Evaluation of the viability of recycling railroad ballast for reusing in railroads

The main objective of this study is to assess the reuse of naturally old ballast that was removed from an operating railroad. In order to verify the viability of its reuse, laboratory tests were carried out, based on the procedures and parameters established in literature. The reuse of ballast would reduce costs, minimize the disposal of this material and reduce quarry extraction. There are several standards regulations the ballast’s (gravel) properties, such as size, shape, hardness, abrasion resistance and composition to provide better performance of the rail platform, due to the wide variety of materials and environmental conditions to which they are subjected. Ballast specifications are based on the execution of characterization tests and can be divided according to strength properties and geometric properties. Thus, several specifications have been used by different railway organizations around the world to meet the needs of their projects. One test used to analyze ballast quality is the Los Angeles Abrasion, which provides data on resistance to fragmentation. The durability of the ballast depends on the quality of the gravel related to the original rock composition. This is an important parameter that can be associated with railroad maintenance, which is expensive. A series of tests were carried out to evaluate the ballast properties, as well as an analysis of the geometric and mineralogical characteristics of the gravel, and the impact of the variation of these properties in the performance of the ballast. The viability of reusing the ballast removed from an operating road was then evaluated, and it was concluded that the material is still suitable for reusing, although its properties have undergone a few changes, without modifying its main characteristics and functions.

Mineralogical Study of Levels with Magnesian Clay Minerals in the Santos Basin, Aptian Pre-Salt Brazil

The object of this study is magnesian clay minerals present in carbonate rocks of the post-rift phase of the pre-salt in the Santos Basin. These rocks developed in an Aptian-age alkaline lacustrine environment. This study summarizes the formation of clay minerals associated with different lithotypes in a range of 19 m and a depth of more than 5100 m. They were characterized from petrographic analysis by optical microscopy, X-ray diffraction (total sample and clay fraction), and modeling by Newmod®; and examined and analyzed by scanning electron microscopy. An approach based on identifying lithotypes and characterization of microsites allowed us to understand the occurrence of different clay minerals. Kerolite was the most abundant mineral in the sampled range. It occurs in lamellar aggregates under greater preservation of the original rock lamination and in association with spherulites and shrubs. The Stv/Ker mixed layers occurs in the same association, and formed finer unlaminated aggregates associated with the more intense dolomitization and silicification processes. Saponite occurs associated with detrital minerals forming clayey levels intercalated with microcrystalline carbonates. Fluids with a high Mg/Si and pH < 9 favor the precipitation of kerolite. The increase in pH during diagenesis may be responsible for the formation of Stv/Ker mixed layers.

Effect of Advancing Direction of Working Face on Mining Stress Distribution in Deep Coal Mine

Deep mining has become the normal state of coal mining; compared with the mine with shallow buried depth, the consequent high level of in situ stress and complex distribution have brought severe threats to the stability of the stope and the surrounding rock of the roadway. In this research, taking the 121304 working face of Kouzidong Mine as the engineering background, the characteristics of mining-induced stress distribution under complex in situ stress environment in deep mining are analyzed by using on-site measurement of the original rock stress and mining stress, establishing a theoretical model centered on the middle section of the working face, and establishing large-scale numerical calculation models for different advancing directions. It was found that under deep mining conditions, the maximum stress of the original rock is 25.12 MPa, and the direction is vertical. The advanced influence range of mining stress is about 150 m, and the abutment pressure presents a three-peak distribution characteristic in front of the working face. The research results provide important theoretical guiding value for guiding the mining of coal mines with similar geological conditions.

Weathering Features of A Five-Story Stone Pagoda Compared To Its Quarrying Site In Geumgolsan Mountain, Korea

