Mitigation of Risks Associated with Deep Excavations: State of the Art Review (original) (raw)
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In this state-of-the-art report, the following aspects are highlighted: 1. Factors affecting the deformations associated with deep excavations; 2. Assessment of the ground deformations outside the deep excavation using different approaches (viz., empirical/semi-empirical, numerical; analytical, physical modeling and ANN approaches); 3. Influence of the presence of buildings on the displacements; 4. Structural damage criteria; 5. Monitoring programs for deep excavation projects; & 6. Risk management and mitigation for deep excavation projects In addition to the International studies presented in this state-of-the-art covering the abovementioned points, National experiences in assessments of the deformations induced by deep excavations, monitoring programs, risk assessment and risk mitigation are also highlighted.
Effects of deep excavations on existing buildings: a case study
2011
In this paper the issue of evaluating the effects produced by deep excavations on the built environment in urban areas and historical centres is discussed. Deep excavations unavoidably cause a fi eld of soil deformations affecting the surrounding buildings. A second level probabilistic analysis on these effects is described for a case-study. In particular, a comparison between the obtained results and those estimated by using widely adopted empirical methods is carried out. The aim is to give a contribution towards defi ning probabilistic methods in order to predict buildings damage on varying excavation depths and edge distances and towards supporting design decisions taking into account the need for both requirements of urban development and protection of the built environment.
Applied Sciences, 2021
Currently, new housing in city centers is more and more often developed on small plots of land, or existing buildings on such plots are rebuilt to such an extent that only their façade walls remain. In both cases, as a rule, a deep excavation is also made, either at the existing object or within its area. Serious damage often occurs because of the carried out work. It is not possible to accurately determine the response of a building to the deformation associated with the excavation due to the variability of many factors that influence it. As a result, the response of the building must be estimated on the basis of constant monitoring and approximate calculations. Depending on the size of the predicted ground displacements and the technical condition of buildings, it is often necessary to protect or strengthen their structural elements. In the paper, the authors analyzed various risk factors for the implementation of infill buildings and the revitalization of historic buildings using...
Structural safety of existing buildings near deep excavations
International Journal of Structural Engineering, 2014
Structural safety of existing buildings near deep excavations is evaluated by computing exceeding probabilities of different damage criteria within a simplified probabilistic methodology based on monovariate or multivariate probabilistic analyses employing the results of a numerical model of the boundary value problem. Different limit domains, defined on one or more deformation parameters and associated to limit states, are used to contemplate: the type of the structural system (i.e., reinforced concrete or masonry buildings); the foundation typology (i.e., strip/raft or pad foundations). The sensitivity analysis is developed considering the design of a new underground station in Naples (Italy).
Evaluating Damage Potential in Buildings Affected by Excavations
Journal of Geotechnical and Geoenvironmental Engineering, 2005
Predicting building damage due to ground movements caused by excavations is an important design consideration when building in a congested urban environment. Current predictive approaches range from empirical methods to detailed finite element calculations. Limitations inherent in the simpler of these models preclude them from accurately predicting damage in cases where important assumptions are invalid. A new simple model for representing buildings is presented to allow a designer to make realistic simplifications to a building system that is consistent with major features of the structure so that the response to ground movements can be adequately represented. This model assumes that the floors restrain bending deformations and the walls, whether load bearing or in-fill between columns, resist shear deformations. Closedform equations are presented that relate bending and shear stiffness to normalized deflection ratios. The proposed model is shown to adequately represent the response of a three-story framed structure which was affected by an adjacent deep excavation. The proposed model represents a reasonable compromise between overly simplistic empirical methods and complex, burdensome detailed analyses.
