Application of Cascade Forward Backpropagation Neural Networks for Selecting Mining Methods

Decision-making is very important in many fields, such as mining engineering. In addition, there has been a growth of computer applications in all fields, especially mining operations. One of these application fields is mine design and the selection of suitable mining methods, and computer applications can help mine engineers to decide upon and choose more satisfactory methods. The selection of mining methods depends on the rock-layer specification. All rock characteristics should be classified in terms of technical and economic concerns related to mining rock specifications, such as mechanical and physical properties, and evaluated according to their weights and ratings. Methodologically, in this study, the criteria considered in the University of British Columbia (UBC) method were used as references to establish general criteria. These criteria consist of general shape, ore thickness, ore plunge, and grade distribution, in addition to the rock quality designation (ore zone, hanging wall, and foot wall) and rock substance strength (ore zone, hanging wall, and foot wall). The technique for order of preference by similarity to ideal solution (TOPSIS) was adopted, and an improved TOPSIS method was developed based on experimental testing and checked by means of the application of cascade forward backpropagation neural networks in mining method selection. The results provide indicators that decision makers can use to choose between different mining methods based on the total points given to all ore properties. The best mining method is cut and fill stopping, with a rank of 0.70, and the second is top slicing, with a rank of 0.67.

PEMODELAN SEISMIK PADA STRUKTUR GEOLOGI KOMPLEKS MENGGUNAKAN METODE COMMON REFLECTION SURFACE (CRS)

Pemodelan seismik merupakan tahap penting untuk memahami respon bawah permukaan bumi terhadap gelombang seismik yang digambarkan dalam bentuk energi seismik refleksi. Walaupun saat ini teknologi pengolahan data seismik telah meningkat dengan pesat, ketidakakuratan posisi reflektor dalam penampang seismik yang dihasilkan tetap saja sering ditemukan, terutama pada daerah dengan struktur geologi kompleks. Model geologi struktur kompleks pada penelitian ini mengacu pada arsitektur glasiotektonik di daerah Fur Knudeklint, Denmark yang memiliki banyak patahan dan lipatan dengan skala kecil. Hasil simulasi perambatan gelombang dengan metode penjalaran sinar dilakukan dari dua arah akuisisi berbeda menggunakan perangkat lunak Norsar 2D untuk mendapatkan seismogram sintetik. Data yang dihasilkan kemudian digunakan sebagai masukan untuk pengolahan data seismik secara konvensional maupun menggunakan metode Common Reflector Surface (CRS) Stack. Hasilnya menunjukkan bahwa akuisisi data dari arah foot wall memberikan citra reflektor yang lebih representatif dibandingkan dari arah sebaliknya. Penegasan kualitas reflektor terlihat jelas di tiga area utama, yaitu CDP 20-100, CDP 120-180 dan CDP 160-330. Dengan demikian, metode CRS Stack berhasil merekonstruksi reflektor-reflektor berupa lipatan kecil dan perlapisan tipis pada struktur geologi kompleks dengan kualitas lebih baik dibandingkan metode konvensional.

New Technology Yields High-Resolution 3D Modeling for Fracture Analyses

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203108, “High-Resolution Fracture Analyses and 3D DMX DFN Modeling of Triassic Dolomites, Wadi Bih, Ras Al Khaimah, UAE,” by Janpieter van Dijk and Raffik Lazzar, GeoModl, prepared for the 2020 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, held virtually 9–12 November. The paper has not been peer reviewed. The complete paper outlines a high-resolution 3D fracture modeling exercise using the DMX protocol applied to Triassic dolomites of the United Arab Emirates. The outcropping rocks show a low primary porosity, are well bedded, and are highly fractured (jointed) up to centimeter scale. The exercise shows the relevance of applying new technologies to outcrop observations and shows several elements and related technologies that, to the authors’ knowledge, have not been presented previously. Introduction The focus area of the complete paper is a small outcrop situated in Wadi Bih in the territory of Ras Al Khaimah (Fig. 1) along a small road near a recently constructed artificial lake. This outcrop, which is approximately 150 m2 in size, shows well-bedded, highly fractured Triassic dolomites. Both section views and bedding-plane views can be observed. The outcrop was selected because it represents an analog of the Triassic Khuff formation, an important hydrocarbon-producing reservoir in the region. The outcrop is easily accessible and displays a clearly defined fracture (joint) network with recognizable sets, also showing truncation relationships between fractures, joints, and bedding that can be examined. Geological Context The area shows a complete series of Permian to Cretaceous, mostly carbonate sediments, outcropping in a series of north/south to north-northeast/south-southwest anticlines and synclines bounded by mostly west-vergent thrust faults. The Wadi Bih outcrop is situated on the moderately east-dipping flank of the north/south-trending Hagab Anticline, also called the Hagil Window after the area of the nearby Wadi Hagil, where the deepest Permian series are outcropping in the core of the anticline. This anticline is situated on the foot-wall of a major north/south-trending thrust fault. The geological history of the area is connected to the initial Mesozoic deposition of the series on the shelf area along the northeast flank of the Arabian shield. In the outcrop study, the focus is on the joint network. The authors write that this network is tilted together with the bedding as part of the flank of the anticline. No relation can be detected between the joint network sets and the fault and anticline axis pattern dominating the area. The joint network, therefore, most probably was formed in the early stages after lithification and dolomitization of the rock.

