Vertical Shaft Research Articles

Numerical modelling of flow field at shaft spillways with circular piano-key inlets

Shaft spillways are commonly provided with adequate submergence to avoid air entrainment and swirling flows. However, other structural approaches can also be considered for this purpose if the required approach flow conditions cannot be met. Optimising the inlet shape, for example by installing a circular piano-key (CPK) inlet over the shaft spillway, is an economic way of reducing air entrainment and the swirling flow strength. In this study, numerical modelling was performed to investigate the flow field around a shaft spillway with a CPK inlet. The effects of the CPK inlet in increasing the performance of a simple shaft spillway under orifice control flow – an unfavourable flow condition for the operation of hydraulic systems – was examined. Given its special configuration, a CPK inlet reduces the swirling flow strength and significantly increases flow discharge through the shaft. The finite-volume method was used to solve the governing differential equations of motion in a cylindrical coordinate system. A two-phase air–water flow was applied on the water free surface along with a standard k–ε turbulence model. The effects of different CPK geometries on the hydraulic characteristics of flow were also investigated. The results showed that CPK inlets significantly increase the flow discharge and reduce the turbulent flow intensity compared with a simple shaft or even a morning glory spillway. To maximise the efficiency of vertical shaft spillways, optimal geometries of the CPK inlets were derived.

P-105. Probiotics supplementation increases the risk for preeclampsia

According to the copious research conducted on emergency ventilation in tunnel during fire, when plug-holing and boundary layer separation occur, the actual smoke extraction efficiency is unable to satisfy the emergency ventilation design criteria in tunnels. By and large, so necessary and precious is it that a novel method would be presented in order to improve smoke extraction efficiency of ventilation systems with vertical mid-tunnel shafts to provide visibility and possibility of scape for passengers, and rescue services. This research has been carried out to investigate the simultaneous effects that adding a board-coupled shaft and using a bevel-angle connection between shaft and ceiling could have on plug-holing and boundary layer separation. Placing a slim board beneath the shaft and substituting the right-angle with a bevel-angle connection, extremely attenuated the negative effects of the aforementioned phenomena and led to higher smoke extraction efficiency. Mass flow rate of smoke through the outlet of the mid-tunnel shaft was compared numerically for different board gaps, sizes and connection angles using fire dynamic simulator. The results have good agreement with the experimental data in literature. Furthermore, the mentioned changes in the mid-tunnel shaft lead to higher mass flow rates, which is to approximately two times higher smoke extraction efficiency than those in the previous studies. Ultimately, through the prediction model, which is performed through numerical simulation data and machine learning algorithm called neural network, the optimal values of the connection angle, dimensionless area and gap range from 65° to 68°, 5.4 to 9.6 and 0.7 to 0.85, respectively.

Experimental Study of Flow Characteristics in Vortex Drop Shaft

AbstractVortex drop shafts are utilized to dissipate and transport the energy of flows in sewerage networks. A vortex drop shaft is composed of three parts: the inlet structure, the vertical shaft,...

Noise Control design for a Ventilation Fan - Case Study

A ventilation system was design and installed for a multi story garage. The ventilation system system had a vertical concrete shaft with the ventilation fan located on the top floor at street level. The ventilation fan is separated from the outside by a set of metal louvers. Adjacent to the louvers is an open pedestrian area. The exhaust fan as installed had an inline duct silencer but this was insufficient in terms of providing the desired noise mitigation. The project desire was not to make changes to the fan or its inline silencer or the external louvers so an alternative noise mitigation option had to be explored. Based on the provided sound power characteristics of the fan, the exterior noise levels as calculated matched the expected levels coming out of the metal louvers. The interior of the ventilation shaft is bare concrete with the fan installed though a hole in the concrete top floor. The predominate noise was the very high reverberation inside the ventilation shaft. The owner of the property made an attempt at installing noise absorption but this was not sufficient. Based on the field data the sound levels with the preliminary absorption solution matched expectation, but further noise reduction was required. A complete sound absorption on the walls of the concrete ventilation shaft noise mitigation solution was design, and the expected levels predicted to show that significant noise reductions can be obtained by a comprehensive noise absorption solution. The noise mitigation solution was implemented and exterior sound level measurements performed at the completion of the project. The measured sound levels outside of the metal louvers were in very good agreement with the predicted levels. Based on the success of this first noise mitigation solution, noise mitigation for a second ventilation system is not being considered.

