Dynamic Model Development and Simulation Analysis of China’s Total Integrated Deep Ocean Mining Pilot System

With the increasing development of computational sciences in aerospace technologies, numerical methods have become a useful tool for engineering researchers. Tractive performance studies and soil-tool interactions analysis have been widely favored by the finite element method (FEM) and the discrete element method (DEM). In order to validate the current design of a tire tread and drill for its use in a space exploration rover named "Pachacutec", a research has been conducted by Kamayuc Team in the Smart Machines Laboratory at Universidad Nacional de Ingeniería. The research consisted in characterize a granular terrain to simulate tire-soil and drill-soil interactions in off-road conditions using DEM and FEM models. Parameters such as tractive force, axial load and terrain compaction were analyzed to predict both tire and drill real performance. The results shows that the tire tread was able to provide the necessary traction for the movement and stability of the rover. In addition, the material assigned to the drill resulted in a high mechanical strength, ensuring its safe operation. To develop a further work, the authors suggest to recollect Martian regolith simulant from a Mars Analog and reproduce the same methodology proposed in this study to validate the mechanical design in these conditions.

Investigation of strain-sensitive properties of porous media through micro-CT imaging and numerical modelling

In this paper, a nonlinear integrated multi-body dynamic (MBD) model of a deep-sea mining (DSM) system was developed. A particular nonlinear interaction model between the mining vehicle and the seabed sediment was derived. The fluid resistance and the resistance torque acting on the vehicle were obtained by the computational fluid dynamics (CFD) numerical simulations. In addition, a rigid-flexible coupled discrete element method (DEM) was adopted to model an extremely long mining riser efficiently and accurately. Developed by the C# program, a user-defined subprogram was intended to establish the DEM model of the riser. A motion control system model for trajectory tracking of the vehicle was developed in which the fuzzy control algorithm and the fuzzy adaptive PID control algorithm were used to control the speed and speed ratio of the tracks, respectively. Furthermore, the collaborative simulation between the dynamic model and the control model was achieved, and a coordinated motion mode for the total mining system was proposed and simulated. Accordingly, the trajectory tracking accuracy and slip of the vehicle, the spatial state change of the riser, and the interaction forces among subsystems were analyzed. This paper can provide a valuable theoretical basis and technical reference for the integrated design, performance prediction, and operation control of the practical DSM system.

Discrete element method (DEM) is a numerical technique that models the material as a combination of discrete particles which interact with each other through the contacts springs. While modelling soil in finite element method (FEM), approximations are made which considers soil as a continuous material. Hence certain properties such as void ratio which are intrinsic properties of the soil cannot be directly modelled or monitored. FEM also requires the failure criteria to be defined to predict the post elastic behaviour of the soil. DEM overcomes such drawbacks and the particle contacts are the only parameters that has to be defined. In the present work the contact parameters for sand grains are estimated for the purpose of being modelled in DEM, using direct measurement approach. The parameters required for defining the contact springs between the particles are the young's modulus, coefficient of restitution, friction coefficient, Poisson's ratio and density. The estimated parameters from the experiments were used to model the soil behaviour in an oedometer test. The obtained results from the DEM modelling are compared with the experimental results to benchmark the parameters estimated for the sand grains.

In the mining process of deep coal mines with a thick and hard roof, it is easy to form a large overhanging roof and accumulate a lot of strain energy. The sudden breaking of the suspended roof may induce seisms, which seriously threaten the safety of underground miners and equipment. To reveal the mechanism of weakening the thick and hard roof by blasting in deep mining, the four times deep-hole blasting in 63upper06 panel of Dongtan coal mine are considered. First, the temporal and spatial distribution of seismicity events monitored before and after blasting is investigated. Second, the process of deep-hole blasting is simulated using finite element and discrete element methods. After blasting, the small-energy mining-induced seismicities within 20 m of the roof suddenly increase and gradually transfer to the mined-out area and the front of the working face. Meanwhile, the high rock stratum is broken and a large amount of strain energy is released, which causes the range of fall zone enlarge a lot, and the stress in the roof is decreased obviously. With the increase in the number of deep-hole blasting, the pressure relief effect becomes more obvious, and the newly developed fracture is mainly located in the low strata. Microseismic monitoring results agree with the calculated results. Moreover, the rock caving steps are easily formed after deep-hole blasting, and the collapse is more sufficient. Furthermore, blasting cracks are most restrained in the vertical direction of the maximum principal stress. Moreover, the delayed blasting method is more conducive to the expansion and penetration of blasting cracks. Results show that the deep-hole blasting technology has a significant effect on weakening the roof of coal seam and preventing and controlling large-energy mining-induced seismicities.

