bluuebunny/crossref_metadata_2025_split huggingface dataset:
Empirical mode decomposition approach to simplify the fracture roughness for numerical models
Authors: Ma Enlin , Rinne Mikael , Torkan Masoud , Janiszewski Mateusz 
Published: January 2023

Abstract
The shear strength of natural, unfilled rock fractures is influenced by surface roughness. The surface curve of a fracture can be viewed as a waveform graph, and in general, it is of the characteristic that high-frequency represents the low amplitude (local variation) and low-frequency represents the high amplitude (general trend). In this work, the signal processing method, Empirical Mode Decomposition (EMD) was employed to decompose the original fracture surface scanned by photogrammetry to several frequency-dependent curves. Low-frequency curves were selected and composed as the element geometry while high-frequency curves were ignored and replaced by parameters related to the roughness in each surface element in Abaqus. The process of push-shear test is simulated using the simplified fracture curve, showing the geometry simplification by EMD can help model the shear failure of rock fractures.
Morphological and physical-mechanical characterization of a syenogranite weathering profile developed on tropical climate
Authors: Jaques Daniel Silva , Marques Eduardo Antonio Gomes , dos Santos Lemos Carolina Crissafe , de Souza Pires Costa Carolina , Ferreira Eduardo Pereira Silveira , Marcellino Lázaro Corrêa 
Published: January 2023

Abstract
In regions of tropical climate weathering processes tend to be very active in engineering time in terms of range and effectives, producing alteration mantles that are often deep and well developed when compared to weathering profiles similar rocks developed on temperate climate. In the municipality of Cachoeiro de Itapemirim, Southeastern Brazil there are many syenogranite weathering profiles on ornamental stone quarries, in which it is possible to observe the effects of weathering at different levels. Considering the importance of knowing the behaviour of these different transition materials in civil and mining engineering design, it becomes relevant to characterize their morphology and physical properties. Among the weathering profiles visited, the focus of this study is a weathering profile that presented the higher heterogeneity, with more alteration levels and better accessibility for sample collection, in situ tests and morphology characterization and description. Samples were collected and the following lab tests were performed for the physical-mechanical characterization: physical indexes (apparent dry density, apparent porosity, absorption capacity and void index), P-wave velocity, Schmidt hammer rebound value and point load index. The preliminary results indicate there is a strong structural control in the development of weathering and that shape of the relief contribute to accelerate the processes of alteration and quick dissection of the relief, avoiding the formation of a profile with more gradual transitions between different weathering levels. As for the physical-mechanical characteristics, a considerable maximum loss of resistance, about 99% in point load index, and maximum increase of the porosity, about 97 %, is observed with the increase on the degree of weathering, being these two parameters more sensitive for the studied granite.
Biaxial Loading of Brazilian Disc Samples
Authors: Serati M , Mottaghi R , Williams D J , Chen Z 
Published: January 2023

Abstract
The Brazilian test method has been widely used over the past 50 years to determine the indirect tensile strength of brittle materials, such as rocks and concrete. While the behaviour of Brazilian samples under conventional indirect tensile testing has been the subject of much research, the biaxial loading of a Brazilian sample under both horizontal and vertical compressive forces has rarely been studied. This study investigates the ultimate strength, crack propagation speed, fracture mode, and damage evolution in sandstone Brazilain samples using high-speed photography methods integrated with a newly designed hybrid biaxial-impact testing facility. The result shows that the samples fail under lower tensile stress than their Indirect Tensile Strength based on the principle of superposition.
Is soft rock also non-abrasive rock? An evaluation from lab testing campaigns
Authors: Kaspar M , Latal C , Blümel M , Pittino G 
Published: January 2023

Abstract
Soft rocks are traditionally regarded in terms of low uniaxial compressive strength (UCS <25 MPa). However, other geomechanical and geological properties such as mineralogical composition, and microstructure should be considered when characterizing the properties of soft rocks. The term soft rocks includes a broad variety of rocks coming from various geological origins. Fabric and state of weathering control inherent anisotropic properties of strength and abrasivity of the various rock types. In this study, a suite of rocks from different geologic settings in the Austrian Alps and surrounding countries is analyzed to evaluate connections between the UCS, CERCHAR Abrasivity Index (CAI), and mineralogical composition (equivalent quartz content - FEQu) with emphasis on soft rocks. It is shown, that in order to assess the properties of soft rocks more accurately, the classification scheme can be expanded beyond the simple UCS approach by including mineralogical information and abrasivity values. This holistic approach more adequately captures the breadth of soft rock properties and allows a differentiated distinction of soft rocks in terms of strength and hardness.
The effect of notches on breakdown pressure during hydraulic fracturing at various stress regimes
Authors: Powlay B , Karakus M , Amrouch K , Chester C 
Published: January 2023

