Zongxian Zhang

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• PhD
• Professor at University of Oulu

Carbon dioxide phase transition fracturing (CDPTF) represents an environmentally sustainable method for rock fragmentation, with applications in coal seam permeability enhancement, tunnel excavation, and open-pit mining operations. However, current CDPTF research primarily focuses on rock specimens without inherent flaws, leaving uncertainties rega...

Focussing on the effect of the temporal characteristics of blast loading on rock fragmentation and damage, a self-developed constitutive model considering equivalent stress history is adopted for numerical simulation studies. Fitting and statistics of published test data on rock dynamic strength indicate that the incubation characteristic time that...

Limited progress in understanding blast mechanisms has led to significant discrepancies between the outcomes of existing blasting simulation techniques and actual blasting results, making it difficult to predict muckpile characteristics, optimize blasting designs, and guide on-site production. To address this challenge, this study presents a machin...

In rock and mining engineering, it is essential to predict rock cutt-ability and drillability for estimating drilling costs, selecting suitable drilling/cutting machine and tools, and achieving high productivity. To predict the drillability and cuttability, many destructive methods have been developed. However, they are often expensive and time-con...

This paper introduces a new experimental method for studying rock collision by making full use of the beauty of stress wave theory. In this method, a newly developed energy transmission component was placed between the gas gun and the transmitted bar of a split Hopkinson pressure bar (SHPB). The forementioned component consists of an incident bar w...

DIC 技术揭示试样的岩爆过程和应变场演化特征。试验结果表明，不同断面形状试样洞壁岩爆过程可归纳为 4 个阶段： 平静期阶段→裂纹萌生、扩展、贯穿阶段→板裂阶段→岩片弹射阶段。不同断面形状试样洞壁岩爆特征具有显著 差异：圆形孔试样应变集中区位于孔洞中心线处，裂纹从弧形过渡到"V"形，岩爆破坏程度最轻，围岩破坏模 式为张拉破坏；马蹄形孔试样应变集中区位于拱脚和拱肩之间的直墙区域，裂纹从弧形过渡到"V"形，以张拉 和张拉-剪切破坏模式为主；矩形孔试样岩爆破坏程度最严重，应变集中区贯穿整个洞壁，裂纹从直线形过渡到 "V"形，以张拉和张拉-剪切破坏模式为主。矩形孔试样整体变形速率较快，应变数值最大为 0.003 4，其次为 马蹄形试样，最大应变数值为 0.002 9，圆形孔试样变形程度相对较低，最大...

This study explored the fracture process of granite cylinders with a centric charge, varying decoupling ratios by conducting laboratory-scale experiments and numerical simulations. In experiments, the three-dimensional (3D) digital image correlation (DIC) technique was employed, using frames captured by two synchronized high-speed cameras. This ins...

To solve the safe containment and recovery efficiencies of gas in rock masses, a study on fracture process zone (FPZ) and crack propagation is conducted. By using digital image correlation technology, the displacement of three-point bending specimens was measured. By analyzing the distributions of displacement at different loading stages, a specifi...

A spherical weathering body, also called a boulder, is an element of complex geological strata and presents a significant challenge to tunnelling by a tunnel-boring machine (TBM). In this study, ground-based drilling and blasting were used to precondition boulders. To determine the specific charge needed for preconditioning blasting, model blasts w...

In this study, relations between characteristic impedance (product of sonic wave velocity and density), energy transformation and dynamic stress induced faults in rock specimen were investigated. To achieve this, peridotite and pyroxenite from Boliden Kevitsa mine in Sodankylä, Finland was prepared to length and diameter ratio of 1:1 in accordance...

The effect of detonator placement on rock fragmentation by blasting was studied in the Kevitsa open-pit mine. Considering rock mass properties, explosives properties, and blast parameters, a comprehensive analysis of 37 production blasts confirms that the middle detonator yields finer fragmentation than the bottom detonator in the full range of inv...

