# Blasting of Unstable Rock Elements on Steep Slopes
## 1 Introduction
Alternative methods, such as slope reinforcement, may be more suitable depending on the site's specific circumstances. It is essential to consider all available options and consult experienced professionals to determine the most effective approach for improving safety conditions on unstable rock slopes. When addressing unstable rock elements on slopes, it is essential to conduct thorough site assessments, consider the underlying geology and hydrology, and prioritize safety at all times. Implementing a combination of stabilization measures tailored to the specific site conditions can help mitigate risks and ensure the long-term stability of the slope. In a simplified approach, it should be possible to design ordinary blasting and controlled blasting. Ordinary blasting works for tunnel excavation, quarry production, etc., and is associated with well-coded parameters as result of many experiences over the years, depending on the available techniques and results obtained. These parameters are mainly geometrics (blasthole diameter, blasthole depth, spacing, burden, etc. ), but there is a synthetic parameter that reflects the characteristics of the blasting, the rock features, and the fragmentation to be obtained, which is the powder factor (PF), which can be defined as the weight of explosives used (in kilograms) per broken rock volume (in cubic meters) [2]. Generally, the PF is a crucial parameter in blasting design, as it helps to determine the amount of explosive needed to efficiently break the rock while minimizing waste and controlling the fragmentation size. A higher PF generally results in more energy being applied to the rock, which can lead to larger fragmentation and better productivity in some cases. However, excessive powder factors can lead to overbreak, increased vibration, and environmental concerns. The optimal PF depends on various factors such as the rock type, geology, desired fragmentation, environmental considerations, and safety requirements. The PF can be estimated and adjusted based on these factors to achieve the desired results with minimal adverse effects. Controlled blasting techniques aim to take great care of the resulting profile, to avoid damage to rock surfaces left in place, and to minimize induced vibrations; they are used to efficiently distribute explosive charge in the rock mass volume, thereby minimizing the fracturing of rock beyond the crestline of the highwall or designed boundary of main excavation zones. The value of the PF hinges significantly on the presence or absence of free surfaces that facilitate the blasting process. Rock blasting leads to volume expansion. When a free surface is available, this volume increase can dissipate outward. Otherwise, in scenarios lacking a free surface, additional energy is required to displace the broken material and create space for the material blasted sequentially by a series of micro-delayed mines. This fundamental principle underscores why, as a rule, a blind tunnel excavation typically yields shows higher PF values compared to a stepped quarry configuration [1]. In the latter, where a free surface extends for the entire height of each step, the possibility of material displacement is notably enhanced. In standard geometric situations, the PF has become a synthetic control parameter indicative of the accuracy of the blasting design. In more complex cases, where the geometry is irregular and the presence of free surfaces varies from case to case, it is much more difficult to standardize the PF and then use it as a control parameter. Typically, the demolition of unstable blocks on a slope reflects this last situation, with shapes, positions, geological and structural characteristics, and free surfaces being extremely variable from case to case. Blasting for isolated rock elements differs significantly from other projects, such as quarry or tunnel blasting, due to its focus on minimizing collateral damage and ensuring post-blast stability.