Numerical Analyses of Soil Deformations Around Deep Excavations
2013
In this study, the deep excavation of Cincin Station located along the Bağcılar-Otogar metro line which is currently under construction in Istanbul is modeled numerically. The excavation (depth 32.5 m) of the station is carried out with a surrounding slurry trench diaphragm wall and top-down construction method. The six slabs of the station building and the foundation mat are used as support elements. Lateral soil displacements are measured with inclinometers placed in the wall and nearby soil layers. The results of numerical analysis using soil profile and geotechnical parameters obtained from conventional field and laboratory tests and measured lateral displacements are compared. Then using the same soil model, soil displacements expected to occur if some other alternative excavation support systems were used is investigated. As alternative support systems use of steel pipes as internal bracing and a piled wall with pre-stressed tie-backs are considered. The calculated soil displacements for different support systems are compared with each other and the measured values. The effects of certain design parameters such as the rigidity of internal bracing elements, the pile diameters and the pre-stressing level of tie-backs are investigated through numerical analysis.
Effect of Deep Excavations on Adjacent Structures and Importance of Deep Excavation Support
Proceedings of the 6th World Congress on Civil, Structural, and Environmental Engineering, 2021
When deeply excavating close to existing structures, displacements in the soil under the base of the existing structure will occur. Therefore, considerable settlement will take place. Accordingly, it’s so necessary to understand and evaluate the soil’s behavior for excavations adjacent to existing structures. The goal of this paper is to evaluate the response of structures when deeply excavating near them. Finite Element models are generated using both 2D and 3D PLAXIS software. The excavation is reinforced by diaphragm walls, struts, and wales. The influence of the supporting system on the adjacent existing structure is examined and analyzed in details. A parametric study is carried out to examinate the factors that may have influence on the excavation. For the final step, some conclusions and recommendations of future researches will be sorted out.
Analysis and numerical modeling of deep excavations
Geotechnical Aspects of Underground Construction in Soft Ground, 2008
The sixteen papers comprising the general theme "Analysis and Numerical Modeling of Deep Excavations" of the 6th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground are summarized herein. General characteristics of all papers are presented as are brief summaries of each paper. Most papers included presentation of results of finite element simulations and attendant comparisons with various aspects of observed field performance. Some of the pitfalls for making comparisons between numerical results and field observations of deep excavation performance are discussed briefly. In particular, the effects of modeling construction details and selection of appropriate constitutive models are presented. Recommendations are tendered regarding the essential information that should be conveyed in papers that present results of numerical calculations.
Importance of Deep Excavation Support and Its Influence on Adjacent Buildings
This paper aims to investigate the important role of deep excavation support and its effect on nearby existing buildings, especially those founded on shallow foundations. Excavation of basement or foundations induces movements as a consequence of stress-release from earthwork and an increase in overburden pressure in the retained ground. Ground movements throughout excavation result in damage to existing structure located nearby. An intensive literature of previous experiences on supporting deep excavation and their impact on neighboring structures reviewed. This paper presents three case histories and two local current cases of excavations, which caused damages either on their own projects or on adjacent buildings. The results revealed that there are numerous sources of risk associated with performing deep excavations in urban areas, they must be considered in the design and execution of the excavation works for a minimum cost. General conclusions have been drawn from the study findings.
Finite element-based geotechnical risk analysis for anchor-supported deep excavations
Arabian Journal of Geosciences
Evaluation of the reliability of deep excavation support systems requires the inclusion of the soil variability in conjunction with probabilistic analysis. This is often considered a complicated process; therefore, the method is usually not followed in routine engineering practice. Recent developments in finite element modelling now enable probabilistic analyses to be performed more conveniently. As an illustrative example, the case history of a 20 m-deep excavation supported by anchored drilled shafts in the Sogutozu district of Ankara was investigated. Experimental results indicate that saturated sand-gravel bands, which are common within Ankara Clay, have the potential to cause a significant decrease in the anchor capacity. Ergo the excavation performance, including structural capacity and wall lateral displacements, was evaluated taking into regard the probabilistic nature of the effect of these bands and the variability of the soil parameters. Back-analysis was performed and co...