bluuebunny/crossref_metadata_2025_split huggingface dataset:
A review on the application of cohesive zone model in hydraulic fracturing
Authors: Li X J , Zhao H F , Xu K Q , He Y L , Wang C W , Yao W J 
Published: January 2023

Abstract
Hydraulic fracturing is an effective measure to increase production and injection and blockage removal in oil and gas field development. Accurate prediction of fracture morphologies is the key to the optimized design of hydraulic fracturing. The cohesive zone model (CZM) has been widely used in the numerical simulation of fracture initiation and propagation during hydraulic fracturing. The fractures formed by the numerical simulation vary significantly with different CZMs. In the current numerical simulation, the CZM generally adopts the bilinear model, which is more suitable for describing brittle fracture, while rocks are quasi-brittle materials and have nonlinear CZMs. This deviation should be corrected. Moreover, the CZM parameters are generally determined based on experience, without a reliable basis and standard determination method. This article focused on the CZM, systematically introduced its concept and classification, and clarified the correlation between the types of CZMs and the brittleness, quasi-brittleness, and ductility of rock fracture. The application of CZM in hydraulic fracturing was reviewed, and the existing problems, corresponding countermeasures and future research trends were presented. An integrated method of combining laboratory experiments, data mining and numerical simulation to determine the CZMs of mode I, mode II, and I/II mixed mode cohesive cracks was proposed.
A Bayesian regression analysis of in situ stress using overcoring data
Authors: Javaid M A , Harrison J P , Ivars D Mas , Kasani H A 
Published: January 2023

Abstract
Characterising the state of in situ stress at a target depth is crucial for all underground engineering projects. Consequently, on critical projects such as nuclear waste repositories extensive campaigns are implemented with the goal of estimating the in situ stress state. These campaigns often comprise both direct measurement and indirect estimation methods, but the data obtained across a project volume may exhibit significant variability. This poses significant challenges in both quantifying the variability and uncertainty of in situ stress, and determining the stress state to be used for design purposes.
It is often assumed that the state of in situ stress increases linearly with depth, and thus linear regression of principal stress magnitude against depth are often found in the literature. As such methods not honouring the tensorial nature of stress are, strictly, incorrect. To show how this limitation may be overcome, here we present a Bayesian regression analysis of in situ stress with depth that uses the Cartesian stress tensor. The analysis is performed using over 100 overcoring data obtained at the SKB Forsmark site in Sweden.
A comparison between the customary and Bayesian approaches is presented, which shows the superiority of the tensorial technique.
Energy Release Resulting from Sudden Excavation Shape Changes during Two-sided Strainbursts
Authors: Gonzalez F J , Kaiser P K , Diederichs M S 
Published: January 2023

Abstract
When tunnels in underground hard rock mines experience strainbursts, the effective shape of the tunnel suddenly changes as part of the rock fails, notches form and the broken rock bulks inside the strainburst volume. For circular tunnels, this dynamic rupture and bulking process causes a shape change with associated displacements and velocities in the surrounding elastic rockmass and at the excavation walls. This process can be approximated for circular tunnel bursting in elastic rock by a shape change from circular to elliptical and Maugi’s solution [1] can be adapted to estimate related displacements and average ground velocities. If these velocities are imposed on a volume of rock or shotcrete with a given mass, the mass can be ejected, and the corresponding kinetic energy can be estimated. When combined with the sudden bulking of the fractured rock, displacements and velocities are magnified between the elliptical shape and the pre-burst (circular) shape of the tunnel. This study focuses on the effect of the combined excavation response with elastic and bulking deformations to assess frequently observed excavation damage processes involving ‘shotcrete rain’ and heave of floor slabs caused by these shape changes. An analytical solution is presented for circular tunnels to estimate the elastic and bulking displacements, the resulting velocities, and energy demands.
A refined evaluation method for the stress field of the Chang 73 shale oil reservoir of northern Shaanxi
Authors: Zhang Yu , Hou Bing , Wang Yizhao , Ma Wenzhong , Dan Weidong , Zhuang Li 
Published: January 2023

