Assessment and control of the mine tremor disaster induced by the energy accumulation and dispersion of thick-hard roofs

In order to solve the problem that current theory models cannot accurately describe thick-hard roof(THR)elastic energy and assess the mine tremor disasters,a theoretical method,a Timoshenko beam theory on Winkler foundation was adopted to establish the THR’s periodic breaking model.The superposition principle was used for this complex model to derive the calculation formulas of the elastic energy and impact load on hydraulic supports.Then,the influence of roof thickness h,cantilever length L_(1),and load q on THR’s elastic energy and impact load was analyzed.And,the effect of mine tremor disasters was assessed.Finally,it is revealed that:(1)The THR’s elastic energy U exhibits power-law variations,with the fitted relationships U=0.0096L_(1)^(3.5866^),U=5943.9h^(-1.935),and U=21.049q^(2).(2)The impact load on hydraulic supports F_(ZJ) increases linearly with an increase in the cantilever length,thickness,and applied load.The fitted relationships are F_(ZJ)=1067.3L_(1)+6361.1,F_(ZJ)=125.89h+15100,and F_(ZJ)=10420q+3912.6.(3)Ground hydraulic fracturing and liquid explosive deep-hole blasting techniques effectively reduce the THR’s cantilever length at periodic breakages,thus eliminating mine tremor disasters.

Physical and numerical investigations of target stratum selection for ground hydraulic fracturing of multiple hard roofs

Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof,making it imperative to identify the most suitable target stratum for effective control.Physical experiments are conducted based on engineering properties to simulate the gradual collapse of the roof during longwall top coal caving(LTCC).A numerical model is established using the material point method(MPM)and the strain-softening damage constitutive model according to the structure of the physical model.Numerical simulations are conducted to analyze the LTCC process under different hard roofs for ground hydraulic fracturing.The results show that ground hydraulic fracturing releases the energy and stress of the target stratum,resulting in a substantial lag in the fracturing of the overburden before collapse occurs in the hydraulic fracturing stratum.Ground hydraulic fracturing of a low hard roof reduces the lag effect of hydraulic fractures,dissipates the energy consumed by the fracture of the hard roof,and reduces the abutment stress.Therefore,it is advisable to prioritize the selection of the lower hard roof as the target stratum.

Experimental Assessment of the Thermal Performance of Two Corrugated Metal Roofs

This experimental study is a contribution to the search for solutions to reduce indoor heat gain through sheet metal roofing in hot weather. It has evaluated the thermal impact of two different sheet metal roofs inside of two identical test buildings in sunny weather and cloudy weather conditions. Test building 1 has a single sheet corrugated roof and the building 2 is covered with roof made from top to bottom with corrugated sheet metal, a 12 mm thick serpentine copper tube in which water is circulated, a sheet of aluminium foil acting as a heat reflector, a 4 cm thick polystyrene panel and a 1.5 cm thick plywood. A maximum reduction of 15.1˚C in the temperature of the inner face of the test Building 2 roof was obtained comparatively to the temperature of the inner face of the test Building 1 roof consisting of a single sheet of metal at the warmest hours. In addition, the simple corrugated sheet metal roof of the test building generates high and varied temperatures inside the building. Whereas the proposed heat recovery roof favours low and relatively uniform temperatures inside the building. The proposed sheet metal roof construction technique is very effective in reducing the heat gain through the roof considerably;thus improving the thermal comfort inside sheet metal roofed dwellings. Hot water has been produced by recovering heat from the metal sheet of the roof of test building 2. The temperature of the hot water produced reached of 39˚C. This study could be also an alternative for the reduction of energy consumption due to the use of mechanical means for cooling of sheet metal roofed houses and the reduction of the use of fossil fuels for domestic hot water production.

Experimental Investigation on the Effect of Seal Presence on the Behavior of Double-Deck Floating Roofs in Cylindrical Steel Storage Tanks

Liquid storage,particularly oil and petrochemical products which are considered hazardous liquid,are an important part of the oil industry.Thin-walled vertical cylindrical steel storage tanks are widely used in recent years.Due to high sensitivity of these structures in an earthquake and other external excitations may lead to catastrophic consequences.For instance,huge economic losses,environmental damages,and casualities,many studies have been done about these structures.past studies showed that liquid storage tanks,equipped with a floating roof,are potentially vulnerable while subjected to seismic loads and earthquake has been considered as one of the most destructive natural hazards.The reason is that such tanks are made of two separated parts(shell and roof)which each may have its own responses;sometimes causing resonance phenomenon and so that,roof movements,rooffluid interaction,roof-shell interaction,and also the way they are attached should still be investigated.Experimental tests of floating roof’s vertical fluctuation was performed in a full-scale reservoir tank and assessing of the results demonstrated that presence of a seal between floating roof and shell plate can significantly increase damping ratio in liquid sloshing and also suppress the roof`s vertical displacements.In other words,seal can control a floating roof and make it stop moving vertically over few cycles.

