Rock Boulders Research Articles

Experimental Analysis of Rock Boulder Impacts on Brick Walls to Support Numerical Modelling of Building Damage

Experimental Analysis of Rock Boulder Impacts on Brick Walls to Support Numerical Modelling of Building Damage

DIGITAL INVESTIGATION OF LAMNIFORM SHARK VERTEBRAE FROM THE SIBILLINI MTS. (NORTHERN APENNINES, ITALY)

During the sampling of a stratigraphic section along the shore of the Fiastra Lake (Carg Project - Sheet 313 “Camerino” of the Geological Map of Italy at 1:50 000 scale), a small rock boulder with partially exposed bony material was discovered at the base of a small cliff at the northern termination of the Sibillini Mts. In this area, the classical facies of Umbria-Marche stratigraphic succession are well exposed. The Oligocene-Miocene portion of the succession is represented by the ~200 m-thick Scaglia Cinerea Formation, passing upwards to the ~100 m-thick Bisciaro Formation. The microfossil assemblage has allowed the specimen to be constrained to the lower Burdigalian. The skeletal remains were examined using a CT-SCAN, a non-invasive method that has proven to be highly performing. The analysis revealed some articulated vertebrae, deformed by lithostatic compaction, which are attributed to a shark of the Order Lamniformes. Subsequently, the vertebrae were digitally isolated, extracted from the surrounding matrix, and rendered into three-dimensional prints. Through digital retro-deformation, the body length of the lamniform shark was estimated to be approximately 4 metres. Further considerations on the vertebrae allowed us to infer that the studied shark had similarities to either Isurus oxyrinchus Rafinesque, 1810 or Carcharodon carcharias Linnaeus, 1758. The development of a dead-fall microbial community likely facilitated the preservation of the vertebrae. The studied specimen represents the first occurrence of a lamniform shark in the Lower Miocene of the Umbria-Marche Domain and represents one of the very rare recorded occurrences of lamniforms from the Lower Miocene of Italy.

Morphological analysis of polar landing regions for a solar powered ice drilling mission

Planning of mission toward the lunar polar region is supported here by the analysis and better understanding of the most frequent landforms: craters on the Moon in the polar region between 79.30 and 84.35 southern latitude. This work surveys impact crater morphologies and spatial density based age estimation and slopes for eight earlier selected, large candidate landing regions of the Luna-27 solar powered ice drilling mission at the southern lunar polar region. The morphological, morphometrical, slope and dating analysis provided the following results: The d/D values of craters follow the earlier found d/D trend for larger craters, but there is a scatter in depth values related to the ageing of craters. The occurrence of shallow craters looks to be somewhat more abundant here than at lower lunar latitudes, in agreement with Mahanti et al. (2015). Beside fresh craters, rock boulders also occur at some km sized local topographic elevations, indicating erosion of ∼1 m thick regolith layer by micro-scale impacts roughly on the scale of 100 Ma.Characteristic temporal sequence of change in the morphology of about 100 m-sized craters confirmed earlier results. The sequence starts from the freshest craters, with mass wasting produced stripes in the interior slope, later diminish of high-reflectance proximal ejecta happens, then boulders, and even later elevated rims diminish. The surveyed large terrains showed crater statistics-derived model ages ranged between 3.9 and 4.2 Ga, indicating below a thin pulverised surface regolith layer, the topography of the poorly fragmented bedrock below it still holds the Late Heavy Bombardment aged basement. The equilibrium crater population was possibly identified below the 100–200 m diameter range. Surveying crater retention at >30° slopes indicates exposure of 78–140 Ma for steep terrains, and 330–150 Ma for flat <5° slope surfaces considering the size domain below 100 m diameter. This observation indicates rejuvenation of the top few m thin layer of slopes produces faster mixing than on plains.The surveyed kilometre sized craters formed about 1–2 Ga ago, and show correlation between formation age and depth, indicating an infilling rate around 100 m thickness in 1 Ga duration. This is 2 orders of magnitude larger than the 1–2 m impact driven regolith mixing depth during the same period. Thus, while impact mixing desiccates the shallow top regolith layer, inside km scale craters earlier accumulated ice might still be there shielded by faster rock debris accumulation.The surveyed candidate landing regions were evaluated according to general landing safety, lower temperature (to support ice preservation), and solar illumination (for energy supply). Comparing the eight regions, altogether 5.1% of their total area was found to meet with the threshold values of slope angle below 8°, modelled 1 m deep subsurface temperature below 125 K and at least 20% of time available solar illumination and Earth visibility. The largest continuous area that fulfil the used constraints are present in the candidate LS8 area at −82.70°, −82.72°.