Abstract
Shale oil resources are abundant in the Chang 73 reservoir in the eastern Ordos Basin. The thin interbeds of shale in the Chang 73 section of the Yanchang Formation in the oil-bearing section are developed with solid interlayer inhomogeneity and unclear longitudinal interlayer stress difference. This has resulted in unpredictable high seam extension heights during hydraulic fracturing. Based on the results of the Kaiser experiments, the lithological variability was finely described by combining with downhole core observations, and the longitudinal interlayer stress difference coefficient in the Chang 73 section was finely interpreted by using logging data to evaluate the regional distribution pattern of ground stress in the Chang 73 shale reservoir in northern Shaanxi. After studying 600 wells in north of Shaanxi, it was found that: the maximum longitudinal ground stress variation in the Chang 73 reservoir with a thickness of 30-50 m was 35-55 MPa, the minimum ground stress variation was 30-50 MPa, and the minimum was 30 MPa. The horizontal stress difference in the Chang 73 reservoir north of Shaanxi was 3.2-8.6 MPa. The maximum horizontal stress was high in the northwest and low in the southeast, with high values distributed in Jiyuan and Dingbian areas and low values distributed in Zhidan. The refined evaluation of the ground stress results guides the selection of the fracturing layer and the optimal design of the horizontal well trajectory in the field.
Assessment of static performance of welded mesh along mesh overlap used at Kiirunavaara mine
Authors: Zhang Ping , Eriksson Fredrik 
Published: January 2023

Abstract
Localized failure of mesh, i.e., the mesh was cut or torn by rock blocks as a result of a seismic event, was observed at LKAB’s Kiirunavaara mine. This is especially common along mesh overlap where mesh sheets are joined together. However, the performance of welded mesh along mesh overlap is not well understood. A series of tests was conducted at the laboratory at Luleå University of Technology, Sweden. The tested mesh sheets are made of 5.5 mm diameter wires welded along orthogonal directions spaced on a grid of 75 mm by 75 mm. The mesh sheet(s) was placed on a steel rig and fixed with bolts with spacing of 1.0 m by 1.0 m. A 300 mm loading plate made of concrete was placed underneath the mesh and pull/push load was applied on the mesh through the plate. For comparison purpose, the loading plate was placed at the mesh center following a dice five pattern as well as in the middle between two bolts (overlap position). The force-displacement curves of different test configurations were measured and failure modes of the mesh were observed. Laboratory test results show that the load-carrying and deformation capacity of the mesh is highly dependent on the load spreading and loading position relative to the holding points. When the mesh overlap was loaded, it shows: i) the highest stiffness; ii) the highest rupture load; iii) lower residual load-carrying capacity; and iv) the lowest deformation capacity. Two failure modes were observed in the conducted tests. Heat affected zone failure is the most common one and the second is the tensile failure along wires. Based on the laboratory results, an optimized mesh layout and bolting pattern was suggested for the Swedish underground mines.
Tunneling in heterogeneous ground: an update of the PBE code accounting for the uncertainty in estimates of block quantities from site investigations
Authors: Napoli M L , Barbero M 
Published: January 2023

Abstract
Hard rock blocks embedded in a soft matrix can be found in many geological units. When tunneling in these heterogeneous formations, many technical problems can be caused by the presence of cobbles and boulders. These risks depend on the excavation method selected, and typically increase as the block content, dimension and frequency increase. Therefore, successful tunneling projects require cobble-boulder properties to be accurately predicted, in order to select the best tunneling method and design the most appropriate cutterhead. A recent and extensive statistically-based methodology was developed to estimate the probability of encountering rock blocks located totally or partially within the tunnel excavation area, resulting in a free executable code, named PBE. A significant limitation of this code is that it requires, among other input parameters, the block content expected within the tunnel zone. This parameter can be estimated from 1D (i.e. borings/scanlines) or 2D (i.e. geological maps, outcrops, photographs) measurements. However, the block quantity inferred from these measurements is generally affected by a high magnitude of error. In this paper, an extension of the PBE is presented, that accounts for the uncertainty in estimates of block quantities from site investigations. The updated version of the executable code is also provided.
Laboratory study of the behaviour of grouted cable bolts under static and dynamic axial loading
Authors: Anzanpour S , Aziz N , Remennikov A , Nemcik J , Mirzaghorbanali A , Rastegarmanesh A 
Published: January 2023

