Case Study on the Stability Control of Broken Surrounding Rock in Roadway Excavation on the Edge of a Collapsed Stope Area

Predicting and controlling the collapse of surrounding rock (especially broken rock masses) in underground chambers is an important topic in mining and geotechnical engineering. Based on an example, this paper introduces a case study of surrounding rock stability control technology in stope mining around abandoned areas. Based on on-site coring, mechanical properties of rock samples, and on-site grouting reinforcement technology, the TRT6000 advanced geological prediction system was used to predict the stability status of the surrounding rock of the underground chamber. AUTODYNA software was used to build a dynamic coupling model for numerical simulation prediction and optimization of blasting parameters and to reveal the dynamic variation in the surrounding rock. The dynamic failure process of the surrounding rock of the chamber before and after optimization of the blasting parameters is simulated, and the deformation characteristics and damage and acoustic emission characteristics of the surrounding rock are clearly shown. The surrounding rock failure first appeared around the surface of the underground chamber because of the high stress concentration around the surface of the chamber after blasting; with the interaction between the explosive gas and the rock mass, the damaged area further propagated into the external rock, eventually leading to a large damage area. At the same time, there is a large tensile failure in the rock, resulting in expansion and rupture around the underground chamber. Finally, the 3D laser scanning method is used to verify the superiority of the optimized blasting initiation sequence. The new edge hole detonation sequence can effectively improve the blasting vibration and successfully control the further damage of the surrounding rock of the underground chamber, thus proving the edge hole drug pack. Moreover, the initiation mode of the delay stage of the side hole charge is determined. This study provides a useful reference for the stability control of surrounding rock in mining in mining areas.

Investigating the Effect of Temperature Changes on the Physical Field of Surrounding Rock in a Deep Gold Mine

To explore the fracture mechanism of surrounding rock for thermal-mechanical coupling in deep mining, the theoretical solution of the internal temperature and stress evolution of the underground chamber cold boundary subjected to cold impact was obtained by thermoelastic theory. The conduction law of temperature and the evolution characteristics of stress were studied by theoretical formulas, and the influence of the convective heat transfer coefficient on the rate of tensile stress reduction was analyzed. The results show that the theoretical solution is in good agreement with the field measured value, which proves that the theoretical calculation method adopted in this paper is reliable and accurate. When the surface of the underground chamber is impacted by the change of temperature, the cold boundary temperature drops sharply at first, then gradually slows down, and finally reaches the same temperature as the air; the tensile stress decreases sharply from the initial high-stress value, then gradually decreases, and finally tends to be stable. The effects of different convective heat transfer coefficients on the change of temperature resistance of rocks were considered by numerical simulation. The numerical simulation results show that increasing the convective heat transfer coefficient not only increases the tensile stress of the heat transfer boundary but also increases the possibility of cracks, which makes the rock easier to crack. Based on the research results, we introduced the thermal-mechanical coupling disturbance range coefficient β = L/2D (β = 6–8) and proposed that the convective heat transfer coefficient is the reference index of the deep mining support structure, which can provide a theoretical basis and technical support for the selection of support materials.

Modeling of filtration processes of technological solutions in block underground leaching

