Impulse-based discrete element modelling of rock impact and fragmentation, with applications to block cave mining

Impulse-based methods efficiently and accurately model high-frequency collisions of complex shapes based on the enforcement of non-penetrating constraints. It does not rely on penalty parameters nor requires the computation of penetration between bodies. This work presents a novel necessary condition for energy conservation in impulse-based methods. In previous versions of the impulse methods, such as sequential and simultaneous impulse methods, the relative velocity at the contact points after collision is directly derived from the relative velocity before collision, in a purely simultaneous or sequential manner. This work presents a novel energy tracking method (ETM), in which the relative velocities are iteratively but gradually adjusted, simultaneously modelling their interaction at each iteration. ETM ensures the energy conservation while capturing the propagation of forces during collision. The ETM is applied to model the dynamics of fragment collision in the context of fragmentation. Two approaches of fragmentation are proposed: a finite-discrete element approach, and a low cost, fragmentation pattern-based approach. The first approach models the growth of fractures using the finite element method (FEM) and advanced re-meshing technology. This finite-discrete element approach suffers from the drawback of massive computational cost. The low-cost, fragmentation pattern-based approach separate colliding bodies directly. The fragmentation pattern is generated using Weibull distribution equations, the patterns and size distributions computed using full finite/discrete element simulations and experimental results. This work investigates the influence of fragmentation on the frequency of hang-up events and on the gravity flow of rock fragments within a block caving system. Numerical results indicate that models that do not consider fragmentation tend to overestimate the frequency of hang-up accidents.Open Acces

Research on Real-Time Prediction of Hydrogen Sulfide Leakage Diffusion Concentration of New Energy Based on Machine Learning

China’s sour gas reservoir is very rich in reserves, taking the largest whole offshore natural gas field in China-Puguang gas field as an example, its hydrogen sulfide content reaches 14.1%. The use of renewable energy, such as solar energy through photocatalytic technology, can decompose hydrogen sulfide into hydrogen and monomeric sulfur, thus realizing the conversion and resourceization of hydrogen sulfide gas, which has important research value. In this study, a concentration sample database of a hydrogen sulfide leakage scenario in a chemical park is constructed by Fluent software simulation, and then a leakage concentration prediction model is constructed based on the data samples to predict the hydrogen sulfide leakage diffusion concentration in real-time. Several machine learning algorithms, such as neural networks, support vector machines, and deep confidence networks, are implemented and compared to find the model algorithm with the best prediction performance. The prediction performance of the support vector machine model optimized by the sparrow search algorithm is found to be the best. The prediction model ensures the accuracy of the prediction results while greatly reducing the computational time cost, and the accuracy meets the requirements of practical engineering applications

Assessing the transmission performance of iGMAS real-time data streams

The use of the BeiDou Navigation Satellite System (BDS) has been increasing in the Asian-Pacific region. Thus, the construction of the international GNSS Monitoring and Assessment System (iGMAS) is accelerating to meet the demanding requirements for highprecision real-time products. Latency and packet loss, two critical data transmission parameters, have great impact on the applications of real-time data streams. This paper aims to propose a Homology-Reverse method to investigate the data transmission performance of the iGMAS stations in local and wide area networks. The proposed method enables not only assessment on receivers but pretesting on network conditions of alternative tracking stations. This paper is expected to provide a reference for the construction of the iGMAS, Continuous Operational Reference System (CORS), and Satellite Based Augmentation Systems (SBAS)

Use of NTRIP for Optimizing the Decoding Algorithm for Real-Time Data Streams

As a network transmission protocol, Networked Transport of RTCM via Internet Protocol (NTRIP) is widely used in GPS and Global Orbiting Navigational Satellite System (GLONASS) Augmentation systems, such as Continuous Operational Reference System (CORS), Wide Area Augmentation System (WAAS) and Satellite Based Augmentation Systems (SBAS). With the deployment of BeiDou Navigation Satellite system(BDS) to serve the Asia-Pacific region, there are increasing needs for ground monitoring of the BeiDou Navigation Satellite system and the development of the high-precision real-time BeiDou products. This paper aims to optimize the decoding algorithm of NTRIP Client data streams and the user authentication strategies of the NTRIP Caster based on NTRIP. The proposed method greatly enhances the handling efficiency and significantly reduces the data transmission delay compared with the Federal Agency for Cartography and Geodesy (BKG) NTRIP. Meanwhile, a transcoding method is proposed to facilitate the data transformation from the BINary EXchange (BINEX) format to the RTCM format. The transformation scheme thus solves the problem of handing real-time data streams from Trimble receivers in the BeiDou Navigation Satellite System indigenously developed by China