Modern technologies for preheating scrap before charging it into electric arc steelmaking furnace

There are a number of technical solutions to utilize the waste gases of electric arc furnaces (EAF) for scrap preheating thus returning back the heat into the technological process. The waste gases can be utilized also for steam or hot water production. The preliminary scrap heating before charging it into EAF is more perspective. Technical features of various types scrap heaters considered, including conveyer and shaft scrap heating technologies with continuous (Contiarc, Consteel, Comelt, BBC-Brusa) and periodic charging (Fuchs Systemtechnik, COSS, backet). It was shown that application of scrap heaters for EAF ensures saving of electric energy, increase of metal yield, decrease of dust and gases level in the shop, decrease of negative impact on environment. The disadvantages include frequent and costly repairs of the facilities, impossibility to control some factors having effect on the process of scrap heating. It was shown that when designing new EAFs with a charge exceeding 100 t, horizontal facilities are more preferrable, while for EAFs of small volumes shaft heaters suit better. At EAF modernizing it is recommended to use shaft heaters and back­et-thermos, since it is easier to construct a vertical furnace than a horizontal one with minimal length of 100 m. It was noted that hor­izontal heaters operate better in terms of technology, since ensure continuous charging by scrap, but at that occupy a considerable space in the shop. When comparing vertical heaters and backet by all the characteristics including heat-engineering and designingones, vertical shaft heaters prevail.

Spot Image Segmentation of Lifting Container Vibration Based on Improved Threshold Method and Mathematical Morphology

Because the mine is damp and dark, it is not easy to detect the rigid tank channel’s structural failure directly. Therefore, we judged the tank channel’s surface condition by detecting the magnitude of the vibration displacement of the lifting container. In our study, we used a laser vision system to measure the structural vibration displacement. In order to accurately segment the laser spot information from the vibration image, we proposed an approach that links the relationship between the gray value of the area adjacent to the threshold point and the background’s gray value to the target in the image. We used MCE to evaluate the segmentation effect of threshold segmentation and verified the improved algorithm’s accuracy by detecting the pixel centroid of laser spots. Results show that the improved algorithm in our study has the best threshold segmentation effect, the error classification can be close to 0.0003, and the minimum deviation of the obtained vibration displacement is close to 0.1 pixels, which can realize the accurate extraction of the vibration signal of the vertical shaft tank. The novelty of this method lies in the accurate threshold segmentation and noise reduction processing of the laser speck vibration image under various interference environments in the operation of the mine hoisting system and the accurate acquisition of vibration signals. The research work provides a basis for the accurate evaluation of mechanical faults of automation technology.

Evaluation of several relevant fractionation processes as possible explanation for radioxenon isotopic activity ratios in samples taken near underground nuclear explosions in shafts and tunnels

