Hard Rock Samples Research Articles

Design and performance investigation of an underwater ultrasonic percussive drill for seabed mineral exploration

Abstract To address the limitations of traditional drilling equipment, such as large size, high power consumption, and difficulties with waterproofing, an underwater ultrasonic percussive drill (UUPD) based on piezoelectric drive is proposed. The structure and size parameters of the piezoelectric actuator are designed and its performance is experimentally verified. The maximum output amplitude of the piezoelectric actuator is 78.6 μm in air and 52.3 μm in water. Additionally, the dynamic characteristics of the UUPD are calculated theoretically and analyzed by simulation, and the influence of system parameters on vibration characteristics is revealed. A prototype of the UUPD is developed, and a performance testing platform is established, and drilling comparison experiments and power consumption test are carried out to evaluate the performance of the UUPD. Experimental results demonstrate that the UUPD is capable of breaking rocks with varying hardness (5 MPa–50 MPa) under small drilling pressure (around 6 N) and low power consumption (approximately 57 W). The UUPD proposed in this paper offers advantages, including low drilling pressure, low power consumption, light weight and compact structure, showing a good application prospect and providing an effective technical means for deep-sea hard mineral rock drilling and sampling.

Geological and Geomechanical Characterization of Phosphate Mine Waste Rock in View of Their Potential Civil Applications: A Case Study of the Benguerir Mine Site, Morocco

Sedimentary phosphate extraction in open-pit operations generates large volumes of waste rock (WR), which are mainly overburdens and interburdens. Traditionally, the WR is mixed and stored on the surface in waste rock piles (WRPs). This paper presents a case study of the Benguerir mine site in Morocco. It investigates the potential valorization of each WR lithology based on the geological and geomechanical properties to reduce their environmental footprint and create added value to “waste.” The WR samples (soils and rocks) were collected from drill cores and mining trenches in the Benguerir mine. The geological characterization results using petrographic descriptions indicate the presence of nine phosphate layers and, in addition to the overburdens, eight interburdens. Four types of WR are identified: carbonate, siliceous, marly clay, and phosphate. The geomechanical characterization of soil-like samples showed an average plasticity index (PI) of 50% according to the methylene blue value (MBV) of 7.1, classifying them in the A3–A4 categories as plastic and clayey marl soils. The hard rock samples have excellent mechanical properties in terms of their uniaxial compressive strength (UCS), Los Angeles abrasion value (LA), and micro-Deval value (MD). The average compressive strength is 104 MPa for the flint, 35 MPa for the phosphate flint, 32 MPa for the silexite, 26 MPa for the limestone, 11 MPa for the indurated phosphate, and 8 MPa for the marly limestone. Based on the obtained results, these WRs can be considered as an excellent alternative secondary raw material for use in civil engineering applications, ceramics, and cement industries.

Оценка удароопасности скальных горных пород Ждановского месторождения (Кольский полуостров)

he paper presents the results of uniaxial and triaxial compression tests of hard rock samples from the Zhdanovskoe deposit. Two criteria were used to assess the tendency of rocks to fail in dynamic mode (rockburst hazard). In the first case, the A.N. Stavrogin's criterion was used, which requires testing of specimens using “rigid” presses. In the second case, the criterion developed at the Mining Institute of the Kola Scientific Center of the Russian Academy of Sciences was applied to estimate the rockburst hazard of rocks based on the test results of samples using the standard presses. It is shown that the studied rocks of the Zhdanovskoe deposit are prone to failure in dynamic mode according to the two criteria considered. It was found that with the transition from uniaxial to triaxial compression conditions at the lateral pressures up to 40 MPa, the tendency of rocks to dynamic failure is maintained.

