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Engineering rock masses typically feature natural discontinuities that span different scales, with filled joints as macroscopic discontinuities and microdefects as mesoscopic ones. However, the mechanism of wave propagation in the filled joints has been unclear. This study develops a novel dual-scale equivalent rock model to investigate the wave propagation in jointed rock masses. Firstly, two combination models at different scales were developed by using thin layers and contact interfaces to simulate filled joints and microdefects, respectively. Subsequently, a wave propagation equation was derived through a time-domain recursive method, and validated against the experimental data and the predictions of traditional models. Finally, a parametric analysis was conducted on the frequency response of wave propagation in jointed rock masses. The results show that this novel model can describe the wave dispersion and attenuation in dual-scale discontinuous rock masses, and its equation exhibits robustness. It is revealed that two independent mechanisms induce the wave dispersion in a single joint: multiple wave reflections inside the joint and the viscosity of the filling material. The effect of microdefects on wave attenuation mainly depends on propagation distance, while the influence of filled joints on wave propagation can be determined by the quality factor, thickness, effective wave velocity, and density of the filling. The wave velocity of the filling has a significantly higher influence on the transmission coefficient than the filling density. This challenges the conventional concept that the wave impedance of filling is a basic parameter for estimating the transmission coefficient. Highlights: A novel dual-scale equivalent model was proposed for wave propagation in jointed rock masses. The multiple reflection effects at rock joints were revealed to be the main cause of wave dispersion. Using wave impedance of joint filling to predict the transmission coefficient was found to be inaccurate. The frequency response difference in macroscopic and mesoscopic discontinuities of rock masses was revealed. [ABSTRACT FROM AUTHOR]

The impact of fractures on the hydro-mechanical behavior of fractured rock masses is analyzed by means of equivalent Biot (α ¯) and Skempton (B ¯) coefficients. We assume the derivation proposed by De Simone et al. (Rock Mech Rock Eng 56:8907–8925, 2023), in which the equivalent coefficients depend on the combination of fracture size, orientation and mechanical properties, with the mechanical properties of the intact rock. We extend this theory to incorporate more complex and realistic assumptions on fractures, such as the dependence of aperture and normal stiffness on size and confining stress. Under this setting, we explore the range of variability of the two equivalent coefficients with respect to the stochastic distribution of fracture size and orientation in the rock mass, as well as to depth and stress faulting regime. We find that, although α ¯ and B ¯ increase with fracture density, they are larger if the network is populated by a few large fractures than if populated by many small fractures because large fracture are more compliant. Orientation and depth also greatly impact the coefficients. Fractures oriented such that the applied normal stress is maximized, lead to larger equivalent Skempton coefficients and smaller equivalent Biot coefficient. However, the initial confining stress maximizes both coefficients when fractures are shallow and parallel to the maximum principal stress. Therefore, fracture orientation may differently impact the equivalent coefficients depending on the initial and applied stress tensors. Overall, fracture contribution is larger in shallow rocks containing large fractures that are oriented parallel to the largest principal initial stress and normal to the applied stress. Highlights: Fracture network characteristics strongly impact the equivalent Biot and Skempton coefficients of fractured rocks The coefficients increase with fracture density and porosity of the fractured portion Fracture contribution is larger in systems containing large fractures oriented parallel to the largest principal initial stress and normal to the applied stress. [ABSTRACT FROM AUTHOR]

This study investigates the potential and limitations of using partial image orientation in Structure from Motion (SfM) photogrammetry to assess geometric properties of rock mass discontinuities investigated under various conditions. The photogrammetric point clouds were produced from images taken with a low-cost camera. An arbitrary (local) coordinate system was established by aligning a leveled 3D box with all axes oriented to the geographical North. Consequently, the need for terrestrial surveys to obtain ground control points was eliminated as the translation parameters required for photogrammetric image orientation could be disregarded in the proposed method. The investigations were conducted at various experimental sites to measure discontinuities in rock masses with diverse structural properties. The discontinuity properties such as orientation, persistence, weathering, aperture, filling, roughness, and waviness were measured by applying traditional scan-line surveys. Traditional orientation measurements and photogrammetric point cloud values were compared across different rock masses and discontinuity conditions. The results indicated that using a smartphone for image capture and a prismatic scale box for partial absolute orientation produced highly accurate point cloud data for characterizing rock mass discontinuities. Additionally, a new method, LCP + LSPF (Least Cost Path + Least Square Plane Fitting), was introduced for measuring partially closed-trace discontinuities. This method was found to be essential for sedimentary formations, primarily characterized by bedding planes. Moreover, it became evident that as the level of structural blocking increased and the interlocking of rock fragments decreased, the LCP + LSPF method was crucial for accurately representing rock masses, especially when considering Geological Strength Index (GSI) values. [ABSTRACT FROM AUTHOR]

The ultimate bearing capacity of a strip footing placed horizontally over the edge of a sloping rock mass has been determined on the basis of the stress characteristics method (SCM) using the generalized Hoek–Brown yield criterion. The effect of footing–rock interface roughness on the results has also been analyzed. The problem has been solved, in addition, with the usage of the adaptive mesh–based finite-element limit analysis (FELA) method. The results are provided in the form of nondimensional bearing capacity factor (Nσ) as a function of different input material parameters for several slope inclinations. After analyzing all the results, an expression on the basis of the regression analysis has also been generated to compute the factor Nσ as a function of different input variables. The bearing capacity obtained from the SCM has been found to lie between the lower and upper bounds of the FELA, and the failure patterns from the two sets of analyses match quite closely with each other for both smooth and rough footings. The results are also found to be in good agreement with the existing solutions from the literature. [ABSTRACT FROM AUTHOR]

