The main objective of the work presented in this paper was to develop a customized safety training program that can be incorporated into the demolition projects undertaken as part of blight reduction efforts in urban ...The main objective of the work presented in this paper was to develop a customized safety training program that can be incorporated into the demolition projects undertaken as part of blight reduction efforts in urban centers. A subsidiary objective was to devise and implement a safety program evaluation methodology, and gain insights on the relationships between knowledge acquisition through training and trainee demographics. Salient aspects of blight elimination efforts, as well as the main facets of building demolition practices and requirements, were reviewed. Information on various related safety and health hazards was studied in depth with a focus on demolition operations dealing with blighted properties. A unique safety hazard awareness training program was created for demolition workers, contractors and inspectors based on this research. In addition to devising a curriculum of relevant training topics along with traditional and online delivery systems to be employed, effectiveness evaluation instruments were formulated. Based on the limited data collected from the trainees it was concluded that the program was well-received by them and provided effective learning. It was also found that no statistically significant associations existed between the knowledge gain of the trainees, and either their experience level or union status, after taking this training.展开更多
This study aims to reveal the macroscopic permanent deformation(PD)behavior and the internal structural evolution of construction and demolition waste(CDW)under loading.Firstly,the initial matric suction of CDW was me...This study aims to reveal the macroscopic permanent deformation(PD)behavior and the internal structural evolution of construction and demolition waste(CDW)under loading.Firstly,the initial matric suction of CDW was measured by the filter paper method.Secondly,the PD of CDW with different humidity and stress states was investigated by repeated load triaxial tests,and a comprehensive prediction model was established.Finally,the discrete element method was performed to analyze the internal structural evolution of CDW during deformation.These results showed that the VAN-GENUCHTEN model could describe the soil-water characteristic curve of CDW well.The PD increases with the increase of the deviator stress and the number of cyclic loading,but the opposite trend was observed when the initial matric suction and confining pressure increased.The proposed model in this study provides a satisfactory prediction of PD.The discrete element method could accurately simulate the macroscopic PD of CDW,and the shear force,interlock force and sliding content increase with the increase of deviator stress during the deformation.The research could provide useful reference for the deformation stability analysis of CDW under cyclic loading.展开更多
The hard roof difficult to collapse easily causes gas accumulation,which threatens the production safety of coal mine.Therefore,roof pre-cracking is required.Although blasting and hydraulic fracturing can also crack t...The hard roof difficult to collapse easily causes gas accumulation,which threatens the production safety of coal mine.Therefore,roof pre-cracking is required.Although blasting and hydraulic fracturing can also crack the roof,blasting can easily induce rock bursts,whereas hydraulic fracturing needs complex equipment.In contrast,soundless cracking demolition agents(SCDAs)with noise-free,dust-free,and safe characteristics have obvious advantages.The main component of SCDA is calcium oxide,which reacts with water to produce higher expansion pressure.In this paper,focused on the angles of the borehole,the effect of SCDA is analyzed by numerical simulation based on Pingdingshan coal mine.The research results showed that the azimuthal angle a(between borehole projection and the roadway direction)does not significantly affect the efficacy of SCDAs,whereas the influence of borehole elevation angle b is far more significant than that of the azimuthal angle.Therefore,the angle b is a dominant factor influencing the effect of SCDAs.Based on different effects of SCDAs at different angle of boreholes,the weakening unit was established,so the SCDAs could give full play to roof fracturing.Moreover,field tests validated the importance of borehole angle on weakening the hard roofs.展开更多
The mechanism of ground vibration in building demolition blasting was investigated,taking into account the prevailing influential factors, including the building's heightof mass center, the quantity size, the stru...The mechanism of ground vibration in building demolition blasting was investigated,taking into account the prevailing influential factors, including the building's heightof mass center, the quantity size, the structural feature, the component material quantity,the demolition method, the geological structure of the region, earthquake resistance rank,as well as the earthquake wave dissemination.The proposed method was applied efficientlyto reduce the blasting effects on the environment, which enriches the control theoriesof vibration caused by collapse in the blasting process and may provide a good referencefor the related engineering practices.展开更多
