Finite element modeling and analysis of a cardboard shelter

Constructing shelters from corrugated cardboard panels represents an innovative approach in the construction industry. The cardboard shelters can be used for permanent living or as temporary houses in post natural disaster events. Due to their light weight and also due to the ease of packing, cardboard sheets can be easily shipped to remote areas. This study includes a comprehensive stress analysis of a full-scale cardboard shelter subjected to different wind load conditions. The cardboard is modeled using a laminated orthotropic shell element. The material properties incorporated in the model are based on the results of mechanical tests conducted on individual cardboard components. The study describes in detail the numerical model that was developed to simulate the global and local behavior of full-scale cardboard shelters under wind loads. Seven finite element analyses covering various loading and geometry configurations, including the effect of door and window openings, are conducted. Maximum strains found from the analyses are compared to the ultimate strains obtained from the component tests in order to judge on the level of safety provided by the shelters.     

Laboratory evaluation of smoke detectors for use in underground mines

Laboratory experiments were conducted to determine the responses of a prototype smoke detector and a commercially available photoelectric smoke detector to smoke particles generated from various combustion sources. The prototype smoke detector combines optical scattering measurements with ionization chamber measurements in order to reduce/eliminate nuisance alarms due to the presence of airborne dusts or diesel exhaust particles. The commercially available smoke detector is designed for use in harsh environments where airborne dust represents a major problem due to both nuisance alarms and detector contamination. In the experiments, the responses of the two detectors were measured when exposed to smoke particles from the exhaust of a diesel engine and from a variety of fire sources, including wood, coal, styrene butadiene rubber, and No. 2 diesel fuel. For the solid fuels, data were obtained for both smoldering and flaming combustions. This report describes the experiments, their results, and the use of these results as they apply to early-warning fire sensors capable of the rapid and reliable detection of fires in atmospheres that may or may not be contaminated by either airborne dust or the products produced from diesel engines.     

工程机械停用前的封存保养

较系统地介绍了工程机械在长时间停用前,为避免机械性能下降或质量变化而采取的封存保养的措施和方法。     

Predicting roof displacement of roadways in underground coal mines using adaptive neuro-fuzzy inference system optimized by various physics-based optimization algorithms

Due to the rapid industrialization and the development of the economy in each country, the demand for energy is increasing rapidly. The coal mines have to pace up the mining operations with large production to meet the energy demand. This requirement has led underground coal mines to go deeper with more difficult conditions, especially the mining hazards, such as large deformations, rockburst, coal burst, roof collapse, to name a few. Therefore, this study aims at investigating and predicting the stability of the roadways in underground coal mines exploited by longwall mining method, using various novel intelligent techniques based on physics-based optimization algorithms (i.e. multi-verse optimizer (MVO), equilibrium optimizer (EO), simulated annealing (SA), and Henry gas solubility optimization (HGSO)) and adaptive neuro-fuzzy inference system (ANFIS), named as MVO-ANFIS, EO-ANFIS, SA-ANFIS and HGSO-ANFIS models. Accordingly, 162 roof displacement events were investigated based on the characteristics of surrounding rocks, such as cohesion, Young's modulus, density, shear strength, angle of internal friction, uniaxial compressive strength, quench durability index, rock mass rating, and tensile strength. The MVO-ANFIS, EO-ANFIS, SA-ANFIS and HGSO-ANFIS models were then developed and evaluated based on this dataset for predicting roof displacements in roadways of underground mines. The results indicated that the proposed intelligent techniques could accurately predict the roof displacements in roadways of underground mines with an accuracy in the range of 83%–92%. Remarkably, the SA-ANFIS model yielded the most dominant accuracy (i.e. 92%). Based on the accurate predictions from the proposed techniques, the reinforced solutions can be timely suggested to ensure the stability of roadways during exploiting coal, especially in the underground coal mines exploited by the longwall mining.     

Interpretable deep learning for roof fall hazard detection in underground mines

Roof falls due to geological conditions are major hazards in the mining industry, causing work time loss, injuries, and fatalities. There are roof fall problems caused by high horizontal stress in several large-opening limestone mines in the eastern and midwestern United States. The typical hazard management approach for this type of roof fall hazards relies heavily on visual inspections and expert knowledge. In this context, we proposed a deep learning system for detection of the roof fall hazards caused by high horizontal stress. We used images depicting hazardous and non-hazardous roof conditions to develop a convolutional neural network (CNN) for autonomous detection of hazardous roof conditions. To compensate for limited input data, we utilized a transfer learning approach. In the transfer learning approach, an already-trained network is used as a starting point for classification in a similar domain. Results show that this approach works well for classifying roof conditions as hazardous or safe, achieving a statistical accuracy of 86.4%. This result is also compared with a random forest classifier, and the deep learning approach is more successful at classification of roof conditions. However, accuracy alone is not enough to ensure a reliable hazard management system. System constraints and reliability are improved when the features used by the network are understood. Therefore, we used a deep learning interpretation technique called integrated gradients to identify the important geological features in each image for prediction. The analysis of integrated gradients shows that the system uses the same roof features as the experts do on roof fall hazards detection. The system developed in this paper demonstrates the potential of deep learning in geotechnical hazard management to complement human experts, and likely to become an essential part of autonomous operations in cases where hazard identification heavily depends on expert knowledge. Moreover, deep learning-based systems reduce expert exposure to hazardous conditions.     