The stability of strip footings subjected to eccentrically inclined loads is critical for reliable foundation design. This study investigates the effect of a circular unlined tunnel in a rock mass on the ultimate bearing capacity (UBC) of a foundation with width B under inclined and eccentric loads. Adaptive finite element limit analysis was employed to evaluate the reduction in UBC of the footing resting above a tunnel. The examined critical parameters include normalized load eccentricity (e/B), load inclination (β), and horizontal and vertical distances of the tunnel from the foundation (P/B and Q/B, respectively), along with rock mass properties. The results reveal that for e/B ≥ 0.25 and β ≤ 60°, the reduction coefficient, Rc ≥ 0.90, suggesting that the presence of a tunnel has a minimal impact on the load-bearing capacity of the footing, with failure primarily governed by load eccentricity and inclination. Additionally, potential failure mechanisms are explored, showing that at lower e/B, higher β, and lower Q/B, the tunnel significantly affects footing's failure envelope. Conversely, at higher e/B and lower β, failure is due to rotational effects of footing, regardless of the tunnel's position. To predict the Rc more accurately, due to the time-consuming nature of direct calculations, both MLR and ANN models were developed. The MLR model provided a baseline for comparison, while the ANN model, with a coefficient of determination (R2) of 0.98, demonstrated superior accuracy compared to the R2 = 0.96 of MLR. Using both approaches ensured robust and efficient predictions of Rc. Since Rc does not directly provide the reduced UBC of footing due to presence of tunnel, the study introduced bearing capacity factor (Nc) to enable direct calculation of the reduced UBC of footing. These findings offer theoretical guidelines for preliminary design and provide practitioners with an effective tool for evaluating UBC reduction in complex loading scenarios involving tunnels. [ABSTRACT FROM AUTHOR]

Rock mass consists of many discontinuities, such as faults, joints, etc., and layered joints are a common kind of rock mass structure. The joints affect the stress wave propagation, and blasting is an economical and efficient rock fragmentation method for rock mass engineering. So, the rock mass fragmentation effect and construction progress are affected by these layered joints. Numerical studies were carried out to analyze the damage evolution process of intact rock and rock mass with layered joints subjected to blasting loads based on the Riedel–Hiermaier–Thoma (RHT) model in LS-DYNA software (smp s R11.0.), and the effects of the location of initiation points and the fracture distribution on dynamic damage evolution of the rock mass were discussed. Bottom initiation tends to direct the blasting energy toward the blasthole mouth, resulting in effective rock fragmentation and ejection. Gradually adjusting the initiation point upward can improve the stress and damage distribution, allowing some of the blasting stress waves to propagate toward the bottom and enhance the fragmentation of the rock at the bottom. The distribution of layered joints exacerbates the damage to the rock mass on the upstream surface, but also acts as a certain shield to the propagation of stress waves, increasing the asymmetry of the damage distribution. It is useful to know the damage mechanism of the rock mass with layered joints to improve the effect of rock mass fragmentation by blasting. These results have very important theoretical significance and application value for the optimization of blasting construction technology. [ABSTRACT FROM AUTHOR]

Tunnels stand as indispensable pillars of transportation infrastructure, assuming a central and transformative role in fostering the sustainable evolution of urban. The excavation process of tunnels presents a spectrum of geological challenges, encompassing the potential for instability and collapse. Ensuring the stability of the tunnel is a top priority in tunnel construction. The destabilization leading to collapse in certain tunnels is intricately connected to the structural planes of the rock mass. Accurately obtaining the distribution of structural planes within the rock mass is the necessary basis for maintaining the stability of the tunnel. The conventional Monte Carlo method generates each parameter of stochastic structural planes separately without considering the correlations between the parameters. To address this limitation, we propose a stochastic structural plane generation method based on deep generative model (DGM). The model takes the measured factual structural plane data as input, and the neural network realizes the generation of structural plane data with automatic learning of the distribution law of structural planes and the correlations between each parameters without assuming the probability distribution of stochastic structural planes in advance. This method has been used for stochastic structural plane generation of the rock mass in the Yuelongmen tunnel located in Mianyang City, Sichuan Province. The validation results show that the proposed DGM‐based method automatically captures the correlation between structural plane parameters while ensuring the greater accuracy of the generated structural planes. [ABSTRACT FROM AUTHOR]

The technique of multi-long-hole blasting with large empty holes has been used in practice to break rock mass. However, the damage mechanism of rock mass surrounded by empty holes and boreholes under this type of blasting has not yet been well-understood and identified, which may lead to inappropriate design of the configurations of empty holes for multi-long-hole blasting. The present study investigates the damage modes and mechanism of rock mass under multi-long-hole blasting with large empty holes by conducting a field test and numerical simulations. The results show that multi-long-hole blasting with empty holes mainly causes compressive damage of rock mass around boreholes, reflected tensile damage near empty holes and ground surface, bending-induced tensile damage between empty holes and boreholes, shear damage along the side tangents and bottom of empty holes and boreholes, and tensile damage along the connection of boreholes caused by the superposition of stress waves. In addition, parametric studies are conducted to examine the effects of depths and diameters of empty holes and the spacing between boreholes and empty holes on the damage and fragmentation of rock mass under blast loads. It is found that the flexural stiffness and confined levels of rock mass can be greatly influenced by the variation of configurations of empty holes, which thus induces different damage and fragmentation under multi-long-hole blasting. Analytical formulas for the evaluation of shear and bending-induced damage of rock mass under multi-long-hole blasting are finally proposed to provide references for the design of empty holes in multi-long-hole blasting. Highlights: Damage modes and mechanisms of multi-long-hole blasting with large empty holes are identified. Rock fragmentation characteristics under this blasting are examined. Effects of configurations of empty holes on the performance of multi-long-hole blasting are revealed. Analytical formulas are developed to evaluate rock damage under this blasting. [ABSTRACT FROM AUTHOR]

The distribution and development of rock mass discontinuities in 3D space control the deformation and failure characteristics of the rock mass, which in turn affect the strength, permeability, and stability of rock masses. Therefore, it is essential to accurately and efficiently characterize these discontinuities. Light Detection and Ranging (LiDAR) now allows for fast and precise 3D data collection, which supports the creation of new methods for characterizing rock mass discontinuities. However, uneven density distribution and local surface undulations can limit the accuracy of discontinuity characterization. To address this, we propose a method for characterizing complex rock mass discontinuities based on laser point cloud data. This method is capable of processing datasets with varying densities and can reduce over-segmentation in non-planar areas. The suggested approach involves a five-stage process that includes: (1) adaptive resampling of point cloud data based on density comparison; (2) normal vector calculation using Principal Component Analysis (PCA); (3) identifying non-planar areas using a watershed-like algorithm, and determine the main discontinuity sets using Multi-threshold Mean Shift (MTMS); (4) identify single discontinuity clusters using Density-Based Spatial Clustering of Applications with Noise (DBSCAN); (5) fitting discontinuity planes with Random Sample Consensus (RANSAC) and determining discontinuity orientations using analytic geometry. This method was applied to three rock slope datasets and compared with previous research results and manual measurement results. The results indicate that this method can effectively reduce over-segmentation and the characterization results have high accuracy. [ABSTRACT FROM AUTHOR]