Abstract
As a typical roof-supporting system of tunnels, Cable bolts are subjected to static and dynamic loading conditions caused by ground movements and mining activities. As mining goes deeper, the chance of undetermined ground stress concentrations increases and subsequently, the probability of sudden unexpected failures such as rock bursts increases. Many studies have been carried out to simulate the axial loading condition of the tendons, especially cable bolts, under static and dynamic loading modes; however, it barely can be seen that both behaviours have been studied and compared simultaneously. From other points of view, although research has been conducted on Barrel and Wedge and load-bearing plates, these components have hardly been considered together in axial loading studies. In this laboratory study, a new pullout testing mechanism has been introduced, which is capable of implementing axial loading of cable bolts in both static and dynamic loading conditions. In addition, in a parametric study, the role of bulbs of the cable bolts as well as barrel and wedges on the load-bearing capacity of the anchors have been examined. The bond between cable bolts and grout material in the bulbed cables behaves almost 30% stronger in static and 40% stronger in dynamic tests in comparison with plain cables. In general, the required pullout energy in dynamic tests was 25-50% less than in static tests.
Application of seismic sensors on measurement while drilling for real-time rock property detection
Authors: Khanal M , Shen B , Duan Y , Luo X 
Published: January 2023

Abstract
Rock type and geological structures are often characterized with geotechnical and geological data gathered from boreholes that are drilled considerable distances apart. Such characterization may not identify localized variations associated with rock mass. The continual acquisition of rock data while drilling on a local scale has a potential to provide confidence in detecting rock types and interpreting rock properties, and depending on the application, may inform downstream operations.
Drill returned parameters, such as, rotary speed, penetration rate, sound, torque, vibration, can provide insights into rock geotechnical properties. In the past, most of the researches in this area are limited to the use of conventional drill parameters such as penetration rate, rotary speed, torque and weight on bit. Noisy signals from drilling operations often pose a major challenge from using these conventional parameters to reliably interpret rock properties. To overcome this issue, in addition to the conventional drill parameters, the feasibility and application of seismic sensors on identifying relative rock properties have been explored in the current research. The interaction between the drill bit and rock mass being drilled generates seismic signals, which vary with different rock conditions and drilling operations. These seismic signals can be interpreted to detect rock types, rock properties, rock-ore interfaces and geological structures on a local scale.
Laboratory experiments with a rotary drilling machine on synthesized rock samples with and without interfaces have been conducted. Preliminary laboratory results show clear seismic signatures when drilling through the rocks with various strengths and interfaces. The results obtained using the conventional drill parameters and seismic data have also been compared in this paper.
Consideration of the mechanical behaviour and the influence on ground of vertical pre-reinforcement
Authors: Amemiya T , Nagata T , Isago N , Kawata K , Shiroma H , Nishimura K 
Published: January 2023

Abstract
The vertical pre-reinforcement bolt method is used to stabilize the ground at the top of tunnels with shallow overburden to prevent ground surface settlement and to stabilize slopes. However, the design of this method is mainly empirical, based on similar construction cases, and a quantitative design method has not been established. Model tests simulating the vertical pre-reinforcement bolt method and its numerical analysis were conducted to establish a rational design concept for the vertical pre-reinforcement bolt method. The results of the model test showed that the vertical pre-reinforcement bolt method can improve the continuity of the ground regardless of overburden and slope angle. It was found from numerical analysis that the spacing, width and properties of the bolts were related to the reinforcement effect.
Drilling boreholes in sulphureous groundwater areas: elements of some case studies in Portugal
Authors: Ferreira-Gomes L M 
Published: January 2023

