up from the base of the wall with well-compacted silty sand backfill material (SE 30). The wall is displaced perpendicular to its longitudinal axis. Wing walls are constructed with low-friction interfaces to simulate 2D conditions. The backfill extends below the base of the wall to ensure that the failure surface occurs entirely within the sand backfill soil, which was confirmed following testing. The specimen was constructed and tested under boundary conditions in which the wall was displaced laterally into the backfill and not allowed to displace vertically.A maximum passive capacity of 497 kips was attained at a wall displacement of about 2.0 in, which corresponds to a passive earth pressure coefficient Kp of 16.3. Strain softening occurs following the peak resistance, and a residual resistance of approximately 460 kips is achieved for displacements > 3.0 inch. The equivalent residual passive earth pressure coefficient is Kp = 15.1 and the equivalent uniform passive pressure at residual is approximately 5.1 ksf, which nearly matches the value in the 2004 Seismic Design Criteria of 5.0 ksf. The average abutment stiffness K50 was defined as a secant stiffness through the origin and the point of 50% of the ultimate passive force. For an abutment wall with a backfill height H of 5.5 ft, this stiffness was found to be K50 = 50 kip/in per foot of wall. The load-deflection behavior of the wall-backfill system is reasonably well described by a hyperbolic curve.The passive pressure resultant is under predicted using classical Rankine or Coulomb earth pressure theories. Good estimates of capacity are obtained using the log-spiral formulation and the method-of-slices. The method-of-slices approach is implemented with a log-spiral hyperbolic method of evaluating backbone curves that provides a good match to the data.

This study considered the possibility of using steel gabion baskets made of welded mesh for a soil-strengthening function. Examples of such applications are known for meshes made of wires with diameters from 6.3 to 12.7 mm and mesh openings from 125 to 225 mm. In the case of a welded grid, the pulling resistance of fine-grained soil consists of two factors: frictional resistance and bearing resistance. Therefore, for the purposes of this issue, a simplified laboratory pullout test was carried out with four types of welded steel grid (common in Europe) embedded in the fine sand. The geometry of the grid (opening size: 76.2 × 76.2 mm), the type of steel (low carbon steel, tensile strength from 500 to 700 MPa), the diameter of the wire (2.7–4.5 mm) and its cover (ZN + PVC or ZnAl) were taken into account during the analysis. It was unequivocally stated that as the stiffness of the steel grid itself increases, its strength increases during the pullout test, which is not so obvious in the case of popular steel woven meshes. In addition, it has been shown that steel welded meshes with wire diameters less than 6 mm are suitable for soil reinforcement in structures with gabion facing, and the determined apparent friction coefficient (μk = 0.39–1.47) takes values similar to the friction coefficient given in references for welded meshes of larger diameters. This is a positive premise for starting further research on the use of wires of smaller diameters for welded mesh production used as soil reinforcement.

Some retaining structures can be designed on a temporary basis, in accordance to the geotechnical design and a predefined construction plan. Off course this may not be valid elsewhere, but in Brasília, where residual and laterized soils do prevail, best mechanical resistances are obtained in the porous clay setrata along the dry season. That means, it is controlled by soil´s suction, i.e. soil behavior presents a dependency on the unsaturated response of the medium. In numerical terms, to predict the soil-structure behavior it is necessary to include the atmosphere-soil interaction in the computational tool, using a hypoplastic model. The paper thus details on this aspect and on the numerical simulations of an existing retaining structure founded in the tropical soil of Brasília. The structure was monitored in terms of displacement, along local dry and wet seasons, and was simulated by a constitutive law calibrated by means of unsaturated laboratory tests.

The road network of the Austrian state of Styria, comprises of about 5,000 retaining structures along a total distance of about 5,100 km. In order to be able to carry out a useful and efficient inspection methode to this number of structures, a risk management (priority management) concept has been developed in collaboration with a university. This is based on the recording of significant parameters regarding the stability of these structures. In addition, the damage potential resulting from a failure of a structure is given, which enables an estimation of the associated risk. These documents can also be used as a design basis or for the determination of necessary inspection measures. The approach presented here is the first version of this concept for existing retaining structures in the state road network and is currently in a phase of trial and validation. [ABSTRACT FROM AUTHOR]