Displacement Measurements and Numerical Analysis of Long-Term Rock Slope Deformation at Higashi-Shikagoe Limestone Quarry, Japan

The Higashi-Shikagoe limestone quarry is an open-pit mine situated in Hokkaido Prefecture, Japan, that has experienced four slope failure incidents since 1996. The rock slope behaviour has been monitored since the first failure event by measuring the rock slope surface displacement using an automated polar system. Recent measurements have revealed a gradual decrease of the distance between the beam generator and mirrors over time; however, the displacements and decrease rate differs between the centre and left- and right-hand sides of the quarry. This implies that the deformation characteristics of the rock slope and factors influencing the slope deformation differ at the centre and left- and right-hand sides of the quarry. In this study, the two-dimensional finite element method was used to identify the causes of slope deformation by investigating the effects of limestone excavation at the foot of the rock slope, the deterioration of a ∼70 m-thick clay layer at the rock slope foot wall, and shear failure owing to rainfall infiltration. The numerical results show that slope deformation on the left-hand side and centre of the quarry are induced by clay deterioration, whereas the right-hand side of the quarry is deformed owing to floor excavation and/or shear sliding. The rock slope is presently stable because the magnitude of the rate of displacement decrease is small and no acceleration is observed.

Design and analysis of a new frame-foot wall-climbing robot

This paper designs and develops a new type of frame-foot wall-climbing robot structure. According to the bionic principle, a new parallel telescopic leg structure is proposed, and the 3D design of the overall structure of the wall-climbing robot is completed. Secondly, the kinematics analysis of the robot is carried out, and the forward and inverse solution models of the leg structure position are completed to verify the feasibility of the leg structure stability. Based on the polynomial motion equations, the robot motion planning and gait design are established, and the speed and acceleration change graphs of the leg structure slider are obtained, which avoids the rigid impact between the parts, and realizes the alternate adsorption and continuous movement of the robot legs, which the rationality of the legs structure design and the stability of the movement are verified. Through simulation and experimental results, it is shown that during the robot’s movement, the leg structure can adjust the step distance and step height according to obstacles, so as to achieve the expected obstacle crossing goal. The leg structure is adjusted according to the working environment to ensure that the fuselage and the working surface are always kept parallel to improve the stability of the overall structure.

Validation of Coupled FDM-DEM Approach on the Soil-Raft Foundation Interaction Subjected to Normal Faulting

<p>Recent earthquake events have shown that besides the strong ground motions, the coseismic faulting often caused substantial ground deformation and destructions of near-fault structures. In Taiwan, many high-rise buildings with raft foundation are close to the active fault due to the dense population. The Shanchiao Fault, which is a famous active fault, is the potentially dangerous normal fault to the capital of Taiwan (Taipei). This study aims to use coupled FDM-DEM approach for parametrically analyzing the soil-raft foundation interaction subjected to normal faulting. The coupled FDM-DEM approach includes two numerical frameworks: the DEM-based model to capture the deformation behavior of overburden soil, and the FDM-based model to investigate the responses of raft foundation. The analytical approach was first verified by three  benchmark cases and theoretical solutions. After the verification, a series of small-scale sandbox model was used to validate the performance of the coupled FDM-DEM model in simulating deformation behaviors of overburden soil and structure elements. The full-scale numerical models were then built to understand the effects of relative location between the fault tip and foundation in the normal fault-soil-raft foundation behavior. Preliminary results show that the raft foundation located above the fault tip suffered to greater displacement, rotation, and inclination due to the intense deformation of the triangular shear zone in the overburden soil. The raft foundation also exhibited distortion during faulting. Based on the results, we suggest different adaptive strategies for the raft foundation located on foot wall and hanging wall if the buildings are necessary to be constructed within the active fault zone. It is the first time that the coupled FDM-DEM approach has been carefully validated and applied to study the normal fault-soil-raft foundation problems. The novel numerical framework is expected to contribute to design aids in future practical engineering.</p><p><strong>Keywords</strong>: Coupled FDM-DEM approach; normal faulting; ground deformation; soil-foundation interaction; raft foundation.</p>