Ice holes microrefugia harbor genetically and functionally distinct populations of Vaccinium vitis-idaea (Ericaceae)

In the mountain terrain, ice holes are little depressions between rock boulders that are characterized by the exit of cold air able to cool down the rock surface even in summer. This cold air creates cold microrefugia in warmer surroundings that preserve plant species probably over thousands of years under extra-zonal climatic conditions. We hypothesized that ice hole populations of the model species Vaccinium vitis-idaea (Ericaceae) show genetic differentiation from nearby zonal subalpine populations, and high functional trait distinctiveness, in agreement with genetic patterns. We genotyped almost 30,000 single nucleotide polymorphisms using restriction site-associated DNA sequencing and measured eight functional traits indicative of individual performance and ecological strategies. Genetic results showed high differentiation among the six populations suggesting isolation. On siliceous bedrock, ice hole individuals exhibited higher levels of admixture than those from subalpine populations which could have experienced more bottlenecks during demographic fluctuations related to glacial cycles. Ice hole and subalpine calcareous populations clearly separated from siliceous populations, indicating a possible effect of bedrock in shaping genetic patterns. Trait analysis reflected the bedrock effect on populations’ differentiation. The significant correlation between trait and genetic distances suggests the genetic contribution in shaping intraspecific functional differentiation. In conclusion, extra-zonal populations reveal a prominent genetic and phenotypic differentiation determined by history and ecological contingency. Therefore, microrefugia populations can contribute to the overall variability of the species and lead to intraspecific-driven responses to upcoming environmental changes.

The use of OBIA and petrography in the study of stone masonry: The case of La Palma, Sierra Nevada de Santa Marta

AbstractIn this case study, rubble masonry walls from the Sierra Nevada de Santa Marta in Northern Colombia were investigated. We applied a combined object‐based image analysis (OBIA), photogrammetry, and petrography method to characterize and determine the provenance of the materials used in three targeted terraces of the archaeological site of La Palma. In situ data acquisition included detailed photographic records and petrographic descriptions of a selected section of masonry walls, as well as mapping of local geological units. Photographs were processed using OBIA. The data obtained allowed characterization and systematization of the constructive elements, via parameters that include architectural function within the construction (headers, stretchers, and wedges), roundness, and lithotype. This methodology enabled us to identify the source of the lithotypes from local rock outcrops (metagranodiorite and schist) as well as rock boulders and cobbles from the nearby riverbeds. The results suggest that pre‐Hispanic communities had knowledge of the properties of the geological resources available in the region, which they used to build masonry that has endured more than five centuries. Vertical differences identified in segments of different terrace walls suggest changes in the constructive process and therefore may serve to determine a construction chronology.

Effect of ore heterogeneity on the ball mill wear rate during a grinding process at gold mines of Saudi Arabia (KSA)

Purpose. The current research aims to study the effect of gold ore grinding on the wear rate of grinding balls. Methods. Six boulder rock samples were selected from some KSA mines; five core samples were taken from each of them to identify the mechanical properties (compressive strength, Young’s modulus, and Poisson’s ratio). These mechanical properties were applied to identify the hardness class of all 30 core samples. Five samples with different mechanical properties from the same boulder sample were milled to study the effect of the compressive strength difference and grinding time on wear rate. Then, six samples were taken from different regions with similar mechanical properties but different petrographic characteristics. They were also milled under the same grinding conditions to study the effect of the microscopic mineral composition on the wear rate. Findings. The results showed that the wear rate increased with the improving mechanical properties and with the increa-sing grinding time. On the other hand, the results based on different microscopic descriptions of the six samples showed that despite similar mechanical properties, the wear rates differed. Petrographic characteristics confirmed the presence of quartz in most of the samples as an associated mineral; it is likely that it has the greatest effect on the grinding ball wear. Originality. The paper proposes a method for investigating ore heterogeneity, which has a major impact on the wear rate during a grinding process, as well as on the reducing costs and improving efficiency of grinding media. Practical implications. The research emphasizes the importance of investigating variables (e.g. ore heterogeneity) other than ball size, grinding medium composition, and wet or dry grinding that have a substantial impact on grinding efficiency. The findings could be applied in feasibility studies to calculate and evaluate grinding costs versus grinding efficiency.