Rock fragment movement during blasting operations is a major cause of ore and profit losses in hard rock open-pit mines having a complex-orebody. To address this issue, a novel multilayer dig-limit approach, which well considers blast movement in dig-limit optimization, was proposed in this study by combining machine learning techniques and practic...

In the original publication [...]

Understanding the shear strength of granular materials like rockfills and mine waste dumps is paramount for ensuring structural stability. This paper presents a comprehensive review of over five decades of research on granular material shear strength. Investigating resistance under shear forces and normal loads, this study explores the intricate in...

In this review paper, existing mining techniques and technologies are scrutinized for the purpose of superterrestrial use. Different aspects and challenges of a space mining mission are examined in light of the viable iron-nickel quarry operation on M-Type (metallic) asteroids. The research and findings presented in this work cover different discip...

In this paper, the effects of static stresses on the blast-induced crack in poly-methyl methacrylate specimens with an empty hole were investigated by caustic system. The propagation behavior and re-initiation process of blast-induced crack under initial static stress and high stress unloading were investigated. The results show that when the direc...

The strength of rockfills and waste materials is significantly influenced by their particle size distribution (PSD). For large waste rockfills, PSD is fundamental to determine the shear behavior. Traditionally, PSD for rockfill, used in materials like coarse-grained aggregates, has been obtained through physical sieving. However, the particle sizes...

A new CTOD calculation method is investigated in this study, considering the FPZ and the effective Young’s modulus. The calculated CTOD values from four theoretical models are compared with the measured CTOD values from the three-point beam experiments, and the differences between them are analyzed. The measured CTOD consists of two parts: (1) the...

The Brazilian disc (BD) specimens were heated to high temperatures up to 100–500 °C followed by immersion in chemical solutions or irradiation in a microwave oven. The Brazilian splitting tests were then performed at high temperatures, and acoustic emission (AE) events were recorded. Meanwhile, the longitudinal wave velocity and open porosity of th...

The dynamic compressive strength (DCS) of frozen-thawed rock influences the stability of rock mass in cold regions, especially when rock masses are possibly disturbed by dynamic loads. Laboratory freeze-thaw weathering treatment is usually time-consuming, and the dynamic strength test is destructive. Therefore, this paper attempts to quickly predic...

In cold regions, the dynamic compressive strength (DCS) of rock damaged by freeze-thaw weathering significantly influences the stability of rock engineering. Nevertheless, testing the dynamic strength under freeze-thaw weathering conditions is often both time-consuming and expensive. Therefore, this study considers the effect of characteristic impe...

This study utilizes digital image correlation (DIC) technology to measure the far-field displacements and strains of rock specimens during the entire loading and unloading. Through analyzing the distributions of strain, displacement and their variations per unit length at different stages, the variations of both length and migration velocity of the...

In this study, the effects of preloaded uniaxial compressive stress and defect (prefabricated by laser cutting) curvature on blast-induced cracks and stress wave propagation were investigated in polymethyl methacrylate (PMMA) specimens using caustics theory. Based on the mathematical relationship between stress and optics, the fracture behavior (th...

Monitoring the carbon dioxide blast wave is an efficient method for determining the power of carbon dioxide blasting. Due to the harsh measurement environment, noise is inevitably mixed into the recorded signals. This work proposed a hybrid denoising strategy based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), per...

By means of digital image correlation (DIC) technology, the displacements and strains on the fracture ligaments of rock specimens were measured during loading. By analyzing the displacement distribution of each fracture ligament at different loading stages, the displacement fluctuation coefficient method was proposed to describe the development of...

Modern particle size statistics uses many different statistical distributions, but these distributions are empirical approximations for theoretically unknown relationships. This also holds true for the famous RRSB (Rosin-Rammler-Sperling-Bennett) distribution. Based on the compound Poisson process, this paper introduces a simple stochastic model th...

Sublevel caving (SLC) is a mass mining method having high productivity and high safety. However, this method often causes a considerable amount of permanent ore loss. Interestingly, all lost ores are buried in the broken waste rocks that come mostly from the caved hanging wall and partly from the ore body in which ore and waste rock are original...