Abstract
High stress environments are becoming more common as the trend and need to develop deeper block cave mines economically and safely continue. Hydraulic fracturing (HF) is considered to be a powerful tool in the success of hard rock block cave mines as it assists with caveability, economic recovery, and seismic risk mitigation. Therefore, determining critical design parameters such as breakdown pressure and the impact of notching on this parameter is paramount for designing and implementing a successful preconditioning campaign. To better understand the impact of notches on the breakdown and propagation pressure, a series of lab experiments were undertaken with variations in stress regime, stress magnitudes and the presence and number of notches were evaluated. This enabled us to explore the impact of confining pressure and spacing of notches on the breakdown and fracture propagation pressures. Various types of samples including Adelaide Black Granite, Engineered plastic (PMMA) were tested to give ranges and balance for homogeneity and real-world mining applications. We observed the fracture initiation and propagation through breakdown pressures along with acoustic emission measurements. The experimental results confirm that increasing confining stress on a sample increases the breakdown pressure. The works also validate the non-impact of axial stresses and the variation of tensile strength on a sample on the breakdown pressure.
The influence of roof lithology on the fracture propagation of horizontal well multistage fracturing in the roof of broken soft coal seams
Authors: Li X J , Zhao H F , Liu C S , Xiong Y G , Lan J L , Han H 
Published: January 2023

Abstract
Horizontal well multistage fracturing in the roof of broken soft coal seams has been demonstrated to be an effective technique to extract coalbed methane (CBM). However, fracture propagation behaviours under this technology vary significantly with different roof lithologies. Therefore, the influence of roof lithology on fracture propagation was investigated in this study. Based on the No. 5 and No. 11 coal seams in the Hancheng block of the Ordos Basin in China, field tests of horizontal well multistage fracturing in the sandstone and mudstone roof of crushed soft coal seams were performed and fractures were detected by microseismic monitoring. Corresponding hydraulic fracturing physical simulation experiments were conducted. The results show that the effectively propped fractures in the roof can provide flow channels for CBM. The better microseismic monitoring fractures and higher CBM production than direct fracturing in coal seams demonstrated the desirable feasibility of this technology. For the sandstone roof, the morphologies of hydraulic fractures were regular and one main fracture was formed by each perforation cluster. For the mudstone roof, the shapes of fractures were irregular and complicated fracture networks were formed. The findings can improve the design of horizontal well multistage fracturing in the roof of broken soft coal seams.
Laboratory-Scale Rockburst Physical Model Testing Using a True-Triaxial Cell
Authors: Wibisono D Y , Arora K , Majumder D , Gutierrez M 
Published: January 2023

Abstract
Assessment of rockburst risk is one of the most fundamental challenges in tunnel design and construction in rocks. The rockburst phenomenon is typically related to rock brittle failure properties, which result in significant strain-energy release, spalling, fractures, and damage near the tunnel opening. This research aims to present a preliminary analysis of rockburst in an unsupported circular tunnel using a novel experimental approach to model tunnel boring machine excavated opening through brittle fracture material. In this physical model testing, the true-triaxial cell utilizes a cube of synthetic sandstone of 300 mm dimensions with a freshly excavated 51 mm diameter tunnel, 150 mm depth on the center top side using a miniature tunnel boring machine. The six sides of the specimen cube are loaded in a true-triaxial manner, allowing for various magnitudes of principal stresses and stress levels that reflect actual in-situ conditions. In addition, the experimental setup employs acoustic emission monitoring to observe the tunnel response during excavation and loading increment. However, the sample in this preliminary experiment was loaded under hydrostatic circumstances and gradually increased until the sample showed a reduction in the acoustic emission activity and failed. The experiment results suggest that the physical model can better understand rockburst in a tunnel through the acoustic emission analysis. The model can outline the damage and spalling during strain energy release near the tunnel boundary.
Static and Dynamic Stability of Rock Boulders on Slopes
Authors: Aydan Ö. , Murayama Y. , Ito T. , Özcan N. Tunar 
Published: January 2023

Abstract
The authors have been involved with the risk assessment of cliff failures as well as mobilization of rock boulders on slopes nearby settlements and roadways in Miyagi Island in Okinawa Prefecture of Japan. The main purpose of this study is to evaluate the de-stabilization of rock boulders with regular and irregular shape due to forces resulting from earthquakes as well as groundwater. A shaking table was used to investigate the motions to cause the destabilization of rock boulders made of Ryukyu limestone on flat and sloping base made of weathered sandstone beneath limestone cliffs in Miyagijima Island. Furthermore, some analytical and numerical computations were carried out to simulate the experimental results. The outcomes of these investigations are presented and discussed in this paper.
Joint behaviour during shear process using an innovative equivalent geometrical and 3D printing technology
Authors: Aad E Abi , Conin M , Deck O , Heib M Al 
Published: January 2023