Important crystal faces that dominate the crystal morphology of royal demolition explosive （RDX） in vacuum were analyzed with the attachment energy （AE） method. Molecular dynamics （MD） simulations were used to c...Important crystal faces that dominate the crystal morphology of royal demolition explosive （RDX） in vacuum were analyzed with the attachment energy （AE） method. Molecular dynamics （MD） simulations were used to calculate the interaction energies between these crystal faces and different solvent molecules for an attachment energy correction. Growth habits in the presence of different solvents were generated. The results showed that some crystal faces in solutions became morphologically more important than that in vacuum while others became less important. Thus, crystal shape and surface property changed a lot with the variation of crystal faces. The results from calcula- tion were in agreement with those from the re-crystallization experiment, which indicated that cyclohexanone （CH） was a promising solvent to modify the crystal morphology of RDX for obtaining products with regular shape and high purity, while butyrolactone （BL） played a great role in improving the surface electrostatic property of RDX.展开更多
The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing s...The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing steel bar frame of blasting fragmented pier and sequenced collapsed dynamic model were established for quanti- tative blasting design. Technologies of water pressure blasting were applied in multi-cell box girder fragmenta- tion. The detonating network of non-electric duplication crossover was adopted for the safety and reliability of ultra-long delay. The rationality of blasting scheme and parameters were validated by physical model test. Harm- ful effects were forecasted and controlled by integrated protective technologies. Specialization, cooperation, pre- cision, execution （SCPE） project management method was put forward for precision management. The key tech- nologies of precision demolition blasting can provide reference for similar proiects.展开更多
Based on blasting demolition of high thin-wall hyperbolic reinforced concrete cool tower, by virtue of engineering practice of blasting the tube concrete structures, the analysis and research were made on the mechanis...Based on blasting demolition of high thin-wall hyperbolic reinforced concrete cool tower, by virtue of engineering practice of blasting the tube concrete structures, the analysis and research were made on the mechanism of cool tower collapse through selecting blasting parameters and selecting gap form, gap size and gap angle. The cool tower was twisted, collapsed directionally and broken well according to the design requirements. The expected results and purposes of blasting were obtained with no back blow, total blasted pile approximates to 4 - 5 m, no occurrence of flying stones and no damage to fixed buildings and equipment, the large-sized hyperbolic thin-wall reinforced concrete cool towers are twisted during blasting and it collapses well with good breaking. The test and measurement of blasting vibrating velocity was carried out during blasting and the measuring results are much less than critical values specified by Safety Regulations for Blasting. The study shows that gap form, gap size and gap angle are the key factors to cool tower collapse and will give beneficial references to related theoretical study and field application.展开更多
CDW （construction and demolition wastes） present a high amount of aggregate chips covered with mortar. This results in high absorption of water with a direct impact in particle breakage or disaggregation. It is supp...CDW （construction and demolition wastes） present a high amount of aggregate chips covered with mortar. This results in high absorption of water with a direct impact in particle breakage or disaggregation. It is supposed that intra particle suction plays an important role in this phenomenon. However, WRCs （water retention curves） of CDW are not well understood. In this work, the WRCs of dynamically compacted specimens of aggregates recycled from the demolition of the National Stadium in Brasilia are studied. The objective of this study is to obtain WRCs of the recycled materials by using the pressure plate and filter paper methods. The breaking effect during compaction is quantified from the grain size distribution curves. The particle breakage during compaction increases when the energy is augmented. The results from the WRCs were incorporated into a pore size capillary model to predict pore size distribution.展开更多
The method of drilling and blasting with explosives is widely used in rock fragmentation applications in the mining industry for mine development and ore production.However,the use of explosives is associated with rig...The method of drilling and blasting with explosives is widely used in rock fragmentation applications in the mining industry for mine development and ore production.However,the use of explosives is associated with rigorous safety and environmental constraints as blasting creates toxic fumes,ground vibrations,and dust.This study is focused on the use of Soundless Chemical Demolition Agents(SCDA)as a more environmentally friendly method for rock breakage and a potential replacement of explosives.In this paper,the results of a series of experimental tests are reported to identify the efect of SCDA on hard rock breakage under no load and under uniaxial loading conditions.Stanstead granite prismatic specimens of 152.4 mm(6″)×152.4–203.2 mm(6–8″)×406.4 mm(16″)are used to test the infuence of borehole size on the time to fracturing with SCDA borehole size of 25.4 mm(1″),31.75 mm(1.25″)and 38.1 mm(1.5″).It is shown that the fracturing time decreases with increasing borehole size.It is also shown that specimens subjected to uniaxial compression of 5 MPa fracture as early as 7 h after SCDA mixing.A borehole spacing to borehole diameter ratio of 12.8 to 14.6 is suggested for practical applications.展开更多