In this study, the application of characteristic impedance in estimating specific energy and average fragment size of rocks was investigated during rock breakage at high strain rates. To achieve this, rock specimen was prepared in accordance with recommendations of the International Society for Rock Mechanics and broken at high strain rates using t...

Considering the energy consumption of the crushed zone caused by blasting, the energy dissipa-tion characteristics were investigated through theoretical calculation and a plug-in for calculation of energy reduction was made. As a result, an improved CDEM method suitable for studying blast-induced crack propagation was proposed. The improved CDEM me...

Tunnelling and underground mining face many risks threatening underground operations. Such hazards include sudden incidents of dangerous and violent rock bursts and cave-ins. We propose that stationary muography arrays in underground settings could map potentially risky areas.

The objective of this paper is to deeply understand and analytically characterize the dynamic strength enhancement of rock. Inspired by the incubation time criterion, a modified dynamic fracture criterion considering whole stress history, called the incubation characteristic time criterion, is proposed. The physical meaning of the modified criterio...

To investigate the mechanism of fault slips in coal mines, a biaxial shear experiment was carried out under unloading condition based on the fault F16 in Yima city, China. Two rock samples were used in the experiment and each sample was composed of two triangular sandstone blocks which were put together to simulate the fault. One rock sample was us...

To reduce the ore loss and dilution caused by blast-induced rock movement in open-pit bench blasting, a dividing open-pit blast (DOPB) method was theoretically analyzed, numerically simulated and applied to the Husab Uranium Mine, Namibia. First, a general open-pit bench blasting process was analyzed, and the DOPB method was introduced after compar...

To reduce the ore loss and dilution caused by blast-induced rock movement in open-pit bench blasting, a dividing open-pit blast (DOPB) method was theoretically analyzed, numerically simulated and applied to the Husab Uranium Mine, Namibia. First, a general open-pit bench blasting process was analyzed, and the DOPB method was introduced after compar...

Many current methods for evaluation of rock drillability require destructive laboratory or field tests. Such tests are not only costly but also time-consuming. This preliminary study indicates that the characteristic impedance, the product of density and sonic velocity, of rock has a good relation with two currently-used drillability indices and th...

Fault-slip seismic waves could result in rockbursts in various scales depending on the power of the waves as well as the stressing and fracturing conditions of the rock mass surrounding the underground opening. In the case that the surrounding rock is highly stressed but not yet failed, a strain burst could be triggered by seismic waves combined wi...

This paper focuses on a new test method and theoretical model for measuring and evaluating the reopening pressure during hot dry rock hydraulic fracturing. Firstly, rock blocks of four lithologies were collected from the hot dry rock strata. Hydraulic fracturing tests at high temperatures in real-time were conducted using drilled cubic specimens an...

The construction of the relation between the critical energy release rate, GIc, and the mode I fracture toughness, KIc, is of great significance for understanding the fracture mechanism and facilitating its application in engineering. In this study, fracture experiments using NSCB and CCCD specimens were conducted. The effects of specimen sizes, lo...

The characteristic impedance of a rock is defined as the product of the sonic velocity and the density of the rock. Based on previous studies, this article finds that: (1) For an intact rock, its characteristic impedance is a comprehensive physical property, since it is closely related with strengths, fracture toughness, Young’s modulus, and Poisso...

Dynamic properties of rocks are essential for planning sustainable engineering structures in regions prone to dynamic loading as well as effective fragment size distributions during quarrying activities. Due to the vast application of dynamic rock properties, several studies have been conducted on the context. However, studies on relations between...

Fracture process zone (FPZ) is an irreversible deformation and damage zone in the front of a crack tip in rock. Only a few of them experimentally focused on the size development of FPZ during the loading process. Therefore, the DIC technology was used to monitor the development of FPZ in three-point bending beam rock specimens. The far-field displa...

Fracture processes of granite cylinders (a diameter of 240mm and a length of 300mm) subjected to blast loading were investigated using data from three-dimensional digital image correlation (DIC) method on images captured with two high-speed cameras. The five cylinders had a centric decoupled charge (PETN) of approximately 3 g or 4 g. The centric bo...