Multicomponent granular mixing in a Bohle bin Blender-Experiments and simulation.

Clay consolidation has generally been considered from a macro-scale perspective by measuring the macro-scale compression of a clay soil over time. Clay particles in consolidation tests experience shear and normal forces at the inter-particle level due to force applied to the soil at the macro-scale. These shear and normal forces cause the particles to slide at the micro-scale and produce macro-scale changes in soil volume and shape. By considering the inter-particle interactions at the micro- scale interfaces, the shear force - normal force - velocity relationship can be described by the theoretically derived Rate Process Theory (RPT). This paper presents a Discrete Element Method (DEM) model to numerically calculate thin, disk-shaped clay particle movement in three dimensions during compression using the RPT contact model. The coefficient of secondary compression obtained from the DEM model using RPT parameters supported by previous research was 0.059. The coefficient of secondary compression obtained from macro-scale consolidation tests for a montmorillonite clay was 0.031. Differences between the numerical model and experimental measurements are attributed to particle shape, size distribution, and particle number. The influence of the number of bonds and bond strength on clay creep behavior are also quantified and discussed.

Particle mixing is a crucial operation in various industrial production processes. However, phenomena like segregation or local accumulation can arise, especially when particles differ in properties like radius and density. Numerical simulation of particles using Discrete Element Method (DEM) allows for the manipulation of control variables in batches, generating a large amount of data and facilitating quantitative research. In this study, the mixing behaviors of binary particles in rotating drums are systematically investigated. The DEM model is first validated with experimental data and then rotating drums with varying obstacles, rotation speeds, particle radii, and densities are simulated. Moreover, a Gaussian process-based optimization is conducted by correlating Lacey mixing index (MI) and parameterized shape of obstacle to find the optimized mixing condition. Experimental validations are further performed on the optimized condition to verify the design. It is shown that this integrated approach holds significant potential for enhancing the efficiency, effectiveness of industrial mixing processes and the consideration of energy consumption when balancing the mixing efficiency and optimal rotating speed.

In this paper, the mesocalibration test was used to measure the contact parameters (restitution coefficient, rolling friction coefficient, static friction coefficient, and surface energy) between coarse aggregate particles and mortar particles in Discrete Element Method (DEM) model of concrete. Then, the DEM model of concrete slump was established according to the coarse aggregate gradation to study the flow behavior of coarse aggregate in fresh concrete. The slump test result was compared with the output of the slump DEM model with high consistent, indicating the promising reliability of the mesocalibration test. Finally, based on the mesocalibration test results, the DEM model of pumping concrete was established. It was obtained that the pumping pressure calculated by the numerical model was similar to that of the pumping test with satisfactory accuracy better than the concrete pumping pressure calculated according to the rheological test results of concrete and lubricating layer. On this basis, the movement trajectory of coarse aggregate in the pump pipe was analyzed and the influence of coarse aggregate on the pumping performance of concrete was revealed.

