Behavior Of Retaining Walls Research Articles

Soil structure interaction studies on earth retaining wall

Abstract The paper offers a brand-new analytical technique for figuring out retaining wall natural frequencies, which are essential for seismic design. Using translational and torsion springs to account for soil-backfill interaction and foundation flexibility, the approach applies the theory of beams on elastic foundations. There are three closed-form techniques offered for figuring out the natural frequencies of flexural and stiff modes. The analytical model takes into account several kinds of retaining walls and the interactions between soil and structure that go along with them, such as active, passive, and dynamic earth pressures. To make the analysis simpler, certain assumptions are made about the behaviour of the structure and the state of the soil. The suggested technique provides a trustworthy means of assessing retaining wall behaviour during seismic events, which is crucial for guaranteeing structural stability and averting failure.

Sand deformation mechanisms and earth pressures mobilised with passive rigid retaining wall movements

A series of centrifuge tests was conducted to explore the deformation mechanisms and earth pressures mobilised in loose and dense sand for a complete set of passive movement modes of a rigid retaining wall: rotation about the top and base and translation. Sand deformations were measured by particle image velocimetry and earth pressures were observed by a Tekscan pressure mapping system. Simplified linkages between wall displacements, sand strains and earth pressures were built. Superposition of such results would allow designers to predict retaining wall behaviour in sand during the construction sequence as well as ultimate collapse in a mobilisable strength design procedure.

Experimental study on effect of underground excavation distance on the behavior of retaining wall

The changes in earth pressure and ground settlement due to underground excavation near an existing retaining wall were studied experimentally according to the separation distance between the underground excavation and the retaining wall. In addition, this study attempted to experimentally prove that the arching phenomenon occurred during the construction of the underground space. A model tank having 120 cm in length, 160 cm in height, and 40 cm in width was manufactured to simulate underground excavation through the use of five separated base wall bodies. The variation of earth pressure on the retaining wall was measured according to the underground excavation phase through the use of 10 separated right wall bodies. The results showed that the earth pressure on the retaining wall was changed by the lowering of the first base bottom wall; however, the earth pressure was not changed significantly by the lowering of the third base bottom wall, since the third base wall had sufficient separation distance from the retaining wall. Lowering of the first base wall induced a decrease in the earth pressure in the lower part of the retaining wall; in contrast, lowering of the first base wall induced an increase in the earth pressure in the middle part of the retaining wall, proving the arching effect experimentally. It is necessary to consider the changes in earth pressure on the retaining wall in designing earth retaining structures for sections where the arching effect occurs.

Thermal and mechanical aspects of the response of embedded retaining walls used as shallow geothermal heat exchangers

Engineering structures embedded in the ground can be utilised as the heat exchange circuit in shallow geothermal energy systems. Thermally-activated retaining walls supporting the sides of tunnels and basements have been completed in a small number of projects but limited operational information has been published. Such information that is available suggests that in tunnels, climatic temperature changes may dominate the thermo-mechanical response of the wall system. This article first presents an overview of thermally-activated retaining wall behaviour and observations of tunnel environments generally, which points to the importance of the tunnel/air void characteristics in the thermal performance of such systems. In a numerical study it is shown that the main mechanism for heat exchange is between the air-void and the wall rather than the ground and that the thermal characterisation of the boundary between the wall and the air void requires greater scrutiny, to ensure realistic predictions of energy performance. The numerical study also shows that changes to the wall mechanical response are dominated by seasonal temperature changes, and using the wall for heat exchange has a rather small effect. It is apparent that these seasonal changes are not insignificant and their magnitude is also a function of the ratio of the coefficient of thermal expansion of the structural elements and that of the surrounding ground, and should be considered in design.

Behaviour of Retaining Wall Founded on Collapsible Soil – A Prototype Laboratory Study

Retaining walls may be required in a location where gypsum may present in soil in large percentages .The behavior of retaining walls on ordinary soils is well known but the behavior of retaining walls resting on gypseons soils may be not well understood as the case of ordinary soils.In this study it is intended to reflect the behavior of gravity retaining wall resting on collapsible soil. And to do so a small prototype model (600mm*500mm*200mm) is used with soil mixed in presumed percentages with different gypsum percentages (5%, 20%, 30%, 50%). In addition to a model with 30% gypsum and treated with 2.7% Cement dust mixed with soil founded retaining wall structure. After preparing the foundation gypseous soil, a small glass made retaining wall filled with sand, which represent gravity wall, is put over such bed and backfilled with ordinary sandy soil. Dial gauges are placed to side and top of wall to measure the rotation settlement behavior and collapse of system. 4kPa stress are applied to backfill soil as to accelerate collapse with leaching process commenced. Data are recorded and analyzed completely, which shows the behavior of such structures embedded with different gypsum content.The improvement in rotation settlement and collapse for the retaining wall model reaches more than 89%, was gained after treating the embedded gypseous soil layer, with 2.7% cement dust.

Retaining wall behaviour in Dublin's estuarine deposits, Ireland

Practising engineers in the Dublin, Ireland, area have much experience in dealing with the boulder clay which underlies much of the city. However, significant deposits of estuarine soils, some of them soft, exist along the east side of the city and in particular in Dublin docklands. Some construction difficulties have previously been encountered in these materials and significant developments, including a large tunnel project, are planned in the area overlying these deposits. Few published data exist on retaining wall schemes in the deposits. Data from nine sites, including three detailed case histories, are presented which confirm that construction of deep propped excavations and cantilever walls up to 7·5 m are feasible in these deposits and can perform well. A key issue is the soil that is located at excavation level and competent deposits here are essential to prevent large displacements or possible instability. The resulting movement will also be sensitive to the overall system stiffness. There seems to be scope for more efficient future design, including more use of cantilever walls, particularly for temporary works purposes. Beam-on-spring type computer analyses tend to give conservative results for these deposits and more sophisticated finite-element analyses may be warranted for future schemes.