Understanding the Challenges of Implementing Green Roofs in Multi-Family Apartment Buildings:A Case Study in Khulna

Green roofs are widely recognized for their multifaceted benefits to the environment,economy,and society,constituting the fundamental pillars of sustainability.These roofs contribute to the enhancement of bio-physical diversity,provision of food resources,regulation of temperature and rainfall-runoff patterns,creation of wildlife habitats,and augmentation of aesthetic and recreational value.While Bangladesh,with its favourable climatic conditions and rapid urbanization,possesses immense potential for harnessing the advantages of green roofs,their adoption remains limited in both research and practical applications within the country.Addressing this research gap,the present study aims to investigate the barriers impeding the implementation of green roofs in existing or new multi-family apartment buildings,focusing specifically on the city of Khulna.Through a combination of case studies and a comprehensive questionnaire survey administered to diverse stakeholders including apartment dwellers/owners,architects,developers,and government officials with varying levels of expertise,this research sheds light on the obstacles hindering Green Roof Implementation(GRI).The identified barriers encompass a lack of governmental policies,inadequate technological advancements,inaccurate estimation of economic benefits,and individual resistance.In light of the perspectives of various GRI stakeholders,strategic proposals encompassing policy,technical,economic,and social dimensions are presented to surmount these barriers.The outcomes of this study contribute to the dissemination of knowledge pertaining to the impediments to GRI implementation,thereby inspiring further research endeavours and enabling decision-makers to formulate robust policies facilitating the widespread adoption of green roofs.

PV-green Roofs植被层高度对系统性能影响

绿化屋顶(GR)和光伏发电系统(PV)在调节室内热湿环境与降低建筑能耗中发挥着重要作用,利用两系统互效性耦合而成的光伏-绿化屋顶(PV-green Roofs)是推进建筑节能的创新型举措。结合PV-green Roofs数学模型,分析植物高度对系统性能的影响,通过实验测定,以落地生根和佛甲草为绿化屋顶植被层材料,实测不同工况下PV-green Roofs系统的电量输出值,同时结合EnergyPlus数值模拟结果分析采用不同植株高度的PV-green Roofs系统对建筑消耗净能量的影响。结果表明:植物高度通过改变绿化屋顶种植层蒸发阻力和植被层冠状层风速影响系统性能;在夏热冬冷的气候条件下,植物生命中期对应的高度对光伏系统工作环境的冷却效果最为明显,引起输出电量的增值最大,且环境湿度对系统性能存在影响。

Analysis on nonlinear wind-induced dynamic response of membrane roofs with aerodynamic effects

Based on the characteristics of membrane structures and the air influence factors,this paper presented a method to simulate the air aerodynamic force effects including the added air mass,the acoustic radiation damping and the pneumatic stiffness.The infinite air was modeled using the acoustic fluid element of commercial FE software and the finite element membrane roof models were coupled with fluid models.A comparison between the results obtained by FE computation and those obtained by the vibration experiment for a cable-membrane verified the validity of the method.Furthermore,applying the method to a flat membrane roof structure and using its wind tunnel test results,the analysis of nonlinear wind-induced dynamic responses for such geometrically nonlinear roofs,including the roof-air coupled model was performed.The result shows that the air has large influence on vibrating membrane roofs according to results of comparing the nodal time-history displacements,accelerations and stress of the two different cases.Meantime,numerical studies show that the method developed can successfully solve the nonlinear wind-induced dynamic response of the membrane roof with aerodynamic effects.

Characteristics of wind pressure pulse on large-span flat roofs

The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechanism of wind pressure pulse events, the peak over threshold method was employed to study properties of this kind of events. The event duration time, the energy contribution, the number of the pulse events, and the distribution of average peak pressure were calculated. Probability density functions of some typical samples in separation region were also given. Results show that the non-Gaussian roof pressure is strong in the flow separation region owing to the wind pressure pulse events. Evaluations of the extreme peak pressures, which can be determined by the peak over threshold method effectively, are important to the design of building cladding.

High Alumina Refractory Bricks for Electric Arc Furnace Roofs

This standard specifies the sort, technical requirement, test method, inspection rules, marking, packing, transportation, storage and quality certification of high alumina refractory bricks for electric arc furnace roofs.