Deep Neural Networks for the Estimation of Masonry Structures Failures under Rockfalls

Although the principal aim of the rockfall management is to prevent rock boulders from reaching the buildings instead of the buildings resisting the boulder impacts, there usually exists a residual risk that has to be assessed, even when structural protection measurements are taken. The evaluation of the expected damage of buildings due to rockfalls using empirical data from past events is not always possible, as transferring and applying damage observations from one area to another can be unrealistic. In order to simulate potential rockfall scenarios and their damage on buildings, numerical methods can be an alternative. However due to their increased requirements in expertise and computational costs, their integration into the risk analysis is limited, and simpler tools to assess the rockfall vulnerability of buildings are needed. This paper focuses on the application of artificial intelligence AI methods for providing the expected damage of masonry walls which are subjected to rockfall impacts. First, a damage database with 672 datasets was created numerically using the particle finite element method and the finite element method. The input variables are the rock volume (VR), the rock velocity (RV), the masonry wall (t) and the masonry tensile strength fm. The output variable is a damage index (DI) equal to the percentage of the damaged wall area. Different AI algorithms were investigated and the ANN LM 4-21-1 model was selected to optimally assess the expected wall damage. The optimum model is provided here (a) as an analytical equation and (b) in the form of contour graphs, mapping the DI value. Known the VR and the RV, the DI can be directly used as an input for the vulnerability of masonry walls into the quantitative rockfall risk assessment equation.

A New Insight into the Stability of Precariously Balanced Rocks

Large granitic boulders resting on steep slopes represent considerable safety hazards that largely depend on the location of the contact surface characterized by the impression d, denoting the parallel distance between the contact surface and the original rock surface. On the other hand, this impression reflecting the often convex nature of the contact between boulders and resting platforms, cannot be measured precisely, so Factors of Safety (FoS) computed with this input may have significant uncertainties. Using geometric 3D analysis, here, we present the concept of computing FoS as a function of the impression d, admitting a much more reliable estimate of the actual hazards. Beyond introducing the FoS functions, we also identify all failure modes, some of which have not yet been investigated. We compute the FoS functions for the boulder Pena do Equilibrio, located in Spain. Our computations for FoS against sliding match all earlier results. However, we also compute FoS against toppling and against torsion and show that the latter may be critical. Since our methods are general, this suggests that torsion phenomena, which have been scarcely studied so far, may be relevant to analyze the stability of other natural rock boulders.

Melt migration in rubble-pile planetesimals: Implications for the formation of primitive achondrites

Primitive achondrites represent residual mantle material of planetesimals from which up to 20% partial melts were extracted. Melting experiments on chondritic compositions suggest that melts produced by ≲20% partial melting are rich in silica and alkali elements. Such melts are highly viscous (≳103Pa⋅s), and percolation models predict that they would only migrate negligible distances over timescales of 1–10Myr. After these timescales, a planetesimal would either be melted into a magma ocean by radiogenic heating from Al26, if it formed early; or it would cool below solidus, if it formed relatively late. However, melt migration is also controlled by permeability, which could be high for aggregates of rock boulders (compared to those of mineral grains). Specifically, the theory of planet formation suggests that collisions occurred frequently between planetesimals in the early solar system. These collisions may have shattered the planetesimals into fragments with sizes of meters to tens of meters, which would have accreted gravitationally into one or more daughter bodies. We develop a model to investigate melt migration in “rubble-pile” planetesimals; in particular, the melt exchange between partially molten rock boulders and the void space between them. The results suggest that, with typical properties of primitive achondrite materials at the conditions of low-degree partial melting, melts may have been squeezed into the voids between boulders, and migrated rapidly through these channels. Therefore, primitive achondrites may record melt migration in rubble-pile bodies reaccreted from fragments of partially molten planetesimals.

