Shaft Location Research Articles

Optimization of ventilation efficiency in tunnel-type underground spaces using response surface methodology: a case study of Yunlong Mountain civil defense in Xuzhou

Civil defense projects, designed as wartime underground spaces, often lack effective natural ventilation and have considerable depth, which complicates their use as public spaces in peacetime. However, the application of passive ventilation technologies can create effective airflow channels within these structures, significantly enhancing ventilation efficiency and thus improving the overall thermal comfort level. For this study, air age, along with average wind speed, temperature, and relative humidity as stipulated by the “Requirements for Environmental Sanitation of Civil Air Defense Works during Peacetime Use” (GBT 17216-2012), were selected as evaluation metrics. This paper compares the ventilation effectiveness between single ventilation shafts and multiple ventilation shafts under positive and negative pressure conditions in underground civil defense structures. The results indicate that negative pressure ventilation in multiple shaft configurations performs optimally across various ventilation approaches. Subsequently, the Response Surface Methodology (RSM) was utilized to further optimize the positioning of multiple ventilation shafts. The study examined the impact of three ventilation shaft locations on average wind speed, temperature, relative humidity, and air age, leading to an optimized design. Specifically, the optimal positions are 54.76 m for Shaft A, 51.45 m for Shaft B, and 79.85 m for Shaft C, achieving an average wind speed of 0.222 m/s, a temperature of 26 °C, a relative humidity reduction to 85.47%, and an average air age of 10.57 s. This research provides practical insights for the optimization of ventilation in underground civil defense facilities.

Deep learning-based detection of qanat underground water distribution systems using HEXAGON spy satellite imagery

Qanats are a remarkable type of ancient hydraulic structure for sustainable water distribution in arid environments that use subterranean channels to transport water from highland or mountainous areas. The presence of the qanat system is marked by a line of regularly spaced shafts visible from the surface, which can be used to detect qanats using satellite imagery. Typically, qanats have been documented by field mapping or manual digitisation within a Geographic Information System (GIS) environment. This process is time-consuming due to the numerous shafts within each qanat line. However, several automated methods for detecting qanat structures have been explored, using techniques such as morphological filters, custom convolutional neural networks (CNN) and, more recently, YOLOv5 and Mask R-CNN. These approaches used high-resolution RGB images and CORONA images. However, the use of black and white CORONA in CNNs has been limited in its applicability due to a high rate of false positives.This paper explores the potential of YOLOv9 in processing the black and white HEXAGON (KH-9) high-resolution spy satellite system launched in 1971. Two areas in Afghanistan (Maiwand) and Iran (Gorgan Plain) were selected to train the system images extracted from HEXAGON imagery and artificial synthetic data. The training dataset was augmented using the Albumentation library, which increased the number of tiles used. The model was tested using two types of HEXAGON imagery for selected areas in Afghanistan (Maiwand), Iran (Gorgan Plain) and Morocco (Rissani), and CORONA imagery in Iran (Gorgan Plain).Our study provided a model capable of predicting the location of qanat shafts with a precision of over 0.881 and a recall of 0.627 for most of the case studies tested. This is the first case study aimed at detecting qanats in different landscapes using different types of satellite imagery. Using real, augmented, and artificial data allowed us to generalise the representation of qanats into lineal groups of circular features. Thanks to applying labelling for individual qanats and their pairs as separate classes, our approach eliminated most of the isolated and clustered false positives.

Numerical Modeling the Rock Mass Stress-Strain State Near Vertical Excavations in Combined Mining

In recent years, the development of the mining industry in the Republic of Kazakhstan has been accompanied by the commissioning of new underground levels for many existing mineral deposits, which were initially developed through open-pit mining. As the depth of open-pit mining increases, the volume of overburden rises sharply, making open-pit mining unprofitable due to the significant amount of additional mining work required. For this reason, most open-pit mines in Kazakhstan are transitioning to underground mining, or combined mining. Many researchers have examined the timing of this transition and have worked on optimizing it to determine the best economic efficiency and manage risks. However, there is limited information available on how to determine the optimal location for a vertical mine shaft when transitioning from open-pit to underground mining. The purpose of this study is to identify a safe location for a vertical shaft in combined mining operations. Specifically, the study assesses the impact of the open-pit mine on the selection of the mine shaft’s location, considering the stress-strain state of the rock mass during combined mining methods. To address these objectives, numerical modeling of the stress-strain state around vertical excavations during combined mining was performed. The results provide a solution to the critical issue of determining the location of the mine shaft in combined geotechnology and lay the groundwork for further research on shaft placement in Kazakhstan. The novelty of this study lies in identifying the shaft location by considering the geometric shape of the open-pit mine and the depth of development. Doi: 10.28991/CEJ-2024-010-09-010 Full Text: PDF