Ground vibration accelerations caused by the collapse of blasting demolition of urban viaducts was recorded in ordered to analyze the engineering characteristics and effects on the surrounding buildings. Through the a...Ground vibration accelerations caused by the collapse of blasting demolition of urban viaducts was recorded in ordered to analyze the engineering characteristics and effects on the surrounding buildings. Through the analysis of peak ground acceleration,peak frequency,duration and response spectra of the recorded vibrations in different acceleration arrays,some conclusions are drawn: the peak ground acceleration decreases with increasing distance, and the amplitude of vertical component is higher than that of the horizontal components,especially in near source region. The peak frequency of ground acceleration decreases with distance,and in near source region,it is larger than the natural frequency of the surrounding buildings,and thus it will not have much effect on the buildings. The duration of ground acceleration caused by collapse is longer than that caused by blasting itself. The vertical response spectrum is the largest of the three components,and it decreases rapidly in the near source region of about 30 m,but beyond that the distance decreases slowly.The horizontal components are smaller than the local seismic design spectrum,while the vertical component for natural period under 0.15 s exceeds the seismic design spectrum,but the natural periods of general buildings are usually beyond that domain,so this will not have much effect on the nearby buildings.展开更多
The Italian earthquakes of recent decades created an emergency situation that required immediate post-earthquake reconstruction policies, which led to an increase in the demand for construction minerals. In particular...The Italian earthquakes of recent decades created an emergency situation that required immediate post-earthquake reconstruction policies, which led to an increase in the demand for construction minerals. In particular, extraction in active quarries has been intensified, and new quarries opened according to extraordinary procedures notwithstanding current regulations. The objective of this work is to investigate the consequences that a seismic event may produce on both the built-up environment, i.e. the totality of urban and suburban settlements and infrastructure, and the natural environment, which is often compromised by hasty emergency procedures aimed at mineral extraction. As a result, correct evaluation of the demand for minerals and the recycling of earthquake debris are the fundamental elements of coherent post seismic reconstruction, by means of which post-earthquake policies could be reconciled with environmental protection.展开更多
To analyze the characteristics of ground vibration caused by blasting demolition of urban overpass, in this paper we introduced the measurement method and then studied the characteristics of recorded ground vi- bratio...To analyze the characteristics of ground vibration caused by blasting demolition of urban overpass, in this paper we introduced the measurement method and then studied the characteristics of recorded ground vi- brations. Through the analysis of peak acceleration, peak frequency and duration, results indicated that the ver- tical component of vibration is the most important in the region close to the collapse point; the collapse of bridge segments will lead to superposition of ground vibration, and isolation measures can reduce the peak ac- celeration but increase the duration of vibration; blasting and collapse vibration cause no damage to the re- served structure which indicates that blastin~ demolition is a safe and effective method.展开更多
The research focused on the analysis of construction and demolition debris in a sample Brazilian city with the objective to propose a management scheme tailored to private initiative intervention. The debris was found...The research focused on the analysis of construction and demolition debris in a sample Brazilian city with the objective to propose a management scheme tailored to private initiative intervention. The debris was found to be produced at a rate of 1.55 kg per person per day for a total of 5177 tons per month. The composition report showed 75% material reusable for construction purposes, 15% material recyclable through reverse logistics and 10% refuse to be disposed of at landfills. The study developed legal and managerial instruments that stimulate private operators to achieve landfill diversions in the order of 90% of this waste. The arguments were supported by a flow diagram that indicates the correct destination of all waste items and an economic balance of private waste movement. Proactive legal scriptures were sketched out that can assist the local administration in setting the timeframe for reaching the diversion target.展开更多
The applications of numerical simulation in demolition blasting were reviewed.Several methods of numerical simulation in demolition blasting were introduced.The strength and weakness of the numerical methods mentioned...The applications of numerical simulation in demolition blasting were reviewed.Several methods of numerical simulation in demolition blasting were introduced.The strength and weakness of the numerical methods mentioned in this paper were also indicated,respectively.Furthermore,the solid lattice model in the frame of discrete element method(DEM),which was developed by the author and his team,was detailedly described.The existed problems in the current numerical simulation methods of demolition blasting were presented and the future trend of the numerical simulation is finally prospected.展开更多
Concrete is multicomponent composite material, consisting of coarse aggregate, fine aggregate, cement and water. Natural aggregates, as well as aggregates obtained after the reprocessing of buildings＇ demolition wast...Concrete is multicomponent composite material, consisting of coarse aggregate, fine aggregate, cement and water. Natural aggregates, as well as aggregates obtained after the reprocessing of buildings＇ demolition waste, can be used as coarse and fine aggregates. Characteristics of the hardened concrete depend on the raw materials, used for the preparation of concrete mixture, and their characteristics. The objective of the research is to analyse the sources of demolition waste, to describe the reprocessing technology of concrete waste, to investigate the production of the aggregate from the concrete waste, to analyse the main properties of these aggregates -- particles＇ density, bulk density, granulometric composition, hollowness and other properties, as well as to compare the obtained results with the requirements applicable to the aggregates based on natural materials.展开更多