Experimental investigation of multiple rock indentations on hard rock using a conical cutter at different cutting depths

To apply roadheaders to deep hard rock mines, one must investigate the influence of multiple rock indentations and cutting depths on rock breakage. In this study, multiple rock indentations using a conical cutter were performed on hard rock samples at different cutting depths. The relationship between the cutting depth and the parameters reflecting the rock cuttability was regressed. The experimental results of the single and multiple rock indentations were compared. They showed that the failure pattern affects the cutting parameters. In the case of partial splitting, the cutting parameters increase with the increase of the cutting depth. Meanwhile, in the case of complete splitting, the force and the work required to break the rock did not show any obvious relationship with the cutting depth, but were directly proportional to the area of the formed fracture surface. Moreover, the free and fracture surfaces formed by multiple rock indentations facilitated the subsequent rock breakage.

Arsenic fate in upper Indus river basin (UIRB) aquifers: Controls of hydrochemical processes, provenances and water-aquifer matrix interaction

Major river basins of the Himalayas contain a significant amount of arsenic (As) in the geological matrix, which tends to contaminate the groundwater at a local and regional scale. Although As enrichment in Quaternary deposits has been linked to primary provenances (Himalayan orogeny), limited studies have reported As enrichment in bedrock aquifers. In the present study, the hard rock and groundwater samples were collected across the upper Indus river basin (UIRB), Ladakh to assess the hydrogeochemical processes and environments responsible for As mobilization and release. The higher As concentrations were found in Khardung volcanics followed by Ophiolitic melange, Dras volcanics, Nindam sandstone, and Nindam Shale. The variability in As concentration among different rock samples is largely governed by the presence of felsic minerals and the type of magmatic setting. The groundwater is less mineralized, with moderate electrical conductivity (EC), and weakly acidic to alkaline in nature. The results indicated that mineral weathering, dissolution, and active cation exchange reactions have a strong influence on the major ion chemistry of the groundwater. Redox-sensitive processes are influencing the As mobilization and release under reducing environmental conditions. As in groundwater poses a serious threat to human health hence awareness is urgent towards achieving sustainable As mitigation globally. The study provided a significant dataset to better understand the processes and environmental conditions responsible for hydrogeochemical evolution, sources of solutes, and As mobilization and release in groundwater which will help in sustainable water resource management policies and ecosystem restoration across the Himalayas.

Experimental study of the effect of cooling/lubricating fluids on penetration rate in hard and soft rock drilling process

Rock drilling is the process of penetrating and crushing rocks, which is characterized by the low rate of penetration (ROP) and drilling rate because of the amount of cuttings that remain in the drilling environment and the thermal stresses generated at the bit-rock interface. Any improvement in ROP and drilling rate can be of great technical and economic value for drilling projects. ROP can be improved through the proper use of cooling-lubricating fluids during drilling. ROP is a key indicator of drilling performance and the ability to predict this rate can be very useful for mining projects. ROP prediction can also be used to estimate the total cost of a drilling operation. ROP depends on a variety of parameters, which, when available, can be used to estimate ROP. To reach a better understanding of the parameters affecting ROP and how it can be optimized, in this study, the results of 492 laboratory drilling tests were analyzed by linear and nonlinear multivariate regression in SPSS to build a number of models for ROP prediction. These tests were conducted on seven soft and hard rock samples while using six fluids as the cooling-lubricating agent. The tests were performed with a laboratory-scale drilling rig on cubic specimens at several different rotation speeds and thrust forces. The results showed that the drilling achieved significantly higher ROP in the presence of the cooling-lubricating agent. After reviewing the results, several models that were able to produce ROP predictions with the lowest average estimation error were picked as suitable choices for predicting ROP in the presence of cooling-lubricating fluids. The results of statistical tests of these models showed with over 90% confidence that they can produce highly accurate ROP estimates based on mechanical properties of the rock, physical characteristics of the cooling-lubricating fluid, and operating parameters of the drilling rig.

Numerical Study of Skin Friction Behavior of Piles in Limestone Rock

An effective tool for studying the behavior of the skin friction of piles in a rock formation is through a numerical analysis. Four pile load experiments were conducted on hard limestone rock samples to describe the behavior of the load transfer solely through the skin friction on reinforced concrete piles with different diameters and lengths. Finite element analysis was performed using PLAXIS 3D software to simulate the models and verify the experimental results. The parameters used to simulate the model were obtained from laboratory experiments on the samples or calculated from empirical formulas. The piles were subjected to an ultimate axial load until reaching failure, which was determined based on loosening of the skin friction. No end bearing resistance was considered because a soft material was placed beneath the pile. The results of this study include a comparison between the load-displacement curves for the experimental and numerical analyses. As the results of the numerical analysis indicate, the calculated results from the numerical study are very close to those measured from the pile load experiments.

