Stability analysis of historic underground quarries

This work, carried out at the Department of Civil, Environmental and Territory Engineering and Architecture (DICATeA) of the University of Parma, analyzes the stability conditions of the ancient underground quarries of Viggiù (Varese, Italy). The objective of the study is to verify the actual structural predisposition to instability phenomena of the old Viggiù quarries, within the context of a historical and cultural valorization and recovery of the ancient ornamental stone quarries. These quarries, that are now completely abandoned, could be used as a tourist attraction and/or as a teaching environment. They are a wonderful example of industrial architecture by presenting an audacious composition of filled in trenches and room and pillar techniques. An experimental campaign based on in situ measurements and laboratory measurements has been carried out to characterize the rock mass and to determine rock mass mechanical features. A numerical model of the entire rock mass has been developed in order to analyze the stability of the entire underground openings. A preliminary monitoring phase has been realized, aimed at controlling abandoned rock structure movements at the most significant discontinuities. Some measurements of the vertical stress in the pillars and in the walls have been performed, as well, and used for the model calibration. Once the model has been calibrated, the analysis of the actual stress and deformation conditions has been evaluated, the stability condition of the entire structure computed and a forecasting analysis of any intervention that could be realized to guarantee the underground public access has been performed.     

The topographic signature of a major typhoon

In August 2009, the typhoon Morakot, characterized by a cumulative rainfall up to 2884 mm in about three days, triggered thousands of landslides in Taiwan. The availability of LiDAR surveys before (2005) and after (2010) this event offers a unique opportunity to investigate the topographic signatures of a major typhoon. The analysis considers the comparison of slope–area relationships derived by LiDAR digital terrain models (DTMs). This approach has been successfully used to distinguish hillslope from channelized processes, as a basis to develop landscape evolution models and theories, and understand the linkages between landscape morphology and tectonics, climate, and geology. We considered six catchments affected by a different degree of erosion: three affected by shallow and deep‐seated landslides, and three not affected by erosion. For each of these catchments, 2 m DTMs were derived from LiDAR data. The scaling regimes of local slope versus drainage area suggested that for the catchments affected by landslides: (i) the hillslope‐to‐valley transitions morphology, for a given value of drainage area, is shifted towards higher value of slopes, thus indicating a likely migration of the channelized processes and erosion toward the catchment boundary (the catchment head becomes steeper because of erosion); (ii) the topographic gradient along valley profiles tends to decrease progressively (the valley profile becomes gentler because of sediment deposition after the typhoon). The catchments without any landslides present a statistically indistinguishable slope–area scaling regime. These results are interesting since for the first time, using multi‐temporal high‐resolution topography derived by LiDAR, we demonstrated that a single climate event is able to cause significant major geomorphic changes on the landscape, detectable using slope–area scaling analysis. This provides new insights about landscape evolution under major climate forcing. Copyright © 2015 John Wiley & Sons, Ltd.     

Late Holocene sea-level changes in the northwest Tuamotu islands, French Polynesia

Field surveys of several sea-level indicators (exposed in situ reef framework, conglomerates, coral colonies and Tridacna shells in a growth position, sea-corrosion notches) carried out on six atolls from the NW Tuamotus (Mataiva, Rangiroa, Arutua, Kaukura, Apataki and Takapoto) and data from four subsurface boreholes drilled through Mataiva show that during the late Holocene mean sea level (MSL) reached a maximum elevation at approximately + 0.9 m. It remained above the present MSL from between 6000 and 5500 yr B.P. until at least 1200 yr B.P. Human settlements on the atolls were extremely unlikely and probably impossible throughout this time. The area investigated seems to have been tectonically quite stable during the late Holocene. A local curve of MSL variations may be representative of the regional eustatic pattern.     

Variations in multiscale curvature distribution and signatures of LiDAR DTM errors

The development of high resolution LiDAR digital terrain models (DTMs) has enabled the exploration of the statistical signature of morphology on curvature distributions. This work analyzes Minimum Curvature distributions to identify the statistical signature of two types of LiDAR‐DTM errors (outliers and striping artifacts) in the derived estimates, rather than morphology itself. The analysis shows the importance of modeling these errors correctly, in relation to the scale of analysis and DTM resolution, in order to have reliable curvature estimates. Nine DTMs of different morphological areas are considered, and grouped into a training dataset (without errors) and a test dataset (with errors). In the training dataset, the original DTMs are considered as true values; errors are then applied to these data. Minimum Curvature is computed at multiple scales from each DTM: changes in curvature distributions due only to morphology and scale are characterized from the original data; error effects are then identified from the datasets with simulated errors, and validated against the test dataset. The analysis shows that outliers and striping artifacts can be realistically simulated by heavily left tailed distributions. For DTMs without errors, the scale‐dependent change in curvature distribution is primarily controlled by real morphology. When DTMs include errors, curvature distributions become controlled by these errors, whose propagation depends on error distribution, error spatial correlation, and the scale of analysis. This study shows that the curvature distributions are impacted upon differently by striping artifacts and outliers, and that these are clearly distinguishable from the signal of morphological features: a scale‐dependent change in curvature distribution can therefore be interpreted as the signature of these specific errors, rather than morphology. Copyright © 2012 John Wiley & Sons, Ltd.     