PAO “Priargunsky Production Mining and Chemical Association” has been working on reserves of uranium deposits of the Streltsovsky ore field for more than 50 years. During this period, most of the rich ores have been worked out by traditional mining and physical technology. The share of poor and ordinary ores remains significant, but traditional technology does not provide the necessary level of profitability. Therefore, the widespread introduction of physicochemical technology: underground block (BPV) and heap leaching (KV) can be a decisive moment in the continuation of the operation of these deposits. The applied technology of underground block leaching has one significant drawback – a low rate of uranium recovery into a productive solution, which significantly reduces the effectiveness of this technology in the development of poor uranium deposits. To increase the yield of uranium into the productive solution, it is necessary to analyze the entire preparation and leaching process and establish the main reasons for the low rates of transition of uranium to a mobile state. For this purpose, it is proposed to simulate the underground leaching process by building visual models of halos spreading of solutions along shrinked ore mining mass accumulated in an underground chamber. During the simulation, it was found that the distribution of the size classes of the broken ore pieces in the chamber can be predicted at the stage of drilling and blasting operations, and when determining the line of least resistance W and the distance between the ends of the wells, take into account the diameter of the controlled crushing zone R_p. At the same time, 3 zones of granulometric compositions are formed: a re-grinding zone, an optimum zone and a non-carbarite exit zone. The flow of solutions through these zones will differ the more significantly, the higher the height of the chamber. In a zone with larger crushing, an almost steep distribution of the solution spreading front is expected. Accordingly, the smaller the fraction, the lower the front to the horizontal is. The following functions are offered to simulate filtering processes: – it is possible to control the flow of working solutions to the fan of irrigation wells in order to achieve optimal leaching parameters, i.e. to quickly control the process; – knowledge of the law of distribution of irrigation flares makes it possible to select the optimal grid of location of single sprinklers

A Few Words About the Ice House of the Konsum Store in the Nineteenth-Century Priest’s Mill Factory and Residential Complex in Łódź

The issue of ice houses, both those found among manor and farm buildings and those connected with industrial plants, is a research issue frequently raised in many countries of Western Europe and in the United States. In the Polish literature, however, it does not attract much interest, which is why knowledge of it – or at least the knowledge shared – is usually limited to the awareness of the existence of ice houses and their purpose, and only occasionally do they become subjects of more extensive research. This also concerns the very material substance of such buildings. In 2015, on the Priest’s Mill estate in Łodź, erected along with the extension of Karol Scheibler’s cotton plant at the beginning of the 1870s, rescue excavations were conducted under the supervision of archaeologists Maciej Milczarek and Zbigniew Rybacki. They concerned the remains of an ice house built for the estate general store (including a grocery) called Konsum. Its preserved form is a result of a few construction stages completed in quick succession. During the third one (between 1883/1884 and 1889) the ice house we are interested in was built. It was not big as its capacity was approximately 100 cubic metres, and its structure was rather typical of larger industrial ice houses, with the upper (aboveground) chamber used as an ice warehouse, and the lower (underground) chamber serving as the store’s cold storage. Most probably, it was not used for long, however, there is no data that would allow to determine the time of its liquidation.

Research on residual shear strength of surrounding rock base on elastic-plastic softening model

With the rapid development of infrastructure construction, the edge shape analysis of underground chamber excavation in water conservancy and hydropower projects has received more and more attention. This paper takes an underground chamber of a hydropower project as the research object and uses an ideal elastoplastic stress-strain softening model to study the relationship between deformation, stress, plastic zone and strength parameters. The results show that the value of each shear strength parameter has a significant effect on the distance of the plastic zone, and the calculation result may provide a basis for the design.

Caves

After his conversion, Ignatius of Loyola stopped in Manresa, Spain, on his way to the Holy Land. There he entered into a dark period of depression, staying in a cave for several months outside of town where he wrote his Spiritual Exercises. Caves evoke an uncommon terror even as they disclose a treasured wisdom. Tales of descending into a dark cave and finding your way out again run through the literature and folklore of many cultures—from Theseus in his labyrinth on Crete to the cave in the Misty Mountains where Bilbo Baggins found Gollum’s “Precious,” the ring of power. But the cave is also the womb of Mother Earth, a place of birth and renewal. In Plato’s myth of the cave, the philosopher moves through a world of shadows into the light of reason and beauty. St. Benedict lived in a cave in the mountains southeast of Rome for three years before starting his monastic community. Muhammad, in a cave on Mount Hira, heard the voice of the Angel Gabriel reciting the words of the holy Quran. The underground chamber becomes a portal between worlds—a place of illumination where the hero finds the dragon’s treasure, where new life emerges. The author explores this reality as he spends a night alone in the depths of a Missouri cave, entering into something of Ignatius’ own experience of Jesus.