Benthic foraminifera of the Maastrichtian sediments from the Maliboğazi (Kalecik, Ankara) and Irmak (Kırıkkale) areas in Türkiye

The investigation focuses on benthic foraminifera and their paleoecology, particularly on the Orbitoides genus in the Maaastrichtian sediments from the northern and western Ankara City (Turkey). The hard and soft rock samples from two measured sections, namely as Malibogazi (N Ankara) and Daryaka-Irmak (W Ankara, Kirikkale) were evaluated. More than one hundred equatorial and axial sections of the Orbitoides genus were prepared. The benthic foraminifera of the Maastrichtian sediments are as follows: Dorothia sp., Marssonella sp., Lenticulina sp., Saracenaria sp., Oolina sp., Cibicides sp., Gavelinella sp., Orbitoides apiculatus, O. gruenbachensis, O. medius, Pseudomphalocyclus sp., Omphalocyclus macroporus, Lepidorbitoides sp., Sirtina sp., Sulcoperculina globosa, S. vermunti, Siderolites calcitrapoides, Laffitteina mengaudi, Laffitteina sp. In the Malibogazi area, biometric data based on the internal and external parameters of the Orbitoides genus present reliable interpretations for paleoecological approaches of the Maastrichtian time. The calcareous siliciclastics comprise abundant Orbitoides apiculatus and O. gruenbachensis species. We have identified two ichnospecies as Maeandropolydora osmaneliensis and Curvichnus semorbis in the Orbitoides tests. It is thought that meandered microboring activity are related to parasitic life modes while cave shaped ones are associated with hermit type life modes. Orbitoides bearing siliciclastics overlies reefal sediments including biostromal limestones with rich rudist fauna, Thalassoniodes rich carbonates and massive, thick bedded limestones in the Maliboğazi area. In contrast, siliciclastics indicating open sea sediments outcrop widespreadly in the Irmak area. The obtained stratigraphical, sedimantological and paleontological data show that northern part of the Ankara was shallower than western part of the Ankara during the late Maastrichtian.

Experimental study on drilling basalt with small diameter drilling tools

Basalt is one of the potential hard rock targets for drilling sampling in asteroid exploration, and low sampling reaction forces are required in drilling sampling activities of an asteroid. In this paper, the experimental study of drilling basalt with small diameter cemented carbide triangular bit and diamond trepanning drill was carried out, and the drilling thrust force models of basalt drilled by cemented carbide triangular bit and diamond trepanning drill were established, respectively. The ratio of volume removal rate to drilling thrust force was proposed as the evaluation index for the primary selection of drilling tools. The test results showed that the Φ4 mm cemented carbide triangular bit was the preferred small diameter tool for drilling basalt when the minimum drilling thrust force is 40 N. The Φ8 mm electroplated diamond trepanning drill was also the preferred small diameter tool for drilling basalt, Its minimum critical drilling thrust is between 100 and 110 N. Further analysis of the drilling thrust model of the two types of drilling tools showed that the drilling thrust force of cemented carbide triangular bit drilling basalt increased with the feed rate, and it increased with the increase of the apex angle of cemented carbide triangular bit. There was minimum and maximum critical drilling thrust force in drilling basalt with diamond trepanning drill. When the drilling thrust force was between the minimum and maximum critical drilling thrust force, the volume removal rate can be improved by increasing the rotating speed of the diamond trepanning drill. This experimental study helps to optimize the drilling tools and set the drilling thrust force and rotating speed when further studying of hard rock sampling for asteroid drilling.