Massive amounts of brick waste are obtained from demolition of old buildings and structures around the world. With the increased stress on sustainable construction, and environmentally friendly materials and greener c...Massive amounts of brick waste are obtained from demolition of old buildings and structures around the world. With the increased stress on sustainable construction, and environmentally friendly materials and greener concreting practices, a large proportion of such waste bricks are crushed and mixed with normal aggregates for use in concrete. The performance of concrete containing waste brick aggregates partially replacing normal aggregates have not been investigated for their performance. This paper covers investigations carried out on concrete with such aggregates obtained from demolition waste and mixed with varying proportions of normal aggregates to produce concrete. Two types of crushed brick aggregates were mixed with gravel in the ratios of 30:70 and 40:60 by weight and specimen were cast for investigations. Two w/c ratios were investigated. Various tests were carried out to assess the compressive strength of cubes and cylinders of mixed aggregates concrete along with f1exural strength, stress/strain behavior, moduli of elasticity, ultrasonic pulse velocity determination, densities, surface absorption, shrinkage and frost resistance. The values obtained from these tests were compared with the values of concrete with normal aggregates (gravel) with similar w/c ratios. While the strength tests and durability tests more or less gave satisfactory results however the larger moisture absorption by the waste brick aggregates reduces the frost resistance capacity somewhat thereby care needs to be exercised in using these mixes in regions/areas susceptible to frost.展开更多
This study evaluated the influence of the Portland cement replacement by 0, 5</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span sty...This study evaluated the influence of the Portland cement replacement by 0, 5</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 10</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 15</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> and 20% of Construction and Demolition Waste (CDW) filler </span><span style="font-family:Verdana;">contents in the production of self-compacting concrete (SCC). The SCC mixtures </span><span style="font-family:Verdana;">were evaluated on fresh state by slump flow, J-ring, resistance of segre</span><span style="font-family:Verdana;">gation, specific gravity, and on hardened state by compressive and splitting tensile </span><span style="font-family:Verdana;">strength, specific gravity, air voids and absorption rate. The results indicated that all SCC produced with CDW filler met the limits established at any level of substitution without changes of the w/c ratio or superplasticizer content. It was possible to verify that the presence of CDW filler, in substitution of cement, by volume, improves the resistance to segregation and up to 5% of CDW filler decreases the loss of fluidity with time as compared to reference. It was found that all SCC mixtures, at 28 days, had the average compressive strength above 50 MPa, without showing significant loss with up to 20% of CDW filler. For splitting tensile strength, SCC recycled mixtures reached up to 92.5% of the SCC used as reference. Absorption rate and air voids index of SCC recycled mixtures had a maximum increase of 1.60%Compared to the reference one. So, it is possible to conclude that the use of the CDW filler up to 20% in substitution of cement, by volume, is feasible for SCC production.展开更多
In the current, the urban renewal for demolition and reconstruction is as the principally means of the old city transformation in Shenzhen, it is a process to realize the benefit balance in the gambling for three stak...In the current, the urban renewal for demolition and reconstruction is as the principally means of the old city transformation in Shenzhen, it is a process to realize the benefit balance in the gambling for three stakeholders about government, developers, and rural residents. The game relation between government and developers and between government and urban village residents in the demolition and reconstruction of renewal by government guidance are analyzed, and these tow game models are built. And then the problem in urban renewal of Shenzhen is pointed out, and the reasonable way of optimize urban renewal for the problem is discussed in this paper.展开更多
Globally, the construction industry is one of the leading producers of solid waste. The city of Praia, the capital of the Republic of Cape Verde has been suffering from environmental degradation with the irregular dis...Globally, the construction industry is one of the leading producers of solid waste. The city of Praia, the capital of the Republic of Cape Verde has been suffering from environmental degradation with the irregular disposal of waste caused by inadequate management of waste from construction and also the demolition. The research was developed based on local inspections in the context of environmental laws, in semi-structured interviews with people who deal with this activity and bibliographic references. The main conclusion is that the city does not have a CDW management plan consequently leading to environmental problems. On the other hand, waste of recycled construction can be used as inert reducing the consumption of raw materials that can be used as base and sub-base for paving, landfills, aggregate in mortars and raw materials to be manufactured blocks, bricks concrete tiles, etc.展开更多
Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and ...Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and in addition an economic benefit to it in the construction. This study explores the possibility of replacing natural coarse aggregate with recycled concrete construction and demolition waste aggregate for general purpose concrete (i.e. plain concrete and low strength structural concrete). Different samples of CDW were extracted from different demolition sites and landfill locations around Tanta city area for the experimental investigation. CDW was crushed with all its hard constituents (e.g. concrete, brick etc.) found in the landfill. Coarse size crushed CDW was used as a coarse aggregate for concrete. Main characteristics of CDW aggregate determined in addition to the main properties of concrete which was made using this aggregate were measured. The results showed that the CDW could be transformed into recycled concrete aggregate leading to reduction in the concrete compressive strength ranged from 37% to 62% depending on the type of the CDW constituents.展开更多
文摘The main objective of the work presented in this paper was to develop a customized safety training program that can be incorporated into the demolition projects undertaken as part of blight reduction efforts in urban centers. A subsidiary objective was to devise and implement a safety program evaluation methodology, and gain insights on the relationships between knowledge acquisition through training and trainee demographics. Salient aspects of blight elimination efforts, as well as the main facets of building demolition practices and requirements, were reviewed. Information on various related safety and health hazards was studied in depth with a focus on demolition operations dealing with blighted properties. A unique safety hazard awareness training program was created for demolition workers, contractors and inspectors based on this research. In addition to devising a curriculum of relevant training topics along with traditional and online delivery systems to be employed, effectiveness evaluation instruments were formulated. Based on the limited data collected from the trainees it was concluded that the program was well-received by them and provided effective learning. It was also found that no statistically significant associations existed between the knowledge gain of the trainees, and either their experience level or union status, after taking this training.
基金Project(52025085)supported by the National Science Fund for Distinguished Young Scholars,ChinaProjects(51927814,51878078)supported by the National Natural Science Foundation of China+3 种基金Project(2018-025)supported by the Training Program for High-level Technical Personnel in Transportation Industry,ChinaProject(CTKY-PTRC 2018-003)supported by the Design Theory,Method and Demonstration of Durability Asphalt Pavement Based on Heavy-duty Traffic Conditions in Shanghai Area,ChinaProject(2020RC4048)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(SJCX202001)supported by the Construction Project for Graduate Students of Changsha University of Science&Technology,China。
文摘This study aims to reveal the macroscopic permanent deformation(PD)behavior and the internal structural evolution of construction and demolition waste(CDW)under loading.Firstly,the initial matric suction of CDW was measured by the filter paper method.Secondly,the PD of CDW with different humidity and stress states was investigated by repeated load triaxial tests,and a comprehensive prediction model was established.Finally,the discrete element method was performed to analyze the internal structural evolution of CDW during deformation.These results showed that the VAN-GENUCHTEN model could describe the soil-water characteristic curve of CDW well.The PD increases with the increase of the deviator stress and the number of cyclic loading,but the opposite trend was observed when the initial matric suction and confining pressure increased.The proposed model in this study provides a satisfactory prediction of PD.The discrete element method could accurately simulate the macroscopic PD of CDW,and the shear force,interlock force and sliding content increase with the increase of deviator stress during the deformation.The research could provide useful reference for the deformation stability analysis of CDW under cyclic loading.
基金financially supported by the National Key R&D Program of China(2020YFA0711800)the National Science Fund for Distinguished Young Scholars(51925404)the National Natural Science Foundation of China(51774278)。
文摘The hard roof difficult to collapse easily causes gas accumulation,which threatens the production safety of coal mine.Therefore,roof pre-cracking is required.Although blasting and hydraulic fracturing can also crack the roof,blasting can easily induce rock bursts,whereas hydraulic fracturing needs complex equipment.In contrast,soundless cracking demolition agents(SCDAs)with noise-free,dust-free,and safe characteristics have obvious advantages.The main component of SCDA is calcium oxide,which reacts with water to produce higher expansion pressure.In this paper,focused on the angles of the borehole,the effect of SCDA is analyzed by numerical simulation based on Pingdingshan coal mine.The research results showed that the azimuthal angle a(between borehole projection and the roadway direction)does not significantly affect the efficacy of SCDAs,whereas the influence of borehole elevation angle b is far more significant than that of the azimuthal angle.Therefore,the angle b is a dominant factor influencing the effect of SCDAs.Based on different effects of SCDAs at different angle of boreholes,the weakening unit was established,so the SCDAs could give full play to roof fracturing.Moreover,field tests validated the importance of borehole angle on weakening the hard roofs.