Experimental study on ventilation shaft locations for alleviating transient pressure induced by high-speed trains passing through underground station

Experimental study on ventilation shaft locations for alleviating transient pressure induced by high-speed trains passing through underground station

Quantitative evaluation of service health condition for cutting tools on cutterhead in long-distance mechanized shield tunneling

Inspection, repair and replacement of mechanized shield cutting tools is a necessary but time-consuming, dangerous, risky and costly process. Yet, the current practice of cutting tool inspection and management does not always result in anticipated benefits. In this paper, a quantitative method for evaluating the overall service health condition (OSHC) of a cutterhead was proposed for the first time and applied to two parallel twin tunnels in Beijing Daxing International Airport Express Line. The findings indicate that one shield performed well without wear inspection and cutting parts replacement. However, the cutterhead of the other shield with mismatched new and old cutting parts after inspection and partial replacement had an unexpected worse OSHC in the subsequent tunneling. A quantitative relationship between the OSHC of a cutterhead and tunneling distance was proposed to guide the determination of an inspection shaft location for performing on-demand cutting tool inspection and replacement. The proposed method has the potential to enable data-driven, on-demand cutting tool inspection and management that is critical for achieving faster, less disruptive and cost-saving tunneling, especially beneath a highly populated urban area.

Surgical treatment for ipsilateral femoral neck and shaft fracture

To retrospectively analyze efficacy of single structure internal fixation and double structure internal fixation in the treatment of ipsilateral femoral shaft and neck fracture, and analyze their indications. From June 2015 to December 2020, 21 patients with ipsilateral femoral shaft and femoral neck fracture were treated, including 14 males and 7 females, aged 23 to 69 years old with an average of(38.1±12.9) years old. According to different femoral shaft fracture sites, some patients were fixed with cephalomedullary implant for both femoral neck and the femoral shaft(single structure, InterTan or PFNA Ⅱ), some patients were fixed with cannulated screws for the femoral neck and a retrograde locking nail for the femoral shaft (dual structure), and postoperative function and complications were recorded during follow-up. In 10 cases of single-structure fixation, the femoral necks were all basicervical fractures, and the femoral shaft fractures were located in the proximal isthmus;11 cases were double-structure fixation, 9 cases in 11 were basal type of femoral neck, 2 cases in 11 were neck type, and the femoral shaft fractures were located in the isthmus and the distal isthmus. All patients were followed up for 12 to 27 months. No femoral head necrosis, deformity, delay or nonunion occurred in the patients with single-structure fixation, and no delayed union or nonunion occurred in femoral shaft fractures;At the final follow-up, Harris score of patients with single-structure fixation was 91.8±4.1, with 8 cases were excellent and 2 cases were good. The fractures of patients with dual-structure fixation achieved good union without femoral head necrosis, except 1 case of femoral shaft fracture had delayed union;At the final follow-up, Harris score of patients with dual-structure fixation was 92.4±5.9, 7 cases were excellent, 3 cases were good, and 1 case was fair. Good reduction and fixation is the key to the treatment of such fractures. Both the single-structure fixation and the dual-structure fixation are good methods, and it should be selected according to the locations of femoral shaft and femoral neck fractures. Single-structure fixation is a good choice for femoral shaft fractures located at the proximal isthmus and basal femoral neck fractures. For isthmus and distal femoral shaft fractures combined with ipsilateral femoral neck fractures, dual-structure fixation is recommended.

