In the Montserrat Massif (in Catalonia, NE of Spain) a common mechanism of rockfall generation is the differential erosion of thin weak layers, composed by fine-grained rocks commonly described as lutites or mudstones, interleaved within the conglomeratic rock mass which shows a long-term durability. Both materials are terrigenous and detrital clastic rocks, formed in an alluvial fan delta during the Eocene epoch, and exhibit very different behavior against weathering. This difference is explored in the laboratory through durability tests, before and after being subjected to freeze-thaw and wetting and drying ageing tests, and then correlated with theirs textural and mineralogical properties. The findings allow to explain the morphologies and detaching mechanisms observed in the field. The laboratory tests performed are X-ray mineralogical analysis, petrographic analysis of thin sheet samples, simple compression with strain gauges, Brasilian indirect tensile strength, Slake durability, and ageing by freeze-thaw and wet-dry cycles. Five different detrital textures from conglomerate to fine sandstone with muddy matrix (wackestones) have been identified and grouped into two main geotechnical units related to rockfall dynamics. On the one hand, the rock blocks of conglomerate and coarse sandstone susceptible to fall; on the other hand, the weak levels producing under digging of the previous ones formed by fine-sandy wackes and muddy wackes. Despite geomechanical similarities in intact conditions, they differ clearly once weathering cycles are applied by humidity and temperature. Thermal weathering is found as very relevant when explaining the rockfall preparation mechanism leading to toppling. A synoptic model of this mechanism is drawn accordingly. Different influencing factors on the rock block stability are analyzed. Thanks to the monitoring of the rock mass carried out in Montserrat, representative examples of the flexure-toppling mechanism on rock blocks and needles are found. The annual thermal cyclic behavior is shown as composed by elastic and plastic components that evidence the weakening of the base.

In recent years, the historic centre of Florence, enlisted as a UNESCO World Heritage site, has experienced several incidents where fragments have detached from the structural or decorative elements of its historical buildings. Notable examples include the detachment at the Basilica di Santa Croce in 2017 (which led to the death of a Spanish tourist) and the ones at Palazzo Corsini in 2018, at Palazzo Ginori Conti in 2019, and at Palazzo Pucci Sansedoni in 2020. The detachment phenomenon is a common issue in urban areas where stone materials are used in historical constructions; Florence`s stone-built heritage, however, presents unique characteristics that amplify the risk of significant detachments. Specifically, the types of sandstone used in Florentine historical constructions, known as "Pietraforte" and "Pietra Serena," contribute to the increased risk of sudden collapses due to specific attributes that make them susceptible to detachment and structural instability over time. For example, convolute laminations and calcite veins, typical macroscopic characteristics of Pietraforte, often represent critical discontinuities in an otherwise compact matrix. Currently, the detachments issue has been managed through continuous monitoring and periodic removal of loose and instable material. However, this approach is not cost nor time effective and fails to provide a sustainable long-term solution for both the preservation of UNESCO World Heritage List monuments and the safety of visitors. The existing safety regulations and protocols do not offer specific guidelines for interpreting and addressing these detachment phenomena, so the personnel in charge of emergency safety interventions must rely on empirical assessments, lacking comprehensive recommendations for dealing with the complexities of these natural and variable materials. To better understand and address this problem, a new approach is therefore needed and its foundations are presented in this study. To address the lack of specific risk assessment methods for these unique facades within existing protocols, we propose the adoption of a rock mechanics perspective to adequately account for the diverse lithologies and their variable mechanical behaviour. By utilizing tools from slope stability and rock mass analysis, such as intact rock characterization via NDT (Non-Destructive Testing) surveys and discontinuity characterization trough geomechanical survey and Point Clouds analysis, we aim to define risk parameters that are more suitable for these particular structures, establishing the operational framework for a diagnostic protocol that aids decision makers to better direct and assess the need for conservative and safety interventions.

The depletion of mineral reserves has led to deeper underground mining which comes with challenges such as rockbursts, large deformations, and inaccurate dilution estimations. Therefore, stope stability remains a significant safety factor in underground deep mining. In fact, assessing the stability of stopes is essential to better predict instabilities and sloughing around the excavations. This study compares the stability analysis of open stopes using stability graphs and numerical modelling, to evaluate the effect of different variables on the stability of excavations. The study concludes that using stability graphs alone does not suffice to determine stope stability; numerical modeling is also essential to complement the findings. Additionally, the stability analysis of a stope in a 1000 m deep mine will differ from a stope in a 2000 m deep mine, with similar geometry and geological conditions. In conclusion, using the stability graphs in deeper mines may underestimate the stability of the stope.

Stable slope performance is a crucial aspect in the early stage of pit commencement to achieve the plan of ore extraction during the operational phase immediately after complet-ing the feasibility study. Understanding of geotechnical conditions increases with the ex-posure of the excavated slope during pit development. A reliable slope parameter shall be proven once the proposed geometry is correctly applied, resulting in a stable slope. How-ever, on some occasions, unforeseen risks may arise due to limited geotechnical infor-mation during the feasibility study. This paper discusses the efforts performed at the Bozshakol copper mine in the early stages of pit development, including the establishment of geotechnical programs, implementation of control measures for early instability concerns, addressing groundwater issues, interacting with the mine plan for design adjustment processes, and eventually optimizing pit design throughout the development stages.

ABSTRACT: Hydraulic erosion occurring at dam spillways can be critical for the dam struc-ture. Current assessment methods rely on empirical correlations between water erosive force and rock mass resistance, yet they stem from limited data, affecting their accuracy. This problem is addressed by using a laboratory-scale physical model simulating spillway condition. This model assesses various rock mass parameters, including water pressure, joint characteristics, and block size. By modifying concrete block arrangements, different geomechanical conditions are repre-sented, allowing pressure evaluation. Key parameters like joint opening and orientation, and block shear strength are studied in various conditions. The model's test section, equipped with pressure sensors, facilitates an analysis of hydraulic erosion processes, enhancing our understanding of spillway rock mass erosion dynamics. This innovative model promises a better evaluation of hy-draulic erosion's complexities, a crucial aspect of effective spillway design and maintenance.

Hoek-Brown failure criterion is one of the most widely used failure criterion for rocks in the world. For its use, the mi empirical parameter for a specific rock type is needed. To determine the mi constant, a triaxial test is recommended, which gives a linear relationship s1-s3. How-ever, the full stress path for every rock starts with uniaxial tension and this gives a nonlinear envelope. 55 series of tests are carried out for 4 rock types: sandstone, claystone, limestone and conglomerate - to show what is the difference between the results of the mi determina-tion, using two different approaches. The analysis of the results shows that the consistency with the regression models developed by researchers is higher if using the second set of re-sults – with average tensile strength. So this approach allows to determine the mi parameter more precisely for every tested type of rock.