bluuebunny/crossref_metadata_2025_split huggingface dataset:
Guidelines to minimize the occurrence of mega-wedge falls in rock caverns
Authors: Vaskou P , Gatelier N 
Published: September 2021

Abstract
Over the last decade, large rock caverns have been developed for storing vast volumes of hydrocarbons and in particular crude oil. In this context, large rock caverns have light support made of grouted steel or fibreglass rock bolts. Reinforcing cables are strictly prohibited to avoid leak paths for the product. Therefore, the risk of mega-wedge occurrence is high since the size of the potential mega-wedges is proportional to the cavern size. Some geometrical situations are more detrimental than others and the possibility of a local or extensive collapse be very high, including in rock masses which can be ranked as good and above. Such an apparent paradox could have been detrimental to the concept of large caverns because mega-wedges are extremely difficult to stabilize once discovered because rock bolts are generally too short to stabilize them. Anticipation is therefore the key. First, we clarify the term mega-wedge and then, analyse the various possibilities of occurrence in large caverns, as well as classical tunnels. Guidelines are proposed to identify whether the conditions are met for experiencing mega-wedge failure at hand. Two main geological structures, shear fractures and smooth-persistent-planar-spaced (SPPS) joints, are favourable for mega-wedge formation. These two fracture types are analysed and criteria are given to ensure a quick and efficient determination procedure. The field approach is synthesised by a decision chart, to be used at site, during the excavation works.
Numerical method of tunnel face pressure estimation considering progressive failure due to excavation
Authors: Togashi Yota , Shota Iguchi , Osada Masahiko , Kawanoue Ryo 
Published: September 2021

Abstract
The stability of the tunnel face is a top priority in a tunnel construction. The estimation of the earth pressure acting in front of the face is essential for the stability evaluation of the face, and many model experiments have been conducted to understand the characteristics of face stability. On the other hand, there are many cases in which the stability of the tunnel face is evaluated by limiting analysis assuming a constant slip region by applying the loosening earth pressure derived by Terzaghi as a boundary condition, but the actual slip region is not always constant and expanded progressively accompanying by the collapse of the face. There are few past studies that have considered this phenomenon. In this study, a estimation method of the tunnel face pressure are developed in consideration of the progress of face collapse. The proposed method is a kind of limit equilibrium method. Assuming a slip line with two ellipses with the same center and different radii, the first-order linear differential equation of earth pressure in the tunnel face direction is calculated from the equilibrium for infinitesimal elements in the circumferential direction.
Application of a bonded critical state model to design tunnel support for rockmass bulking
Authors: Ciantia M O , Arroyo M , Kaiser P 
Published: September 2021

Abstract
Gabion-type support is a favoured option to restrain bulking in pillar walls of mine footprint tunnels. It uses closely spaced short reinforcements in tunnel walls (typically fully grouted rebar) in combination with surface support (rock fragment retention systems such as shotcrete, weld wire mesh, straps, etc.). The system is installed while the rock is still mostly intact and is conceived to maintain support capacity even when, the rock attains a fully fragmented state, acting then like a gabion or earth-reinforced type retaining wall. In this paper the interaction between the support system and the highly stressed pillar walls is investigated numerically by means of finite element analyses within the framework of displacement-based design. Because the material response should capture the passage from intact rock to fully fragmented state, an advanced elasto-plastic bonded constitutive model was adopted as a simulation framework. The model is calibrated to replicate the mechanical behaviour of Bursnip Sandstone and Amarelo Pais Granite. These two rocks were selected because of high quality triaxial tests results from the literature. After showing the good performance of the model to reproduce both low and high pressure triaxial compression behaviour an extensive parametric study investigating the effects of bolt types on gabion response is presented.
Monitoring and risk-control of large-scale toppling failures - a case study from Ok Tedi
Authors: Casagrande D , Klawitter M , Koek M 
Published: September 2021

Abstract
This paper presents the monitoring and management of a large-scale toppling failure that was first observed in 2005 at the Ok Tedi mine. Ok Tedi is a large open-cut copper gold mine in the Western Province of Papua New Guinea and is one of the wettest mines in the world (>10 m annual rainfall). The management of large-scale failures in open-pit mines expresses geotechnical challenges in terms of balancing economical designs and safe operations. The failure located at the southern end of the West Wall was reactivated in June 2019 due to continuous mining and prolonged rainfall events. Erosion, cracking, and rock toppling associated with lateral displacements, evolved rapidly. Hence, ground control and groundwater management plans, including a Trigger Action Response Plan (TARP) and measurements to monitor movement across the wall, were implemented. This monitoring system, associated with daily visual inspections, enhanced the understanding of the necessary controls to maintain a safe mining operation. Furthermore, the water management plan was crucial in managing this failure. The successful risk-control of this large-scale toppling failure at Ok Tedi ensured continuous mining with a functional balance between economic and safety during operations.
Geomechanical study and rock fall hazard analysis in the historical Centre of Forza d’Agrò (Messina - Italy)
Authors: Barbagallo  , Calvi F 
Published: September 2021