Fluctuation in the Water Level of the Air Hole of the Gate Shaft in the Pumped Storage Power Station

In some pumped storage stations, water spray from the air hole occurs during load rejection. In order to avoid this phenomenon, it is necessary to study the change of the air hole water level during the transient process of the power station. A transient simulation of a pumped storage power station was carried out to study the variation in the maximum water level of the air hole and gate shaft. The transition process of a power station with or without a surge tank was analyzed, and the changes in the water level of the gate shaft and air hole were compared based on different gate shaft areas, and the influence of the gate shaft location on the changes in the water level of the gate shaft and air hole was determined. The following results were obtained: when the power station has a surge tank, the maximum water levels of the gate shaft and air hole are basically consistent; when the station has no surge tank, the maximum water level difference between the gate shaft and air hole gradually increases as the gate shaft area increases; the greater the distance between the gate shaft and inlet, the larger the maximum water level difference between the air hole and gate shaft; overflow measures for the air hole are required if the maximum water level of the air hole exceeds the design value.

Research on Headway of Ventilation Shaft Design under Different Control Modes

Tracking headway time is an important target the Metro capacity. In order to meet the 150 second design capacity in the Shanghai Chongming Line long tunnel section, this article firstly analyzes the train tracking headway time under different ventilation shaft control modes. Then, it develops a simulation tool for optimizing the location of ventilation shafts in long tunnel sections. And it develops different tracking control model algorithms for train in the ventilation shaft sections. Finally, it takes the long tunnel section between Changxingdao Station and Chenjiazhen Station in the Shanghai Chongming Line as an example to demonstrate the usability of this simulation system and the reference value of simulation results.

Mixed ventilation approach combined with single-shaft complementary system for highway tunnels

Highway tunnel ventilation systems are associated with high civil construction and operation costs, as well as large differences in the total required air volume for uphill and downhill tunnels. Thus, in the current study, a complementary ventilation system is applied to the shaft segmented longitudinal ventilation mode to form the mixed ventilation mode of the complementary combined ventilation shaft. The mixed ventilation formula is derived based on the tunnel ventilation theory. Combined with the design process of tunnel ventilation, the design process from the location of the ventilation shaft, design air volume, the air interchange channel location, the air exchange ratio of air interchange channel to pollutant concentration is determined, and the mixed ventilation mode conditions are analyzed. Moreover, an engineering example is employed to analyze the mixed ventilation, and to compare the traffic wind utilization rate, operation energy consumption and the civil construction scale between conventional segmented longitudinal ventilation and mixed ventilation. The results reveal that compared with the conventional segmented longitudinal ventilation mode, the mixed ventilation mode effectively improves the utilization rate of traffic wind, reduces the adverse effect of surplus traffic wind pressure on tunnel ventilation and minimizes mechanical power usage. In terms of operating energy consumption, taking a vehicle speed of 60 km/h as an example, the mixed ventilation method fully utilizes the traffic wind pressure in the tunnel. Although it is necessary to turn on the jet fan in the tunnel to increase the power, the energy consumption of the axial flow fan is reduced by 31.9 %, and the total power is reduced by 9.5 %, greatly lowering the energy consumption of the tunnel operation. Despite the addition of the traverse ventilation channels by the mixed ventilation method, reductions are observed in the construction of a ventilation shaft, the connecting channels, the overall ventilation civil engineering volume, and the initial civil construction investment cost. Moreover, the mixed ventilation method includes a smoke exhaust channel, thus solving the smoke exhaust problem of tunnel fires.

SOFTWARE GUIDED NAVIGATION OF CORONARY WIRE FOR CHRONIC TOTAL OCCLUSION RECANALIZATION: A BENCH STUDY OF NAVIWIRE APPLICATION

Objectives: Chronic Total Occlusion usually requires specialized wires. These specialized wires should not be rotated haphazardly and as this can lead to rotation of wire inside subintimal space and leading to creation of large subintimal space and collapse of main lumen and making difficult wire reentry. Only controlled and intentional rotation of wire is necessary for higher procedural success. Coronary arteries are 3 dimensional structures and fluoroscopy has limitation to locate the wire in three dimensional vessels. 3D wiring is one method for accurate guidewire location in CTO lesions. Previously some authors have proposed methods to make a mental picture of 3D wiring. In order to make this process even less cumbersome. We propose a software application named NAVIWire that does the job in cath-lab with in two steps. The purpose of this study is to assess the accuracy of our software to locate a wire shaft and tip inside 3D printed coronary vessel.
 Methodology: A 3D printed coronary vessel is printed in such a way that it is divided into 9 quadrants. One operator inserted wire into one of these quadrants. The wire had 1mm tip bend like use in CTO. This operator knew the location of wire and tip orientation. Operator 2 (first time user) and operator (expert user) who were blinded to original location imaged this model under biplane fluoroscope using LAO 45 and RAO 45. The process was repeated 36 times and randomly the first operator changed the location and orientation of tip each time. They inserted the data from these two views into the NAVIWire software and it output the predicted location of wire in these quadrant and tip orientation. We compared this predicted location with original location. We also reported inter-observer variability between first time user and expert user. In addition, we also reported a case of successful crossing of LAD CTO using NAVIWire software. This case report will help operators understand the usage of NAVIWire in real life settings.
 Results: The location of wire shaft inside all 9 quadrants was 100% correctly predicted by all operators. Although the expert user (operator 2) correctly predicted the tip orientation all 36 times but first time user predicted with 94.4% accuracy. The case report of patient shows successful crossing of CTO wire using NAVIWire assisted 3D wiring.
 Conclusion: NAVIWire correctly predicts CTO wire location and tip orientation in 3D printed coronary vessel and the case report also reiterate the finding in real life setting.

