Tunnel induced settlement damage: A case study to improve damage prediction for facades

The tunnel boring process introduces soil settlements. Damage to nearby building could occur if settlements become too large. A reliable damage prediction model is necessary too asses the risks of damage to tunnel induced settlements. A widely used method for damage prediction is the Limiting Tensile Strain Method (LTSM). The LTSM models a masonry building as a weightless, isotropic, linear-elastic, rectangular beam on 2 supports. Although the LTSM is an easy method to use, it has its limitations. For facades for instance the perforation of the wall, which introduces weak spots in the wall and reduces the stiffness, is neglected. In this project the applicability of the LTSM in the case of facades is studied to improve damage predictions in the case of facades. A case study is performed to examine the response of facades in the Daniel Stalpertstraat due to settlements caused by the tunnelling process of the North/Southline. This field data is used to find a calibrated 2D numerical model of the facades. The calibrated numerical model is then subjected to larger settlements to obtain the behaviour of the facades at large settlements. Using linear and nonlinear analyses of the numerical model it is evaluated how accurate and how conservative 4 damage prediction models are. The first two LTSM models were examined: the standard LTSM model with E/G=2.6 and one with E/G=12.5. Based on the findings in the linear analyses also two models based on conventional beam theory were examined for their applicability: portal frame model and Forget-Me-Not model. With linear analyses it is checked how reliable the methods are in terms of strains and deformation under the imposed settlements. With nonlinear analyses the conservativeness of each method in terms of damage is evaluated by comparing the crack with found I the numerical model to the crack width calculated with the damage prediction models. The LTSM with E/G=12.5 gives the best results according to linear numerical analyses results. The LTSM with E/G provided the same curvature and shear distortion as found din the numerical analyses, the strains were approximated with 90%. The Forget-Me-Not model shows the best results according to the nonlinear analyses results. At large settlements this model provides the same results as found in the nonlinear numerical analysis results.Structural MechanicsStructural EngineeringCivil Engineering and Geoscience