Towards Representative Metallurgical Sampling and Gold Recovery Testwork Programmes

When developing a process flowsheet, the risks in achieving positive financial outcomes are minimised by ensuring representative metallurgical samples and high quality testwork. The quality and type of samples used are as important as the testwork itself. The key characteristic required of any set of samples is that they represent a given domain and quantify its variability. There are those who think that stating a sample(s) is representative makes it representative without justification. There is a need to consider both (1) in-situ and (2) testwork sub-sample representativity. Early ore/waste characterisation and domain definition are required, so that sampling and testwork protocols can be designed to suit the style of mineralisation in question. The Theory of Sampling (TOS) provides an insight into the causes and magnitude of errors that may occur during the sampling of particulate materials (e.g., broken rock) and is wholly applicable to metallurgical sampling. Quality assurance/quality control (QAQC) is critical throughout all programmes. Metallurgical sampling and testwork should be fully integrated into geometallurgical studies. Traditional metallurgical testwork is critical for plant design and is an inherent part of geometallurgy. In a geometallurgical study, multiple spatially distributed small-scale tests are used as proxies for process parameters. These will be validated against traditional testwork results. This paper focusses on sampling and testwork for gold recovery determination. It aims to provide the reader with the background to move towards the design, implementation and reporting of representative and fit-for-purpose sampling and testwork programmes. While the paper does not intend to provide a definitive commentary, it critically assesses the hard-rock sampling methods used and their optimal collection and preparation. The need for representative sampling and quality testwork to avoid financial and intangible losses is emphasised.

Effects of microfabric on drillability of rocks

Quantifying the rock microfabric is one of the most important research interests and challenges in the field of rock drilling and excavation. In this study, the relationship between quantitative parameters of the rock microfabric and the rate of top-hammer drilling was studied. For this purpose, a drilling operation was performed on five soft rock samples and three hard rock samples and drilling rates were recorded. Thin sections from the rock samples were prepared and micrographs of the sections were reviewed using AutoCAD software and digital boundaries of the grains were clarified and drawn. After preparation and filtering of the digitized thin sections, four basic properties of each grain, including maximum diameter, minimum diameter, area and perimeter, were calculated with the help of the software. These parameters were then analyzed statistically and used to obtain six indexes including equivalent diameter, grain compactness, shape factor, aspect ratio, interlocking index and grain size homogeneity index. Finally, the microfabric and drilling rate data were subjected to regression analysis and the significance of the relationships between the grain parameter values and drilling rate were explored. Drilling rate was found to increase with increasing equivalent diameter and shape factor. In contrast, drilling rate decreased with increasing grain compactness, aspect ratio, grain size homogeneity and grain interlocking index. Grain compactness showed the most significant relationship (R 2 = 0.8) with drilling rate among the studied parameters.

New models to predict rock failure by linking the volume dilatant point with the peak stress point

The rock mass failure process can be divided into several distinct deformation stages: the compaction stage, elastic stage, stable failure stage, accelerated failure stage, and post-peak stage. Although each stage has been well studied, the relationship among the stages has not been established. Here, we establish two models which are the Strain model Q and Energy density model S by using the renormalization group theory and investigate the mechanical relationship between the volume dilatant point and peak stress point on the rock stress-strain curve. Our models show that the strain ratio (e f /e c ) and energy ratio (E f /E c ) at the volume dilatant point and peak stress point are solely functions of the shape parameter m. To verify our models, we further studied the failure process of rock specimens through several uniaxial compression experiments and found that the relationship between e f /e c or E f /E c and m shares a notably similar pattern to that from our theoretical model. However, the e f /e c and E f /E c values in our experiments are slightly smaller than those predicted by the models. In brief, we demonstrate that our models can be used to predict the failure process of the laboratory-scale hard brittle rock samples.