Automatic Mapping of Karez in Turpan Basin Based on Google Earth Images and the YOLOv5 Model

As a large-scale irrigation and water conservancy project in ancient times, karez are common in Central Asia and arid regions with a history of thousands of years. Turpan, which is located in the Xinjiang Uyghur Autonomous Region, has the most extensive and concentrated distribution of karez shafts in China. There are tens of thousands of shafts, some of which are in use and are living cultural heritage. According to radiocarbon (14C) dating, some karezs are over 600 years old. The karez is of great significance to the research on geology, hydrology, oasis, climate change, and development history of karez in Turpan. With the development of the population, arable land, industrialization, and urbanization, karez systems are facing the risk of abandonment. Detailed karez distribution mapping or dynamic monitoring data are important for their management or analysis; although there are related methods, due to Turpan’s large desert and “Gobi” environments, field surveys are time- and energy-consuming, and some areas are difficult to access. Precise shaft locations and distribution maps are scarce and often lack georeferencing. The distribution and preservation of karez have not yet been fully grasped. In this study, we evaluated the effectiveness of You Only Look Once version 5 (YOLOv5) in automatically detecting karez in high-resolution images of the Turpan region. We propose post-processing steps to reduce the false karez identified by YOLOv5. Our results demonstrate the feasibility of using YOLOv5 and post-processing techniques to detect karez automatically, and the detected results are sufficient to capture the linear alignment of karez. Target detection based on YOLOv5 and post-processing can greatly improve automatic shaft identification and is therefore useful for the fine mapping of karez. We also applied this method in Shanshan County (for which no detailed mapping data on karez has been obtained before) and successfully detected some karez that had not been archived before. The number of shafts in Turpan is 82,493. Through DBSCAN clustering, it was identified which karez line belonged to which shaft; the number of sections of karez that have been used is 5057, which have a total length of 2387.2 km. The karez line obtained was overlaid with the crop-land data, and the positional relationship between the karez line and the crop land was analyzed. The cultivated area is basically surrounded by karez. Our method can potentially be applied to construct an inventory for all karez shafts globally.

Field Measurement and Evaluation of Effective Ventilation and Particulate Matter Discharge Efficiency of Air Shafts in Subway Tunnels

The ventilation performance of air shafts is important to the air quality of subway tunnels, but there is no unified evaluation index of ventilation performance. In this paper, the air shafts at different locations in subway tunnels were taken as research objects, and the wind speed as well as the particulate matter concentration of each air shaft was tested. The effective ventilation volume and PM2.5 discharge efficiency of the air shafts were defined to evaluate the ventilation performance. It was found that on average, during the subway train service, the station air shaft on the train-arriving side can discharge 2050 m3 of dirty air in the tunnels and inhale 218 m3 of fresh air from the outside environment, while the station air shaft on the train-leaving side can absorb 2430 m3 of fresh air but can hardly effectively discharge dirty air; meanwhile, the middle air shaft can not only effectively exhaust 1519 m3 of dirty air but can also absorb 7572 m3 of fresh air. In addition, the middle air shaft has better ventilation performance if its inner opening is set on the top rather than on the side of the tunnel. The PM2.5 discharge efficiency of the station air shaft on the train-arriving side is 52.0~62.8%, higher than that of the middle air shaft of which the value is 26.8~40.7%. This research can provide guidance for ventilation performance evaluation of subway air shafts and provide a reference for subway tunnel air shaft location design.

