Instability mechanism of mining roadway passing through fault at different angles in kilometre-deep mine and control measures of roof cutting and NPR cables

The angle α between the fault strike and the axial direction of the roadway produces different damage characteristics. In this paper, the research methodology includes theoretical analyses, numerical simulations and field experiments in the context of the Daqiang coal mine located in Shenyang, China. The stability control countermeasure of "pre-splitting cutting roof + NPR anchor cable"(PSCR-NPR) is simultaneously proposed. According to the different deformation characteristics of the roadway, the faults are innovatively classified into three types, with α of type I being 0°-30°, α of type II being 30°-60°, and α of type III being 60°-90°. The full-cycle stress evolution paths during mining roadway traverses across different types of faults are investigated by numerical simulation. Different pinch angles α lead to high stress concentration areas at different locations in the surrounding rock. The non-uniform stress field formed in the shallow surrounding rock is an important reason for the instability of the roadway. The pre-cracked cut top shifted the high stress region to the deep rock mass and formed a low stress region in the shallow rock mass. The high prestressing NPR anchor cable transforms the non-uniform stress field of the shallow surrounding rock into a uniform stress field. PSCR-NPR is applied in the fault-through roadway of Daqiang mine. The low stress area of the surrounding rock was enlarged by 3-7 times, and the cumulative convergence was reduced by 45%-50%. It provides a reference for the stability control of the deep fault-through mining roadway.

Research on Ventilation and Heat Insulation Layer Design of Split-Type Roof Greening Based on Topological Interlocking Principle

In this paper,the roof ventilation and heat insulation layer modules are combined with the roof greening,and each module is assembled through the principle of topological interlocking.The assembly of these modules does not require any rivets or cement mortar,and the structural stability of the overall assembled roof is achieved only through the interlocking and limiting the movements of the interlocked units.The green roof designed in this paper has strong applicability and can be applied to roofs of different shapes.Such a roof can not only meet the aesthetic needs,but also beautify the urban environment and reduce carbon emissions.

Ground response and failure mechanism of gob-side entry by roof cutting with hard main roof

This study is the result of long-term efforts of the authors’team to assess ground response of gob-side entry by roof cutting(GSERC)with hard main roof,aiming at scientific control for GSERC deformation.A comprehensive field measurement program was conducted to determine entry deformation,roof fracture zone,and anchor bolt(cable)loading.The results indicate that GSERC deformation presents asymmetric characteristics.The maximum convergence near roof cutting side is 458 mm during the primary use process and 1120 mm during the secondary reuse process.The entry deformation is closely associated with the primary development stage,primary use stage,and secondary reuse stage.The key block movement of roof cutting structure,a complex stress environment,and a mismatch in the supporting design scheme are the failure mechanism of GSERC.A controlling ideology for mining states,including regional and stage divisions,was proposed.Both dynamic and permanent support schemes have been implemented in the field.Engineering practice results indicate that the new support scheme can efficiently ensure long-term entry safety and could be a reliable approach for other engineering practices.

Fuzzy inference system using genetic algorithm and pattern search for predicting roof fall rate in underground coal mines

One of the most dangerous safety hazard in underground coal mines is roof falls during retreat mining.Roof falls may cause life-threatening and non-fatal injuries to miners and impede mining and transportation operations.As a result,a reliable roof fall prediction model is essential to tackle such challenges.Different parameters that substantially impact roof falls are ill-defined and intangible,making this an uncertain and challenging research issue.The National Institute for Occupational Safety and Health assembled a national database of roof performance from 37 coal mines to explore the factors contributing to roof falls.Data acquired for 37 mines is limited due to several restrictions,which increased the likelihood of incompleteness.Fuzzy logic is a technique for coping with ambiguity,incompleteness,and uncertainty.Therefore,In this paper,the fuzzy inference method is presented,which employs a genetic algorithm to create fuzzy rules based on 109 records of roof fall data and pattern search to refine the membership functions of parameters.The performance of the deployed model is evaluated using statistical measures such as the Root-Mean-Square Error,Mean-Absolute-Error,and coefficient of determination(R_(2)).Based on these criteria,the suggested model outperforms the existing models to precisely predict roof fall rates using fewer fuzzy rules.

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.