Abstract
The morphology of rock joints has been recognized as the key factor controlling its mechanical behavior, including its pre-peak and post peak phases. It is playing a significant role in joint aperture in association with asperities crushing, and rock matrix yielding deformation. The purpose of the paper is to examine how the joint aperture or closure occur in the joint, discussing the relationship with normal stress, joint morphology and intact matrix mechanical properties. To do this, an innovative methodology based on 3DP technology using a sand and phenolic binder was applied to construct the matrix and joint. The surface roughness was considered to have fractal properties with a self–affine replication, in accordance with natural observations. The constructed joint underwent eighteen shear tests with constant normal stress. Preliminary results revealed that, for each of pre-peak and post-peak phases, the joint behavior was controlled by a specific range of asperities sizes. Three behaviors were observed depending on the applied normal stress: (i) at low normal stress the waviness causes dilation; (ii) at normal stress over 40% of the UCS value, tensile and/or slip cracks are observed around the waviness, led to a crushing and beheading of these asperities; (iii) at intermediate normal stress, the two mechanisms were conjointly observed.
A multi-scale roughness shear joint model using wear theory
Authors: Gao M , Zhang C , Oh J 
Published: January 2023

Abstract
Fracture is the weakest structure and dominates the shear strength of the natural rock mass. This structure potentially leads to many engineering hazards. Although various shear constitutive models have been developed previously their limitations have not been fully explained. Among them, there is an argument that the shear-off component added in the same manner with the basic sliding friction lacks physical meaning. Many models have been developed based on the lab-scale joint samples, thereby being less reliable when evaluating shear strength of field-scale joint. A new shear constitutive model incorporated with lab-scale has been developed in which the degradations of the irregularities are simulated based on the wear theory. Semi-empirical equations are proposed to estimate the wear coefficients to avoid the back-analyses of the experimental results in order to obtain input values. As different scaled roughness has different effects on both mechanical and hydraulic behaviours, multiscale roughness parameters are employed in the mechanical model. The proposed mechanical model potentially can be expanded to the development of the coupled hydromechanical model.
The rock mass and the development of joints during the tunnel excavation
Authors: Naime W , García R 
Published: January 2023

Abstract
The term joint has been historically used imprecisely when carrying out geomechanical characterization of rock mass. The current classification systems consider the different fracture planes simply as they are observed visually, assuming independence of dimensions and other fixed patterns with depth. That can lead to over-design underground works. Joint patterns in a rock mass depend on the change of the stress field acting on the rock from its original confinement state. The stress field on the rock mass is not constant and varies with changing distance in any underground excavation. In tunnel analyses, empirical classifications consider the parameters related to the joints in the rock mass as constant variables. Those classifications, constitute more than 75% of the valuation without considering the effect of the development and frequencies of joints according to the change of the stress field. In this work, it is considered the necessity to broaden the definition of joints as non-moving fractures for which the development of the fracture plane depends on the change of the stress field in the rock mass. Regarding the discontinuity term, it is important to differentiate the joints from the stratification and foliation planes, which are terms associated with the classification of rocks according to its origin, particularly for sedimentary and metamorphic, respectively. These are made up of continuous planes that control the mechanical behavior according to the stresses acting in the rock mass. Considering a tunnel excavated in an igneous rock mass, the decompression due to the opening effect differs from a stratified or foliated massif. The first one depends on the development of joints, and the second, mainly on the phenomenon of bending of layers within the rock mass, according to the relative dimensions of layer thickness to tunnel diameter. In this article, several practical examples are presented which support the hypothesis that joints develop as a function of the change in the stress field. Also, by means of examples applying numerical methods, it is shown that the deformations of a rock mass with constant parameters are bigger than those when a zoned rock mass is considered, including changes in the geomechanical characteristics related to the distance in the tunnel excavation. The results have an impact on the thickness of supporting elements, yielding lower construction costs.
A Methodology for the Analysis of Tunnel Intersections Using Two-dimensional Numerical Modeling
Authors: Cohen S , Mitelman A , Elmo D 
Published: January 2023

Abstract
Intersections of tunnels are an integral component of most underground applications. The design and construction of tunnel intersections can be the most technically challenging element of a tunnel project. Yet, there are relatively few publications and methods regarding tunnel intersection design. Tunnel intersections are essentially a three-dimensional problem. However, 3D models require significantly longer time for solving and interpreting, greater computer resources, and higher user expertise. Hence, there is a great incentive to develop simpler and quicker analysis methods for tunnel intersections. In this paper, a methodology is developed so that a 3D tunnel intersection problem can be modelled using an equivalent 2D numerical model. For this purpose, it is proposed that the main tunnel cross section is modelled with an additional horizontal expansion component that represents the cross tunnel. Multiple 3D and 2D models were computed for the purpose of finding the expansion distances in the 2D models that yield similar deformations to the 3D models. Based on the results, regression analysis was employed to derive a formula relating the ratio of equivalent diameters of the main to cross tunnel to the proper expansion distance. This formula provides a useful and practical tool for preliminary tunnel intersection design. The current work relies on a number of assumptions, mainly that the rock mass is elastic. More work can be carried out to extend and modify the proposed method for more complex conditions.
The exploration of force chains in bonded granular materials: A numerical study
Authors: Zhang M , Konietzky H 
Published: January 2023