Employing Green Roofs to Support Endangered Plant Species: The Eastern Suburbs Banksia Scrub in Australia

The purpose and context for the study relates to urban growth. Australian cities are experiencing particularly rapid urbanization, taking the form of land clearing to accommodate outward expansion as well as developing to higher densities in existing urban areas. Both forms of development degrade native biodiversity, resulting in loss of vegetation with the possibility that the remnant indigenous plants will become locally extinct. One endangered ecological community in Sydney, the Eastern Suburbs Banksia Scrub (ESBS), still survives along some sections of Sydney’s heavily urbanized coastline. At the time of European settlement, the ESBS covered approximately 5300 ha, but it is now a highly fragmented 146 ha across 24 sites with some sites under imminent threat of development. Conservation legislation enacted by the state of New South Wales (NSW), Australia has declared the ESBS as critically endangered. Despite recovery plans, in 2016 the NSW Threatened Species Scientific Committee indicated that the community faces an extremely high risk of extinction in Australia in the immediate future. A practical option in the face of declining open space in our cities is to examine the potential of urban rooftops for conserving and propagating threatened or endangered flora. While there is a limited amount of international research on using green roofs for endangered plant protection, there is no information from Australia about how green roofs perform in this geographic region. The approach taken in this research has been firstly, to review the current academic and “grey” literature from a global perspective to identify options for conserving endangered flora on green roofs. We derive an evidence-based research protocol to be used to test the green roof environment in Sydney for propagating the endangered ESBS. We establish the general applicability of green roofs for protecting vanishing flora through the literature review and conclude that our research design will be a suitable framework for the task for monitoring growth and germination performance over the ESBS community’s development cycle, with the longer-term objective of establishing a viable rooftop seed orchard.

Dynamic Pressures on Tunnel Roofs due to Vehicle Passages

Pressure and proximity measurements made in a tunnel indicate that a typical vehicle passage produced on the tunnel roof an initial pressure increase of small magnitude,followed by a sharp and more substantial drop in pressure below atmospheric.The magnitude of the pressure drop was found to increase with smaller clearances between the vehicle top and the tunnel roof,consistent with the Bernoulli relation and the vehicle speed.The dynamic pressures potentially may have significant effects on the vibration and noise environments on the lower floors of“air rights construction”buildings that span highways.

Gold Roofs Shine Above the Potala Palace

In the last five years,the hardest task was to remove,repair,clean and reinstall the gold roofs.We did them with extreme care.

Mechanism and control technology of strong ground pressure behaviour induced by high-position hard roofs in extra-thick coal seam mining

This work aimed at revealing the mechanism of strong ground pressure behaviour(SGPB)induced by high-position hard roof(HHR).Based on the supporting structures model of HHR,a modified voussoir beam mechanical model for HHR was established by considering the gangue support coefficient,through which the modified expressions of limit breaking span and breaking energy of HHR were deduced.Combined with the relationship between the dynamic-static loading stress of supporting body(hydraulic support and coal wall)and its comprehensive supporting strength,the criteria of ground pressure behaviour(GPB)induced by HHR were discussed.The types of Ⅰ_(1),Ⅰ_(2),Ⅱ_(1),andⅡ_(2) of GPB were interpreted.Results showed that types Ⅰ_(1) and Ⅰ_(2) were the main forms of SGPB in extra-thick coal seam mining.The main manifestation of SGPB was static stress,which was mainly derived from the instability of HHR rather than fracture.Accordingly,an innovative control technology was proposed,which can weaken static load by vertical-well separated fracturing HHR.The research results have been successfully applied to the 8101 working face in Tashan coal mine,Shanxi Province,China.The results of a digital borehole camera observation and stress monitoring proved the rationality of the GPB criteria.The control technology was successful,paving the way for new possibilities to HHR control for safety mining.

Stability analysis of subgrade cave roofs in karst region

According to the engineering features of subgrade cave roof in karst region, the clamped beam model of subgrade cave roof in karst region was set up. Based on the catastrophe theory, the cusp catastrophe model for bearing capacity of subgrade cave roof and safe thickness of subgrade cave roof in karst region was established. The necessary instability conditions of subgrade cave roof were deduced, and then the methods to determine safe thickness of cave roofs under piles and bearing capacity of subgrade cave roof were proposed. At the same time, a practical engineering project was applied to verifying this method, which has been proved successfu1ly. At last, the major factors that affect the stability on cave roof under pile in karst region were deeply discussed and some results in quality were acquired.

Failure of hanging roofs in sublevel caving by shock collision and stress superposition

Hanging roofs or high hang-ups.a common problem in sublevel caving mining,usually result in a large ore loss and undermine mining safety.This paper analyzed the formation of a hanging roof and showed that increased confining pressure and reduced free surface were its main characteristics.In order to break down a hanging roof,a new method based on shock wave collision and stress superposition was developed.In this method,two blastholes containing multi-primer at different positions are simultaneously initiated at first.By doing this,a new free surface and a swell room can be created.After these holes are fired,a long delay time is given to the next blasthole so that the fragments from the first twohole blasting have enough time to fall down.This new method was applied to three hanging roofs in one production area,and all of them were successfully broken down.Field inspection indicated that almost no damage was caused in the nearby drifts/tunnels due to the new method.In addition,the far field vibrations were found to be smaller than the maximum vibrations induced by some other blasts.