Gas samples taken from two historic underground nuclear tests done in 1989 at the Nevada National Security Site (NNSS), formerly the Nevada Test Site (NTS), were examined to determine how xenon isotopes fractionate because of early-time cavity processes, transport through the rock, or dispersal through tunnels. Xenon isotopes are currently being used to distinguish civilian sources of xenon in the atmosphere from sources associated with underground nuclear explosions (UNEs). The two nuclear tests included (1) BARNWELL, a test conducted in a vertical shaft approximately 600 m below ground surface at Pahute Mesa, and (2) DISKO ELM, a horizontal line-of-sight test done in P-tunnel approximately 261 m below the surface of Aqueduct Mesa. Numerical flow and transport models developed for the two sites had mixed success when attempting to match the observed xenon isotope ratios. At the BARNWELL site, the simulated xenon isotope ratios were consistent with measurements from the chimney and ground surface, and appeared to have been affected primarily by fractionation during subsurface transport. At the DISKO ELM site, samples taken from two elevations in the chimney failed to show the degree of fractionation predicted by the models during transport, and did not show evidence for significant fractionation due to early-time condensation of refractory xenon-precursor radionuclides into the melt glass. Gas samples taken from the adjacent tunnels in the days following the test showed mixed evidence for early-time separation of xenon isotopes from their iodine precursors.

Experimental and numerical studies on the smoke extraction strategies by longitudinal ventilation with shafts during tunnel fire

With the surge of extra-long tunnels, the vertical shafts are widely used to shorten the construction period and become a part of the ventilation system during the operation period. Because of the towering mountains, the depth of vertical shafts is usually about 100 m or more, which is quite different from those of urban road tunnels. As a result, it is indispensable to set up perfect smoke extraction strategies, including exhaust velocity and supply velocity, featuring longitudinal ventilation system with vertical shafts to reduce the great loss during tunnel fire. To control smoke better, 1: 4.8 reduced-scale tests were carried out. In addition, a series of full-scale numerical simulations were established, using FDS, to refine the supply velocity of three HRRs of three fire source locations. From this study, some conclusions were drawn: (1) Without ventilation system, the temperature at the junction of the main tunnel and shaft is higher, because of more smoke vents and stronger stack effect provided by vertical shafts. (2) Due to the stack effect of vertical shafts, the exhaust velocity is smaller than the supply velocity under a bigger HRR. (3) The HRRs and the fire locations made no difference to the exhaust velocity which is 3 m/s. When the fire source is located at the exhaust region and middle region, the respective supply velocity is in the range of 3 ~ 4 m/s and 4 ~ 6 m/s. When the fire source is situated in the supply region, the supply velocity of 6 m/s is suitable for all three HRRs. (4) The fitting formulas of the exhaust region and middle region are expressed. The results in this work will provide references for tunnel designers and engineers to devise smoke extraction strategies during tunnel fires.

Mining industry in Mozambique

At present time,Mozambiqueis called the “Rising Star of South Africa” mainly due to the rapid development of its mining industry. Mineral resources sector ofMozambiqueis one of the most dynamically developing sectors of the country’s economy.China,BrazilandIndiahave recently become the main partners forMozambique. Recently, a number of projects is being implemented in the country, for example, Auroch Minerals Manica Gold in gold production. Increasing coal production is connected with commissioning of the Moatize open pit, which is being developed by Brazilian Vale Company, as well as Benga mining company owned by Indian ICVL consortium. The analysis of the extraction of certain mineral types inMozambiquepresented in the paper demonstrates general picture of mining industry development in the country. The analysis findings allow identifying the causes of negative phenomena in the industry, manifesting themselves in decreasing production of certain types of minerals. For instance, the main reasons for the decline in coal production were dropping labor productivity, deterioration of mining conditions, and depletion of the most accessible coal reserves, extractable by open pit mining. In this regard, development of underground mining methods providing for opening of deep deposits by vertical shaft sets is highly relevant. The experience of the neighboringRepublicofSouth Africashows that, in the mining and geological conditions of the south of the African continent, highspeed shaft sinking methods accelerating deposit development can be successfully applied.