Analysis of construction parameters for underground structures installed with use of jet geotechnology

A new approach to physical bases for calculation of parameters of the production process used to install underground structures by jet geotechnology is formulated. Flushing equations are presented for plane and three-dimensional structures. Formulas are derived for approximate determination of the flushing of soil aggregate during jet-induced erosion of cohesive soils.     

长沙南站钢结构防火涂料施工技术

结合某工程实例,探讨了防火涂料的选用和防火机理,归纳了钢结构防火涂料施工前的准备工作,重点阐述了其施工工艺和质量保证措施,通过严格进行质量控制,涂层厚度均达到了规范要求。     

Disturbance of mining operations to a deep underground workshop

An underground workshop was located at a depth of 880 m in a metal mine, Sweden. A few years after its excavation, the workshop was subjected to a certain extent of damage. A number of fractures appeared on the walls of the workshop. Shotcrete separated from the rock surface and even fell down to the floor. The mine worried about what happened and wondered how the mining operations underneath would affect the workshop. A further question was if the workshop should be closed and a new one should be excavated. Those questions therefore concerned not only with the matter of safety but also of economy. An investigation of the instability in the workshop was conducted in 2000. It was carried out through geological surveys, in situ deformation measurements and also numerical modelling. The study revealed that the problem of instability in the workshop was associated with the mining operations at the level of the workshop even though the mine stopes were over 90-m away from the workshop. It was also assessed that the mining operations underneath would not disturb the workshop and thus the workshop could continue its service as usual. The mining operations underneath was finished in 2003. The results of a follow-up programme confirmed the assessments made in the study. Measurements of rock deformation showed that the workshop was stable during the whole period of mining underneath. Two lessons are learned from this case: (1) permanent underground infrastructures should not be placed in geological contact zones even if they are not necessarily weak zones; (2) the horizontal extent of the disturbance zone around an opening at depth can be very large. For the case in question, the horizontal stretch of the disturbance zone around the mine stope was approximately in the same order as the height of the stope.     

上海浦东浦江茗园地下车库防水堵漏施工

上海浦东某高层建筑地下室和地下车库发生渗漏，根据工程特点，对墙体和顶板分别采用电动泵高压灌浆和手压泵传统灌浆，并结合刚性防水涂料和聚合物砂浆面层设防，取得了预期效果。     

小城镇地下管线建设对策初探

分析了小城镇地下管线的建设现状,针对小城镇地下管线建设管理工作中存在的问题,从体制改革、实行市场化动作和实施共同沟建设两方面阐述了地下管线的建设对策,以促进小城镇建设的可持续发展。     

Measurement and scaling of air-surface mercury exchange from substrates in the vicinity of two Nevada gold mines

The state of Nevada has extensive mineral resources, and is the largest producer of gold in the USA as well as fourth in world gold production. Mercury (Hg) is often present in the hydrothermal systems that produce gold deposits, and can be found in elevated concentrations in gold ore. As a result, mining of gold ore in Nevada has been shown to release Hg to the atmosphere from point and non-point sources. This project focused on measurement of air-soil Hg exchange associated with undisturbed soils and bedrock outcrops in the vicinity of two large gold mines. Field and laboratory data collected were used to identify the important variables controlling Hg flux from these surfaces, and to estimate a net flux from the areas adjacent to the active mines as well as that occurring from the mined area pre-disturbance. Mean daily flux by substrate type ranged from 9 ng m^− 2 day^− 1 to 140 ng m^− 2 day^− 1. Periods of net deposition of elemental Hg were observed when air masses originating from a mine site moved over sampling locations. Based on these observations and measured soil Hg concentrations we suggest that emissions from point and non-point sources at the mines are a source of Hg to the surrounding substrates with the amount deposited not being of an environmental concern but of interest mainly with respect to the cycling of atmospheric elemental Hg. Observations indicate that while some component of the deposited Hg is sequestered in the soil, this Hg is gradually released back to the atmosphere over time. Estimated pre-disturbance emissions from the current mine footprints based on field data were 0.1 and 1.7 kg yr^− 1, compared to that estimated for the current non-point mining sources of 19 and 109 kg yr^− 1, respectively.     