Understanding the long- and short-term weathering features according to rock type is very important for maintaining the original form of stone heritages. In this study, the material characteristics of a deteriorated five-story stone pagoda were compared with those of fresh rocks from its quarrying site at nearby Geumgolsan Mountain, Korea to diagnose the degree of damage and develop a comprehensive interpretation of the weathering mechanism. The stone pagoda was built from lithic tuff comprising pumice and phenocrysts such as quartz, K-feldspar, plagioclase, and mica based on plagioclase substrates; the mineralogical and geochemical characteristics are similar to those of the fresh rocks. The lithic tuff of the stone pagoda demonstrated a low ultrasonic velocity of 2863 m/s and a high water absorption rate and porosity of 9.5% and 19.2%, respectively, which are poorer than the physical properties of the fresh rocks (i.e., ultrasonic velocity of 3336 m/s, water absorption rate of 8.65%, and porosity of 17.83%). The lithological characteristics and physical properties demonstrated a considerable influence on the weathering and stability of the stone pagoda. In particular, fragments of relatively weak pumice detached from the original rock to form cavities of various sizes. These cavities introduced moisture within the rock, which produced oxides and hydroxides of iron and manganese. In addition, contaminants such as dust, salt crystals, clay minerals, and microorganisms adhering to the surface of the stone pagoda accelerated its physical, chemical, and biological weathering. The results of this study will be important for realizing the stable and long-term conservation of the five-story stone pagoda at Geumgolsan Mountain.

Caracterização Física e Mineralógica de Materiais Intempéricos na Área Urbana de Juiz de Fora – MG, através de Análise Macroscópica, Difratrômetro de Raios-X (DRX) e Microscópio Eletrônico de Varredura (MEV)

Materiais saprolíticos constituem importantes seções no recorte vertical da paisagem. São materiais ainda pouco conhecidos e demandam maior dedicação. Para caracterização destes materiais pode-se fazer uso de técnicas mineralogia e micromorfologia como a difração de Raios-X (DRX) e o Microscópio Eletrônico de Varredura (MEV). O DRX é uma técnica de caracterização de estruturas cristalinas. O MEV é um tipo de microscópio capaz de produzir imagens de alta resolução da superfície de materiais sólidos. O objetivo é caracterizar amostras de materiais intemperizados de diferentes rochas. Foram selecionados cinco perfis de intemperismo em Juiz de Fora - MG. Os parâmetros utilizados para a análise física e mineralógica foram os seguintes: cor, textura, consistência, rocha de origem e grau de alteração, mineralogia e micromorfologia. A cor é variável entre e intra amostras, é dependente dos minerais constituintes e do grau de alteração. A textura está ligada aos minerais constituintes e seus tamanhos, que são dependentes de seus graus de alteração. A consistência é dependente da resistência dos minerais constituintes e da alteração. As rochas de origem são o quartzito ou o gnaisse. Os principais minerais encontrados foram quartzo, biotita, muscovita e caulinita. Quanto maior a porcentagem de argila, menor a consistência e maior o grau de alteração. A presença de minerais mais resistentes tende a dificultar a pedogênese, resultando em perfis mais arenosos, com poucos minerais de argila e sem atividade biológica. Nos perfis em que predomina o quartzo, apesar da presença desse mineral, o grau de alteração é elevado. Physical and Mineralogical Characterization of Weathering Materials in the Urban Area of Juiz de Fora - MG through Macroscopic Analysis, X-Ray Diffractometer and Scanning Electron Microscope ABSTRACTSaprolitic materials are important sections in the vertical cutout of the landscape. These materials are still little known and demand greater dedication. To characterize these materials, we can use mineral and micromorphological techniques such as X-ray diffraction, a technique for characterizing crystalline structures and the Scanning Electron Microscope, a type of microscope capable of producing high-resolution images of the surface of solid materials. The objective is to characterize weathered colors of different stones. Five weathering profiles were selected in Juiz de Fora - MG. The parameters used for physical and mineralogical analysis were as follows: color, texture, consistency, original rock and degree of change, mineralogy and micromorphology. The color is variable, depends on the constituent minerals and the degree of change. The texture is linked to the constituent minerals and their sizes, which depend on their degree of change. The consistency is dependent on the strength of the constituent minerals and the degree of change. The original rocks are quartzite and gneiss. The main minerals found were quartz, biotite, muscovite and kaolinite. The higher the clay percentage, the lower the consistency and the greater the degree of change. The presence of more resistant mineralsmakes pedogenesis difficult, resulting in more sandy profiles, with few clay minerals and without biological activity. In profiles that predominate quartz, despite the presence of this mineral, the degree of change is high.Keywords: Mineralogy; Micromorphology; Weathering material.