Abstract
The present study shows the result of a rock fall hazard evaluation of the area downstream the Norman Castle that overlooks Forza d’Agro (Messina Province - Italy). The study was aimed at evaluating the penetration capacity of a rockfall in the inhabited center, to evaluate the number of houses involved in the transit area of the boulders. On the basis of the data obtained, a hazard assessment was developed that took into account not only the type and magnitude of the landslide phenomenon, but also the probability of occurrence of the event or its return time.
Sets of stress path as a strategy to study efficiently the geomechanical trending behavior in CSS projects
Authors: Herrera-Schlesinger M C , Cartagena-Pérez D F , Torres-Hernández C A , Araujo-Guerrero E F , Alzate-Espinosa G , Benitez-Pelaez C A , Higuita-Carvajal E , Naranjo-Agudelo A , Castro-Caicedo A J , Burgoa-Suarez L O 
Published: September 2021

Abstract
Thermal recovery techniques such as CSS (Cyclic Steam Stimulation) induce significant changes in the stress path at the reservoir formation due to the induced thermal stresses in the wellbore and surrounding area. The understanding of phenomena regarding these stress paths is crucial to ensure safe operation and optimization of well productivity. Therefore, stress path analysis in CSS entails a challenge related to the number of focal points throughout the reservoir in which the stress paths should be studied. The reduction on the number of focal points is an advantageous step to ensure the appropriate analysis in extensive reservoirs with multiple sands and layers with different geomechanical and yield parameters. In the proposed grouping strategy, temperature and pore pressure are found to be key variables when determining the sets of stress paths with a common phenomenological trending behavior. In the current case study located in Middle Magdalena Valley basin, this grouping strategy allows a comprehensive analysis of 3 sets of stress path strategically located on the borehole wall, inside and outside the steam front with the aid of numerical simulation software (CMG). Considering that stress paths usually represent a single focal point behavior within the reservoir, once this grouping strategy is implemented, an analysis of the whole reservoir is simultaneously performed during CSS.
Stress shadow effect during multi-stage hydraulic fracturing with different wellbore arrangements
Authors: Wasantha P L P , Konietzky H , Xu T , Xu B 
Published: September 2021

Abstract
Multi-stage hydraulic fracturing was simulated using a two-dimensional universal distinct element code (UDEC). Five fracturing stages were considered along horizontally (i.e. parallel to the minor principal stress direction)- and diagonally (i.e. inclined to the minor principal stress direction)-positioned wellbores within the pay zone, where the spacing between wells was changed to 50 m and 100 m. Progressive fracture propagation and the evolution of stress shadow with sequential multi-stage fracturing were monitored. A marked stress shadow was observed for closer well spacings under both horizontal and diagonal well arrangements, leading to a significantly asymmetric fracture propagation about the wellbore. The diagonal well arrangement showed a nearly unidirectional fracture propagation after the first stage for the closer well spacing case. Fractures of sequential stages predominantly developed in alternating directions at greater well spacings irrespective of the wellbore arrangement. Progressive fracture development also showed that fractures created at earlier stages could further extend due to the stress shadow of later fracturing stages, and this effect is more pronounced for closer well spacings. After five stages, the overall fracture lengths indicate that a higher fractured area was created by horizontal well arrangement for any case of well spacing. Finally, the importance of optimizing the fractured area and fracture controllability to contain the fractures within the pay zone was highlighted.
Numerical analysis of deep twin excavations and boreholes for heavy oil production
Authors: Emci M E , Ozturk H 
Published: September 2021

Abstract
One of the plans for the production of Turkey’s largest oil reserve, Bati Raman (1.85 billion barrels), is to use Mining-Assisted Heavy Oil Production (MAHOP). In this method, twin declines are excavated from the surface to the reservoir and a series of excavations (galleries) continue along the bottom of the reservoir. Fan-shaped steam injection and production holes are drilled in the reservoir from the crown of the galleries to use conventional Steam-Assisted Gravity Drainage (SAGD). The Bati Raman reservoir is situated at an average depth of 1450 m, producing 12° API heavy oil from a 60m thick calcareous reservoir rock. This research aims to numerically investigate the stability of excavations together with the initiation, formation and propagation of fracture networks between the fan-shaped boreholes and around typical twin excavations using FLAC3D. It is shown that the stability of twin excavations and pillars between them can be guaranteed with suitable support types. In addition, this innovative approach in heavy oil production in hard rock media successfully showed that the fracture networks created by MAHOP could be used effectively for oil recovery of reservoir rocks using SAGD.
Hydrofracturing tests on granite samples using a true triaxial device equipped with acoustic emission sensors
Authors: Herbón-Penabad M , Muñoz-Ibáñez A , Delgado-Martín J , González-Molano N , Alvarellos-Iglesias J , Canal-Vila J 
Published: September 2021