Deformation structure and peak-metamorphic temperature in Kodiak accretionary complex, Alaska

<p>The Kodiak archipelago (Southwest Alaska) represents a well exposed paleo-accretionary prism with its modern equivalent to the modern Alaskan Trench further southeast. The complex consists of metasedimentary and magmatic rocks, whose age span from the Triassic-Jurassic units on the northwestern side of the archipelago towards the Miocene units on the southeast. The complex dominantly consists of trench sediments, in which the sedimentary stratification is still visible. In addition, two tectonic mélanges, composed of lenses of metabasites embedded in sheared metasediments, are intercalated between the coherent formations. We carried out an extensive field survey to describe the kinematics and temperature conditions of deformation across the whole subduction complex.</p><p>Mélange terrains are characterized by subduction-related deformation in the form of a pervasive network of top-to-the-trench shear zones. In contrast, we observed wider range of deformation geometries in coherent units: The Kodiak Landward belt is characterized by top-to-the-trench simple shear. In the Kodiak Central belt, strain geometry varies spatially from dominant top-to-the-trench simple shear to horizontal extension evidenced by conjugate sets of extensional shear bands. Further to southeast, the Kodiak Seaward belt and the Ghost Rocks Formation are characterized by horizontal shortening with conjugate thrust faults and symmetric folds. Post-Paleocene deformation includes strike-slip faulting in the southeastern part as well as in the Kodiak granite, which was previously described as completely undeformed. The main tectonic contact in the area is the Uganik Thrust, delimiting the Uyak Complex and the Kodiak Formation. The thrust consists of a meter-thick mylonitic zone of the hanging wall material (Uyak Complex), with significantly deformed foot wall (Kodiak Formation). Finally, extension can be observed in the Narrow Cape Formation, unconformably overlying the Ghost Rocks mélange in the SE margin of the belt. Such extension predates the very recent-to-present deformation, characterized by normal faulting and block tilting within the SE margin.</p><p>Preliminary results of Raman spectroscopy of carbonaceous material (RSCM) provide essential information as to the large-scale thermal structure of the accretionary prism. In the investigated profile, running from southeastern margin towards the northwest, the temperature does not increase monotonically towards the inner part of the wedge. Indeed, the highest temperatures (>300 ℃) are found within the central part of the complex, in very thick turbiditic series accreted in a short period of time in the Paleocene. The thermal gap at the unconformity between the Ghost Rocks and Narrow Cape formations indicates fast uplift after accretion, followed by erosion, subsidence and sedimentation of Narrow Cape sediments. On the other side, no thermal gap is found around the Uganik Thrust like described at other OOST thrusts, which suggests that its activity predates exposure to the peak temperature.</p><p> </p>

Analysis and Monitoring of Small-Scale Rock Fracture Zone Deformation and Shaft Failure in a Metal Mine

Rock fracture zones were distributed in a metal mine, and their deformation was always neglected because they are available on a small scale. However, the deformation of the small-scale fracture zone may lead to serious consequences, such as underground building and structure failure. Combined with the ground movement and surface fissure monitoring, the deformation of several fracture zones was analyzed by field monitoring, experimental test, and numerical simulation. The results showed that fracture deformation promoted the surface fissure movement. The horizontal movement of the foot wall rock of the fracture was found to be larger than the hanging wall rock. Deep mining engineering resulted in the squeezing of the shallow fracture, and the shallow fracture deformed more severely than the deep fracture. In the study area, fracture zone displacements were estimated according to a numerical model. The deformation and stress comparison of the shallow fracture zone and the deep fracture zone provided the characteristic of the broken structure in the field investigation.