Abstract
In Portugal there is a special market niche, which is the medical spa sector. These are supplied by special groundwater, being the sulphureous type water, the most frequent water in this activity. These waters essentially have a long geohydraulic circuit, associated to granite massifs, in confined to semi-confined aquifer systems of the fissural type, and natural discharge sites are often associated with structurally very complex areas, with faults sometimes of great thickness, that lead to sudden variations, from very fresh rock to clay. However, this situation is very favourable to unexpected collapses of the borehole under construction, with terrible problems to overcome, sometimes leading to involuntary deviations in the spatial position of the drilling in progress. On the other hand, because one of the current solutions is the use of cementations, associated with re-drilling, there is also the problem, of the difficulties of cement grouts in a common situation, not gaining strength, due to the chemical composition of sulphureous groundwater. It should be noted that these aquifer systems have the potential to provide natural hot water, when the boreholes reach great depths and can leverage geothermal uses, at the same time as uses in medical spas. Therefore, it is necessary to know these aquifer systems well, to lead to more efficient projects in the future. Therefore, in that sense, after presenting the typical chemical composition of the sulphureous groundwaters understudy, the experiences acquired in the drilling of some boreholes in Portugal, namely in the Carvalhal Medical Spa, Longroiva Medical Spa, Águas do Graben, Unhais da Serra Medical Spa, and the new mineral water of Granjal (Santa Comba Dão), are briefly presented. The comparison of the objectives defined at the beginning with the results obtained is generically presented, namely the depth of drilling, giving emphasis to the problems of collapse of the walls of the boreholes, cementing, additives, among others. At last, some final notes are presented in the sense that the drillings in this type of hydrogeological systems, in the future come to be increasingly efficient and reach greater depth, not only to acquire water with quality freer of interferences with fluids of superficial aquifers, but also, in the sense of reaching temperatures that make the use of geothermal energy viable.
A preliminary study of hydro-mechanical properties for bentonite-sand mixture
Authors: Motoshima T , Iso S , Nishimura T 
Published: January 2023

Abstract
Radioactive waste is a consequence of treatment radioactive material in industrial, medical, military and research applications for remaining electrical energy. For high-level waste (HLW), spent fuel (SF) and long-lived waste categories, geological disposal at depths of much hundreds of maters is considered in safety design. This study has aim to appear that swelling pressures due to hydration effort, hydraulic conductivity and stress-strain properties associated to evaluation to stress paths using two different bentonite-sand mixture, which are Sodium type bentonite and Calcium type bentonite. These materials have key feature in hydro-mechanical properties established in many reported obtained from laboratory test and underground investigations. Swelling pressure test, hydraulic conductivity test and triaxial compression test are conducted out, and developed apparatus are useful to results for series of some testing programs. Particularly, salinity concentration with increasing and decreasing on considering salinity effort is so interesting that further changing is applied to hydraulic conductivity for bentonite. While large lateral pressures are applied the bentonite at triaxial compression test, depending on lateral pressure is obviously to strength parameters that are apparent cohesion and angle of internal friction.
Verification of Spalling Tensile Strength of Rocks using 3D GPGPU-accelerated Hybrid FEM/DEM
Authors: Min G. , Fukuda D. , Oh S. , Liu H. , Cho S. 
Published: January 2023