Given that traditional joint set identification faces challenges due to labor intensity, safety concerns with accessing steep slopes, and limited sampling locations for measurements, there is an urgent need for more efficient techniques to align with the pace of mine development. This study proposes a deep learning technique for the automated identification of joint sets within 3D point cloud models of rock masses. The process commences with the classification of joints on the 3D surface of a rock mass, accomplished through the training of a deep neural network architecture, and validation using manually labeled datasets. Following this, individual joint surfaces are distinguished using the Density-Based Scan with Noise clustering algorithm. Subsequently, the orientations of the identified joint surfaces are determined by fitting least-square planes using the Random Sample Consensus method. Finally, the joint planes are categorized into distinct joint sets, and the dip direction and dip angle for each set are computed. The effectiveness of this methodology is assessed through a case study, demonstrating that the proposed approach is rapid, precise, and resilient. [ABSTRACT FROM AUTHOR]

In situ stress is a significant characteristic of underground rock masses. In this work, based on the time-domain recursive method (TDRM), a new theoretical approach is proposed to study the oblique propagation of an S-wave across an in situ stressed joint wherein the normal and shear deformations are both treated nonlinearly. Equations are first established for the propagation of stress waves across a rock mass subjected to a combination of gravitational and tectonic stress. The veracity of the wave propagation equations is then investigated by comparing our theoretical results with those obtained using the Universal Distinct Element Code (UDEC). A comparison of the waveforms predicted using the continuously yielding and existing models is also presented to investigate their differences. Finally, parametric studies are conducted to investigate the effects of joint angle, in situ stress, lateral pressure coefficient, and incident wave amplitude on the propagation of the wave. The results show that the effect of in situ stress on wave propagation is related to the joint angle and lateral pressure coefficient because these factors decide the initial stress and contact states of the joint. [ABSTRACT FROM AUTHOR]

Abstract Evaluating physical properties and mechanical parameters of rock slopes and their spatial variability is challenging, particularly at locations inaccessible for fieldwork. This obstacle can be bypassed by acquiring spatially-distributed field data indirectly. InfraRed Thermography (IRT) has emerged as a promising technology to statistically infer rock properties and inform slope stability models. Here, we explore the use of Cooling Rate Indices (CRIs) to quantify the thermal response of a granodiorite rock wall within the recently established Požáry Test Site in Czechia. We observe distinct cooling patterns across different segments of the wall, compatible with the different degrees of weathering evaluated in the laboratory and suggested by IRT observations of cored samples. Our findings support previous examinations of the efficacy of this method and unveil correlations between cooling phases in the field and in the laboratory. We discuss the scale-dependency of the Informative Time Window (ITW) of the CRIs, noting that it may serve as a reference for conducting systematic IRT field surveys. We contend that our approach not only represents a viable and scientifically robust strategy for characterising rock slopes but also holds the potential for identifying unstable areas.

Structural planes are one of the key factors controlling the stability of rock masses. A comprehensive understanding of the spatial distribution characteristics of structural planes is essential for accurately identifying key blocks, analyzing rock mass stability, and addressing various rock engineering challenges. This study compares the effectiveness of four stochastic structural plane generation methods—the Monte Carlo method, the Copula-based method, generative adversarial networks (GAN), and denoised diffusion models (DDPM)—in generating stochastic structural planes and capturing potential correlations between structural plane parameters. The Monte Carlo method employs the mean and variance of three parameters of the measured factual structural planes to generate data that follow the same distributions. The other three methods take the entire set of measured factual structural planes as the overall input to generate structural planes that exhibit the same probability distributions. Five sets of structural planes on four rock slopes in Norway are examined as an example. The validation and analysis were performed using histogram comparison, data feature comparison, scatter plot comparison, and linear regression analysis. The results show that the Monte Carlo method fails to capture the potential correlation between the dip direction and dip angle despite the best fit to the measured factual structural planes. The Copula-based method performs better with smaller datasets, and GAN and DDPM are better at capturing the correlation of measured factual structural planes in the case of large datasets. Therefore, in the case of a limited number of measured structural planes, it is advisable to employ the Copula-based method. In scenarios where the dataset is extensive, the deep generative model is recommended due to its ability to capture complex data structures. The results of this study can be utilized as a valuable point of reference for the accurate generation of stochastic structural planes within rock masses. [ABSTRACT FROM AUTHOR]

Flexural toppling occurs when a series of layered rock masses bend towards their free face. It is important to evaluate the maximum bending degree and the requirement of supports of flexural toppling rock mass to prevent rock mass cracking and even failure leading to a landslide. Based on the rock tensile strain-softening model, this study proposes a method for calculating the maximum curvature (Cppmax) of flexural toppling rock masses. By applying this method to calculate Cppmax of 9 types of rock masses with different hardness and rock layer thickness, some conclusions are drawn: (1) the internal key factors affecting Cppmax are E⋆ (E⋆= Ess/E0, where E0 and Ess are the mean deformation moduli of the rock before and after reaching its peak tensile strength, respectively), the strain εt corresponding to the tensile strength of rock, and the thickness (h) of rock layers; (2) hard rock layers are more likely to develop into block toppling than soft rock layers; and (3) thin rock layers are more likely to remain in flexural toppling state than thick rock layers. In addition, it is found that Cppmax for flexural toppling rock masses composed of bedded rocks such as gneiss is related to the tensile direction. [ABSTRACT FROM AUTHOR]