Combined blasting for protection of gob-side roadway with thick and hard roof

The deformation control of surrounding rock in gobside roadway with thick and hard roof poses a significant challenge to the safety and efficiency of coal mining.To address this issue,a novel approach combining directional and non-directional blasting techniques,known as combined blasting,was proposed.This study focuses on the experimental investigation of the proposed method in the 122108 working face in Caojiatan Coal Mine as the engineering background.The initial phase of the study involves physical model experiments to reveal the underlying mechanisms of combined blasting for protecting gob-side roadway with thick and hard roof.The results demonstrate that this approach effectively accelerates the collapse of thick and hard roofs,enhances the fragmentation and expansion coefficient of gangue,facilitates the filling of the goaf with gangue,and provides support to the overlying strata,thus reducing the subsidence of the overlying strata above the goaf.Additionally,the method involves cutting the main roof into shorter beams to decrease the stress and disrupt stress transmission pathways.Subsequent numerical simulations were conducted to corroborate the findings of the physical model experiments,thus validating the accuracy of the experimental results.Furthermore,field engineering experiments were performed,affirming the efficacy of the combined blasting method in mitigating the deformation of surrounding rock and achieving the desired protection of the gob-side roadway.

Bearing mechanism of roof and rib support structure in automatically formed roadway and its support design method

Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation.The stability control of automatically formed roadway is the key to the successful application of the new method.In order to realize the stability control of the roadway surrounding rock,the mechanical model of the roof and rib support structure is established,and the influence mechanism of the automatically formed roadway parameters on the compound force is revealed.On this basis,the roof and rib support structure technology of confined lightweight concrete is proposed,and its mechanical tests under different eccentricity are carried out.The results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete specimens.The bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel specimens.By comparing the test results with the theoretical calculated results of the confined concrete,the calculation method of the bearing capacity for the confined lightweight concrete structure is selected.The design method of confined lightweight concrete support structure is established,and is successfully applied in the extra-large mine,Ningtiaota Coal Mine,China.

Cost Control Strategies for Hubei General Highway Greening Project

In order to respond to the national policy of focusing on the service of building a new development pattern and promoting high-quality development,and to reduce the cost of greening projects while ensuring the effect of highway landscape,a process and cost control points of highway greening design,construction,and maintenance are summarized through a review of the literature.Additionally,this paper examines the attributes of highway greening and proposes cost control strategies that are aligned with these attributes.It is proposed that the implementation of cost control strategies for highway greening should commence at the project establishment phase,with the objective of establishing a comprehensive and effective cost management control system.While guaranteeing the greening landscape effect and the duration of the project,it is essential to regulate the crucial nodes in each phase of the design,construction,and maintenance process.Furthermore,it is vital to facilitate close collaboration between all parties involved,thereby reducing costs,conserving resources,and lowering energy consumption.This approach can also lead to enhanced economic and social benefits for highway greening projects.

Fracture propagation and evolution law of indirect fracturing in the roof of broken soft coal seams

Indirect fracturing in the roof of broken soft coal seams has been demonstrated to be a feasible technology.In this work,the No.5 coal seam in the Hancheng block was taken as the research object.Based on the findings of true triaxial hydraulic fracturing experiments and field pilot under this technology and the cohesive element method,a 3D numerical model of indirect fracturing in the roof of broken soft coal seams was established,the fracture morphology propagation and evolution law under different conditions was investigated,and analysis of main controlling factors of fracture parameters was conducted with the combination weight method,which was based on grey incidence,analytic hierarchy process and entropy weight method.The results show that“士”-shaped fractures,T-shaped fractures,cross fractures,H-shaped fractures,and“干”-shaped fractures dominated by horizontal fractures were formed.Different parameter combinations can form different fracture morphologies.When the coal seam permeability is lower and the minimum horizontal principal stress difference between layers and fracturing fluid injection rate are both larger,it tends to form“士”-shaped fractures.When the coal seam permeability and minimum horizontal principal stress between layers and perforation position are moderate,cross fractures are easily generated.Different fracture parameters have different main controlling factors.Engineering factors of perforation location,fracturing fluid injection rate and viscosity are the dominant factors of hydraulic fracture shape parameters.This study can provide a reference for the design of indirect fracturing in the roof of broken soft coal seams.

Performance of Thermal Insulation of Different Composite Walls and Roofs Materials Used for Energy Efficient Building Construction in Iraq

This study numerically involves the performance of thermal insulation of different types of composite walls and roofs to demonstrate the best model that can be used for energy-efficient building construction in Iraq.The mathematical model is solved by building its code using the Transmission Matrix Method in MATLAB software.The weather data of 21st July 2022 in Baghdad City/Iraq is selected as a test day.The wall types are selected:the first type consists of cement mortar,brick,and gypsum,the second type consists of cement mortar,brick,gypsum,and plaster and the third type consists of cement mortar,brick,gypsum,air cavity,and sheathing timber.The roof types are chosen:the first type consists of reinforced concrete,gypsum,and plaster,and the second type consists of the precast concrete flag,river sand,tar,reinforced concrete,gypsum,and plaster.The obtained solutions are compared with previous studies for the same city but with different types of walls and roofs.The findings display that the second and third types of walls reduce the entry heat flux by 4%and 10%as compared to the first type of wall.Also,the results indicate that the second type of roof reduces the entry heat flux by 21%as compared to the first type of roof.The results confirm that the best models of walls and roofs in Iraq are the third and second types,respectively,as compared to other models and hence,the performance of insulation material strongly depends on the materials used while building them.