文摘The mechanism of ground vibration in building demolition blasting was investigated,taking into account the prevailing influential factors, including the building's heightof mass center, the quantity size, the structural feature, the component material quantity,the demolition method, the geological structure of the region, earthquake resistance rank,as well as the earthquake wave dissemination.The proposed method was applied efficientlyto reduce the blasting effects on the environment, which enriches the control theoriesof vibration caused by collapse in the blasting process and may provide a good referencefor the related engineering practices.
文摘Important crystal faces that dominate the crystal morphology of royal demolition explosive （RDX） in vacuum were analyzed with the attachment energy （AE） method. Molecular dynamics （MD） simulations were used to calculate the interaction energies between these crystal faces and different solvent molecules for an attachment energy correction. Growth habits in the presence of different solvents were generated. The results showed that some crystal faces in solutions became morphologically more important than that in vacuum while others became less important. Thus, crystal shape and surface property changed a lot with the variation of crystal faces. The results from calcula- tion were in agreement with those from the re-crystallization experiment, which indicated that cyclohexanone （CH） was a promising solvent to modify the crystal morphology of RDX for obtaining products with regular shape and high purity, while butyrolactone （BL） played a great role in improving the surface electrostatic property of RDX.
文摘The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing steel bar frame of blasting fragmented pier and sequenced collapsed dynamic model were established for quanti- tative blasting design. Technologies of water pressure blasting were applied in multi-cell box girder fragmenta- tion. The detonating network of non-electric duplication crossover was adopted for the safety and reliability of ultra-long delay. The rationality of blasting scheme and parameters were validated by physical model test. Harm- ful effects were forecasted and controlled by integrated protective technologies. Specialization, cooperation, pre- cision, execution （SCPE） project management method was put forward for precision management. The key tech- nologies of precision demolition blasting can provide reference for similar proiects.
文摘Based on blasting demolition of high thin-wall hyperbolic reinforced concrete cool tower, by virtue of engineering practice of blasting the tube concrete structures, the analysis and research were made on the mechanism of cool tower collapse through selecting blasting parameters and selecting gap form, gap size and gap angle. The cool tower was twisted, collapsed directionally and broken well according to the design requirements. The expected results and purposes of blasting were obtained with no back blow, total blasted pile approximates to 4 - 5 m, no occurrence of flying stones and no damage to fixed buildings and equipment, the large-sized hyperbolic thin-wall reinforced concrete cool towers are twisted during blasting and it collapses well with good breaking. The test and measurement of blasting vibrating velocity was carried out during blasting and the measuring results are much less than critical values specified by Safety Regulations for Blasting. The study shows that gap form, gap size and gap angle are the key factors to cool tower collapse and will give beneficial references to related theoretical study and field application.
文摘CDW （construction and demolition wastes） present a high amount of aggregate chips covered with mortar. This results in high absorption of water with a direct impact in particle breakage or disaggregation. It is supposed that intra particle suction plays an important role in this phenomenon. However, WRCs （water retention curves） of CDW are not well understood. In this work, the WRCs of dynamically compacted specimens of aggregates recycled from the demolition of the National Stadium in Brasilia are studied. The objective of this study is to obtain WRCs of the recycled materials by using the pressure plate and filter paper methods. The breaking effect during compaction is quantified from the grain size distribution curves. The particle breakage during compaction increases when the energy is augmented. The results from the WRCs were incorporated into a pore size capillary model to predict pore size distribution.