In natural rock masses, joints or fractures usually occur at different penetrations. To study the deformation and failure behavior of rock mass with different fracture penetrations, a series of triaxial compression experiments were conducted on rock specimens containing prefabricated fracture at penetrations of 0%, 25%, 50%, 75% and 100%. The results show that the greater the fracture penetration and the smaller the strength of the rock sample, the more obvious the plastic deformation section of the stress–strain curve. Confining pressure can greatly improve the compressive strength of rock samples. For intact rock samples, confining pressure will change the failure mode from tensile failure to shear failure. For fractured rock samples, the confining pressure will aggravate the degree of damage to the rock sample. PFC 3D simulation shows that the failure process of rock samples is accompanied by the transformation of strain energy to damping energy and particle sliding energy, which can quantitatively characterise the damage process of rock. The increasing trend of crack number is slow-steep-slow, which is the 'S' type. It began to grow rapidly after reaching peak strength and gradually stabilised after reaching residual strength. It is consistent with the trend of energy change. The article carried out multi-scale experimental study of fractured rock mass with the same length and different penetration. The larger the fracture penetration, the lower the strength of the rock sample, and the more complex the crack when it is destroyed. The article analysed and summarised the mechanical properties and failure modes of rock samples with different fissures under different confining pressures and clearly recognised the deterioration effect of fissure penetration on rock samples. PFC 3D was used to simulate the test, which clearly showed the crack propagation process of fractured rock samples under triaxial compression, quantitatively characterised the damage law and revealed the failure mechanism. [ABSTRACT FROM AUTHOR]

Cracks develop in concrete piles under lateral static loading as the tensile stress exceeds the concrete strength, causing a decrease in the pile's flexural rigidity and influencing the load–deflection behavior. This paper presents a three-dimensional finite-element analysis (FEA) performed by PLAXIS 3D (version 2021) to investigate the impact of concrete cracking on the load–deflection behavior of laterally loaded piles in rock mass. Two FEA models were established to assess the influence of concrete cracking on load–deflection behavior. In the first model, nonlinear rock mass behavior was coupled with linear pile behavior (FEANL), while in the second model, nonlinear rock mass behavior was coupled with nonlinear pile behavior (FEANN). The three-dimensional (3D) FEA models were verified with a full-scale test case study for a deep-water pile foundation. The FEANN yields a more accurate simulation of measured deflection than the FEANL. A single run of the FEANN typically requires an entire day of computational time. Thus, a simplified approach was proposed to minimize the computational time process by incorporating the relationship of the change in pile flexural rigidity versus the bending moment (EI–M) into FEANL. In addition, the available EI–M relationships in the literature, such as the American Concrete Institute (ACI) method and beam theory, were evaluated by the EI–M relationship derived from the FEANN. The beam theory yields a lower estimate of pile flexural rigidity than the ACI method. The predicted deflection obtained through the simplified approach exhibits good agreement with the measured deflection utilizing the EI–M relationship derived from the FEANN. On the other hand, the EI–M relationship obtained from the beam theory overestimates the deflection compared to those obtained from the EI–M relationships of the ACI method and FEANN. [ABSTRACT FROM AUTHOR]

An extended ordinary state-based peridynamic model was developed to investigate the crack propagation of surrounding rock due to tunnel excavation. The frost heave effect on the crack surface was described by an equivalent pressure density. Two numerical examples were conducted to verify the effectiveness and robustness of the proposed model. Moreover, the influence of frost heave pressure, buried depth and rock elastic modulus on damage characteristics of the surrounding rock was investigated. The results demonstrate that massive microcrack damage will be formed at the invert when the tunnel is excavated in a deeply buried rock mass or soft rock stratum. A peridynamic model of rock mass under excavation and frost heave was constructed. Damage characteristics of surrounding rock could be simulated efficiently. Frost heave load was exerted on the crack surface by an equivalent pressure density. The effects of frost heave load, buried depth and rock elastic modulus were studied. [ABSTRACT FROM AUTHOR]

Introduction: The research is aimed to identify the vulnerable areas of quarry slopes through the creation of a stress-strain state model for the rock mass at the Vostochny quarry, East Saryoba field of the Zhi-landy Group of cupriferous sandstones, as well as their subsequent strengthening. Methods: The research is based on the development of a database containing information on mining-geological, geophysical, geodetic and aerospace surveys. The authors of the research use modern geodetic, aerospace and geophysical technologies for scientifically based predicting of technogenic disasters and the rock mass stress-strain state modeling to ensure safe and optimal mining of fields in difficult mining-geological conditions. Results: The results obtained show that the strengthening of weakened quarry slopes based on the rock mass stress-strain state modeling contributes to the scientific-practical profitability of field mining and provides safe mining in difficult mining-geological conditions. Discussion: Novelty is in the scientific substantiation of the method for strengthening quarry slopes, which is based on the rock mass stress-strain state modeling. The research is of great practical importance, as the rock mass stressstrain state modeling increases the reliability of predicting the rock mass state during its mining. Strengthening of quarry slopes using the proposed method reduces risks and increases safety and economic efficiency of mining the solid mineral deposits in difficult mining-geological conditions. [ABSTRACT FROM AUTHOR]

The quantification of a rock mass's internal structure and description of discontinuity properties is imperative for modern rock mass characterization. This study builds on decades of rock engineering development by reviewing and revising different parameters such as the rock quality designation (RQD ), volumetric joint count ( J v ), the Pij system and others. Analyses of these parameters are done by means of a Monte Carlo simulation that generated 5000 samples of discrete discontinuity networks including finite, folded and very low to very high discontinuity densities ( J v range: 0.5–117 discontinuities/m3), thus representing a wide range of possible geological scenarios. P 10 , P 20 , P 21 , P 30 , P 32 , RQD and the fractal dimension of the rock mass are virtually measured on these samples and a range of higher level parameters that are used in practical rock engineering computed and their relationships investigated. It is concluded that parameters which are based on subjective estimations of discontinuity spacing, the number of discontinuity sets or RQD are not suited to describe the rock mass structure in cases of demanding geological scenarios featuring many discontinuities, weak and anisotropic rock masses, metamorphic rock masses, folded rock masses, etc. By revising classical parameters and their relationships, this study contributes to basic rock mass characterization and furthermore paves the way for future developments by making the developed discrete discontinuity network dataset and all included codes openly accessible to the rock mechanics community. Highlights: This study contributes to rock mass characterization by reviewing classical parameters based on simulated discrete discontinuity networks. A dataset of 5000 simulated discrete discontinuity networks including a vast variety of geological scenarios is built. Parameters based on numbers of discontinuity sets, discontinuity spacing and the RQD are not suited to describe complex rock mass conditions. The dataset and code of the study is provided openly to enable future advancements in rock mechanics. [ABSTRACT FROM AUTHOR]