Abstract
We present a series of tests performed on granite samples using a true triaxial device designed and built at the Rock Mechanics Laboratory (University of A Coruña). The experiments were performed using cubic rock samples of 150 mm-edge, which were loaded to different stress conditions (σh < σh < σy < 45 MPa) on each loading axis. The device is based on a stiff steel frame that can be coupled to a servo-hydraulic testing machine that provides de vertical stress (av), while two high-pressure pumps are used to deliver the lateral stress (σh and ah). An additional high-pressure pump is used to inject the fluid (mineral oil) into the rock sample at a low constant-flow rate. The aluminium loading platens, which are bevelled at the edges to avoid interaction among adjacent faces, have holes and grooves to introduce acoustic emission sensors that allow the location of fracture propagation. The specimens were drilled using a 6 mm drill bit until reaching the geometrical centre. Then, a 1/8” (~3.18 mm) stainless steel tube is glued to the samples with epoxy. Strain measurements during the experiments were conducted using four strain gages attached to the orthogonal faces of the specimens. The system was further equipped with three LVDTs to account for the bulk displacement on each axis. Our results suggest a linear relationship between the breakdown pressure and the confining stress under hydrostatic conditions but no clear correlation in non-hydrostatic stress regime.
A time-independent reliability based design approach for rockfall net fences: a comparative analysis within the Eurocode framework
Authors: Marchelli Maddalena , Peila Daniele , Biagi Valerio De 
Published: September 2021

Abstract
The design of net fences as passive mitigation measures against rockfall events has represented a challenge since the last decades. The choice of the proper effect of the actions to consider in the design is still under debate. Recently, the Authors have proposed a novel time-independent reliability approach encompassing the large variability of the size and the kinematics of the possible impacting blocks. The entire statistics of all these quantities (size, velocity, and height) enters into the calculations, differently from other approaches that consider specific values of the parameters. In addition, the variability in time of the inputs is tackled, with particular reference to the size of the falling block. The recent approach is herein merged and compared with the current semi-probabilistic ultimate limit state design approach, suggested in the Eurocodes and implemented in the Italian recommendations UNI 11211-4:2018, with the purpose of finding the equivalent partial safety factors of kinetic energy and trajectory height of the impacting block. A sensitivity analysis with different synthetic profiles, representing possible real situations, is performed highlighting that if a set of partial safety factors is assigned to different sites, an intrinsic variability in the failure probability has to be accepted.
Monitoring of preconvergence deformations in a road tunnel: data analysis and validation
Authors: Cavalca E , Valletta A , Carri A , Savi R , Segalini A 
Published: September 2021

Abstract
Tunnels are complex constructions, generally built in difficult geological contexts. When dealing with underground structures, the study of ground deformations is a key aspect to consider in order to guarantee safety during the tunnel excavation and construction quality. One of the main aspects to investigate is related to the development of preconvergence phenomena in the advance core, i.e. deformations involving the volume of rock mass ahead of the tunnel face. This paper presents the application of a new monitoring tool specifically developed to measure preconvergence effects during the excavation phases with a direct approach. The device, called PreConv Array, consists of a series of 3D MEMS (Micro Electro-Mechanical System) and temperature sensors. The system takes advantage of automated procedures for data acquisition, elaboration, and representation, thus achieving a near-real time monitoring of the ground differential vertical settlements ahead of the excavated face. Monitoring results reported in this paper are related to the installation of a PreConv Array during the excavation phases of a road tunnel located in Northern Italy. The collected data allowed to highlight the displacements of the tunnel crown in correspondence of each step of the excavation works. Moreover, the comparison with theoretical Longitudinal Deformation Profiles (LDP) evidenced the good correspondence between PreConv data and the theoretical curves.
Identification of formaldehyde in groundwater using UV-Vis spectrometer
Authors: Rosli N , Jani M , Idris N S U , Mohd Ghazi R , Nik Yusoff N R 
Published: September 2021