Numerical research on stability control of roofs of water-rich roadway

In order to study the strength-weakening law of roofs of water-rich roadway, this study used FLAC software, and simulated and analyzed the failure characteristics of the surrounding rock of water-rich roadway under the condition of different cross sections and support parameters, finally obtained the stress distribution of the principle stress of the roadway as well as the displacement variation of its surrounding rock. Results indicate that the roof stability of roadway with semicircular cross section is better than the roadway with inclined rectangular cross section under water-rich condition. Besides, the surrounding rock deformation of roadway under the action of water shows a pronounced increase compared to the roadway without the action of water due to the fact that water will obviously weaken the surrounding rock of roadway, especially its roof. It is very beneficial to control roof stability of water-rich roadway and guarantee the roadway stability during its service life by improving the pretension of bolt and cable as well as decreasing inter-row spacing of the bolt.

Stability control of water-enriched roofs of coal drifts

Excavation-and-support induced disturbances are likely to make water-enriched roofs to become weathered and fractured.The development and connection of cracks provide new water channels which may result in water loss,seriously affecting the in-tegrity and stability of roofs,leading to incidents of roof fall.Control of water-enriched rocks surrounding coal drifts is quite diffi-cult in China.Based on the practical situation of a water-enriched roof of a coal drift in working face 112201 of the Meihuajing coal mine,we studied the deformation features of surrounding rocks and the development of fractured areas and analyzed the major reasons for the decrease in load-carrying capacity,indicating that the key to maintain roof stability of this kind of coal drift is water retention.In addition,we proposed a staged control technology consisting of:1) surface grouting;2) cable anchor strengthening and 3) roof grouting,which has proven to be successful in this practical application.Our study indicates that,after the problem of water loss from the water-enriched roof had been effectively solved,a combined support system with high performance bolts can maintain the stability of the bearing structure,resulting in the control of roof stability in this kind of coal drift.

Landscape Design of Green Roofs Against the Background of Sponge City Construction: A Case Study of the California Academy of Sciences

In this paper, the green roof of the California Academy of Sciences was selected for example to illustrate the role of green roofs in sustainable urban planning from three aspects: landscape connection, building energy conservation and urban environment and elaborate the innovative design elements of the California Academy of Sciences, and the enlightenment of green roofs on the construction of sponge cities in China and the guiding role for future urban design were analyzed combined with the current urban problems in China and the research status of green roofs at home and abroad.

Wind Force Coefficients for Designing Porous Canopy Roofs

Wind force coefficients for designing porous canopy roofs have been investigated based on a series of wind tunnel experiments. Gable, troughed and mono-sloped roofs were tested. The roof models were made of 0.5 mm thick perforated duralumin plates, the porosity of which was changed from 0 to about 0.4. Overall aerodynamic forces and moments acting on the roof model were measured in a turbulent boundary layer with a six-component force balance for various wind directions. The results indicate that the wind loads on canopy roofs generally decrease with an increase in porosity of the roof. Assuming that the roof is rigid and supported by the four corner columns with no walls, the axial forces induced in the columns are regarded as the most important load effect for discussing the design wind loads. Two loading patterns causing the maximum tension and compression in the columns are considered. Based on a combination of the lift and moment coefficients, the design wind force coefficients on the windward and leeward halves of the roof are presented for the two loading patterns as a function of the roof pitch and porosity. The effect of porosity is taken into account as a reduction factor of the wind loads.

Green roofs for storm water management:a review

The rapid urbanization and industrialization involve an unsustainable use of natural systems,leading to various problems in cities.The urban hydrological system experiences fluctuating amount of surface runoff water when it rains heavily.It has been suggested that green roofs significantly mitigate storm water runoff generation even in tropical climate.Green roofs have become popular due to its proven benefits by mitigating urban heat island effects and protecting biodiversity.The annual rainfall and runoff relationship for green roofs is determined by the depth of the substrate.Water retention capacity mostly depends on substrate's physical conditions such as dry or wetness.Generally 6 mm to 12 mm rainfall is required for dry substrate to initiate runoff whereas response of wet conditions is mostly straight.Besides,there are some other factors affecting runoff dynamics such as type of a green roof and its slope,age of green roof,type of vegetation,soil moisture characteristics,weather.The review indicates that there is not much research in green roofs performance over storm water runoff;hence there is a need for further research.This paper reviews and addresses the role of green roofs in urban storm water management.