Abstract
The spalling test is widely applied for evaluating dynamic tensile strength of rock under high strain-rate condition. The dynamic tensile strength is indirectly measured in the spalling test by theoretically assuming the tensile stress level at the failure position of a cylindrical specimen based on the 1D stress wave propagation theory. However, the theoretical estimation method for dynamic tensile strength have not been fully validated since dynamic tensile strength was determined with insufficient understanding of the fracture process, such as crack propagation and stress distribution in the rock specimen during the spalling test, owing to observational limitations in the experiment. Thus, a proper validation method is required for the proposed method, and numerical simulation can be used to validate the proposed method by reproducing the tensile fracture process of the rock specimen during the spalling test. Thus, the dynamic spalling tensile test for rock specimens was reproduced in this study using the GPGPU-based 3D hybrid FDEM that we recently developed. The dynamic tensile fracturing process was analyzed in the simulation of spalling under various strain-rate conditions. Finally, we discussed the application of various theoretical estimation methods to the 3D spalling test.
A brief review of the effect of wildfires on rockfall occurrence
Authors: Pérez-Rey I , Sarro R , Tomás R , Alejano LR , Gutiérrez LE Hernández , Mateos RM , Riquelme A 
Published: January 2023

Abstract
Wildfires and rockfalls are among the major hazards in forested mountainous regions across Europe. Understanding processes and conditions that lead to rockfalls during and after a wildfire in different geological contexts is, therefore, of great relevance. The increase of rockfalls associated with the occurrence of wildfires is connected to several factors, not only in the detached area but also in the propagation and affected area. Wildfires cause changes in the mechanical properties of rocks and discontinuities as well as the loss of protective capacity from vegetation, complemented by the effect induced by firefighting activities and by extreme temperatures that may deteriorate the installed protective measures. After the occurrence of a wildfire, there is an increase in the frequency and intensity of rockfalls in the burned area, causing a major impact of rockfalls on road networks and inhabited areas. Additionally, the rockfall risk perception is usually increased due to the removal of vegetation by wildfires, exposing both rock blocks and the rock mass. In this review, the main factors that influence the occurrence of rockfalls after a wildfire are briefly reviewed.
Discrete Element Method Simulation of Borehole Breakout Based on the Strain Energy Concept
Authors: Xiang Z , Oh J , Moon T , Si G , Li X , Canbulat I 
Published: January 2023

AbstractThis study focused on studying the V-shaped rock failure around borehole walls and reproducing borehole breakout using numerical simulations. Discrete element method (DEM) is adopted, and a two-dimensional particle flow code (PFC2D) model is built based on Tenino sandstone. The simulations are conducted by applying different maximum horizontal stress values under the same minimum horizontal stress condition, and the results are compared with the true-triaxial breakout experiments on the same rock properties and loading conditions. Due to the absence of vertical stress in 2D simulations, the obtained angular spans are generally larger than the experimental values. On the other hand, the breakout depths are found to be significantly smaller than the experimental results since the failed particles within the breakout zone remained to withstand internal loads and constrain the damage zone. In order to better simulate the rock detachment process during breakout formation, a particle removal algorithm using the strain energy release concept is developed and embedded into the model. With the implementation of the algorithm, the breakout propagation process in the vicinity of the borehole shows a good agreement with the experimental observations, suggesting that the effective removal of failed particles is essential for accurately simulating borehole breakout. The results from this study can provide new insights into the V-shaped breakout formation mechanism and strain energy changes during borehole breakout initiation and propagation.
Riskcoast: A South-European approach for coastal landslide hazard: presentation and results
Authors: Gasc-Barbier M , Thiery Y , Garnier C , Raveneau L , Bernardie S , Chanal A 
Published: January 2023

Abstract
RISKCOAST is a European project, co-funded by the South-West European (SudOE) Interreg V programme (https://riskcoast.eu), which aims to develop tools to prevent and manage coastal geological risks related to global warming: land movements mainly, but also other phenomena such as the evolution of water tables. The aim of this project is to study geological risks in coastal areas related to climate change, with a focus on improving the coordination and effectiveness of means of prevention, disaster management and rehabilitation of disaster areas. After a presentation of the whole project, we will focus on a specific site in the French Basque coast where a landslide impacts a very touristic area. An hydrogeomechanical model of the landslide is realized with FLAC3D and a parametric study is proposed to determine the most important parameters, and to define possible safety factor game value.