A 3D numerical approach to assess the temporal evolution of settlement damage to buildings on cavities subject to weathering

The goal of this paper is to show how a recently developed advanced hydro-chemo-mechanical (HCM) coupled constitutive and numerical model for soft rocks can be applied to predict the temporal evolution of settlement damage to buildings on cavities subject to weathering. In particular, a building damage index (BDI) and its evolution with time is proposed. The definition of the BDI is inspired by the work of Boscardin and Cording (1989) and uses the surface differential settlements obtained by finite element (FE) analyses to assess how far a building is from a non-acceptable service condition. By modelling the reactive transport of chemical species in 3D and using a coupled Chemo-Hydro-Mechanical (CHM) constitutive and numerical model, it is possible to simulate weathering scenarios and monitor the temporal evolution of surface settlements making the BDI time dependent. This approach is applied to evaluate the damage evolution of two buildings lying on two anthropic caves in a calcarenite deposit belonging to the Calcarenite di Gravina Formation. Standard and advanced experimental tests are performed on the in-situ material and the results are used to calibrate the constitutive model. The soundness of both constitutive relationship and reactive transport solver is subsequently tested by simulating two laboratory scale boundary value experiments. The first is a model footing test on dry and wet calcarenite while the second is a small scale pillar that, after the saturation induced short-term water weakening, fails due to a long term dissolution weathering process. Finally, both 2 and 3D coupled finite element (FE) analyses simulating different weathering scenarios and corresponding settlements affecting the buildings above the considered cavities are presented. Particular attention is placed on assessing the BDI and its temporal evolution.