Phyllite is widely distributed in nature, and it deserves to be studied considering rock engineering applications. In this study, uniaxial compression tests were conducted on foliated phyllite with different foliation angles under dry and water-saturated conditions. The impacts of water content and foliation angle on the stress–strain curves and ba...

The worldwide mining industry consumes a vast amount of energy in reduction of fragment size from mining to mineral processing with an extremely low-energy efciency, particularly in ore crushing and grinding. Regarding such a situation, this article describes the efects of rock fragmentation by blasting on the energy consumption, productivity, mi...

The determination of the size of the representative elementary volume (REV) is important to measure or predict mechanical and physical effective properties of heterogeneous materials. This paper presents a numerical procedure to determine the REV size of intact rocks using a polygonal grain-based model. A large number of rock models with side lengt...

To respond to the increased demand for commodities, increased volumes of primary ores need to be mined. This could lead to major challenges with water and tailings management since ore grades are low and many mining operations take place in high water stress areas. The current mineral processing methods used are highly water intensive and, conseque...

The effect of a blasting vibration from an excavating tunnel on an adjacent excavated tunnel is of great importance for the stability and security of twin tunnels. Due to the relatively small distance between the tunnel face of the excavating tunnel and the concrete lining of the excavated tunnel, the impact of blasting could be significant and sho...

Fragmentation of granite cylinders having a centric charge with different decoupling ratios was investigated in blast experiments. Conclusions are made from studying the post-blast specimens and strain measurement. Eight blasting tests were carried out on granite cylinders having a diameter of 240 mm and a length of 300 mm. All the specimens had a...

Rock properties are important for design of surface and underground mines as well as civil engineering projects. Among important rock properties is the characteristic impedance of rock. Characteristic impedance plays a crucial role in solving problems of shock waves in mining engineering. The characteristics impedance of rock has been related with...

Blast-induced rock movement (BIRM) may lead to large ore loss and dilution in many mines using the pre-blast ore boundary to guide shovel loading. In this study, a simulation approach consisting of the finite element method for blast loading calculation and the bonded-particle method for bench blasting simulation was applied to study the BIRM. Firs...

Cosmic‐ray muography has several current and many promising future applications in geosciences, geotechnical engineering, and mining engineering. Muography, if applied to these disciplines, is based on alternating muon flux attenuation in soils and rocks due to anomalous density heterogeneity in the media. Muography can be used for detecting and im...

Based on the review of a wide range of literature, this paper fnds that: (1) the average specifc surface energy of various single crystals is only 0.8 J/m2 . (2) The average specifc fracture energy of the rocks with a pre-crack under static cleavage tests is 4.6 J/m2 . (3) The average specifc fracture energy of the rocks with a pre-cut notch but...

This presentation covers most applications of rock dynamics in mining engineering.

The effect of detonator position on rock fragmentation was studied at the Kevitsa open pit mine. Five full-scale field tests were conducted where the blasts were divided into test and reference areas, and compared with each other. In the test areas, the detonators were placed at or near the middle point of the explosive column, and in the reference...

Small-scale model blasting plays an important role in understanding mechanism of rock fragmentation by blasting and improving blast technology in rock and mining engineering. Because a specimen (or model) often needs to be placed on either a ground or another material in model blasting, an additional interface appears between the specimen and the g...

With continuously increasing urban construction, more underground projects require the breaking of rocks near sensitive areas, such as hospitals, schools, and residential areas. On one hand, since conventional blasting that uses explosives has a negative impact on the safety of the surrounding buildings and brings about noise and flying rocks, the...

Based on the data of global mineral production and ore recovery in mining and mineral processing, this paper presents the annual production of 25 minerals and calculates the annual losses of 20 minerals from the year 1920 to 2018. The results indicate that the annual production of 23 minerals has increased by between 1 and 930 times since 1920, sim...