Field Measurement and Evaluation of Effective Ventilation of Air Shafts in Subway Tunnel

The ventilation performance of air shaft is important to the air quality of subway tunnel, but there lacks of unified evaluation index of ventilation performance. In this paper, the air shafts at different locations in subway tunnel were taken as research objects, and the wind speed of each air shaft was tested. The effective ventilation volume of air shafts was defined to evaluate the ventilation performance. It was found that on average, during the subway train serve once, the station air shaft in train-arriving side can discharge 2050 m3 dirty air in the tunnel and inhale 218 m3 fresh air from the outside environment, while the station air shaft in train-leaving side can absorb 2430 m3 fresh air, but can hardly effectively discharge dirty air; meanwhile, the middle air shaft can not only effectively exhaust 1519 m3 dirty air, but also absorb 7572 m3 fresh air. And the middle air shaft has better ventilation performance if its inner opening set on the top rather than on the side of the tunnel. This research can provide guidance for ventilation performance evaluation of subway air shafts and reference for the subway tunnel air shaft location design.

Weight-bearing status may influence rates of radiographic healing following reamed, intramedullary fixation of diaphyseal femur fractures.

Objective:To investigate the effect of weight-bearing status on radiographic healing of diaphyseal femur fractures.Design:Retrospective 1:1 matched cohort study.Setting:Single-level 1 trauma center.Participants:One-hundred forty-four (N = 154) patients matched 1:1 in non-weight bearing (NWB) and weight-bearing as tolerated (WBAT) groups.Intervention:Non-weight bearing following reamed, statically locked intramedullary fixation of diaphyseal femur fracture, generally due to concurrent lower extremity fracture.Main Outcome Measurement:Postoperative radiographic healing using modified Radiographic Union Scale for Tibia fractures (mRUST) scores.Results:Groups were well matched on age, sex, race, prevalence of tobacco and alcohol use, diabetes mellitus status, Injury Severity Score, fracture pattern and shaft location, vascular injury, open fracture prevalence, and operative characteristics. Radiographic follow-up was similar between groups (231 vs 228 days, P = .914). At 6 to 8 weeks status post intramedullary fixation, the median mRUST score in the NWB group (9) was lower than that of the WBAT group (10) (mean: 8.4 vs 9.7, P = .004). At 12 to 16 weeks, the median mRUST in the NWB group (10) was again lower than the WBAT group (12) (mean: 9.9 vs 11.7, P = .003). The median number of days to 3 cortices of bridging callous was 85 in the WBAT group, compared with 122 in the NWB group (P = .029). Median time to mRUST scores of 12 (111 vs 162 days, P = .008), 13 (218 vs 278 days, P = .023), and 14 (255 vs 320 days, P = .028) were all longer in the NWB group compared with the WBAT group.Conclusions:Non-weight bearing after intramedullary fixation of diaphyseal femur fractures delays radiographic healing, with median time to 3 cortices of bridging callous increased from 85 days in WBAT groups to 122 days in NWB groups. These results provide clinicians with an understanding of the expected postoperative course, as well as further support the need to expeditiously advance weight-bearing status.Level of Evidence: IV

Investigation, design and mapping of Shaft O1 on Phase 2 of the Deep Tunnel Sewage System project in Singapore

The Public Utilities Board (PUB) of Singapore is currently progressing Phase 2 of the Deep Tunnel Sewage System (DTSS) project. Leighton Contractors Asia Limited (LCAL) have been awarded Contract T-09 of the project which runs approximately 8 km from the intersection of Clementi Road and the Ayer Rajah Expressway (AYE) to the intersection at Jurong Pier Road and AYE. LCAL have appointed COWI to act as their designer. Contract T-09 includes eight shafts, including Shaft O1 located between the Jurong River to the west and Penjuru Road to the east in the Jurong region of south-west Singapore. This paper discusses the rock engineering aspects of Shaft O1, including the engineering geological aspects and the methods of analysis used to design the reinforcement and support of the section of the shaft excavated in rock. Finally, the conditions encountered and the support installed during the engineering geological mapping of the shaft are described. The geology at Shaft O1 comprises made ground overlying Kallang Formation deposits and then weathered rocks of the Jurong Formation. Development of the ground model included several stages of desk study and ground investigation and ultimately six boreholes and eight probeholes were carried out at and around the shaft location. The analysis methods used included the Q-system, analytical closed-form calculations, use of the Unwedge software package, rock bolt and sprayed concrete design and a stand-up time assessment. The design was prepared during 2018-19 and the shaft was successfully constructed during 2019.

