Vertical stress and stability of interburden over an abandoned pillar working before upward mining: a case study

Upward mining of the residual coal seam over an abandoned pillar working is one of the effective measures to alleviate the contradiction between limited resources and increased consumption. Interburden stability over an abandoned pillar working plays a significant role in guaranteeing the safety of upward mining; however, it has not yet been extensively studied and understood. In this study, the vertical stress of the interburden over an abandoned pillar working was first investigated. The mechanical model of the interburden was established and the damage conditions were analysed. Then, the stability of the interburden over 38502 abandoned workings in Baijiazhuang coal mine was determined by mechanical analysis and field monitoring. The results show that: (i) Vertical stress of the interburden over abandoned mining zones is clearly lower than the initial stress, indicating the existence of a de-stressed effect. Moreover, vertical stress of the interburden over residual coal pillars is greater than the initial stress, which is the evidence of a stress 2 concentration effect. (ii) The interburden over an abandoned pillar working should be regarded as an elastic rectangular plate supported by generalized Kelvin bodies in mechanical modelling. (iii) The interburden over abandoned mining zones may experience two damage stages. In the first stage, initial plastic damage appears at the central region of interburden. In the second stage, the plastic damage evolves from the central point to the surrounding areas. (iv) The mechanical analysis and field monitoring both indicate the initial damage occurred at the central region over 38502 abandoned workings in Baijiazhuang coal mine before upward mining. Related rock control measures should be implemented in that region to guarantee the safe mining of the residual coal seam

Analysis on the Effect of Slideway Friction to the Slider-Type Hydraulic Powered Support

This paper presents a design concept of the slider-type hydraulic powered support. The equivalent mechanical model is established when the hydraulic powered support supporting the stable roof pressure and deriving the numerical calculation formula of the supporting efficiency is based on the slideway frictional coefficient. Meanwhile, theoretical solutions of supporting efficiency at different working heights are obtained. On this basis, the rigid-flexible coupling simulation model of the support was established by using Hypermesh and Adams and the dynamic simulation was carried out under the condition that the roof is bearing the stable pressure, and finally, obtaining the force response curves and the simulation solutions of the supporting efficiency. The final analysis shows the following: The slider-type powered support is suitable for working at high position; with the increase of the friction coefficient between the slider and the slideway, the supporting efficiency increases gradually, the working safety and reliability are enhanced, furthermore, its shock resistance and stability are enhanced

Homogeneous Lean Combustion in Downsized Spark-Ignited Engines

Emissions of greenhouse-gasses and noxious compounds from internal combustion engines propelling personal transportation vehicles is an imminent issue in the society. Therefore, it is vital to find means of reducing these emissions to decrease the impacts of transportation. Despite the current rapid electrification of the light duty vehicle fleet, it is expected that there will still be a substantial share of vehicles, produced and sold, that are propelled either solely or partly by combustion engines in the next decades to come. An advantage of combustion engines is that they consume hydrocarbon fuels, which are energy dense and can be produced from renewable sources enabling elimination of net carbon emissions. These fuels can be distributed using the current infrastructure, allowing for a fast transition into a low-carbon transportation system. The sources of renewables are however limited, and production of renewable fuels requires energy, which is why the fuel efficiency of combustion engines is key.This thesis addresses the need for reduced emissions from personal transportation vehicles by investigating homogeneous lean combustion in downsized spark-ignited engines as a means of improving combustion engine fuel efficiency. Lean combustion offers substantial efficiency improvements to the current already well-developed combustion systems. However, historically, it has been proven difficult to achieve robust lean combustion that achieves both efficiency improvements and sufficiently low emissions of nitrogen oxides. In this thesis, the focus has been to investigate the potentially synergetic combination of high engine loads above 10 bar brake mean effective pressure, a common attribute of downsized engines, and lean combustion. The idea is that lean combustion reduces knocking combustion, a harmful event that limits engine efficiency due to cylinder pressure limitations. Simultaneously, it is hypothesized that higher engine loads will lead to faster and more stable combustion, allowing important reductions in nitrogen oxides.Using engine experiments and simulations, homogeneous lean combustion has been investigated. From the experiments it could be concluded that lean combustion can be sustained at high loads. One of the world’s first two-stage turbochargers designed solely for lean combustion was utilized for this purpose and found to be successful. However, it was discovered that lean combustion does not eliminate knocking combustion completelyKeywords: engine, efficiency, emissions, lean, combustion, nor did high load operation eliminate cyclic dispersion of combustion, which imposes limitations. Using improved in-cylinder charge motion and alternative fuels, these limitations can be mitigated, allowing for stable, efficient, low nitrogen oxide high load lean combustion

Criteria for an environmentally sound reuse of construction and demolition waste in the EU within the concept of circular economy.