Purpose. To create a device for weighing mining rock loaded into the body of a dump truck after each cycle of its excavation. To develop a mathematical block for calculating the net mass of the rock without taking into account extraneous factors affecting the accuracy of the obtained result. To provide operational control of the nominal load of the dump truck by the driver and excavator operator. Methodology. The methodological basis for solving the task is a comprehensive approach which includes electronic modeling of technical processes, methods of mathematical statistics, analysis of results in a mathematical package and their applied application. Findings. A functional and principled electrical diagram of the device for weighing the mining rock loaded into the body of a dump truck and transferring the final information to this excavator has been compiled. A mathematical block of the device was created, capable of memorizing the signals received from the primary information sensors before weighing, and subtracting them from the signals received from these sensors after each weighing cycle. As sensors of primary information, it is proposed to use selsyns, which are part of the transformer mode, which are mass-produced by the industry, reliable in operation and easy to maintain. Originality. The proposed device is made at the level of the invention; its priority is determined by the constructive development and technical solution. Namely, the device is equipped with a multistable memory transformer, to the erasing winding of which a tachogenerator (or tachometer generator) is connected through an amplifier, a chain of series-connected trigger, multivibrator waiting and key, whose output is connected to the recording winding of the multistable memory transformer, as well as the transformer connected to the input winding of the multistable memory transformer. Moreover, the storage capacitor is connected to one of the key inputs, and the input windings of the transformer are connected to the weight sensor. Practical value. The use of the presented device allows for operational control of the nominal load of the dump truck, objective accounting of transported cargo and realized labor costs, as well as for applying optimal maintenance of cargo and transport works in quarries. In the future, this device will form the basis of a radio telemetry system for dispatching the operation of dump trucks. [ABSTRACT FROM AUTHOR]

When evaluating the shear strength of rock mass discontinuities, certain challenges arise due to the difficulty in quantifying the roughness characteristics of surfaces and the strength of asperities. Recent research has focused on enhancing techniques for assessing these characteristics and exploring the application of laser scanning to aid in evaluating discontinuity features. The analysis of reflectivity values (I) obtained through a laser scanner survey presents an efficient method for assessing mechanical characteristics, such as joint compressive strength (JCS). Reflectivity measurements demonstrate correlations with Schmidt hammer rebound values (r). The laser scanner technique would enable the measurement of JCS without the direct application of the Schmidt hammer on rocks in areas where rebound values (r) measurements are unavailable. The use of a laser scanner allows for the acquisition of high-precision geometrical information concerning the 3D roughness and anisotropy of rock surfaces. In this study, an innovative technique was introduced that utilizes laser scanner data from six previous experimental surveys conducted on rock formations in Southern Italy. This technique facilitates the evaluation of roughness profiles, considering potential variations along kinematically admissible sliding directions, allowing for the estimation of the Joint Roughness Coefficient (JRC). This new methodology aids in evaluating the parameters of Barton's equation to determine the strength characteristics of rock mass discontinuities. [ABSTRACT FROM AUTHOR]

It is difficult to implement routine mine-wide programs to measure absolute stress in deep and over-stressed mines because the drilled holes and cores are often damaged during and immediately following the drilling. We evaluated the use of the Diametrical Core Deformation Analysis (DCDA) method, developed by Funato and Ito, to overcome this problem. This non-destructive method can evaluate the absolute shear stresses and measurement errors in the planes orthogonal to the core axes by precisely measuring the ellipticity of the core section orthogonal to the borehole axis. The five readings required to evaluate a single core take only about ten minutes to make. The measurement system is compact enough for a single regular courier parcel or can be checked-in as luggage on a flight. Absolute shear stresses were determined for thirty-five core specimens from fourteen holes drilled in a range of directions in the highly stressed rock mass surrounding a deep South African gold mine. Using the DCDA method we were able to determine the absolute 3D shear stress field averaged over an area of interest. It was consistent with the 3D stress field measured in-situ with an overcoring method, with the maximum principal stress larger than 100 MPa, with a root mean square of residuals of several MPa. Interestingly, the results represent relaxation in shear stress near the fault intersected by the boreholes. The DCDA measurements require a core diameter larger than approximately 40 mm, and a core that is longer than approximately 10 cm. The method assumes that there is no significant inelastic deformation and that the rock is isotropic. [ABSTRACT FROM AUTHOR]

Using a gradient-type model, the authors solve a boundary-value problem on stress redistribution in rock mass during mining. The elastoplastic model takes into account local discontinuity. The condition of smoothness of the displacement field is essentially weakened—instead of one smooth field of displacements, two-dimensional kinematics is described using two independent smooth fields. As a consequence, the model receives a structural parameter including the dimension of length and characterizing local bends of unit volumes. The article gives examples of plastic strain calculations in adjacent rock mass with identification of the increased stress concentration zones. It is shown that inclusion of local bends leads, on the hand, to the reduction of plastic shears in adjacent rock mass and, on the other hand, to deeper expansion of high stress concentration zones in rock mass. [ABSTRACT FROM AUTHOR]

Within the framework of the elastoplastic model, the authors propose a theoretical description procedure for troughs of ground movements with high gradients of subsidence. The approach uses reduction of shear modulus in rock mass bordering a movement trough. The pre-requisite for the shear modulus reduction in such areas is the increased mining-induced pressure, which initiates damage and aggravates the defect structure of rocks through widening of micro-cracks, inter-grain contacts, etc. The estimation procedure of the induced reduction factor for the shear modulus uses the comparative analysis of ground slopes. This approach enables a reliable calculation of ground movements with high gradients of subsidence, and ensures the adequate stress–strain analysis of undermined rock mass, including location of plastic deformation zones. [ABSTRACT FROM AUTHOR]