Rockfall Intensity under Seismic and Aseismic Conditions: The Case of Lefkada Island, Greece

Rockfall analysis is a multiparametric procedure with many uncertainties and the outputs are largely dependent on some critical engineering geological parameters involved in the used simulation model. In this paper, three completely different limestone rock sequences, named Pantokratoras, Vigla, and Paxos limestones along the western coastal slopes of Lefkada island, in Greece, are examined regarding their rockfall susceptibility as expressed by produced kinetic energy, under aseismic and seismic conditions. A rockfall inventory was prepared through detailed field measurements after the extensive rockfalls which were caused by the strong earthquake of November 2015, while engineering geological surveys were systematically conducted on the limestone rock masses. Two case scenarios were adopted for the rockfall simulations: one without the horizontal initial velocity of the detached rock boulder and the other with an estimated value obtained from the peak ground velocity (PGV) of the main seismic shock. Two-dimensional rockfall simulations were performed in selected cross-sections for each rock mass, and spatial distribution maps of the intensity (kinetic energy) were generated. A comparison of the maps has shown a strong maximum variation in the intensity levels among the three rock masses mainly due to the differential size of the detached boulders because of the inherent engineering geological characteristics of the rock masses. The results show that the earthquake ground velocity generally leads to a fluctuating change in the intensity values due to the trajectory shape and increases the rockfall magnitude as the main triggering factor.

Static and Dynamic Stability of Rock Boulders on Slopes

The authors have been involved with the risk assessment of cliff failures as well as mobilization of rock boulders on slopes nearby settlements and roadways in Miyagi Island in Okinawa Prefecture of Japan. The main purpose of this study is to evaluate the de-stabilization of rock boulders with regular and irregular shape due to forces resulting from earthquakes as well as groundwater. A shaking table was used to investigate the motions to cause the destabilization of rock boulders made of Ryukyu limestone on flat and sloping base made of weathered sandstone beneath limestone cliffs in Miyagijima Island. Furthermore, some analytical and numerical computations were carried out to simulate the experimental results. The outcomes of these investigations are presented and discussed in this paper.

Armourstone Quality Analysis for Coastal Construction in Chabahar, Southeast Iran

Natural stones (armourstones) of varying sizes and qualities are frequently used to construct breakwaters to protect coastal engineering structures from wave actions for economic reasons. Time-related armourstone deterioration in the form of abrasion and disintegration may result in structural damage. Therefore, it is necessary to investigate the performance and quality of the armourstones, which should be robust and long-lasting. The study aimed to examine the quality of two distinct types of rocks from three breakwaters used as armourstones in the Chabahar region and compare the results to the observed field performance. This study aimed to illustrate why it is crucial to characterise rocks thoroughly before deciding which ones to use in a particular project and to evaluate how well current classification techniques account for the observed field performance of stones that may have complex geological compositions. The physical and mechanical properties of the rock were evaluated through both on-site observation and laboratory testing. The results indicated that the class of rocks used in the breakwater had a wide range of suitability ratings. It was discovered that sedimentary rocks have the best water absorption and porosity properties. In addition, age is a positive factor, as the rate of destruction decreases with age. Component and particle size can also play a role in lithology, which is a significant factor in the rock’s durability. Also, the findings demonstrated that the marine organisms in the rock component play an important role in the stability of these structures, even though rock mass breakwaters are less qualified for breakwater construction as per international coastal engineering standards. According to the findings, a breakwater made of lumachel rock boulders, or alternatively sandstone boulders, will last the longest.

Alpine rock glacier activity over Holocene to modern timescales (western French Alps)