Retaining wall behaviour in Dublin's fluvio-glacial gravel, Ireland

Practising engineers in the Dublin, Ireland, area have significant experience in dealing with the Boulder Clay which underlies much of the city. However, the 45 m deep buried pre-glacial channel north of the River Liffey is infilled with fluvio-glacial deposits which behave very differently from an engineering point of view. Case history data from eight sites and a detailed examination of the retaining wall behaviour at two of the sites show that retaining wall movements appear to be governed by system stiffness (i.e. a combination of wall stiffness and support configuration). It seems that relatively simple beam–spring type computer programs will provide data for reasonably accurate designs of retaining walls for basements of up to two levels. Input parameters such as K0, φ‘ and soil stiffness need to be carefully specified. Groundwater inflows can be significant but can be dealt with by providing a good cut-off into the underlying glacial till or bedrock and by conventional pumping techniques. Geophysical techniques such as multichannel analysis of surface waves, S/P waves and resistivity can be very useful for the determination of soil properties, such as degree of saturation, density and stiffness, and for material characterisation (i.e. distinguishing the presence of these materials in contrast to the Boulder Clay).

A case history of a deep basement in London Clay

The case history of the deep excavation for the National Gallery extension in London is presented in this paper. Comparisons with data from other sites show that it is typical for that of similar projects in Central London. Class 1 predictions of the retaining wall behaviour (prior to construction) using the Model London Clay constitutive relationship considerably over-estimated wall and ground movements. Retaining wall and ground movements are also considerably over-predicted by analyses using a simple linear elastic/perfectly plastic soil model, despite optimistic parameters being assumed for the soils. Predictions made using the constitutive model BRICK are closer to the measured deflected shape, but are also higher than measured values. Parametric studies of the effect of various parameters suggest that a “best estimate” of the wall movements are still well in excess of those measured. It is concluded that these differences are due to three-dimensional effects and deficiencies in the model. The “beam-spring” computer software for retaining walls FREW gives similar results to the analyses using the simple model. Analyses of the same problem carried out by a different operator using another finite element code, but with the same constitutive model, yielded somewhat different results and highlight the need for careful interpretation of finite element analyses.

Behaviour and Analysis of A Large-Scale Cylindrical Earth Retaining Structure

A cylindrical earth retaining wall 144 m in diameter was adopted for the excavation works of a 500 kV large-scale underground substation building. Various in-situ measurements, which comprised approximately 1,100 measuring points, were carried out throughout the excavation works. Following the examination of the measured data, it was ascertained that the retaining wall behaviour was largely influenced by wall temperature variations in addition to lateral pressures. This paper presents the earth retaining wall behaviours based on the measurement results and the practical analysis methods by introducing the retaining wall temperature variations.

Modelling system uncertainty in the design of embedded retaining walls

The purpose of this paper is to explore some of the aspects of embedded retaining wall design, in particular the interrelationship between system uncertainty and the use of factors of safety in the various design procedures. System uncertainty reflects the mismatch between idealized retaining wall behaviour and what is observed in practice. This feature is modelled using the concept of fuzzy sets where the degree of support for the lateral stress state at failure is considered and related to current limit equilibrium design methods, measured lateral pressures and the results of finite element analyses. The proposed model is shown to have some advantages over current design practice.

The effect of interface properties on retaining wall behaviour

The effect of interface properties on retaining wall behaviour

The effect of interface properties on retaining wall behaviour

A series of finite element analyses have been undertaken to investigate the effects of interface properties on the behaviour of a vertical retaining wall and the deformation of the ground around it. The boundary between a rigid embedded wall and the soil is modelled with zero thickness interface elements. Uniform translation of the wall has been studied. The analyses show the predicted limiting active and passive pressure on the wall are dependent on the maximum wall friction angle and are in reasonable agreement with accepted approximate analytical solutions. The limiting pressure is independent of the stiffness and dilation properties of the interface elements. The dilation properties of the interface have a significant effect on the ground surface deformation around the wall. © 1998 John Wiley & Sons, Ltd.

EMBEDDED RETAINING WALL DESIGN PROCEDURES: SYSTEM UNCERTAINTY AND FUZZY SAFETY MEASURES

Abstract This paper explores some of the aspects of embedded retaining wall design, in particular the interrelationship between system uncertainty and the use of factors of safety in the various design procedures. System uncertainty reflects the mismatch between idealised retaining wall behaviour and what is observed in practice. This feature is modelled using the concept of fuzzy sets where the degree of support for the lateral stress state at failure is considered and related to current limit equilibrium design methods, measured lateral pressures and the results of finite element analyses. The proposed model is shown to have some advantages over current design practice.

Design Of Retaining Walls : SystemUncertainty & Fuzzy Safety Measures

This paper explores some of the aspects of embedded retaining wall design, in particular the interrelationship between system uncertainty and the use of factors of safety in the various design procedures. System uncertainty reflects the mismatch between idealised retaining wall behaviour and what is observed in practice. This feature is modelled using the concept of fuzzy sets where the degree of support for the lateral stress state at failure is considered and related to current limit equilibrium design methods, measured lateral pressures and the results of finite element analyses. The proposed model is shown to have some advantages over current design practice.