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The goal of this paper is to show how a recently developed advanced chemo-hydro-mechanical (CHM)-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 (J Geotech Eng 115:1–21, 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 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 2D and 3D coupled 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.

The paper presents an experimental, theoretical and numerical approach in order to describe the effects of rock weathering on bonded geomaterials. The term rock weathering is used to refer to a number of chemical and physical phenomena that continuously transform a rock mass into granular soil. From an engineering point of view, rock weathering can be interpreted as a generalised decay of the mechanical properties of the original material. It acts at a constitutive level essentially by reducing the strength of the bonds joining the grains together. Such a material degradation can occur in a time scale which is comparable to the average life of engineering structures. Weathering can be crucial for what concerns the stability of slopes, cliffs and abandoned underground caves. In the experimental part of the paper micro and macro experimental investigations performed on calcarenite, a natural soft rock, are shown; short- and long-term debonding processes are identified as characterising rock weathering. A large set of hydro-chemo-mechanical data are recovered to properly characterise debonding processes by means of specific weathering tests. In particular, to reproduce long-term rock weathering in laboratory time, the progressive chemical debonding has been induced through the exposition of the rock to a uniform flow of an acid solution. In the theoretical part, it is shown how the progressive deterioration of the intergranular bonds due to weathering has been modelled satisfactorily by extending a strain hardening elastoplastic model by means of multiscale approach coupling hydro-chemo-mechanical processes. Such a model has been corroborated by simulating some tests of the previous part. Finally, in the numerical part of the work, some boundary value problems are presented, in which weathering effects cannot be neglected.

This paper introduces a novel modular approach for the monitoring of desiccation-induced deterioration in earthen embankments (levees), which are typically used as flood-defense structures. The approach is based on the use of a combination of geotechnical and noninvasive geophysical probes for the continuous monitoring of the water content in the ground. The level of accuracy of the monitoring is adaptable to the available financial resources. The proposed methodology was used and validated on a recently built, 2-km-long river embankment in Galston (Scotland, United Kingdom). A suite of geotechnical probes was installed to monitor the seasonal variation of water content over a 2-year period. Most devices were calibrated in situ. A novel procedure to extrapolate the value of water content from the geotechnical and geophysical probes at any point of the embankment is shown. Desiccation fissuring degrades the resistance of embankments against several failure mechanisms. An index of susceptibility is proposed here. The index is a useful tool to assess the health state of the structure and prioritize remedial interventions.\ud \ud \ud

During the last decade, a large rockslide along the NW slope of the Mont de la Saxe (Courmayeur, AO—Italy) showed a significant increase in the rate of activity in conjunction with snow melting periods and more recently with important amount of rainfall. The ca 8 mm3 rockslide affects a heavily tectonised and intensely fractured mass of black schists, for a surface area of about 150,000 m2. The rockslide failure surface is typically located at depths of 60–80 m b.g.l. Because of the highly valuable exposed elements regional authorities commissioned a comprehensive ground investigation and monitoring campaign, as well as theoretical and numerical analyses, in order to assess slope stability conditions, the possible evolution and the suitable stabilization and mitigation countermeasures. Here we present the recent rockslide evolution till spring 2014 when a major seasonal reactivation of a 400,000 m3 mass occurred. Finally, with the aim to develop a possible tool for displacement prediction, the results of a series of 1D visco-plastic simulations are presented, discussing the possible role of each of the main controlling factors (e.g. groundwater recharge and piezometric level oscillation, rock degradation). .

To model the temporal evolution of complex landslides, a 1D pseudo-dynamic visco-plastic approach, based on Perzyna's theory, has been conceived. In the original version of the model the viscous nucleus has been assumed to be bi-linear: irreversible deformations develop uniquely for positive yield function values whereas, in a more general case, even for negative values. In this work the model has been enriched by considering: i) an exponential viscous nucleus, ii) a strain-rate softening to reduce friction angle as sliding velocity increases and iii) block interaction forces to cope with complex 3D geometries for the sliding mass. The application of the proposed model to the La Saxe rockslide (Italy) clearly shows how a relatively simple model can be applied to a complex landslide by considering a spatial discretization of the sliding mass.

Earth pyramids are tall tapered spires, slender or stocky, made of rock or soil material. This type of features have been marginally studied. Even if they are often included in parks and geosites. We start from this lack of studies to analyse the geometrical and physical-mechanical characteristics considering some case studies in northern Italy. Because of their geometrical characteristics these elements are intrinsically weak and can be used as indicators of past external perturbations. We performed laboratory characterization and numerical modelling to analyse the involved actions, the stability and the reaction to dynamic perturbations.

Physical-mechanical properties and the mechanical behaviour of volcanic rocks are extremely sensitive to their original structure and successive hydrothermal alteration. Various mechanical tests have been performed on different volcanic rocks to evaluate the relationships between chemical and mineralogical composition, microstructure and texture, and physical mechanical properties. A wide-ranging description of mechanical behaviour is obtained through a series of uniaxial, triaxial, isotropic and oedometric tests, and of pre- and post-failure non-destructive analyses. X-ray tomographies show deformation and compaction within the samples and the influence of porosity distribution. Results are interpreted in the key of degree of alteration (lava and tuff series) and of texture differences (pyroclastic and ignimbrite series); empirical relationships between strength and physical properties are presented and discussed, together with trends in change of an Et50 vs UCS ratio. The influence of facies and water saturation on strength and behaviour of ignimbrite rocks is discussed. A 45 to 85% loss both in strength and ultrasonic waves velocity is found for altered lava and pyroclastic rocks. Weak highly porous ignimbrite shows a 50% strength loss under water saturated conditions and the complete collapse of porous structure. © 2013 Elsevier B.V.

After the abandonment occurred in the '70s, the mining system (rooms and pillars) located in S. Lazzaro di Savena (BO, Italy), grown on three levels with the method rooms and pillars, has been progressively more and more affected by degradation processes due to water infiltration. The mine is located underneath a residential area causing significant concern to the local municipality. On the basis of in situ surveys, laboratory and in situ geomechanical tests, some critical scenarios were adopted in the analyses to simulate the progressive collapse of pillars and of roofs in the most critical sectors of the mine. A first set of numerical analyses using 3D geotechnical FEM codes were performed to predict the extension of the subsidence area and its interaction with buildings. Secondly 3D CFD analyses were used to evaluated the amount of water that could be eventually ejected outside the mine and eventually flooding the downstream village. The predicted extension of the subsidence area together with the predicted amount of the ejected water have been used to design possible remedial measurements.

Volcanic rocks are frequently found under weathered/altered conditions. Degradation and transformation can occur both at the surface and at large depth causing a progressive change in the Physical mechanical properties. Degradation can cause an increase in porosity and this can control the rock behavior. In this paper we discuss the relationships between porosity characteristics, micro-structure and texture, and the mechanical behavior of lava at different degrees of weathering (lavas from the Campi Flegrei, Italy). The performed laboratory tests include: uniaxial compression, indirect tension, and uniaxial compression with ultrasonic wave measurements. A description of the mechanical behavior is obtained and a detailed description is performed through a series of pre and post failure non destructive analyses. Porosity values have been related to stress and strain relationship, in addition pore size characterization is presented in a companion abstract/manuscript. Results are interpreted in the key of degree of weathering and its related characteristics. An empirical linking between the change in strength with the degree of alteration is presented and discussed