Numerical simulation study on influence of surface well location on gas distribution in Goaf

Surface well extraction is an important part of coalbed methane development in coal mine area. Taking the 1303 (lower) fully mechanized working face of Yuecheng coal mine as the research object, considering the characteristics of coal and rock accumulation in the three areas of goaf, this paper uses COMSOL numerical software to simulate and analyze the gas migration characteristics of the goaf where the surface wells are located along the strike and inclination of the working face. The results show that the gas concentration in goaf decreases gradually with the progress of drainage, and surface wells in different shaft location basically reach the balance in about 2000s. The shaft location of the surface well and the gas concentration in the upper corner are exponential function. In order to ensure the safety of coal production, the distance between the well distribution and the working face should be controlled within 240m, and close to the area near the return air lane. The research results provide a reference for the selection of surface well location.

Low-energy Gunshot-induced Tibia Fractures: What Proportion Develop Complications?

Gunshot injuries of the extremities are common in the United States, especially among people with nonfatal gunshot wounds. Controversy persists regarding the proper management for low-energy gunshot-induced fractures, likely stemming from varying reports on the likelihood of complications. There has yet to be published a study on a large cohort of patients with gunshot-induced tibia fractures on which to base our understanding of complications after this injury. (1) What percentage of patients with low-energy gunshot-induced tibia fractures developed complications? (2) Was there an association between deep infection and fracture location, injury characteristics, debridement practices, or antibiotic use? This was a multicenter retrospective study. Between January 2009 and December 2018, we saw 201 patients aged 16 years or older with a gunshot-induced fracture who underwent operative treatment; 2% (4 of 201) of those screened had inadequate clinical records, and 38% (76 of 201) of those screened had inadequate follow-up for inclusion. In all, 121 patients with more than 90 days of follow-up were included in the study. Nonunion was defined as a painful fracture with inadequate healing (fewer than three cortices of bridging bone) at 6 months after injury, resulting in revision surgery to achieve union. Deep infection was defined according to the confirmatory criteria of the Fracture-Related Infection Consensus Group. These results were assessed by a fellowship-trained orthopaedic trauma surgeon involved with the study. Complication proportions were tabulated. A Kaplan-Meier chart demonstrated presentations of deep infection by fracture location (proximal, shaft, or distal). Univariate statistics and multivariate Cox regression were used to examine the association between deep infection and fracture location, entry wound size, vascular injury, intravenous (IV) antibiotics in the emergency department (ED), deep and superficial debridement, the duration of postoperative IV antibiotics, and the use of topical antibiotics, while adjusting for age, race/ethnicity, smoking status, and BMI. A power analysis for the result of deep infection demonstrated that we would have had to observe a hazard ratio of 4.28 or greater for shaft versus proximal locations to detect statistically significant results at 80% power and alpha = 0.05. The overall complication proportion was 49% (59 of 121), with proportions of 14% (17 of 121) for infection, 27% (33 of 121) for wound complications, 20% (24 of 121) for nonunion, 9% (11 of 121) for hardware breakage, and 26% (31 of 121) for revision surgery. A positive association was present between deep infection and deep debridement (HR 5.51 [95% confidence interval 1.12 to 27.9]; p = 0.04). With the numbers available, we found no association between deep infection and fracture location, entry wound size, vascular injury, IV antibiotics in the ED, superficial debridement, the duration of postoperative IV antibiotics, and the use of topical antibiotics. In this multicenter study, we found a higher risk of complications in operative gunshot-induced tibia fractures than prior studies have reported. Infection, in particular, was much more common than expected based on prior studies. Consequently, surgeons might consider adopting the general management principles for nongunshot-induced open tibia fractures with gunshot-induced fractures, such as the use of IV antibiotics both initially and after surgery. Further research is needed to test and validate these approaches. Level IV, therapeutic study.