Abstract. Active rock glaciers are some of the most frequent cryospheric landforms in midlatitude high-elevation mountain ranges. Their activity strongly influences the hydrology and geomorphology of alpine environments over short (years to decades) and long (centuries to millennia) timescales. Being conspicuous expressions of mountain permafrost and important water reserves in the form of ground ice, rock glaciers are seen as increasingly important actors in the geomorphological and hydrological evolution of mountain systems, especially in the context of current climate change. Over geological timescales, rock glaciers both reflect paleoclimate conditions and transport rock boulders produced by headwall erosion, and they therefore participate in shaping high mountain slopes. However, the dynamics of rock glaciers and their evolution over different timescales remain under-constrained. In this study, we adopt a multi-method approach, including field observations, remote sensing, and geochronology, to investigate the rock glacier system of the Vallon de la Route (Combeynot Massif, western French Alps). Remotely sensed images and correlation techniques are used to document the displacement field of the rock glacier over timescales ranging from days to decades. Additionally, to estimate displacement over periods from centuries to millennia, we employ terrestrial cosmogenic nuclide (quartz 10Be) surface-exposure dating on rock boulder surfaces located along the central flow line of the rock glacier, targeting different longitudinal positions from the headwall to the rock glacier terminus. The remote sensing analysis demonstrates that between 1960 and 2018 the two lower units of the rock glacier were motionless, the transitional unit presented an integrated surface velocity of 0.03±0.02 m a−1, and the two upper active units above 2600 m a.s.l. showed a velocity between 0.14±0.08 and 0.15±0.05 m a−1. Our results show 10Be surface-exposure ages ranging from 13.10±0.51 to 1.88±0.14 ka. The spatial distribution of dated rock glacier boulders reveals a first-order inverse correlation between 10Be surface-exposure age and elevation and a positive correlation with horizontal distance to the headwall. These observations support the hypothesis of rock boulders falling from the headwall and remaining on the glacier surface as they are transported down valley, and they may therefore be used to estimate rock glacier surface velocity over geological timescales. Our results also suggest that the rock glacier is characterized by two major phases of activity. The first phase, starting around 12 ka, displays a 10Be age gradient with a rock glacier surface velocity of about 0.45 m a−1, following a quiescent period between ca. 6.2 and 3.4 ka before the emplacement of the present-day upper two active units. Climatic conditions have favored an integrated rock glacier motion of around 0.18 m a−1 between 3.4 ka and present day. These results allow us to quantify back-wearing rates of the headwall of between 1.0 and 2.5 mm a−1, higher than catchment-integrated denudation rates estimated over millennial timescales. This suggests that the rock glacier system promotes the maintenance of high rock wall erosion by acting as debris conveyor and allowing freshly exposed bedrock surfaces to be affected by erosion processes.

Hydrodynamic Performance Assessment of a Geo-Synthetic Seawall

In the recent years, various geo-synthetic components find an extensive application in civil and coastal engineering practice. Commonly, geo-synthetics have a wide application for secondary or tertiary purposes, such as filtration, separation, barrier, reinforcement, whereas, they can be potentially exploited for various other applications in the coastal engineering practice. A sustainable seawall cross-section comprising different geo-synthetic products was proposed to be erected along the Pallana Beach ([Formula: see text] N and [Formula: see text] E), located in Alleppey district of Kerala along the south-west Indian coastline. Since the subsoil at the location is poorly graded, it was decided to replace the conventional materials like rock boulders and concrete armour units with geo-synthetic products. A comprehensive physical model study was conducted to assess the hydrodynamic performance (i.e. reflection, run-up, and pressure distribution) of the geo-synthetic seawall cross-section for a wide range of random wave characteristics and two water depth conditions. The relative overtopping rates for the seawall at varying water levels are computed conservatively from the guidelines prescribed by the EurOtop Manual and XGB Overtopping model.

An analytical method for the impact force of a cubic rock boulder colliding onto a rigid barrier

An analytical method for the impact force of a cubic rock boulder colliding onto a rigid barrier

Мобильный локализатор для разрушения негабаритов

Research objective: Development and implementation of a mobile safety screen for secondary breaking. Research methodology: Analysis of secondary breaking of oversize boulders. Research results: blasting creates oversize chunks of rock (boulders) in the pit walls and floor, which affects the productivity of the pit and the mining operation as a whole. Open pit mines with large volumes of rock formations have to handle hundreds of cubic metres of boulders every day bearing significant labour and material costs of these activities. Various methods of boulder breaking are used in open pit mining, including electrical treatment, mechanical impact, blasting, etc. A common disadvantage of these techniques is their relatively low capacity. Out of all the applied methods, drilling and blasting of boulders is the most effective, but the use of this method is limited due to the use of various equipment, increased hazards and the presence of certain other disadvantages. The autonomous mobile safety screen has been developed to solve this bottleneck. The use of this safety screen enables breaking boulders using blasting techniques, reduces the size of the hazardous area, increases the efficiency of the air shock waves, prepares safety trenches in open pits and for road construction, prepares the rock mass for long-distance transport by road or railways. Conclusions: The use of this safety screen enables breaking boulders using blasting techniques, reduces the size of the hazardous area, increases the efficiency of the air shock waves, prepares safety trenches in open pits and, during road construction, prepares the rock mass for long-distance transport by motor and railroads.