Abstract
This research aims to identify the concentration of formaldehyde in groundwater by using UV-Vis spectrophotometer and to assess the physico-chemical parameters of water quality in groundwater. The samples were collected from a cemetery of Kampung Darat Demit, Kubang Kerian, Kota Bharu where the formalin-based specimen/pathological waste was buried. The unknown concentration of the formaldehyde was determined by using chromotropic acid method for the analysis of formaldehyde. A calibration curve was prepared with six different concentrations to determine the unknown concentration of formaldehyde in the samples. Seven parameters of water quality were analyzed using respective methods and the relationship with the presence of formaldehyde in water were discussed. By using the National Water Quality Standard (NWQS) of Malaysia 2008 the class of water for all samples were determined. A statistical study of one-way analysis of variance (ANOVA) was conducted using SPSS 20th version software. The results showed the different concentration of formaldehyde found in all four samples for four consecutive weeks. The classes of water samples for each physical-chemical parameter vary and in range between Class II and III. The presence of formaldehyde in water may has significant effect on the water quality parameters physically, biological and chemically.
Climbers diversity in Agro Techno Park, Universiti Malaysia Kelantan, Jeli Campus
Authors: Ahmad Fikri N , Abdul Karim M F , Mazri N H , Saharizan N , Adnan N S , Mohd Ali N B , Amaludin N A , Zakaria R 
Published: September 2021

Abstract
Species diversity of climbers were inventoried in four nature trails of Agro Techno Park Universiti Malaysia Kelantan (UMK), Jeli campus. The purpose of this study was to determine the diversity, composition and abundances of climbers in Agro Techno Park Universiti Malaysia Kelantan, Jeli Campus. Samples of the climbers were randomly collected from four natural trails for herbarium preparation and preserved using 70% ethanol solution. The preservation was done by putting the samples in zip lock transparent bag that contained of 70% ethanol solution. The samples were oven-dried at 30-40 °C, mounted and labelled before identification. The diversity pattern of the climbers was analyzed by using Shannon Diversity Index, Shannon Evenness Index, Margalef Richness Index, Abundance Parameters and Importance Value Index (IVI). A total of 593 climbers belonging to 35 species were recorded. Family Fabaceae was the most diverse plant from the climbers’ family which consisted of 4 genera and 5 species. This was followed by family Menispermaceae, Melastomataceae, Connaraceae, Apocynaceae, Rubiaceae and Vitaceae. The result obtained indicated that alteration of the ecological environment through natural disturbances influenced the abundance and distribution of climbers.
Identification of groundwater potential zones using AHP in district Kuala Krai, Kelantan, Malaysia
Authors: Jamil R M , Hisham S S , Leong M C , Nawawi S A , Nor A N M , Ibrahim N 
Published: September 2021

Abstract
Groundwater is one of the main sources of water in Kelantan which consumes 70% of the water supply. The rapid development in population, urbanization, agriculture, and industry has led to an increased water supply and demand. Hence, it is necessary to identify new groundwater potential sources to enhance groundwater supply in the study area. This study was carried out at Kuala Krai, Kelantan within latitude 5”36’30° to 5”33’50° N and longitude 102”8’25° to 102”11’10° E. The Analytical Hierarchy Process (AHP) method were used in this study and this method eventually come out with groundwater potential zones. The parameters such as lithology, geomorphology, land use, slope, drainage density, rainfall density, and soil type were chosen and spatially generated using GIS platform. Those parameters were subjected to weighted overlay analysis to obtain the potential zones of groundwater. The weights for the various layers were generated and assigned using the AHP technique which allows the comparison of criteria influencing the potential zone. The results of the study revealed that the good potential zone comprises 36.1%, moderate 32.4%, and poor 31.5% areas respectively. In conclusion, factors such as low elevation, gentle slope, alluvial plains, and vegetation area have given a high potential of groundwater in this study area.
Machine Learning Application in Water Quality Using Satellite Data
Authors: Hassan N , Woo C S 
Published: September 2021

Abstract
Monitoring water quality is a critical aspect of environmental sustainability. Poor water quality has an impact not just on aquatic life but also on the ecosystem. The purpose of this systematic review is to identify peer-reviewed literature on the effectiveness of applying machine learning (ML) methodologies to estimate water quality parameters with satellite data. The data was gathered using the Scopus, Web of Science, and IEEE citation databases. Related articles were extracted, selected, and evaluated using advanced keyword search and the PRISMA approach. The bibliographic information from publications written in journals during the previous two decades were collected. Publications that applied ML to water quality parameter retrieval with a focus on the application of satellite data were identified for further systematic review. A search query of 1796 papers identified 113 eligible studies. Popular ML models application were artificial neural network (ANN), random forest (RF), support vector machines (SVM), regression, cubist, genetic programming (GP) and decision tree (DT). Common water quality parameters extracted were chlorophyll-a (Chl-a), temperature, salinity, colored dissolved organic matter (CDOM), suspended solids and turbidity. According to the systematic analysis, ML can be successfully extended to water quality monitoring, allowing researchers to forecast and learn from natural processes in the environment, as well as assess human impacts on an ecosystem. These efforts will also help with restoration programs to ensure that environmental policy guidelines are followed.