Wear Law and Parameter Optimization Study on the Split Cone of a Vertical Shaft Impact Crusher

During the sand-making process, the wear of the split cone will affect the dynamic balance of the rotor and the sand-making effect of the crusher. This paper focuses on experiments and simulations with the rotor of a vertical shaft impact crusher. A wear model for predicting the wear value of the split cone is established and its effectiveness is verified. The orthogonal test of L 16 4 4 is designed. By using the range analysis method, the influence of the rotor speed, the feed height, the installation angle, and the number of the guide plate on the wear resistance of the split cone are studied. By using the multiple linear regression analysis method, the optimal parameter combination of each factor is obtained. The results of this paper show that the wear resistance of the split cone is the best when the installation angle of the guide plate is 40°, the installation number of the guide plate is 3, the rotor speed is 2800 r/min, and the feed height is 40 mm.

Experimental, analytical, and computational study of natural convection in asymmetrically-heated vertical shafts

During building fires, buoyant smoke is rapidly transported through elevator and ventilation shafts, posing a threat to the safety of occupants on higher floors. Therefore, smoke dynamics in vertical shafts are of interest to fire and building safety engineers. Herein, analytical solutions describing pure natural-convection laminar flows in asymmetrically-heated vertical shafts are introduced and discussed as a model situation. While the analytical solution is limited to laminar flow at relatively low Rayleigh numbers, a practically-relevant turbulent flow is explored experimentally, with a lab-scale 1-m-high shaft, and numerically, with Fire Dynamics Simulator (FDS) software in the same scale. With supplied heating powers of 100–400 W at the left-hand side wall or/and bottom, a circulatory 2D or/and 3D heat-induced convection flow (natural convection) sets in within the shaft. Air near the heated left wall rises due to buoyancy, while air near the cooler right wall descends, yielding a sine-wave-shaped velocity profile with no-slip boundary conditions imposed at both walls. While this sine-wave velocity profile is clearly observed in laminar flow, the buoyancy-driven layers are relatively thin in the corresponding turbulent flow. The temperature profile practically linearly decreases from the left to the right wall for both laminar and turbulent flows. The overall physical insights provided by the laminar analytical solution are consistent with observations in the turbulent flow. The differences between laminar and turbulent flows are investigated and discussed by qualitatively comparing the analytical solutions to the experimental and numerical data.

Evaluation of vertical shaft stability in underground mines: comparison of three weight methods with uncertainty theory

Evaluation of vertical shaft stability in underground mines: comparison of three weight methods with uncertainty theory

Study of Rotational Motions Caused by Multiple Mining Blasts Recorded by Different Types of Rotational Seismometers.

Digging two vertical shafts with the multiple blasts technique gave the opportunity to measure the induced angular motions in a horizontal plane with well-defined positions of sources. Three kinds of rotation rate sensors, sharing an underground location, were used. Two of them—a Fiber-Optic System for Rotational Events & phenomena Monitoring (FOSREM) and a prototypical seismometer housing the liquid-filled torus—sensed the rotation, while a microarray of two double-pendulum seismometers sensed both the rotation and symmetric strain. The FOSREM was sampled at 656.168 Hz, while all the others were only sampled at 100 Hz. There were considerable differences within the results gathered from the mining blasts, which should be attributed to two causes. The first one is the difference in principles of the operation and sampling rates of the devices used, while the other is the complex and spatially variable character of the studied wave fields. Additionally, we established that the liquid-filled sensor, due to its relatively low sensitivity, proved to be viable only during a registration of strong ground motions. Overall, a comparative study of three different rotational seismometers was performed during mining-induced strong ground motions with well-localized sources.

Theory and technology of real-time temperature field monitoring of vertical shaft frozen wall under high-velocity groundwater conditions