3DEC is used herein to study the stability of a circular tunnel opening in stratified rock mass. Numerical analysis indicated that the bedding planes can influence the damage process and the distribution of secondary cracks in rock masses, creating more damaged zones. The bedding planes lead to a nonuniform distribution of water pressure behind the lining. Such nonuniform water pressure may result in localized damage in the tunnel. Water leakage occurs mainly at the top of the tunnel and on both side of the walls. Tunnels situated in vertical bedding planes are more vulnerable to water, especially for underwater projects such as water diversion tunnels and undersea tunnels, where construction in vertical bedding planes should be avoided as much as possible. The maximum deformation of shotcrete occurs at the intersection with the bedding plane, and the displacement on the upper side is greater than that on the lower side. [ABSTRACT FROM AUTHOR]

Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point. This paper develops a drilling process detection (DPD) system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod, geophones at the tunnel face, a laser rangefinder, and an onsite computer. A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling. A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method. Time-frequency analysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seismic exploration wavelet. A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained. Both the borehole core and optical image validate the inverted P-wave velocity field. A numerical simulation of a checkerboard benchmark model is used to test the tomography method. The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.

Possible discontinuities in the subsurface have a major impact on the load‐bearing behavior of post‐installed fastenings. For concrete, the behavior of post‐installed anchors and thus their design can be clearly addressed as concrete is assumed as a homogeneous fastening substrate. This is valid except, for example, in the area of building joints and at joints of precast concrete elements, where the formation of structural joints inevitably occurs and which basically correspond to a separation surface. In contrast, rock mass is characterized by the rock type, but is generally also significantly influenced by its discontinuities. These play a decisive role concerning rock mass stability and show a great impact on the load‐bearing capacity of rock, especially for fasteners with a shallow embedment depth. It is to be assumed that the same also applies to separating surfaces in concrete. Furthermore, the question arises as to the non‐destructive preliminary detectability of such weak zones. For carrying out a comparative study under controlled conditions, artificial interfaces of different geometries were generated in concrete in laboratory tests by inserting PTFE layers at different positions of the test member. Pull‐out tests of post‐installed fastening systems were carried out in their vicinity to determine the load transfer as well as the failure mode. It could be shown that discontinuities have a negative effect on pull‐out loads not only in the rock mass, but also in concrete. However, detection of these by means of a rebound hammer was only possible in the rock mass. [ABSTRACT FROM AUTHOR]

Accurately obtaining rock mass discontinuity information holds particular significance for slope stability analysis and rock mass classification. Currently, non-contact measurement methods have increasingly become a supplementary means to traditional techniques, especially in hazardous and inaccessible areas. This study introduces an innovative semi-automatic method to identify discontinuities from point clouds. A modified convolutional neural network, AlexNet, was established to identify discontinuity sets. The network consists of five convolutional layers and three fully connected layers, utilizing 1 × 3 normal vectors computed by K-nearest neighbor and principal component analysis as input and generating an output value “i” that represents the identified discontinuity set associated with the “i” category. Learning samples for network training were randomly selected from point clouds and automatically categorized using the improved fuzzy C-means (FCM) based on particle swarm optimization (PSO). The orientations of individual discontinuities, identified from the discontinuity set using hierarchical density–based spatial clustering of applications with noise, were calculated. Two outcrop cases were employed to validate the efficacy of the proposed method, and parameter analysis was conducted to determine optimal parameters. The results demonstrated the reliability of the method and highlighted improvements in automation and computational efficiency. [ABSTRACT FROM AUTHOR]

Spillways are essential control structures in hydroelectric dams for evacuating excess water during periods of high-water flow. These structures are generally excavated within a rock mass, without lining, and they take the form of a flow channel or a plunge pool. Rock mass erosion is an important issue facing engineers when designing unlined spillways. Methods commonly used to analyze this phenomenon are based on the threshold line concept, i.e., the correlation between rock mass resistance and its destruction against the erosive force of water. Multiple indices have been proposed for both rock mass quality and water energy (or erosive force) to assess rock mass erosion. The selection of appropriate indices is critical when evaluating hydraulic erosion. The erosive force of water is often represented by energy dissipation; however, other parameters, including average flow velocity and shear stress at the bottom of the flow channel, may also be relevant. Thus, a critical question is framed: which index best represents the erosive force of water? Here, we develop an approach to assess the applicability of the various indices used to represent the erosive force of water by relying on erosional events at more than 100 study sites. We determine that the most relevant parameters are linked to water pressure, as pressure head and flow velocity better explain the erosive force of the water than shear stress and water dissipation energy. [ABSTRACT FROM AUTHOR]

Puerto de Cajas serves as a vital high-altitude passage in Ecuador, connecting the coastal region to the city of Cuenca. The stability of this rocky massif is carefully managed through the assessment of blocks and discontinuities, ensuring safe travel. This study presents a novel approach, employing rapid and cost-effective methods to evaluate an unexplored area within the protected expanse of Cajas. Using terrestrial photogrammetry and strategically positioned geomechanical stations along the slopes, we generated a detailed point cloud capturing elusive terrain features. We have used terrestrial photogrammetry for digitalization of the slope. Validation of the collected data was achieved by comparing directional data from Cloud Compare software with manual readings using a digital compass integrated in a phone at control points. The analysis encompasses three slopes, employing the SMR, Q-slope, and kinematic methodologies. Results from the SMR system closely align with kinematic analysis, indicating satisfactory slope quality. Nonetheless, continued vigilance in stability control remains imperative for ensuring road safety and preserving the site's integrity. Moreover, this research lays the groundwork for the creation of a publicly accessible 3D repository, enhancing visualization capabilities through Google Virtual Reality. This initiative not only aids in replicating the findings but also facilitates access to an augmented reality environment, thereby fostering collaborative research endeavors. [ABSTRACT FROM AUTHOR]