The paper describes a novel method for lifting manganese nodules from the ocean floor to the water surface by means of capsules in a vertical conduit. A mathematical model for vertical capsule transport is given, which is checked by experiments in vertical pipes having a diameter of 0.07 m. and 0.3 m. Based on these test results a deep ocean mining system is designed with emphasis on low energy requirements and high reliability. Test results in the paper show that the vertical transport of the proposed system can be achieved with a much higher efficiency than the reported data for airlifts, jetpumps and underwaterpumps, which makes the system attractive in view of energy requirements. The dual pipe system consists of a vertical 1 m diameter falling pipe ill which the empty capsules are transported downward and a 1 m diameter raising pipe in which the filled capsules are lifted. The underwater filing station is executed as a very simple filling point with elimination of complicated locks, thus achieving a high degree of reliability. INTRODUCTION Vertical transport of ore from the sea-bottom to the sea surface can be accomplished by means of a pipeline. This is also the case for lifting manganese nodules. A great number of 1,2,3 the proposed vertical lifting systems for manganese nodules deals with pipeline transport especially because of the reliability and the simplicity of this method. A drawback of slurry transport for this purpose is the high velocity that has to be maintained in the conduit to keep the nodules moving. Especially large nodules have a considerable settling velocity thus requiring a high water velocity in the pipe. These high transport velocities can cause large pressure drops and high, energy consumption, depending on the pumping method applied. That is the reason that in the Mechanical Engineering Department laboratory of the Twente University of Technology a project was started for the development of a manganese nodule mining system with emphasis on high reliability and low energy requirements. This was achieved by selecting a pipeline system in which the transport velocity could be kept moderate. Such a low velocity vertical transport system is possible by using a capsule pipeline. Capsules can be pumped in a pipeline at a considerable lower velocity than the required velocities in slurry pipelines. For this purpose the capsules can be cylinders without covers. The diameter of the capsule is about 95 to 98 %of the diameter of the pipeline. These cylinders can easily be moved in the pipeline by a waterflow. The difference between vertical slurry transport and capsule transport is depicted in figure 1. For designing capsule pipeline systems the designer needs mathematical models to predict especially capsule velocities, pressure drops and energy requirements. For this reason a simplified mathematical model for vertical capsule transport is introduced.

The paper deals with the issue of modelling elastic wave propagation using the discrete element method (DEM). The case of a longitudinal wave in a rod with a circular cross-section was considered. A novel, complex algorithm consisting of the preparation of models and simulation of elastic waves was developed. A series of DEM models were prepared for simulations, differing in discretisation and material parameters. Additional calculations with the finite element method (FEM) were performed. Numerical wave signals were obtained from each simulation and compared with experimental results to choose the best DEM model based on the correlation between the waveforms. Moreover, dispersion curves were prepared for each model to verify the agreement with the Pochhammer-Chree wave propagation theory. Both experimental and theoretical approaches indicated the same model as the most suitable. The analysis results allowed stating that DEM can be successfully used for modelling wave propagation in structural rods.

DEM simulations on the influence of carbonate precipitation on liquefaction mitigation of sand

A novel approach for 3D discrete element modelling the progressive delamination in unidirectional CFRP composites

The interaction between off-road tires and granular terrain has a great influence on the tractive performance of off-road vehicles. However, the finite element method or the discrete element method cannot effectively study the interaction between off-road tires and granular terrain. The three-dimensional combined finite element and discrete element method is applied to handle this problem. In this study, a calibrated finite element method–discrete element method model is established, in which the finite element model of off-road tire is validated by stiffness tests, while the discrete element model of gravel particles is validated by triaxial compression tests. The calibrated finite element method–discrete element method model can describe the structural mechanics of the off-road tire and the macroscopic mechanical properties of the gravel road. Tractive performance simulations of the off-road tire on gravel road under different slip conditions are performed with the commercial software LS-DYNA. The simulation results are basically corresponded with the soil-bin test results in terms of granular terrain deformation and tractive performance parameters versus the slip rates. Finally, the effects of tread pattern, wheel load, and tire inflation pressure on tractive performance of off-road tire on granular terrain are investigated. It indicates that the calibrated finite element method–discrete element method can be an effective tool for studying the tire–granular terrain interaction and predicting the tractive performance of off-road tire on granular terrain.

The discrete element method (DEM) was used to establish the slump model and J-Ring model of concrete to describe the flow behavior in the slump test and J-Ring test. Then, the contact parameters of particle-particle and particle-geometry for the concrete DEM model, including restitution coefficient, rolling friction coefficient, static friction coefficient, and surface energy, were measured. In order to avoid the influence of the shape and size of the aggregate, this paper used high-precision glass spheres as the aggregate of the concrete for meso-calibration test, slump test, and J-Ring test. Comparing the simulation results of DEM model with slump test result, a very high agreement between the initial stage, the rapid flow stage, and the slow flow stage of the slump flow–time curve can be found as well as the final slump and slump flow. Moreover, similar to the slump DEM model, the DEM models of J-Ring test, V-funnel test, and U-channel test were established to study the passing ability and filling ability of concrete with outstanding accuracy. Therefore, the concrete DEM model with contact parameters and JKR model can be adopted to study the flow behavior of the fresh concrete.