This study aims to address the problems arising from frozen wall closing in prolonged time under high-velocity groundwater in artificial ground freezing. Based on the development and closure law of frozen wall in strata with seepage, an analytical formula of transient temperature rising in frozen soil is derived, and a deterministic relationship between the geometric dimensions of the frozen wall is revealed. Then a longitudinal temperature measurement analysis theory is established. To accurately locate the weak points of the frozen wall and groundwater flow direction in case of groundwater disturbance, the gray correlation analysis is used to uncover the correlation between the weak freezing pipes. These relationships and correlations constitute a systemic framework for monitoring the temperature field during ground freezing under the condition of fast groundwater flow. Finally, the theory is applied to analyze the frozen wall closure of an air shaft in the Dongpang Mine, China. The results show that the smallest radius of the frozen soil column is produced around No. 9 and 20 freezing pipes according the proposed longitudinal temperature theory. Using No. 9 and 20 holes as the parent factors and the analyses based on the gray correlation theory, No. 7 through 10 and 18 through 22 frozen holes with higher correlation coefficients are determined as the weak positions within the frozen wall, and the predicted weak positions were confirmed during the shaft excavation. The proposed theory and method are shown to be effective in identifying frozen wall weak points and preventing accidents related to frozen wall closure under high-velocity groundwater conditions.

Development and testing of a novel mathematical-physical model for the design of ring armor for the vertical shaft impact crushers

This article presents a novel mathematical-physical model for designing and testing a ring armor for vertical shaft impact crusher (VSI) to reduce energy consumption, improve grinding fineness, and enhance product quality. VSI's are crushers for coarse and fine crushing of hard and brittle materials and it is used to improve the particle shape quality of the crushed material. Typical fields of application are in the recycling industry, highway, high-speed railway, high-rise building, hydropower dam construction, concrete mixing station to produce sand and gravel aggregate, and the equipment in artificial sand making and stone shaping.The design of the VSI components has a significant effect on the device's productivity. A suitable contour of the ring armor impact segments has a considerable influence on comminution efficiency. In conventional VSI, the definition of this ring armor contour exclusively empirically, so that the impact angle between the particles of feed material and the ring armor segment is mostly not defined. On the empirical design, the impact angle can be far outside of the optimum impact angle of 90°. In this work, the invention is based on providing ring armor impact segment structure with a high crushing effect. Therefore, a calculation method for designing the ring armor geometry impact segments of VSI is developed and tested. Test results are shown based on a crushing process, a maximum size reduction effect, and the potential of an energy saving of about 8%.

Attenuation of Swirling Motion of a Fire Whirl in a Vertical Shaft

Attenuation of Swirling Motion of a Fire Whirl in a Vertical Shaft

Impact of South Asian brick kiln emission mitigation strategies on select pollutants and near-term Arctic temperature responses

The brick kiln industrial sector in South Asia accounts for large amounts of short-lived climate forcer (SLCF) emissions, namely black carbon (BC), organic carbon (OC), and sulfur dioxide (SO2; the precursor to atmospheric sulfate [SO4]). These SLCFs are air pollutants and have important impacts on both human health and the Arctic, a region currently experiencing more than double the rate of warming relative to the global average. Using previously derived Arctic equilibrium temperature response factors, we estimate the contribution to Arctic temperature impacts from previously reported emissions of BC, OC, and SO2 from four prevalent South Asian brick kiln types (Bull’s Trench [BTK], Down Draught [DDK], Vertical Shaft [VSBK], and Zig-zag). Net annual BC (115 gigagrams [Gg]), OC (17 Gg), and SO2 (350 Gg) baseline emissions from all four South Asian kiln types resulted in 3.36 milliKelvin (mK) of Arctic surface warming. Given these baseline emissions and Arctic temperature responses, we estimate the current and maximum potential emission and temperature mitigation considering two kiln type conversions. Assuming no change in brick production, baseline emissions have been reduced by 17% when considering current BTK to Zig-zag conversions and have the potential to decrease by 82% given a 100% future conversion rate. This results in a 25% and 119% reduction in Arctic warming, respectively. Replacing DDKs with VSBKs increases baseline SLCF emissions by 28% based on current conversions and has the potential to increase by 131%. This conversion still reduces baseline warming by 31% and 149%, respectively. These results show that brick kiln conversions can have different impacts on local air quality and Arctic climate. When considering brick kiln emissions mitigation options, regional and/or local policy action should consider several factors, including local air quality, worker health and safety, cost, quality of bricks, as well as global climate impacts.