Abstract
The bonded particles in DEM simulations have been widely used to reproduce the rock behaviour. Inside the DEM model, forces are transmitted through contacts between particles. It has been found that some chain-like particle groups called ‘force chains’ bear the majority of applied loads in non-cohesive granular materials. It can be supposed that there are also similar chain structures in bonded granular materials, which could be helpful to understand the relationship between the grain-scale structure and macroscopic properties.
The aim of this paper is to explore the force chains or similar chain-like structures in bonded granular materials. Several models were generated representing different structures, such as models comprised of polydisperse particles, and models after random deletion and selective deletion of particles. Then, uniaxial compressive tests were conducted on these numerical models.
The simulation results indicate that there are also chain structures in bonded granular materials and models after deleting particles with large principal stresses have the smallest peak stresses while models in the control group have the same porosity. This verifies that these particles are important for the model stability under external loads. At last, an algorithm was found suitable to extract force chains and the connectivity of force chains was discussed and analysed.
Rational design concept for inverted arch structure for mountain tunnel
Authors: Natsume T , Ishii Y , Nakazato R , Otsu T , Kawata K , Isago N 
Published: January 2023

Abstract
One of the typical countermeasures against ground heaving in mountain tunnels in service is reinforcement by installing or refurbishing new invert, but there are many problems in terms of workability and economy. The purpose of this study is to propose a concept and load-bearing capacity that will contribute to the selection of rational reinforcement measures. As one of the methods, inverts with new shapes were assumed as reasonable structures, and their load-bearing capacity and structural feasibility were examined by model experiment and numerical analysis. As a result, it was confirmed that the behavior during deformation and the tendency of the stresses generated differed depending on the shape of the invert. In addition, there are some cases where it is possible to have a certain load-bearing capacity and expect reinforcement effects in rational construction.
Modelling of progressive failure mechanism of mine pillars
Authors: Cammarata G , Elmo D , Brasile S 
Published: January 2023

Abstract
Rock fracturing process around underground openings is mainly a process of progressive slabbing with the generation of surface-parallel fractures in the initial stage, and shear failure is likely to occur in the final process. The difficulty of capturing this behaviour through conventional continuum modelling has led to the development of advanced constitutive laws for use in continuum models. Recently, an enhanced continuum constitutive approach to simulate strain-softening based on the Hoek-Brown failure criterion has been presented. This advanced Hoek-Brown model with Softening introduces a hyperbolic decay of the material properties affecting the post-peak response and the nonlinear dilation, thus enabling to investigate failure modes in the form of dilatant shear bands. Moreover, to restore the objectivity of the numerical solution during the development of strain localization phenomena, a viscous regularization technique has been implemented within the model. The performance of this constitutive model has been proved and, in this paper, further numerical computations are reported concerning the brittle failure process occurring in mine pillars, thus confirming the capability to capture failure mechanisms during excavation within a strain localization regime.
Experimental study of frictional resistance influences on tunnel face stability
Authors: Kawanoue R , Yagihashi T , Togashi Y , Osada M 
Published: January 2023

Abstract
In recent years, there have been several ground surface collapses due to tunnel excavation in Japan. Although such accident is caused by ground loosening and tunnel face collapses due to excavation, there is no accepted theory for estimating the face stability because this phenomenon is quite complicated and highly influenced by the supports and lining types. Specifically, the loosened area is relatively large for the urban NATM method, which applied in a shallow sedimentary rock layer. Therefore, a method to quantitatively evaluate the tunnel face stability by this kind of mechanical property is essential. In this study, 2D tunnel pull-out test was conducted to observe the influence of frictional resistance on tunnel face failure and loosening area by changing the shear resistance angle using three particle sizes of dry silica sand and different variation of earth covering. The result demonstrated that failure region doesn’t reach the ground surface when the shear resistance angle is 46.4° and covering thickness to tunnel height ratio H/D is over 5 or the angle is 55.8° and H/D is over 3. This study considered that there is an arch effect depending on frictional resistance and earth coverings occurred. Furthermore, even with the same earth covering, the smaller the shear resistance is, the earlier the ground surface collapses. Therefore, it could be said that the higher the frictional resistance is, the later the collapse proceeds.