基金supported by a research grant from Natural Resources Canada,Clean Growth Program,Grant No.CGP-17-1003 and industry partner Newmont Corporation。
文摘The method of drilling and blasting with explosives is widely used in rock fragmentation applications in the mining industry for mine development and ore production.However,the use of explosives is associated with rigorous safety and environmental constraints as blasting creates toxic fumes,ground vibrations,and dust.This study is focused on the use of Soundless Chemical Demolition Agents(SCDA)as a more environmentally friendly method for rock breakage and a potential replacement of explosives.In this paper,the results of a series of experimental tests are reported to identify the efect of SCDA on hard rock breakage under no load and under uniaxial loading conditions.Stanstead granite prismatic specimens of 152.4 mm(6″)×152.4–203.2 mm(6–8″)×406.4 mm(16″)are used to test the infuence of borehole size on the time to fracturing with SCDA borehole size of 25.4 mm(1″),31.75 mm(1.25″)and 38.1 mm(1.5″).It is shown that the fracturing time decreases with increasing borehole size.It is also shown that specimens subjected to uniaxial compression of 5 MPa fracture as early as 7 h after SCDA mixing.A borehole spacing to borehole diameter ratio of 12.8 to 14.6 is suggested for practical applications.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51578516 and 51238012)the Basic Research Foundation of Institute of Engineering Mechanics,CEA(Grant No.2011B02)+1 种基金973 Program(Grant No.2011CB013601)the Wuhan Blasting Company
文摘Ground vibration accelerations caused by the collapse of blasting demolition of urban viaducts was recorded in ordered to analyze the engineering characteristics and effects on the surrounding buildings. Through the analysis of peak ground acceleration,peak frequency,duration and response spectra of the recorded vibrations in different acceleration arrays,some conclusions are drawn: the peak ground acceleration decreases with increasing distance, and the amplitude of vertical component is higher than that of the horizontal components,especially in near source region. The peak frequency of ground acceleration decreases with distance,and in near source region,it is larger than the natural frequency of the surrounding buildings,and thus it will not have much effect on the buildings. The duration of ground acceleration caused by collapse is longer than that caused by blasting itself. The vertical response spectrum is the largest of the three components,and it decreases rapidly in the near source region of about 30 m,but beyond that the distance decreases slowly.The horizontal components are smaller than the local seismic design spectrum,while the vertical component for natural period under 0.15 s exceeds the seismic design spectrum,but the natural periods of general buildings are usually beyond that domain,so this will not have much effect on the nearby buildings.
文摘The Italian earthquakes of recent decades created an emergency situation that required immediate post-earthquake reconstruction policies, which led to an increase in the demand for construction minerals. In particular, extraction in active quarries has been intensified, and new quarries opened according to extraordinary procedures notwithstanding current regulations. The objective of this work is to investigate the consequences that a seismic event may produce on both the built-up environment, i.e. the totality of urban and suburban settlements and infrastructure, and the natural environment, which is often compromised by hasty emergency procedures aimed at mineral extraction. As a result, correct evaluation of the demand for minerals and the recycling of earthquake debris are the fundamental elements of coherent post seismic reconstruction, by means of which post-earthquake policies could be reconciled with environmental protection.
文摘To analyze the characteristics of ground vibration caused by blasting demolition of urban overpass, in this paper we introduced the measurement method and then studied the characteristics of recorded ground vi- brations. Through the analysis of peak acceleration, peak frequency and duration, results indicated that the ver- tical component of vibration is the most important in the region close to the collapse point; the collapse of bridge segments will lead to superposition of ground vibration, and isolation measures can reduce the peak ac- celeration but increase the duration of vibration; blasting and collapse vibration cause no damage to the re- served structure which indicates that blastin~ demolition is a safe and effective method.
文摘The research focused on the analysis of construction and demolition debris in a sample Brazilian city with the objective to propose a management scheme tailored to private initiative intervention. The debris was found to be produced at a rate of 1.55 kg per person per day for a total of 5177 tons per month. The composition report showed 75% material reusable for construction purposes, 15% material recyclable through reverse logistics and 10% refuse to be disposed of at landfills. The study developed legal and managerial instruments that stimulate private operators to achieve landfill diversions in the order of 90% of this waste. The arguments were supported by a flow diagram that indicates the correct destination of all waste items and an economic balance of private waste movement. Proactive legal scriptures were sketched out that can assist the local administration in setting the timeframe for reaching the diversion target.
文摘The applications of numerical simulation in demolition blasting were reviewed.Several methods of numerical simulation in demolition blasting were introduced.The strength and weakness of the numerical methods mentioned in this paper were also indicated,respectively.Furthermore,the solid lattice model in the frame of discrete element method(DEM),which was developed by the author and his team,was detailedly described.The existed problems in the current numerical simulation methods of demolition blasting were presented and the future trend of the numerical simulation is finally prospected.
文摘Concrete is multicomponent composite material, consisting of coarse aggregate, fine aggregate, cement and water. Natural aggregates, as well as aggregates obtained after the reprocessing of buildings＇ demolition waste, can be used as coarse and fine aggregates. Characteristics of the hardened concrete depend on the raw materials, used for the preparation of concrete mixture, and their characteristics. The objective of the research is to analyse the sources of demolition waste, to describe the reprocessing technology of concrete waste, to investigate the production of the aggregate from the concrete waste, to analyse the main properties of these aggregates -- particles＇ density, bulk density, granulometric composition, hollowness and other properties, as well as to compare the obtained results with the requirements applicable to the aggregates based on natural materials.