Laboratory physical modelling of block toppling instability by means of tilt tests

In this paper we present a physical modelling approach where the stability of rock blocks against toppling in the field can be estimated using a tilt table, engineered rock models and 3-D-printed small-scale versions of a natural rock boulder. To achieve this goal, first, simple geometry rock elements are tilted and results interpreted according to analytical formulations. Then, more complex geometry engineered rock blocks, including some whose centers of gravity do not project on the center of the base element, are tested and results properly interpreted. Eventually, the 3-D-printed version of the rock boulder is produced from 3-D point clouds recovered in the field by means of a combination of photogrammetry and laser scanner techniques. Analytical formulations and numerical calculations have been used in order to validate the proposed approach, to explain the physical phenomena involved, and to allow for possible extension of the physical modelling results to different scenarios, such as those considering the influence of water or seismic loading on stability.

Assessing the uniaxial compressive strength and tangent Young’s modulus of basalt rock using the Leeb rebound hardness test

Basalt was used as an ornamental stone in any historic and ancient cities in Jordan. Measuring the uniaxial compressive strength (UCS) and the tangent Young’s modulus (Et) in the laboratory requires premium quality specimens with special core dimensions. This research focuses on correlations both UCS and Et with Leeb Rebound Hardness Test (LRH). In the laboratory, UCS, Et, and LRH were performed on 90 core samples extracted from 30 different rock boulders collected from the neighboring area of Umm al-Jimal, a historic city in northeastern Jordan. A strong power correlation with (R2 = 0.888, RMSE = 5.464) was found between non-destructive LRH value and UCS. On the other hand, a moderately strong linear regression with (R2 = 0.792, RMSE = 4.661) was found between Et and LRH. In conclusion, non-destructive LRHs can be used as indictors for evaluating both UCS and Et during the restoration of the historic city Umm al-Jimal and the rehabilitation of other existing structures.

Collision of Shaped Boulders With Sand Substrate Investigated by Experimental, Stochastic, and Discrete Approaches

This paper focuses on experimental and numerical studies aiming to better characterize the rebound kinematics between a natural soil and rock boulders using single‐block collision models. The variability of the dissipative parameters needed to reproduce the experimental results was studied considering two different approaches: stochastic transfer matrix and discrete element model (DEM). An experimental process taking into account all possible variables related to the collision was setup for small‐scale tests involving cylindrical and triangular boulders that introduces natural variability during impact. The objective of the experimental tests is to identify the relationship between incident and reflected velocities (before and after impact, respectively), in order to improve the predictability of the two numerical proposed approaches. The experimental results help to quantify the amount of energy losses during impacts and thus expands the knowledge to reproduce more realistic rockfall events. This work is divided in three main axes: (i) statistical analysis of experimental trajectories based on experimental tests; (ii) stochastic approach predicting in a simple way from initial velocities the kinematic of blocks after rebounds; and (iii) calibration of a discrete element model including probabilistic analysis based on Monte Carlo approach. This way, the two collision approaches presented in this work are able to predict rebounds in terms of averages, standard deviations, and distributions.

Coupled geomechanical classification and multivariate statistical analysis approach for the optimization of blasting rock boulders

The prediction of blasting rock boulder in discontinuous rock is crucial for the optimization of blasting operations. Therefore, it is necessary to understand the role played by the geological features of a rock mass in controlling oversize fragments. This research is the result of coupled use of multivariate analysis methods and geomechanical indexes in order to identify the main rock mass and blast parameters that affect directly the oversize boulder production during blasting operations. The aggregate quarries selected for this study belong to the Eocene and the Jurassic rock in Tunisia. Diverse techniques were used as atomic absorption, XR diffraction, microscopic study, mechanical test, and scanning electron microscopy image to identify rock matrix. The methodology established by cluster analysis generated from mechanical classification as rock quality designation, rock mass rating, Q-Barton index, and strength index makes possible to classify the studied rock into three classes. A principal component analysis method developed in XLSAT 2018 has been performed on various blast design parameters to illustrate the relation between blasting and rock parameter. For the prediction of oversize fragment resulting from the blasts, a specific formula for every quarry was generated by statistical method. The proposed formulas can be considered as sufficient with an accuracy of more than 80% of the blasted rock after model testing compared with precise boulder percent in twenty blasts.