Research on Stress Distribution Characteristics for Uniquely Shaped Roadway with Hard Roof in Steeply Inclined Coal Seam and Support Technology of Reducing Vibration Impact

This paper presents a comprehensive study of the stress distribution and stability analysis of a uniquely shaped roadway having a steeply dipping hard roof. The coal seam and its roof have a certain impact tendency, which is the internal condition of rock burst. The syncline tectonic stress causes the original rock stress to reach a higher level. The large amount of coal produced in the coal mine and the large movement range of the upper strata cause the huge mining additional stress around the stope. The impact load caused by “cantilever beam” fracture of hard roof can induce and strengthen rock burst. Its engineering geological setting encompasses the mining process and surrounding rock conditions of No. 6 Coal Seam in the 2130 coal mine of Xinjiang. Numerical simulations with theoretical analysis and field measurements investigated a proposed new truss combined support scheme for implementation. A comparison was made of the differences in the state parameters of the road under the new and old support conditions. The application of the new combined support technology changed the form of the stress distribution around the road. Apart from the displacements of the two coal sidewalls, the new support system notably reduced the displacement of roof and floor by 67.8% and 83.6%, respectively. After the implementation of the new support scheme, the frequency of the original rock burst in the working face is greatly reduced, the surrounding rock control and field application effects also remained good, and personnel and equipment safety and production plan have a good guarantee.

Application of TEOS Modular System on the Preservation of Andesite Type Rock

Andesite rock is commonly used as a heritage building in Southeast Asia, especially in Indonesia. However, the study on consolidation of andesite rock is still limited. This study aimed to evaluate the application effectiveness of TEOS-based material on the andesite type rock in heritage materials. TEOS was used as a modular system with andesite powder to form mortar. This andesite-TEOS mortar system was applied to conservation techniques, especially for gap and joint filling. TEOS modular system was successfully applied to the andesite type rock, resulting in chemical and physical properties. The color of the mortar and the compatibility with the original rock color were designed from the rock powder preparation. The excellent repair was obtained by a combination of dot technique gluing using epoxy resin and the TEOS mortar application in the gaps. Furthermore, this technique was successfully applied to the big Buddha Statue Head andesite rock for the emergency intervention of the falling fragment. Keyword: Andesite, Consolidation, TEOS, Mortar

Relationship between advancing abutment pressure and deformation of surrounding rock in a roadway: A case study in Helin coal mine in China

The deformation stages of the working face of a mine in front of the roadway were defined based on the location of the roadway and the coal wall in different deformation zones. Observational data of the advancing abutment pressure and the surrounding rock deformation of the roadway from Helin coal mine were analyzed using least squares fitting. The results show that the distance between the boundary of the rapid deformation stage and the deceleration deformation stage and the position where the advancing abutment pressure is equal to the original rock stress is 0.8 m. The distance between the boundary of the large deformation stage and the stable small deformation stage and the peak value of the advancing abutment pressure is 0.3 m. A theoretical analysis indicated that the boundary between the rapid deformation stage and the deceleration deformation stage is located at the intersection of the advancing abutment pressure curve and the original rock stress curve. The boundary between the large deformation stage and the stable small deformation stage is located at the peak value of the advancing abutment pressure.

Sliding Impact Mechanism of Square Roadway Based on Complex Function Theory

To clarify the process of stress change and plastic zone evolution of square roadways under high-stress conditions, the rotational square expansion plastic zone evolution model of square roadway was established by theoretical analysis, numerical simulation, and engineering verification. The shear slip impact stress criterion of square roadway based on complex variable function theory was studied, and the law of surrounding rock stress distribution, plastic zone expansion, elastic energy density, local energy release rate (LERR), and total energy release of square roadway were analyzed. The results show that the compressive stress is concentrated in the four corners of the roadway after the roadway excavated and transfers with the change of plastic zone. Main shear failures start from the four corners and develop in a rotating square shape, forming square failure zones I and II. The square failure zone I is connected with the roadway contour and rotated 45°. The square failure zone II is connected with the square failure zone I and rotated 45°. When the original rock stress is low, the surrounding rock tends to be stable after the square shear slip line field formed. When the original rock stress is high, the shear failure of the surrounding rock continues to occur after the square failure zone II formed, showing a spiral slip line. Corners of the square roadway and square failure zones I and II are the main energy accumulation and release areas. The maximum elastic energy density and LERR increase exponentially with the ratio of vertical stress to uniaxial compressive strength (Ic). When square corners of the roof are changed to round corners, the plastic zone of the roof expands to form an arch structure. The maximum elastic energy density decreases by 22%, which reduces the energy level and possibility of rock burst. This study enriches the failure mechanism of roadway sliding impact. It can provide a basic theoretical reference for the design of the new roadway section and support form based on the prevention of rock burst.