文摘Massive amounts of brick waste are obtained from demolition of old buildings and structures around the world. With the increased stress on sustainable construction, and environmentally friendly materials and greener concreting practices, a large proportion of such waste bricks are crushed and mixed with normal aggregates for use in concrete. The performance of concrete containing waste brick aggregates partially replacing normal aggregates have not been investigated for their performance. This paper covers investigations carried out on concrete with such aggregates obtained from demolition waste and mixed with varying proportions of normal aggregates to produce concrete. Two types of crushed brick aggregates were mixed with gravel in the ratios of 30:70 and 40:60 by weight and specimen were cast for investigations. Two w/c ratios were investigated. Various tests were carried out to assess the compressive strength of cubes and cylinders of mixed aggregates concrete along with f1exural strength, stress/strain behavior, moduli of elasticity, ultrasonic pulse velocity determination, densities, surface absorption, shrinkage and frost resistance. The values obtained from these tests were compared with the values of concrete with normal aggregates (gravel) with similar w/c ratios. While the strength tests and durability tests more or less gave satisfactory results however the larger moisture absorption by the waste brick aggregates reduces the frost resistance capacity somewhat thereby care needs to be exercised in using these mixes in regions/areas susceptible to frost.
文摘This study evaluated the influence of the Portland cement replacement by 0, 5</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 10</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 15</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> and 20% of Construction and Demolition Waste (CDW) filler </span><span style="font-family:Verdana;">contents in the production of self-compacting concrete (SCC). The SCC mixtures </span><span style="font-family:Verdana;">were evaluated on fresh state by slump flow, J-ring, resistance of segre</span><span style="font-family:Verdana;">gation, specific gravity, and on hardened state by compressive and splitting tensile </span><span style="font-family:Verdana;">strength, specific gravity, air voids and absorption rate. The results indicated that all SCC produced with CDW filler met the limits established at any level of substitution without changes of the w/c ratio or superplasticizer content. It was possible to verify that the presence of CDW filler, in substitution of cement, by volume, improves the resistance to segregation and up to 5% of CDW filler decreases the loss of fluidity with time as compared to reference. It was found that all SCC mixtures, at 28 days, had the average compressive strength above 50 MPa, without showing significant loss with up to 20% of CDW filler. For splitting tensile strength, SCC recycled mixtures reached up to 92.5% of the SCC used as reference. Absorption rate and air voids index of SCC recycled mixtures had a maximum increase of 1.60%Compared to the reference one. So, it is possible to conclude that the use of the CDW filler up to 20% in substitution of cement, by volume, is feasible for SCC production.
文摘In the current, the urban renewal for demolition and reconstruction is as the principally means of the old city transformation in Shenzhen, it is a process to realize the benefit balance in the gambling for three stakeholders about government, developers, and rural residents. The game relation between government and developers and between government and urban village residents in the demolition and reconstruction of renewal by government guidance are analyzed, and these tow game models are built. And then the problem in urban renewal of Shenzhen is pointed out, and the reasonable way of optimize urban renewal for the problem is discussed in this paper.
文摘Globally, the construction industry is one of the leading producers of solid waste. The city of Praia, the capital of the Republic of Cape Verde has been suffering from environmental degradation with the irregular disposal of waste caused by inadequate management of waste from construction and also the demolition. The research was developed based on local inspections in the context of environmental laws, in semi-structured interviews with people who deal with this activity and bibliographic references. The main conclusion is that the city does not have a CDW management plan consequently leading to environmental problems. On the other hand, waste of recycled construction can be used as inert reducing the consumption of raw materials that can be used as base and sub-base for paving, landfills, aggregate in mortars and raw materials to be manufactured blocks, bricks concrete tiles, etc.
文摘Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and in addition an economic benefit to it in the construction. This study explores the possibility of replacing natural coarse aggregate with recycled concrete construction and demolition waste aggregate for general purpose concrete (i.e. plain concrete and low strength structural concrete). Different samples of CDW were extracted from different demolition sites and landfill locations around Tanta city area for the experimental investigation. CDW was crushed with all its hard constituents (e.g. concrete, brick etc.) found in the landfill. Coarse size crushed CDW was used as a coarse aggregate for concrete. Main characteristics of CDW aggregate determined in addition to the main properties of concrete which was made using this aggregate were measured. The results showed that the CDW could be transformed into recycled concrete aggregate leading to reduction in the concrete compressive strength ranged from 37% to 62% depending on the type of the CDW constituents.