MALATYA OLİGO-MİYOSEN İSTİFİNİN BENTİK FORAMİNİFER BİYOSTRATİGRAFİSİ (DOĞU TOROSLAR, DOĞU TÜRKİYE)

The benthic foraminiferal biostratigraphy of Oligo-Miocene aged Muratli and Petekkaya formations which crop out over wide regions around Akcadag town, west of Malatya province in Eastern Taurids were revealed in this study. Systematical sampling was carried out in measured stratigraphical sections in four locations in order to perform stratigraphical and paleontological investigations. Benthic foraminifera taken from 182 hard rock samples were defined and three biozones were determined as; SBZ 21-22, belonging to Oligocene (Rupelian - Early Chattian), SBZ 23 (Late Chattian) and SBZ 25 belonging to Lower Miocene in shallow marine deposits in the region. It was stated that the assemblage of planktic foraminifer and nannoplankton which stratigraphically detected within Chattian - Burdigalian units in the succession most probably indicated Aquitanian age. Besides; Oligo-Miocene transition in the region was approved with this study based on biostratigraphical locations of benthic foraminiferal taxa

A cylindrical guarded capacitor for spectral permittivity measurements of hard rock samples in the MHz-range

A shielded and guarded capacitor for non-destructive measurement of the complex permittivity of cylindrical rock samples has been developed. In combination with a vector network analyzer, the measurement system allows for rapid determination of spectral permittivity. The geometrical construction of the capacitor allows for scanning the properties of cylindrical samples, such as drill cores, and determination of anisotropy. The complex permittivity is calculated from the scattering parameters, which are determined using a network analyzer. The calculation is based on a π-network model for the cell and takes stray capacitances and capacitances related to the guard electrode into account. Using this method, good measurement accuracy is achieved between 10 MHz and 200 MHz. The validity of this method was proven by finite element modeling of the field distributions in the cell based on 3D electromagnetic simulation. The influence of typical geometrical imperfections of drill cores, such as varying diameter, finite length and heterogeneities has been studied and quantified by extensive measurements of test samples. These tests confirmed that due to the short shielded electrode, spatial variations in permittivity can be resolved on a sub-centimeter scale.

BENTHIC FORAMINIFERAL BIOSTRATIGRAPHY OF MALATYA OLIGO-MIOCENE SUCCESSION (EASTERN TAURIDS, EASTERN TURKEY)

The benthic foraminiferal biostratigraphy of Oligo-Miocene aged Muratli and Petekkaya formations which crop out over wide regions around Akcadag town, west of Malatya pro- vince in Eastern Taurids were revealed in this study. Systematical sampling was carried out in measured stratigraphical sections in four locations in order to perform stratigraphical and paleontological investigations. Benthic foraminifera taken from 182 hard rock samples were defined and three biozones were determined as; SBZ 21-22, belonging to Oligocene (Rupe- lian - Early Chattian), SBZ 23 (Late Chattian) and SBZ 25 belonging to Lower Miocene in shallow marine deposits in the region. It was stated that the assemblage of planktic forami- nifer and nannoplankton which stratigraphically detected within Chattian - Burdigalian units in the succession most probably indicated Aquitanian age. Besides; Oligo-Miocene transition in the region was approved with this study based on biostratigraphical locations of benthic foraminiferal taxa.

Numerical study on progressive failure of hard rock samples with an unfilled undulate joint

Roughness is one of the most important parameters of unfilled joint. In this study, a series of numerical tests have been carried out on the progressive failure of rock masses with varied undulate joints. The numerical model reproduced the stress–strain relations obtained in lab tests on the marble samples with smooth joint under the confinement of σ3/σc=0.013 and 0.27; meanwhile, the results of the numerical model on rock mass with rough joint indicated that with the increase of confining stress, the failure of rock mass presents as sliding along the rock joint (Type I), shearing partly through asperity and the joint (Type II) and mostly shearing through the rock block initiated by joint (Type III) respectively. To describe the progressive failure of hard rock samples with an unfilled undulate joint, an index of stress concentration factor (SCF) is presented as the ratio of σ1–σ3 (the localized principal stress difference of one point in the rock sample) to (σ1–σ3)o (the principal stress difference applied onto the rock sample) to denote the degree of heterogeneous stress induced by the undulate joint. It has been found that the progressive failure behavior is largely dependent on the joint roughness and the confining stress, which can be classified into 4 modes as: slipping plastic failure, slipping–shearing brittle failure, shearing brittle failure and shearing plastic failure. For the rock mass with rough joint, the crack initiation and propagation resulted from localized stress concentration at the turning point of rough joint during compression plays an important role in the progressive failure. For the rock mass with the same rough joint, SCFm decreases as the confining pressure increases because the confinement can weaken the heterogeneity of the rock mass.

