Prediction of damage to cement-based structures subject to tunnelling-induced settlements

[摘要] ENGLISH ABSTRACT:Tunneling in busy urban areas is becoming a common practice, caused by the everincreasingnumber of commuters. This causes a decline in the service level that thesurface transportation systems provide in cities. Tunneling induces movement of thesoil directly surrounding the tunnel. These movements are translated into surfacemovements, which are translated into structural displacements of the surroundingsurface infrastructure. These displacements, for which the infrastructure may not havebeen designed, put a question mark on the infrastructure aesthetics, serviceability, aswell as structural stability.Burland and Wroth (1974) proposed a simple analytical damage assessment approach(Limiting tensile strain method (LTS)) to aid in the design of tunnels with respect tothe structural integrity of the affected surface infrastructure. This study is concernedwith the accuracy of this approach applied to the damage assessment of laterallyunconfined, solid masonry walls, subject to a sagging mode of settlement deformationwith no soil to wall friction. It is also concerned with the proposal of modifications tothe approach, where deemed necessary.Finite element models of solid masonry walls are built and analysed in order todetermine the accuracy of the simple analytical damage assessment approach withregard to the prediction of strains in solid masonry walls subject to tunneling-induceddisplacements. The predictions are found to be accurate for walls ofL/H ratio equal to2 and larger. For walls of L/H ratio smaller than 2, the predictions are found to beunderestimates.The simple analytical damage assessment approach is unable to account for thestiffness of the soil directly under the foundation of the wall. The stiffness of the soilplays a major role in the stress and strain distributions in the wall. It is thereforedeemed necessary to modify the simple analytical damage assessment approach byaccounting for the soil to wall interaction and the effect it has on the settlementdamage to solid masonry walls. The soil to wall interaction is found to reduce thenumber of mitigating measures originally recommended for the walls, by the simple analytical damage assessment approach, as it accounts for the bedding of the wall intothe soil previously unaccounted for.This study has reached the point where it is able to accurately predict whether alaterally unconfined, solid masonry wall, subject to a sagging mode of settlementdeformation with no soil to wall friction will experience magnitudes of strainsurpassing the yielding strain of the material. This was fundamentally achieved bydeveloping a better representation of the strains in solid masonry walls as well asaccounting for the inherent soil to wall interactionThis study is intended to pioneer the proliferation of similar studies for various otherstructures. A methodology, applicable for similar investigations envisaged for otherstructures, is hereby developed.

[发布机构] Stellenbosch University