Nine blasts with cylindrical granite specimens were carried out under different stemming conditions. All rock specimens had a diameter of 240 mm and a length of 300 mm. Explosive Pentaerythritol tetranitrate (PETN) with specific charges 0.2 and 0.3 kg/m 3 were used, and the blasts were carried out in a large explosion chamber. Each rock specimen wa...

An analytical relation between burden velocityand ratio of burden to blasthole diameter is developed in this paper. This relation is found to be consistent with the measured burden velocities of all 37 full-scale blasts found from published articles. These blasts include single-hole blasts, multi-hole blasts, and simultaneously-initiated blasts wit...

The novel geophysical remote imaging method of muography is based on cosmic-ray induced muon particles that are detected after passing through the media of interest. If the studied objects are solid, their sizes can vary from meters to up to kilometres. In underground tunnelling, muography has at least four applications: (1) muography can be used t...

Published in MATERIA 2021;2-3:63-66 The idea of mine-to-mill optimization has been tested in various mines in last decades, resulting in higher mill throughput in many mines, but also unsatisfactory results in others. These contrary results have largely confused engineers and leaders in mining industry and have made them to lose the confidence in m...

Empirical relationships for estimating Uniaxial Compressive Strength (UCS) of rock from other rock properties are numerous in literature. This is because the laboratory procedure for determination of UCS from compression tests is cumbersome, time consuming, and often considered expensive, especially for small to medium-sized mining engineering proj...

Crack velocity, gas ejection, and stress waves play an important role in determining delay time, designing a blast and understanding the mechanism of rock fragmentation by blasting. In this paper, the emerging times of the earliest cracks and gas ejection on the lateral surfaces of cylindrical granite specimens with a diameter of 240 mm and a lengt...

To investigate energy dissipation and particle size distribution of rock under dynamic loads, a series of dynamic compression tests of granite specimens were conducted using a conventional split-Hopkinson pressure bar (SHPB) device with a high-speed camera. The experimental results show that the dissipated energy increases linearly with an increasi...

Muography is a novel imaging method using natural cosmic-ray radiation for characterising and monitoring variation in average material density in a diverse range of objects that cannot be imaged by conventional imaging techniques. Muography includes muon radiography and muon tomography. Cosmic-ray-induced muons were discovered in the 1930’s, but ra...

Based on a great number of experimental data on various mechanical properties of rock in the literature, six empirical equations between the characteristic impedance (product of density and P-wave velocity) and mechanical properties of rock are proposed. These properties include uniaxial compressive strength, tensile strength, shear strength, mode...

In order to control the scale of blasting in the excavation of a tunnel and mitigate the blast-caused adverse effects, especially on its neighboring tunnel, the particle velocities of the concrete lining of an excavated tunnel caused by the blasts in its adjacent operating tunnel, were analyzed in ANSYS/LS-DYNA software. The simulated results are c...

Spherical weathering body is one of complex geological strata, and drill and blast method can be used to precondition the boulders. To mitigate the adverse effects caused by boulder blasting, the particle velocities in the water-intake tunnel segments of Taishan nuclear power plant were measured. The measurement results indicated: (1) The particle...

In rock blasting, there are different constraint conditions such as a free surface, a partial free surface and a free surface with a barrier nearby. These conditions were modelled by three groups of blasting tests in this study: (1) A cylindrical granite specimen was blasted with complete free surfaces to model the free surface condition. (2) A cyl...

Ten blasts with cylindrical granite specimens were carried out in four groups with different specific charges and different constraint conditions. All rock specimens came from a granite quarry and they were cylinders with a diameter of 240 mm and a length of 300 mm. Three specific charges-0.2, 0.3 and 0.6 kg/m 3 with Research Department Explosive (...

Professor of Mining Engineering, Oulu Mining School, University of Oulu Explosives are the materials that can rapidly decompose chemically, produce an extremely high pressure, and release a huge amount of energy at a moment. For example, upon detonation, an explosive can produce a pressure over 20 GPa and a temperature above 3000°C (Zhang 2016a). E...