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This paper proposes a semi‐analytical solution for the ultimate bearing capacity qu of both smooth and rough circular shallow foundations on rock mass. Specifically, a three‐dimensional (3D) Hoek–Brown (HB) is adopted, in conjunction with equilibrium equations under axisymmetric conditions, to derive the governing equations. The method of characteristics is utilized to solve the stress and failure characteristics mesh to determine the qu. The proposed solution is verified by using it to analyze test foundations. Comparison with an HB criterion‐based solution is performed to highlight the importance of 3D strength. Furthermore, parametric studies are performed to investigate the effects of rock mass properties (intact rock constant mi${m}_{\mathrm{i}}$, geological strength index GSI, intact rock unconfined compressive strength σc) and foundation diameter (B) on the qu, failure surface size, and vertical stress distribution on the foundation base. The results indicate that ignoring the 3D strength and the rock mass weight would lead to underestimation of qu. Besides, the ultimate bearing capacity factor Nσ${N}_{{\sigma}}$ (ratio of qu to σc) increases with mi${m}_{\mathrm{i}}$, GSI and B but decreases with σc${\sigma }_{\mathrm{c}}$. The failure surface size is significantly affected by mi${m}_{\mathrm{i}}$, GSI, B, σc${\sigma }_{\mathrm{c}}$ and rock mass unit weight. The stress distribution on the foundation base has higher variance (higher possibility of stress concentration) at smaller σc${\sigma }_{\mathrm{c}}$, GSI, and larger B, rock mass unit weight. [ABSTRACT FROM AUTHOR]

Movements and deformations of ground surface at the Almaz-Zhemchuzhina deposit are studied using surveying techniques. The source data in estimation of parameters and patterns of the stress–strain behavior were observations over the recent geodynamic movements using survey markers and GPS / GLONASS technologies. The proposed scientific approach and guidelines on the use of the studies of trend and cycling geodynamic movements made it possible to determine the natural stress–strain parameters and to accomplish zoning of the test area by the intensities of the movements. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar is used to study defects in the form of internal layers in concrete structures. It is found that modulus of deflection coefficient of GPR signals changes as function of the layer thickness and electromagnetic properties of the material filling the layer (sand, wet sand or air). The experimental and numerical research used the method of peak-to-peak amplitude ratio, which enabled determining the Fresnel coefficients for the upper and lower boundaries of a layer. The minimal layer thickness recorded by GPR was 2 mm. [ABSTRACT FROM AUTHOR]

Dam spillways permit the release of excess water from reservoirs; however, these structures can experience erosion during these releases, causing damage to dam infrastructure. To study rock mass erodibility in this context, a scaled physical model of an unlined open-channel flow spillway is built. The set-up used allows studying multiple parameters influencing rock mass erosion, such as joint orientation, joint opening, block protrusion, joint roughness, and block shape and size. The model also permits varying hydraulic parameters, including channel roughness, flow velocity, and flow turbulence. Using this model, it was evaluated how joint opening and surface protrusion (height and configuration) affect hydraulic parameters both on the block surface and inside rock joints responsible for rock block uplift. Dynamic pressure in the joints varied less than on the block top, with less variability as joint opening size decreased. The force acting on the block top, i.e. on the channel surface, was the main force influencing block uplift, and its effectiveness was affected by protrusion configuration, protrusion height, and joint opening. The uplift force under the block, induced mainly by static pressure, remained constant regardless of protrusion configuration and joint opening. However, the block geometry used may have induced less dynamic pressure under the block. Therefore, block geometry may alter the relative effects of protrusion and joint opening on uplift pressure. Future studies should evaluate how block shape affects the role of both parameters on rock mass erodibility. [ABSTRACT FROM AUTHOR]

The study describes the geological and geo-structural setting of an unstable sea arch in a very attractive landscape of Southern Italy. It evaluates the applicability of some reinforcement work designs consisting of rock mass grouting at shallow depths along the arch vault and abutments. To this aim, the hydraulic conductivity of the rock mass and its groutability were evaluated in detail, integrating field geo-mechanical surveys, boreholes, Lugeon tests, and grouting tests with different grout compositions. Results from site tests were compared with grout take values calculated by applying classical empirical approaches available in the literature, based on rock mass permeability, or by using a novel deterministic approach based on geo-mechanical field surveys. Considering the shallow depths of the tests, the results suggest that the former gave high values, inconsistent with grout tests. On the contrary, the novel deterministic approach provided grout take values consistent with the results of grouting tests, resulting in the most reliable approach for the arch’s thin, shallow, and highly fractured structure. The use of different grout compositions in the site tests proved that extensive use of highly dense and viscous slurries is required (bentonite-cement grout) due to the high-grade weathering and karstification of joint surfaces, which deeply increases their hydraulic conductivity. However, the rock mass grouting must be considered complementary to other reinforcement measures such as bolting, especially along the arch vault. [ABSTRACT FROM AUTHOR]

Purpose. The paper aims to classify the rock mass of the Ighrem Aousser (I/A) mine and analyze its fracturing to determine the appropriate excavation supports. Methods. The study begins with a geo-mechanical classification of the mass using widely used methods: Rock Quality Designation (RQD), Rock Mass Rating (RMR), Q-Barton, and Geological Strength Index (GSI). Fracturing surveys were then conducted to identify the main fracture families using DIPS software. Finally, UNWEDGE software was used to measure the support systems. Findings. The study provides a comprehensive geological study, including field observations, core drilling analysis, and structural analysis with DIPS software. Results indicate that the I/A mine rock mass is highly fractured and altered, as confirmed by mechanical tests at the Mohammadia School of Engineers' laboratory and empirical classifications. Based on these findings, appropriate support systems were identified using UNWEDGE software. Originality. This study provides a detailed classification and structural analysis of the I/A rock mass to propose and measure excavation supports. Integrated approach not only advances understanding of rock mass behavior, but also ensures optimized safety, stability, and productivity of mining operations, setting a new standard in sustainable mining development. Practical implications. In the mining industry, classifying rock masses and designing excavation supports enhances safety, increases site productivity by reducing contamination and lowering mining costs. [ABSTRACT FROM AUTHOR]

An increasing number of methods are being used to extract rock discontinuities from 3D point cloud data of rock surfaces. In this paper, a new method for automatic extraction of rock discontinuity based on an improved Naive Bayes classifier is proposed. The method first uses principal component analysis to find the normal vectors of the points, and then generates a certain number of random point sets around the selected training points for training the classifier. The trained, improved Naive Bayes classifier is based on point normal vectors and is able to automatically remove noise points due to various reasons in conjunction with the knee point algorithm, realizing high-precision extraction of the discontinuity sets. Subsequently, the individual discontinuities are segmented using a hierarchical density-based spatial clustering method with noise application. Finally, the PCA algorithm is used to complete the orientation by plane fitting the individual discontinuities. The method was applied in two cases, Kingston and Colorado, and the reliability and advantages of the new method were verified by comparing the results with those of previous research, and the discussion and analysis determined the optimal values of the relevant parameters in the algorithm. [ABSTRACT FROM AUTHOR]