A Bayesian procedure for Probabilistic Tsunami Hazard Assessment

In this paper, a Bayesian procedure is implemented for the Probability Tsunami Hazard Assessment (PTHA). The approach is general and modular incorporating all significant information relevant for the hazard assessment, such as theoretical and empirical background, analytical or numerical models, instrumental and historical data. The procedure provides the posterior probability distribution that integrates the prior probability distribution based on the physical knowledge of the process and the likelihood based on the historical data. Also, the method deals with aleatory and epistemic uncertainties incorporating in a formal way all sources of relevant uncertainty, from the tsunami generation process to the wave propagation and impact on the coasts. The modular structure of the procedure is flexible and easy to modify and/or update as long as new models and/or information are available. Finally, the procedure is applied to an hypothetical region, Neverland, to clarify the PTHA evaluation in a realistic case.     

Influence of Marble’s Texture on its Mechanical Behavior

This research work studied the influence of texture on the mechanical properties of crystalline rocks at the scale of the laboratory sample. The experiments were performed on a marble varying in texture, so that the study was conducted on homogeneous (entirely xenoblastic or totally granoblastic) and heterogeneous (mix of the two textures) specimens. The mechanical behavior of the homogeneous and heterogeneous samples was investigated with static and dynamic, destructive and nondestructive tests, in natural conditions, at the laboratory temperature, and at higher temperatures. The specimens were heated to 100, 200, and 300 °C, in order to examine the effect of heating temperature on the elastic modulus and P-waves velocity. As a result, the pure granoblastic marble exhibits values of the elastic modulus, P-waves velocity, and strengths, both in natural conditions and on heated specimens, lower than xenoblastic samples. Such different behavior can be explained by a higher grain boundaries porosity of the granoblastic marble. On heterogeneous samples, only the Rock Impact Hardness Number (RIHN) appears able to highlight the dependence of the mechanical properties on the rock texture. In particular, the impact strength improves with increasing the percentage of xenoblastic texture inside the specimen.     

Influence of groundwater flow on the estimation of subsurface thermal parameters

International Journal of Earth Sciences - We investigated the influence of groundwater flow on the thermal tests performed in borehole heat exchangers to infer the underground thermal properties....     

Hypersaline groundwater genesis assessment through a multidisciplinary approach: the case of Pozzo del Sale Spring (southern Italy)

A tool, based on a multidisciplinary field investigation approach for studying the characteristics of a hypersaline spring, was developed and its effectiveness tested on a spring in southern Italy; a preliminary model of the aquifer system at medium and local scale was derived. Hydrologic measurements, vertical electric soundings, and chemical and isotopic (δ¹⁸O, δ²H, ³H) analyses were undertaken, along with microbiological analyses and species identification. These demonstrate the coexistence of hypersaline and fresh water, generating a significant diversification of the groundwater hydrochemical signature. The isotopic signature shows that both types of water have a meteoric origin. Microbial contamination of fecal origin indicates the mixing of hyper- and low- saline water related to local infiltration. The hypersaline groundwater flows in confined horizons within a sequence that is mainly of fractured clays. These horizons are probably concentrated where well-developed fracture network and dissolution openings within evaporitic rocks enhance fluid flow. In a wider context, this study determines that microbiological pollution of saline groundwater may not be detected if using nonhalophilic bacterial indicators such as fecal coliforms. Fecal enterococci are better indicators, due to their higher halotolerance.     

A Geostatistical Simulation Approach to a Pollution Case in Northeastern Italy

The study zone is located in the city of Padova (the Veneto region, NE Italy). The industrial activities present in this area since 1950 have produced very high concentrations of Pb, Zn, Cu, Pcb and oils until a depth of 7 m. The unsaturated and the saturated zones are both polluted. Because of the abundance of Pb values it was decided to analyze the lead distribution in the studied zone. In many studies of the polluted sites, the geometry of the investigated volume is highly anisotropic. Generally we have an extension of some hectares in the horizontal plane and of a few meters in depth. It is likely that different horizontal spatial continuity structures in pollution distribution are found at different depths both for the layered nature of the medium and for the transition between unsaturated and saturated conditions. In such conditions the decision to divide a 3D problem into 1D and 2D problems can be useful. Initially the studied volume was divided into seven layers up to 5 m in depth; the study was then approached in two phases. First, the Pb values in the vertical direction were analyzed, considering a derive along z, and estimating the values using the Kriging with Trend (KT) method. Thus it was possible to increase the data in the z direction, especially in the deeper layers. Second, 500 realizations of the Pb distribution for each of the seven layers were simulated using the simulated annealing procedure. Finally, results were presented and discussed for each layer in terms of median and probability maps.     

A procedure for landslide susceptibility zonation by the conditional analysis method

Numerous methods have been proposed for landslide probability zonation of the landscape by means of a Geographic Information System (GIS). Among the multivariate methods, i.e. those methods which simultaneously take into account all the factors contributing to instability, the Conditional Analysis method applied to a subdivision of the territory into Unique Condition Units is particularly straightforward from a conceptual point of view and particularly suited to the use of a GIS. In fact, working on the principle that future landslides are more likely to occur under those conditions which led to past instability, landslide susceptibility is defined by computing the landslide density in correspondence with different combinations of instability factors. The conceptual simplicity of this method, however, does not necessarily imply that it is simple to implement, especially as it requires rather complex operations and a high number of GIS commands. Moreover, there is the possibility that, in order to achieve satisfactory results, the procedure has to be repeated a few times changing the factors or modifying the class subdivision. To solve this problem, we created a shell program which, by combining the shell commands, the GIS Geographical Research Analysis Support System (GRASS) commands and the gawk language commands, carries out the whole procedure automatically. This makes the construction of a Landslide Susceptibility Map easy and fast for large areas too, and even when a high spatial resolution is adopted, as shown by application of the procedure to the Parma River basin, in the Italian Northern Apennines.