Three‐dimensional simulation of the acidizing process under different influencing factors in fractured carbonate reservoirs

Abstract Matrix acidizing is widely used to enhance oil/gas production in the exploitation of carbonate reservoirs. In this work, a three‐dimensional (3D) hydro‐chemical‐thermal (H‐C‐T)‐coupled model was presented to improve the understanding of the acidizing process. The influence of different influencing factors was analyzed, especially the coupling effect of natural fractures and in situ stress. With the increase in acid injection concentration, the minimum pore volume of acid required for breakthrough (PVBT) decreases. The optimal injection rate and the minimum PVBT increase with increasing initial reservoir temperature. With the increasing initial reservoir permeability, the minimum PVBT increases. With the increasing initial reservoir pore diameter and specific surface area, the minimum PVBT and the optimal acid injection rate increase. When the fracture direction is perpendicular to the direction of the maximum principal stress, the fracture apertures decrease with the increase of the maximum principal stress, which leads to an increase in PVBT and wider paths of wormholes. Lastly, the present H‐C‐T‐coupled model was applied in the context of Tahe reservoir exploitation, which shows that optimizing the acid injection rate is able to enhance the connection between wellbores and natural caves

An efficient 3D cell-based discrete fracture-matrix flow model for digitally captured fracture networks

Abstract Complex hydraulic fracture networks are critical for enhancing permeability in unconventional reservoirs and mining industries. However, accurately simulating the fluid flow in realistic fracture networks (compared to the statistical fracture networks) is still challenging due to the fracture complexity and computational burden. This work proposes a simple yet efficient numerical framework for the flow simulation in fractured porous media obtained by 3D high-resolution images, aiming at both computational accuracy and efficiency. The fractured rock with complex fracture geometries is numerically constructed with a cell-based discrete fracture-matrix model (DFM) having implicit fracture apertures. The flow in the complex fractured porous media (including matrix flow, fracture flow, as well as exchange flow) is simulated with a pipe-based cell-centered finite volume method. The performance of this model is validated against analytical/numerical solutions. Then a lab-scale true triaxial hydraulically fractured shale sample is reconstructed, and the fluid flow in this realistic fracture network is simulated. Results suggest that the proposed method achieves a good balance between computational efficiency and accuracy. The complex fracture networks control the fluid flow process, and the opened natural fractures behave as primary fluid pathways. Heterogeneous and anisotropic features of fluid flow are well captured with the present model

Nanoindentation-based characterization of micromechanical properties of greenish mudstone from deep Fushun West open-pit mine (Fushun city, China)

International audienc

The residues 4 to 6 at the N-terminus in particular modulate fibril propagation of β₂-microglobulin

The ΔN6 truncation is the main posttranslational modification of β2-microglobulin (β2M) found in dialysis-related amyloid. Investigation of the interaction of wild-type (WT) β2M with N-terminally truncated variants is therefore of medical relevance. However, it is unclear which residues among the six residues at the N-terminus are crucial to the interactions and the modulation of amyloid fibril propagation of β2M. We herein analyzed homo- and heterotypic seeding of amyloid fibrils of WT human β2M and its N-terminally-truncated variants ΔN1 to ΔN6, lacking up to six residues at the N-terminus. At acidic pH 2.5, we produced amyloid fibrils in vitro from recombinant, WT β2M and its six truncated variants, and found that ΔN6 β2M fibrils exhibit a significantly lower conformational stability than WT β2M fibrils. Importantly, under more physiological conditions (pH 6.2), we assembled amyloid fibrils in vitro only from recombinant, ΔN4, ΔN5, and ΔN6 β2M but not from WT β2M and its three truncated variants ΔN1 to ΔN3. Notably, the removal of the six, five or four residues at the N-terminus leads to enhanced fibril formation, and homo- and heterotypic seeding of ΔN6 fibrils strongly promotes amyloid fibril formation of WT β2M and its six truncated variants, including at more physiological pH 6.2. Collectively, these results demonstrated that the residues 4 to 6 at the N-terminus particularly modulate amyloid fibril propagation of β2M and the interactions of WT β2M with N-terminally truncated variants, potentially indicating the direct relevance to the involvement of the protein’s aggregation in dialysis-related amyloidosis