openEstate sector is energy and material intense industry. Construction and demolition waste represent the highest flux of waste at European Union. As part of the circular economy concept, the European Community has set certain limits on the re-use, recycling and recovery of other materials, including backfill for CDW, in order to make itself sustainable and more independent in terms of material sources. High recycling rate has been achieved in most EU Country as Austria and Italy, anyway to close the loop the main hurdler is the lack of confidence in the quality of the recycling aggregates. Standardised sampling methods and environmental testing increase confidence in the use of aggregates to prevent any environmental and health impacts from their use. They are also required as criteria to establish EoW status together with limit values on certain substances for an environmentally friendly use of recycled aggregates. The regulatory framework of virtuous countries with their sampling methods and analytical tests drawn up for an environmentally compatible use of CDWs was conducted by analysing common strengths and weaknesses. Regulations implemented to date for the reuse of materials from construction and demolition activities, such as the EoW, allow member states to achieve high recovery rates, even though they feed into low-quality recycling. Composite materials and the addition of chemicals in prefabricated materials make recycling an even more difficult challenge. The risk-based method for determining screening values or site-specific risk assessment for environmental reuse of CDWs should be implemented for emerging contaminants.Estate sector is energy and material intense industry. Construction and demolition waste represent the highest flux of waste at European Union. As part of the circular economy concept, the European Community has set certain limits on the re-use, recycling and recovery of other materials, including backfill for CDW, in order to make itself sustainable and more independent in terms of material sources. High recycling rate has been achieved in most EU Country as Austria and Italy, anyway to close the loop the main hurdler is the lack of confidence in the quality of the recycling aggregates. Standardised sampling methods and environmental testing increase confidence in the use of aggregates to prevent any environmental and health impacts from their use. They are also required as criteria to establish EoW status together with limit values on certain substances for an environmentally friendly use of recycled aggregates. The regulatory framework of virtuous countries with their sampling methods and analytical tests drawn up for an environmentally compatible use of CDWs was conducted by analysing common strengths and weaknesses. Regulations implemented to date for the reuse of materials from construction and demolition activities, such as the EoW, allow member states to achieve high recovery rates, even though they feed into low-quality recycling. Composite materials and the addition of chemicals in prefabricated materials make recycling an even more difficult challenge. The risk-based method for determining screening values or site-specific risk assessment for environmental reuse of CDWs should be implemented for emerging contaminants

International Conference on Civil Infrastructure and Construction (CIC 2020)

This is the proceedings of the CIC 2020 Conference, which was held under the patronage of His Excellency Sheikh Khalid bin Khalifa bin Abdulaziz Al Thani in Doha, Qatar from 2 to 5 February 2020. The goal of the conference was to provide a platform to discuss next-generation infrastructure and its construction among key players such as researchers, industry professionals and leaders, local government agencies, clients, construction contractors and policymakers. The conference gathered industry and academia to disseminate their research and field experiences in multiple areas of civil engineering. It was also a unique opportunity for companies and organizations to show the most recent advances in the field of civil infrastructure and construction. The conference covered a wide range of timely topics that address the needs of the construction industry all over the world and particularly in Qatar. All papers were peer reviewed by experts in their field and edited for publication. The conference accepted a total number of 127 papers submitted by authors from five different continents under the following four themes: Theme 1: Construction Management and Process Theme 2: Materials and Transportation Engineering Theme 3: Geotechnical, Environmental, and Geo-environmental Engineering Theme 4: Sustainability, Renovation, and Monitoring of Civil InfrastructureThe list of the Sponsors are listed at page 1

Abstracts of the 1st GeoDays, 14th–17th March 2023, Helsinki, Finland

Non peer reviewe

Soil Geography and Geostatistics - Concepts and Applications

Geostatistics are a useful tool for understanding and mapping the variation of soil properties across the landscapes. They can be applied at different scales regarding the initial punctual datasets the soil scientist has been provided, and regarding the target resolution of the study. This report is a collection of various studies, all dealing with geostatistical methods, which have been done in Hungary, Russia and Mexico, with the financial support of various research grants. It provides also a chapter about the general concepts of geostatistics and a discussion about limitations of geostatistics with an opening discussion on the usage of pedodiversity index. This report is then particularly recommended to soil scientists who are not so familiar with geostatistics and who need support for applying geostatistics in specific conditions.JRC.H.7-Land management and natural hazard

Sustainable Construction Engineering and Management

This Book is a Printed Edition of the Special Issue which covers sustainability as an emerging requirement in the fields of construction management, project management and engineering. We invited authors to submit their theoretical or experimental research articles that address the challenges and opportunities for sustainable construction in all its facets, including technical topics and specific operational or procedural solutions, as well as strategic approaches aimed at the project, company or industry level. Central to developments are smart technologies and sophisticated decision-making mechanisms that augment sustainable outcomes. The Special Issue was received with great interest by the research community and attracted a high number of submissions. The selection process sought to balance the inclusion of a broad representative spread of topics against research quality, with editors and reviewers settling on thirty-three articles for publication. The Editors invite all participating researchers and those interested in sustainable construction engineering and management to read the summary of the Special Issue and of course to access the full-text articles provided in the Book for deeper analyses

Geological problems in radioactive waste isolation - second worldwide review

The first world wide review of the geological problems in radioactive waste isolation was published by Lawrence Berkeley National Laboratory in 1991. This review was a compilation of reports that had been submitted to a workshop held in conjunction with the 28th International Geological Congress that took place July 9-19, 1989 in Washington, D.C. Reports from 15 countries were presented at the workshop and four countries provided reports after the workshop, so that material from 19 different countries was included in the first review. It was apparent from the widespread interest in this first review that the problem of providing a permanent and reliable method of isolating radioactive waste from the biosphere is a topic of great concern among the more advanced, as well as the developing, nations of the world. This is especially the case in connection with high-level waste (HLW) after its removal from nuclear power plants. The general concensus is that an adequate isolation can be accomplished by selecting an appropriate geologic setting and carefully designing the underground system with its engineered barriers. This document contains the Second Worldwide Review of Geological Problems in Radioactive Waste Isolation, dated September 1996