Volumetric analysis of rock mass instability around haulage drifts in underground mines

Haulage networks are vital to underground mining operations as they constitute the arteries through which blasted ore is transported to surface. In the sublevel stoping method and its variations, haulage drifts are excavated in advance near the ore block that will be mined out. Numerical modeling is a technique that is frequently employed to assess the redistribution of mining-induced stresses, and to compare the impact of different stope sequence scenarios on haulage network stability. In this study, typical geological settings in the Canadian Shield were replicated in a numerical model with a steeply-dipping tabular orebody striking EW. All other formations trended in the same direction except for two dykes on either side of the orebody with a WNW–ESE strike. Rock mass properties and in situ stress measurements from a case study mine were used to calibrate the model. Drifts and crosscuts were excavated in the footwall and two stope sequence scenarios – a diminishing pillar and a center-out one – were implemented in 24 mining stages. A combined volumetric-numerical analysis was conducted for two active levels by comparing the extent of unstable rock mass at each stage using shear, compressive, and tensile instability criteria. Comparisons were made between the orebody and the host rock, between the footwall and hanging wall, and between the two stope sequence scenarios. It was determined that in general, the center-out option provided a larger volume of instability with the shear criterion when compared to the diminishing pillar one (625,477 m³ compared to 586,774 m³ in the orebody; 588 m³ compared to 403 m³ in the host rock). However, the reverse was true for tensile (134,298 m³ compared to 128,834 m³ in the orebody; 91,347 m³ compared to 67,655 m³ in the host rock) instability where the diminishing pillar option had the more voluminous share.     

Deformational behaviour of roadways in soft rocks in underground coal mines and principles for stability control

Following a brief introduction to the nature of a roadway excavated in soft rocks in underground coal mines, six characteristics featuring its deformational behaviour are formulated and illustrated extensively with data collected over decades. The characteristics are: (1) a high rate of rapid deformation in response to ground pressure redistribution; (2) evident rheological deformation; (3) high sensitivity to stress changes; (4) high sensitivity to water invasion; (5) deformation occurring in all directions of the roadway cross section; and (6) a predominant floor heave component in the roof-to-floor convergence. In view of the nature of an underground roadway located in soft strata, principles for controlling the roadway stability both effectively and economically for the whole service life span are specified. A case study is also presented in order to demonstrate the application of the outlined principles for the stability control of roadways excavated in such soft rocks using a multiple support system with joints.     

Numerical modeling of thawing in frozen rocks of underground mines caused by backfilling

The thawing effect due to backfilling in permafrost mining rocks is investigated. The heat transfer equation in rock and backfill is obtained by considering the effect of phase change, heat generation due to cement hydration and temperature dependent material properties. The governing equations are solved using a finite volume numerical method and the phase change phenomenon is modeled based on the manipulation of specific heat, thermal conductivity and density of rock and backfill. The harmonic mean method was employed to handle the change of thermal properties. The effects of different influential parameters such as cement content of backfill, water content of rock and backfill, thermal conductivity of rock and filling material, and the number of adjacent stopes are investigated. Eventually, using the resulting temperature and phase field, a new parameter regarded as the radius of thawing, is introduced.     

复杂地层各种地下障碍物清理施工技术

结合具体工程实例,探讨了如何经济、快速清除复杂地层、各种地下障碍物,分别阐述了清除表层覆盖原厂房基础、人防设施的施工方法及木桩的清除方案,对今后同类地下障碍物清除施工具有一定指导意义。     

某地下人防工程土方开挖施工技术

结合某具体案例,从地下人防工程的施工准备、工艺流程、主要工序施工方法、混凝土浇筑、监测等方面全面阐述了地下人防工程的施工过程,积累了相关施工经验,以供类似工程参考。     

地铁车站大面积钢筋混凝土板施工防开裂技术

分析了混凝土开裂的原因及机理,介绍了设计手段和施工技术方面的控制措施,以达到减少或防止裂缝,提高结构的耐久性和外观质量的目的.     

Development and use of underground space for entertainment and cultural activities in the People's Republic of China

Recent socioeconomic changes in China have led to an increased interest in cultural entertainment and recreational activities. As a result, there is a great need for more theatres, cinemas, music and exhibition halls, museums, cultural centers, children's palaces, education centers, gymnasiums and sports centers. Yet at the same time, there is little aboveground space available for developing such facilities. This article discusses the advantages of constructing recreation and entertainment facilities underground; describes a number of existing such facilities; and presents recommendations for their future planning and design.     

地铁车站施工中的监控量测

为实施对施工过程的动态控制,现场监控量测是关键的一环,对现场量测的主要内容逐一进行了介绍,并叙述了监控量测工作的要求以及监控量测的实施阶段,通过对监控量测数据的整理和分析,对可能出现的各种情况作出决策,采取有效措施。