Throughout all the countries in the world, including Vietnam, nations with well-established mining industries have undertaken extensive research on the stability of rock masses when constructing underground tunnels in varied geological conditions. The present study aims to provide a comprehensive overview of the risk assessment related to rock masses during the construction of pit lines in mining operations. Consequently, the standing time of unsupported tunnels is assessed based on different values of the strength index and deformation characteristics of the rock mass. The objective was to perform both experimental and theoretical investigations to analyse how the stand-up time of rock masses surrounding a tunnel affects the unsupported span. The analyses were based on considering the rock parameters, including strain modulus; geological strength index; and allowable displacement values, and consideration of hereditary creep properties. By examining tunnels excavated in rock strata, it was concluded that varying geological strength index values resulted in distinct creep behaviour in the surrounding rock masses. Thus, it was reasonable to compute the unsupported span and stand-up time of tunnels. The research revealed that permissible displacements are significantly influenced by the types of rock materials surrounding the tunnel structure. Recognising the significance of time, the authors introduce a more practical interpretation and evaluation of the stability of rock masses, thus enhancing the precision of commonly available models. [ABSTRACT FROM AUTHOR]

Introduction: The research is aimed to identify the vulnerable areas of quarry slopes through the creation of a stress-strain state model for the rock mass at the Vostochny quarry, East Saryoba field of the Zhi-landy Group of cupriferous sandstones, as well as their subsequent strengthening.Methods: The research is based on the development of a database containing information on mining-geological, geophysical, geodetic and aerospace surveys. The authors of the research use modern geodetic, aerospace and geophysical technologies for scientifically based predicting of technogenic disasters and the rock mass stress-strain state modeling to ensure safe and optimal mining of fields in difficult mining-geological conditions.Results: The results obtained show that the strengthening of weakened quarry slopes based on the rock mass stress-strain state modeling contributes to the scientific-practical profitability of field mining and provides safe mining in difficult mining-geological conditions.Discussion: Novelty is in the scientific substantiation of the method for strengthening quarry slopes, which is based on the rock mass stress-strain state modeling. The research is of great practical importance, as the rock mass stress-strain state modeling increases the reliability of predicting the rock mass state during its mining. Strengthening of quarry slopes using the proposed method reduces risks and increases safety and economic efficiency of mining the solid mineral deposits in difficult mining-geological conditions.

AbstractRock mass strength parameters are critical when applying the permanent-displacement analysis to landslide susceptibility assessment. Previous studies use limited measured data to assign a constant value for each lithology. Since the rock mass strength is spatially heterogeneous, assigning a constant value to each lithology cannot effectively reflect the spatial heterogeneity of rock mass strength, reducing the reliability of seismic landslide susceptibility assessment. Here we present an analysis of a well-documented seismic landslide inventory and the lithological environment, and develop an empirical model to quantify the rock mass strength heterogeneity. The rock mass strength heterogeneity was subsequently taken as an input of the permanent-displacement analysis to assessing regional seismic landslide susceptibility. Results on two case studies show that considering the rock mass strength heterogeneity would significantly improve seismic landslide susceptibility assessment. The findings of this study are valuable for earthquake emergency rescue and post-earthquake land plans.

Rock mass consists of many discontinuities, such as faults, joints, etc., and layered joints are a common kind of rock mass structure. The joints affect the stress wave propagation, and blasting is an economical and efficient rock fragmentation method for rock mass engineering. So, the rock mass fragmentation effect and construction progress are affected by these layered joints. Numerical studies were carried out to analyze the damage evolution process of intact rock and rock mass with layered joints subjected to blasting loads based on the Riedel–Hiermaier–Thoma (RHT) model in LS-DYNA software (smp s R11.0.), and the effects of the location of initiation points and the fracture distribution on dynamic damage evolution of the rock mass were discussed. Bottom initiation tends to direct the blasting energy toward the blasthole mouth, resulting in effective rock fragmentation and ejection. Gradually adjusting the initiation point upward can improve the stress and damage distribution, allowing some of the blasting stress waves to propagate toward the bottom and enhance the fragmentation of the rock at the bottom. The distribution of layered joints exacerbates the damage to the rock mass on the upstream surface, but also acts as a certain shield to the propagation of stress waves, increasing the asymmetry of the damage distribution. It is useful to know the damage mechanism of the rock mass with layered joints to improve the effect of rock mass fragmentation by blasting. These results have very important theoretical significance and application value for the optimization of blasting construction technology.

The distribution and development of rock mass discontinuities in 3D space control the deformation and failure characteristics of the rock mass, which in turn affect the strength, permeability, and stability of rock masses. Therefore, it is essential to accurately and efficiently characterize these discontinuities. Light Detection and Ranging (LiDAR) now allows for fast and precise 3D data collection, which supports the creation of new methods for characterizing rock mass discontinuities. However, uneven density distribution and local surface undulations can limit the accuracy of discontinuity characterization. To address this, we propose a method for characterizing complex rock mass discontinuities based on laser point cloud data. This method is capable of processing datasets with varying densities and can reduce over-segmentation in non-planar areas. The suggested approach involves a five-stage process that includes: (1) adaptive resampling of point cloud data based on density comparison; (2) normal vector calculation using Principal Component Analysis (PCA); (3) identifying non-planar areas using a watershed-like algorithm, and determine the main discontinuity sets using Multi-threshold Mean Shift (MTMS); (4) identify single discontinuity clusters using Density-Based Spatial Clustering of Applications with Noise (DBSCAN); (5) fitting discontinuity planes with Random Sample Consensus (RANSAC) and determining discontinuity orientations using analytic geometry. This method was applied to three rock slope datasets and compared with previous research results and manual measurement results. The results indicate that this method can effectively reduce over-segmentation and the characterization results have high accuracy.