Numerical analysis of deep hole multi-stage cut blasting of vertical shaft using a continuum-based discrete element method

Due to the high in situ stress of the deep rock mass and the restraining effect of the surrounding rock, the deep hole blasting of vertical shaft faces the problems of low borehole utilization rate and poor blasting effect. In this regard, this paper proposes a deep hole multi-stage cut blasting technology of vertical shaft. Preliminary engineering practice shows that such cut blasting technology can make better use of explosive energy, reduce the restraining effect of surrounding rock, and increase the borehole utilization rate. Furthermore, based on the continuum-based discrete element method (CDEM), the fractal damage, fragmentation, and blasting cavity characteristics of deep hole multi-stage cut blasting of vertical shaft are studied and analyzed. The results show that in the multi-stage cut blasting of vertical shaft, if the length proportion of the first stage is too small or too large, it will lead to poor cavity formation along the cut direction. Characteristic parameters such as fractal damage of blasting cavity, fracture degree of element, and fracture degree of interface show a trend of first increasing and then decreasing as the length proportion of the first stage increases, and the length proportion of the first stage has an optimal value. Under the conditions of rock parameters, explosive performance and linear charge density set by the numerical simulation in this paper, when the length proportion of the first stage accounts for 0.42, the multi-stage cut blasting of vertical shaft can make better use of explosive energy and achieve the best blasting effect.

Technical and Economical Assessment of Vertical Shaft Brick Kiln

Infrastructure development, particularly the housing problem, is one of the serious issues in developing countries like Nepal. The development of housing complexes is related to various financial and environmental implications. One of the basic parameters involved in the infrastructure development pertinent to Kathmandu valley is the use of alternative materials to masonry unit, particularly bricks. Vertical Shaft Brick Kiln (VSBK) should be adopted and diffused in Nepal because it is high time for energy-efficient and environmentally friendly technologies. Various studies and monitoring has shown that (VSBK) Vertical Shaft Brick Kiln technology is an improved brick making process. The major advantage of VSBK technology is its energy efficiency and environmental friendliness. VSBK consumes 30 to 40% less energy and reduces environmental pollution by 80 to 90% in comparison to FCBTK technology. The Strength of this brick is also higher than FCBTK brick. Further VSBK provides an improved working environment (Reduced Occupational Health Hazards) to the workers.

Numerical evaluation of discharge coefficient and energy dissipation of flow over a stepped morning glory spillway

A morning glory spillway usually has an ogee shaped crest and conveys spill water flow to its downstream vertical shaft followed by a horizontal tunnel. The ungated morning glory spillways should convey variable discharges, which nonlinearly depends on the reservoir water elevation. The variation of discharge for unit length of the crest may cause challenges on design of downstream crest curve (which affects coefficient of discharge and downstream crest negative pressure). Furthermore, formation of a horizontal vortex flow affects the spillway discharge. In this paper, in order to resolve these problems by energy dissipation and water flow aeration, variable size steps are mapped to downstream of the curved ogee crest of morning glory spillway. A finite volume base numerical flow solver is used to investigate the effects of the considered configurations on the hydraulic design parameters. In this work, having verified the pressure and aeration of the flow over an ordinary stepped spillway, the characteristics of flow over geometry of an ordinary morning glory spillway, as well as stepped spillway, are modelled and compared to the available measurements on laboratory hydraulic models. Finally, an existing ordinary morning glory spillway is computationally modelled by considering an alternative design of variable sized steps at downstream crest (by mapping their edges to the ordinary profile of the morning glory spillway). The stepped morning glory spillway alternatives are numerically simulated for various flow rates, and the computed discharge coefficients and energy dissipations are compared with simulation results for ordinary morning glory spillway of the case.