Dynamic Rupture and Ground Motion Modeling of the 2016 M6.2 Amatrice and M6.5 Norcia, Central Italy, Earthquakes Constrained by Bayesian Dynamic Source Inversion

<p>The complex evolution of earthquake rupture during the 2016 Central Italy sequence and the uniquely dense seismological observations provide an opportunity to better understand the processes controlling earthquake dynamics, strong ground motion, and earthquake interaction. </p><p>We here use fault initial stress and friction conditions constrained by a novel Bayesian dynamic source inversion as a starting point for high-resolution dynamic rupture scenarios. The best-fitting forward models are chosen out of ~10<sup>6</sup> highly efficient simulations restricted to a simple planar dipping fault. Such constrained, highly heterogeneous dynamic models fit strong motion data well. Utilizing the open-source SeisSol software (www.seissol.org), we then take into account non-planar (e.g., listric) fault geometries, inelastic off-fault damage rheology, free surface effects and topography which cannot be accounted for in the highly efficient dynamic source inversion. SeisSol is based on the discontinuous Galerkin method on unstructured tetrahedral meshes optimized for modern supercomputers. </p><p>We investigate the effects of including the realistic modeling ingredients on rupture dynamics and strong ground motions up to 5 Hz. Synthetic PGV mapping reveals that specifically fault listricity decreases ground motion amplitudes by  ~50 percent in the extreme near field on the foot-wall. On the hanging-wall shaking is increased by ~150 percent as a consequence of wave-focusing effects within 10 km away from the fault. Dynamic modeling thus suggests that geometrical fault complexity is important for seismic hazard assessment adjacent to dipping faults but difficult to identify by kinematic source inversions.</p>

Imaging Poro-Elastic Effects induced by a Normal Fault Aseismic-to-Seismic Dislocation in Shales

<p>Understanding fault reactivation as a result of subsurface fluid injection in shales is critical in geologic CO<sub>2</sub> sequestration and in assessing the performance of radioactive waste repositories in shale formations. Since 2015, two semi-controlled fault activation projects, called FS and FS-B, have been conducted in a fault zone intersecting a claystone formation at 300 m depth in the Mont Terri Underground Research Laboratory (Switzerland). In 2015, the FS project involved injection into 5 borehole intervals set at different locations within the fault zone. Detailed pressure and strain monitoring showed that injected fluids can only penetrate the fault when it is at or above the Coulomb failure criterion, highlighting complex mixed opening and slipping activation modes. Rupture modes were strongly driven by the structural complexity of the thick fault. An overall normal fault activation was observed. One key parameter affecting the reactivation behavior is the way the fault’s initial very low permeability dynamically increases at rupture. Such complexity may also explain a complex interplay between aseismic and seismic activation periods. Intact rock pore pressure variations were observed in a large volume around the rupture patch, producing pore pressure drops of ~4 10<sup>-4</sup> MPa up to 20 m away from the ruptured fault patch. Fully coupled three-dimensional numerical analyses indicated that the observed pressure signals are in good accordance with a poro-elastic stress transfer triggered by the fault dislocation.</p><p> </p><p>In 2019, the FS-B experiment started in the same fault, this time activating a larger fault zone volume of about 100 m extent near (and partially including) the initial FS testbed. In addition to the monitoring methods employed in the earlier experiment, FS-B features time-lapse geophysical imaging of long-term fluid flow and rupture processes. Five inclined holes were drilled parallel to the Main Fault dip at a distance of about 2-to-5m from the fault core “boundary”, with three boreholes drilled in the hanging wall and two boreholes drilled in the foot wall. An active seismic source-receiver array deployed in these five inclined boreholes allows tracking the variations of p- and s-wave velocities during fault leakage associated with rupture, post-rupture and eventually self-sealing behavior. The geophysical measurements are complemented by local three-dimensional displacements and pore pressures measurements distributed in three vertical boreholes drilled across the fault zone. DSS, DTS and DAS optical fibers cemented behind casing allow for the distributed strain monitoring in all the boreholes. Twelve acoustic emission sensors are cemented in two boreholes set across the fault zone and close to the injection borehole. Preliminary results from the new FS-B fault activation experiment will be discussed.</p>