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Rock mass is typically characterized by inherent fractures that cause natural blocks of rocks. Unplanned cutting of stone deposits in quarries may lead to over-producing waste (rock debris) or extracting unfi t (fractured) stone blocks. This paper presents two case studies through the use of low and high frequency Ground Penetrating Radar (GPR) antennas to detect fractures in two benches of a quarry. In the fi rst case study, a high frequency GPR antenna was used aiming to: (i) compare the GPR results with a map of the out-cropping fracture intensity in the bench surface, developed using the data of the GPR survey marks and interpolated by the Ordinary Kriging technique, and (ii) present how sub-vertical fractures can be numerically modelled in three dimensions from the GPR results. The second case study was focused on using a low frequency antenna to detect large aperture size of fracture surfaces as deep as possible in order to evaluate a deposit stratum before quarrying. This could be done through studying the refl ections from a 3D cross-sectional GPR model and a 3D transparent GPR model. In the discussion section, an exploitation planning approach, based on modelling fractures as 3D surfaces, is theoretically and graphically proposed to optimize the stone production recovery. The two case studies showed that GPR is a successful tool for the assessment of ornamental stone deposits and a promising tool for recovery optimization.

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Rock mass fractures adversely affect the production of ornamental stone quarries. Fractures cause natural rock blocks, which threaten extraction of the required commercial block size of ornamental stones. Accurate subsurface detection and modeling of fractures are required for pre-exploitation evaluation and planning. This paper introduces a new three-dimensional deterministic fracture modeling approach using ground penetrating radar (GPR) as a data acquisition tool. A case study was performed in a fractured bench of a sandstone quarry in Firenzuola, Italy, using a 400 MHz GPR antenna. To accurately detect fractures at true depth, an in situ calibration based on previous knowledge of the depth of a subsurface reference reflector allowed us to estimate a bulk dielectric constant of the rock mass during the time of data acquisition. A data interpretation tracing technique was developed to model fractures as 3-D surfaces in two forms, either irregular or planes. The modeled fractures were visualized through a multi-platform visualization software package (ParaView). A comparison between the orientations of the fractures measured by the traditional manual method and the orientations of the modeled fractures is presented as a possible geologic validation for the detection and interpretation of fractures. For the objective of pre-exploitation evaluation, a distribution analysis provided an evaluation-based fracture index for the bench in the case study.

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Timber elements are major structural and architectural components in historic buildings and at the same time belong to the category of materials vulnerable to degradation. The recovery of 150-year old timber beams from a roof of a historic building made possible the nondestructive investigation of their response to cyclic loading. The experimental study carried out using the acoustic emission technique provided evidence that historic wood shows the load memory known as the Kaiser effect. The effect was observed for different loading and unloading time windows. The observations open up a new perspective for the determination of defects in wooden objects and constructions, important for assessing their possible structural instability. Kaiser-Effekt in historischen HolzbalkenZusammenfassung Holz ist ein wichtiger tragender und architektonischer Baustoff in historischen Gebäuden, aber gehört gleichzeitig zur Kategorie zerstörungsanfälliger Materialien. An 150 Jahre alten Holzbalken aus dem Dach eines historischen Gebäudes konnte deren Verhalten bei zyklischer Belastung zerstörungsfrei untersucht werden. In Laboruntersuchungen konnte mittels Schallemissionsanalyse nachgewiesen werden, dass historisches Holz das als Kaiser-Effekt bekannte Erinnerungsvermögen an frühere Belastung aufweist. Dieser Effekt wurde bei unterschiedlichen Belastungs-und Entlastungszyklen beobachtet. Diese Ergebnisse eröffnen neue Perspektiven hinsichtlich der Bestimmung von Schäden in Holzbauteilen und -konstruktionen, was für die Beurteilung eventueller baulicher Instabilität wichtig ist.