Identification of mining waste using remote sensing technique: A case study in El Triunfo town, BCS, México

Mining in México is directly responsible for serious environmental impacts due to the lack of control in the management of mining shafts with high concentrations of potential toxic elements (PTE). These residues are subject to erosion and weathering processes, becoming high risk pollution sources for the health of the inhabitants. In the study area, El Triunfo, Baja California Sur, it is necessary to determine the location and composition of the mining shafts to carry out soil remediation in the near future. High resolution multispectral images of Pleiades satellite are appropriate tools for monitoring and classification of environmental risks, especially useful for the study of sediment distribution. For identify and georeferenced mining tailings within a semi-desert environment, we used remote sensing technique, by using the supervised classification tool and Maximum Likelihood algorithm. The results revealed 32 potential zones with mining residues which were visited to validate the technique, confirming that 87.5% had mining residues. Mining tailings in the area are collected in hills up to 20 m in height with scarce to nil vegetation and are composed of uncompacted reddish material. Laser diffraction analysis showed that the mean grain size is medium silt (25 μm). The maximum concentrations of PTE were determined by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry and validated with certified reference material giving the next results: As: 15000 mg/kg; Cd: 327 mg/kg; Cu: 1920 mg/kg; Pb: 88900 mg/kg; and Sb: 20200 mg/kg. We classified the mining wastes as extremely enriched in PTE using the normalized enrichment factor and extremely contaminated using the geoaccumulation index. We concluded that the remote sensing technique is a very useful tool for identifying local mining waste, the composition of which puts the health of inhabitants at risk; it is advisable that remediation work should be carried out in the short term.

Theoretical and numerical study on mass flow rates of smoke exhausted from short vertical shafts in naturally ventilated urban road tunnel fires

The study focuses on the mass flow rate of the buoyancy-driven gases exhausted from the shaft in naturally ventilated urban road tunnel fires. Theoretical analyses and numerical simulations are performed. The model to predict the mass flow rate of the incoming smoke exhausted by the nearest shaft is developed by considering that the smoke is exhausted along the four sides of the shaft separately. Based on the heat balance between the incoming smoke exhausted and the total gas flow exhausted, the model to estimate the total mass flow rate exhausted from the shaft (both smoke and entrained air) is also established. Meanwhile, a series of numerical simulation in a naturally ventilated tunnel considering the heat release rate (HRR), the shaft height, shaft length and width, shaft location was carried out. The simulation results show that the shaft height has a limited contribution to the mass flow rate of the incoming smoke exhausted while a larger shaft cross-sectional area shows a favorable performance in exhausting the smoke. Further, the air entrainment into the shaft increases with both the shaft height and shaft cross-sectional area. Comparisons of the mass flow rates of the incoming smoke and the total mass flow rates exhausted between simple calculations and simulations are made, showing that the simple models perform well. Further, it is found that there exist two regimes for the total mass flow rate corresponding to different smoke modes in the shaft (complete plug-holing, plug-holing and without plug-holing), which is caused by the different driven forces in the shaft. The outcomes of this work could provide some guidance for the design of vertical shaft and smoke control in naturally ventilated tunnel in urban area.

Active flutter control of the wind turbines using double-pitched blades

Classical flutter of a wind turbine blade is a concerned issue to hinder the wind utilization to a large extent. Recent predictions showed a decreasing flutter margin (the ratio of flutter speed to rated rotor speed) with the increase in wind turbine size. To address this issue, a new blade configuration called the double-pitched blade is proposed and analytically investigated for its potential to enhance the flutter suppressing capability of modern large-size wind turbine blades. This new blade comprise an inner part and a tip part, where the tip part can rotate (or pitch) independently with respect to the inner part through a tip actuator commanded by a feedback control law. The aerodynamic loads of blade tip due to the actively controlled rotation of the tip part provide a torque on the inner part, which provides damping for the torsional mode of the wind turbine blade. The effectiveness of this new double-pitched blade for suppressing flutter is verified through a simulation study conducted on a 907-DOF aero-servo-elastic wind turbine model. Parametric studies are performed on two main design parameters, i.e. the length of the tip part and the associated chordwise location of tip shaft with respected to the blade cross section, and flutter control performance are obtained by numerical optimization process. Simulation results show the optimal length of tip part is around 3.3%of blade length, and the associated chordwise location of tip shaft is around 45%of chord length, the flutter amplitude of the conventional blade can be mitigated to around 4%using this double-pitched blade.