A micro-scale random-walk model for radionuclide migration based on image analysis-derived modelling grids

This paper describes the development of a random-walk transport model for the migration of radionuclides in hard-rocks at the grain scale. The physics of diffusion are reviewed and it is described how they are translated into the appropriate model algorithm. Further, the algorithm for recognising solid grain boundaries during the migration step is discussed. The model grid is derived from the analysis of images obtained by optical micro-photography and from autoradiography of hardrock samples impregnated with 14C-marked resins. Sample calculations for tracer-transport cases and simple reaction, i.e. precipitation cases are presented. It is envisaged to couple the code with a geochemical speciation code at a later stage.

Potential of Autoradiography to Detect Spatially Resolved Radiation Patterns in the Context of Trapped Charge Dating

Recent developments in optically stimulated luminescence (OSL) dating allow the determination of signals in increasingly smaller sample amounts. This has led to microdosimetry having a larger impact on equivalent dose (D<sub>E</sub>) distributions and therefore, detection and assessment of spatial distribution of radionuclides has become more important. This study demonstrates the application of autoradiography using imaging plates to determine spatially resolved radiation inhomogeneities in different types of samples. Qualitative evaluations of radiation inhomogeneity are carried out on unconsolidated sediments as well as on hard rock samples. While indicating some limitations of applicability, the results demonstrate that the method is an efficient tool to detect and document spatial variations in a sample's radiation field. It therefore provides a possibility to rapidly screen samples to check whether microdosimetry might affect the D<sub>E</sub> data. Furthermore, an approach to calibrate autoradiographic images for quantitative use is suggested. Using pressed powder pellets of reference materials, a series of calibration images were exposed, from which a functional relation between specific sample activity and greyscale value in the autoradiographic image has been deduced. Testing the calibration on a set of 16 geological samples, of which their radionuclide content is known, shows a good correlation between specific activities calculated from the nuclide content and specific activities deduced from the autoradiographic images. These findings illustrate the potential of autoradiography with imaging plates to detect spatial distributions of radionuclides and to tackle certain aspects of the problem of microdosimetry in modern trapped charge dating.

A simple approach to determine the diffusivity of americium in granite

The diffusivities of the key radionuclides in host rock are important for the performance assessment of repositories. One of the conventional methods for determining the diffusivities of radionuclides is to grind the rock tablet layer by layer and then to measure the radioactivity remaining on the rock tablet before each grinding cycle. Since grinding hard rock samples, especially those with radioactivity, is very difficult, we developed a new approach to determine the diffusivity of americium in granite. The new approach mainly includes two parts: one is to measure the radioactivities from both sides of a rock disk sample by autoradiography with phosphor imaging technique; the other is to study the relationship between the radioactivities and the apparent diffusivity of americium in granite by computer modelling. Because the high contamination risk of grinding radioactive rock samples has been avoided, the new approach is much simpler than the conventional method. It may be a better choice of measuring the diffusivities of radionuclides in rock, especially for those laboratories in which grinding radioactive rock samples is inconvenient.

A guarded cylindrical capacitor for the non-destructive measurement of hard rock core samples

The novel design of a flexible guarded capacitor which conforms to a core sample's cylindrical surface is presented. The proposed device allows non-destructive measurements of hard rock samples produced by diamond drilling, and has numerous advantages over previous methods. No material is lost to sample preparation and a detailed characterization of the entire core, including inclusions and transitions between rock types, may be performed. A detailed methodology for the rapid and cost-effective construction of a robust capacitor is given. Guidelines for its operation to achieve repeatable and accurate measurements of the complex dielectric constant of samples of varying homogeneity in the 1–25 MHz frequency range are presented.