Miscellaneous retaining structures have been used against lateral earth pressure in order to ensure the stability of soils which are interacted with structures constructed at different elevations. In addition, the reinforced soil applications are preferred within highways projects have come into prominence recently. In this study, 82 different steel strip reinforced soil projects built in six regions of Turkey were evaluated. The internal parameters of the natural soil and the backfill materials with the limit values of external factors such as wall height and surcharge load were determined according to the data of the projects. A generalization was made in accordance with the theoretical calculations and the change of design parameters such as reinforcement length and reinforcement thickness were investigated due to these limit values. According to the results, the length of the strip reinforcement varies between 2.02 m and 23.62 m, while the thickness value changes from 0.65 mm to 10.49 mm. The first 5.00 m of wall have importance in terms of reinforcement length. If other variables are kept constant, the effect of the horizontal reinforcement spacing on the strip thickness is more critical than both the surcharge load and design life. [ABSTRACT FROM AUTHOR]

Abstract The Mohr-Coulomb failure criterion, which is typically used to represent soil strength, has been found to overestimate the tensile strength of most soils. Considering this fact, the concept of tensile strength cut-off was adopted to reduce or eliminate the tensile strength from the criterion. Based on that concept, this study proposes a kinematical framework for the estimation of active earth pressure on retaining structures in cohesive backfills. According to the associative flow rule, a valid rotational collapse mechanism is established. The resultant active earth pressure is determined from the work rate balance equation and is expressed as a dimensionless active earth pressure coefficient. The proposed approach is validated by a numerical simulation. Design charts are presented for a parametric study and for simple use in engineering. The results show that the presence of soil cohesion has a favorable influence on the stability of retained soil masses. Accounting for the impact of tension cut-off leads to a more conservative result, and this impact tends to be more obvious with the increase of cohesion. Finally, the assumptions that were made about the validity of the associative flow rule and the action point of the resultant earth pressure are discussed. [ABSTRACT FROM AUTHOR]

This work summarises recent research on the seismic behaviour of displacing or yielding retaining structures, i.e. , structures that can undergo permanent displacements during strong earthquakes without failing. For these systems, energy dissipation on shaking, leading to reduced inertia forces, can be achieved by allowing the activation of ductile plastic mechanisms. These must be correctly identified to guarantee the desired strength hierarchy, and depend on the specific retaining structure under examination. It is shown that the critical acceleration, or the smallest value of acceleration corresponding to the activation of the critical plastic mechanism, is the key ingredient for the performance-based design of yielding retaining structures. In fact, the critical acceleration controls both the maximum internal forces in the structural elements and the magnitude and trend of post-seismic permanent displacements and rotations, required for quantitative serviceability and post-earthquake operability assessment of infrastructures. Based on a clear understanding of the physical mechanisms governing the dynamic behaviour of these systems, pseudostatic limit equilibrium solutions and simplified dynamic methods can be developed for their seismic design. Theoretical predictions are validated against data from reduced scale centrifuge models and results of pseudo-static and fully dynamic numerical analyses. Finally, all the results presented in the paper, including experimental, numerical and theoretical findings, are used to provide suggestions for the performance-based design of retaining structures. • Critical acceleration controls maximum structural forces and seismic displacements. • Pseudostatic limit equilibrium solutions and simplified dynamic methods are developed. • Two rigorous methods are discussed for computing wall seismic-induced displacements. • Theoretical methods are validated against numerical and experimental results. • Acceleration reduction factors to be used in force-based approaches are provided. [ABSTRACT FROM AUTHOR]

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The stability of earth retaining structures in flood prone areas has become a serious problem in many countries. The two most basic causes of failure arising from flooding are scouring and erosion of the foundation of the superstructure. Hence, a number of structures like bridges employ scour-arresting devices, e.g., gabions to acting on the piers and abutments during flooding. Research was therefore undertaken to improve gabion resistance against lateral movement by means of an interlocking configuration instead of the conventional stack-and-pair system. This involved simulating lateral thrusts against two dimensionally identical retaining wall systems configured according to the rectangular and hexagonal gabion type. The evolution of deformation observed suggested that the interlocking design exhibits better structural integrity than the conventional box gabion-based wall in resisting lateral movement and therefore warrants consideration for use as an appropriate scour-arresting device for earth retaining structures.