Influence of wind-blown sand content on the mechanical quality state of ballast bed in sandy railways

During the operation of sandy railways, the challenge posed by wind-blown sand is a persistent issue. An in-depth study on the influence of wind-blown sand content on the macroscopic and microscopic mechanical properties of the ballast bed is of great significance for understanding the potential problems of sandy railways and proposing reasonable and adequate maintenance and repair strategies. Building upon existing research, this study proposes a new assessment indicator for sand content. Utilizing the discrete element method(DEM) and fully considering the complex interactions between ballast and sand particles, three-dimensional(3D) multi-scale analysis models of sandy ballast beds with different wind-blown sand contents are established and validated through field experiments. The effects of varying wind-blown sand content on the microscopic contact distribution and macroscopic mechanical behavior(such as resistance and support stiffness) of ballast beds are carefully analyzed. The results show that with the increase in sand content, the average contact force and coordination number between ballast particles gradually decrease, and the disparity in contact forces between different layers of the ballast bed diminishes. The longitudinal and lateral resistance of the ballast bed initially decreases and then increases, with a critical point at 10% sand content. At 15% sand content, the lateral resistance is mainly shared by the ballast shoulder. The longitudinal resistance sharing ratio is always the largest on the sleeper side, followed by that at the sleeper bottom, and the smallest on the ballast shoulder. When the sand content exceeds 10%, the contribution of sand particles to stiffness significantly increases, leading to an accelerated growth rate of the overall support stiffness of the ballast bed, which is highly detrimental to the long-term service performance of the ballast bed. In conclusion, it is recommended that maintenance and repair operations should be promptly conducted when the sand content of the ballast bed reaches or exceeds 10%.

The Effect of Temperature on Irreducible Water Saturation of Water-wet Cores

The conventional measurement of a relative permeability curve (RPC) is usually conducted at room temperature, which is much lower than the reservoir temperature. Previous research work on high temperature relative permeability mainly take oil-wetted cores as objective. In this paper, laboratory test and measurement are conducted using water-wet cores from the Lunnan Oilfield. Since irreducible water saturation (Swi) is a critical factor that affects and controls the relative permeability curve, special tests are conducted to measure Swi at different temperatures for water-wet cores in the course of the experiment of relative permeability. The experimental results indicate that for the water-wet cores Swi decreased with the increasing temperature from ambient to 105℃,and the relative permeability curve shifted in a low water saturation direction, i.e. moved toward the left, while it moved toward the right for oil wetness reservoirs. Seen from both macroscopic and microcosmic view, the reasons and mechanisms of relative permeability change with temperature are discussed, and factors including core wetness, viscosity force, capillary forces, contact angle, interfacial tension change are considered.

Fast determination of meso-level mechanical parameters of PFC models

To solve the problems of blindness and inefficiency existing in the determination of meso-level mechanical parameters of particle flow code (PFC) models, we firstly designed and numerically carried out orthogonal tests on rock samples to investigate the correlations between macro-and meso-level mechanical parameters of rock-like bonded granular materials. Then based on the artificial intelligent technology, the intelligent prediction systems for nine meso-level mechanical parameters of PFC models were obtained by creating, training and testing the prediction models with the set of data got from the orthogonal tests. Lastly the prediction systems were used to predict the meso-level mechanical parameters of one kind of sandy mudstone, and according to the predicted results the macroscopic properties of the rock were obtained by numerical tests. The maximum relative error between the numerical test results and real rock properties is 3.28% which satisfies the precision requirement in engineering. It shows that this paper provides a fast and accurate method for the determination of meso-level mechanical parameters of PFC models.

Uncompensated Centrifugal Flow about Accelerated Cosmic Expansion

Currently, we are under the perception of a visible universe which has an accelerated expansion, because repeated evidences obtained by several technics since the well known observations performed by Edwin Powell Hubble. The world scientific community was astonished by these observations, and since then until today, countless calculations have been made that only leave the hypothesis of the existence of an unknown cosmic entity that has the particularity of repelling matter from each other when it is sufficiently separated by huge amounts of that entity, which was called as “dark energy”. This “dark energy” is a completely unknown thing, and it is understood by some researchers as the convenient hypothesis, because it is which emerges from deep calculations and observations. Bearing in mind that we already know about all cosmic objects and systems are in rotation, both locally and not so locally, and that everything is full and endowed with intrinsic and extrinsic angular momentum, it seems logical to think that rotational dynamics must also apply to the more extensive, and that if locally (and not so locally) we perceive and infer rotating objects everywhere, then they must also exist globally. So, starting from the idea that rotation is omnipresent, at every level of sizes;from the invisibly small to the invisibly large, I thought that it is really wise to cover it through rotation dynamics, or that in the worst case, we cannot ignore the fact of the omnipresent rotation in any entity to infer. And this is the main reason for the resolution and the motivation of the birth of the publication of this study. Based on this seemingly simple idea, these results and conclusions of this study was reached: following a formal logic and evidence of the accelerated unfolding of the cosmic fabric, another hypothesis is proposed as an alternative to the existence of the “dark energy”: The intensities of centrifugal acceleration fluxes exceed the intensities of gravitational fluxes, which are not sufficient to compensate for the centrifugal flux, which is why baryonic and exotic matter, energy, space and time are extended, in geometric progression with respect to our apparent time. So, this unfolding of the cosmic fabric might not be caused by a “dark energy”, but by centrifugal fields of rotational-orbital domains. Besides all the above, this publication has a double purpose, because it is also intended to cover another matter;these deep attentions to the Rotational Dynamics also derive in another solution or hypothesis regarding the formed mystery after observing the incoherent too high velocity of matter in the far latitudes in spiral galaxies: The hypothesis of the existence of the so-called “dark matter” arises from the observation that, in spiral galaxies, all that matter which is located beyond a critical distance from the galactic rotation axis, travels too fast, while the calculations illustrate an insufficient intensity of gravitational acceleration flux to explain that speed and to retain all that matter while maintaining the orbital distance. However, the concept I present here, is that, in a spiral galaxy, all those matter which is positioned farthest from the main rotation axis, is effectively lost in space as time goes by, or what is the same, the intensity of the centrifugal acceleration field is not compensated by that of the gravitational field, and the destiny of every spiral galaxy is a more or less homogeneous and compact disk-shaped galaxy. As a basic NOTE to be taken into account;in the present article we intend to show the radical, meticulous and delicate relation that exists in the considerations of the classic concept of “isolated system of particles”, with the degrees of the consistencies of the connections between all those “particles”, whether they are inter-material bonds, or, in a relativistic scope, bonds between the same cosmic fabric. And this is so, because the idea of “isolated” falls directly and precisely on the criterion that we put to the degree of consistency of each connection between each “part” or “particle” that integrates the presumed and inferred concept of “isolated system” with respect to the rest of systems or universe.