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.

Diversity and Application of Herbaceous Flowers in Urban Road Greening in Hefei City

In urban road greening,the planting of ground cover flowers is essential,and herbaceous flowers are an important part.Through the investigation on the diversity of herbaceous flowers in urban road green spaces of Hefei City,the types,colors,application frequency and planting of herbaceous flowers in urban road green spaces were statistically analyzed,and the application forms of herbaceous flowers in the road greening of Hefei City were studied.The characteristics and problems of herbaceous flowers in the road greening of Hefei City were found,and some development suggestions were put forward.

Developmental Application of Roof Greening against the Background of “Sponge City”: A Case Study of Ningbo City

In view of the problems of architectural eco-civilization in Ningbo City against the background of "sponge city", this paper proposed that development of roof greening in the city met the development concepts of sponge city, summarized six basic countermeasures and four cooperation mechanisms for the developmental application of roof greening in Ningbo City by analyzing practical experience of roof greening construction in foreign countries.

Evaluation of cold resistance of ornamental species for planting as urban rooftop greening

Rooftop gardening or green roof establishment, one of the methods of afforestation for urban greening, has many benefits for the environment, the economy and urban landscapes. Various environmental stresses including heat, strong wind, sunshine and cold prevent most plants from growing well in extensive green roof systems. For the establishment of urban rooftop gardening in Beijing, we evaluated 13 ornamental plant species [Berberis thunbergii ‘Atropurea Nana’, Euonymus fortune （Turcz.） Hand., Viburnum dilatatum Thunb., Cotinus coggygria Scop., Swida alba Opiz., Weigela florida （Bunge.） A. DC., Jasminum nudiflorum Lindl., Euonymus japonicus Thunb., Euonymus japonicus ‘Cuzhi’, Buddleja davidii Franch., Pyracantha fortuneana （Maxim.） Li., Ligustrum lucidum Ait. and Spiraea salicifolia L.] for greening of flat rooftops. We obtained three indices concerning cold resistance, i.e., electrical conductivity of leaves, amounts of soluble sugars and amounts of free proline, providing a theoretical basis for selection of plants fit for roof and balcony greening. The results show that the six species P. fortuneana （Maxim.） Li., B. thunbergii ‘Atropurea Nana’, J. nudiflorum Lindl., E. fortune （Turcz.） Hand., E. japonicus Thunb. and E. japonicus ‘Cuzhi’ are excellent plants for rooftop gardening, judging from their strong ability in cold resistance. Plants such as L. lucidum Ait., C. coggygria Scop. and W. florida （Bunge） A. DC. showed a medium ability in cold resistance. However, these species can be used in roof and balcony greening after intensive management or acclimatization of variety. The ability to resist cold of plants such as W. florida （Bunge） A. DC., S. salicifolia L., V. rhytidophyllum and S. alba Opiz. （Cornus alba L.） was found to be rather weak. Therefore, cold-proof measures are recommended when using these species.

One-time Shaping Technological System of Lightweight Roof Greening

Lightweight roof greening is an important way for improving urban ecological environment and has good ecological and social benefits, but the investment is- too-high for the investors. Therefore, it is necessary to improve the system of lightweight roof greening. This study introduced a lightweight roof greening mode with low cost, simple construction, rapid formation, good economic benefit and convenient curing.

Sponge-type Composite Vegetation Carpet and Roof Greening Technology

Roof greening is crucial for improving urban eco-environment, showing benefits, ecological y or social y, but it is so hard for investors in terms of capitals or promotion. The research introduced sponge-type composite vegetation carpet techniques and constructionprocess, making a breakthrough in greening form and having formulated a new one.

Study on the Adaptability of Roof Greening Plants to Medium Transferred from Wastes

[Objective] To study the adaptability of roof greening plants to medium transferred from waste.[Method] By applying the orthogonal test of 4 factors and 3 levels,4 kinds of industrial and agricultural waste(fly ash,slag,straw and waste of garden plants) are used to study the adaptability of 8 species of Sedum.[Result] The proper volume ratio of fly ash,slag,straw and waste of garden plants for making suitable medium were 1:1:1:1,1:2:2:2 and 2:1:2:1.Among the 8 test species,Sedum lineare,Sedum sarmentosum Bunge,Sedum hybridum Immergrunchett,Sedum aizoon and Sedum spectable Boreau are of higher adaptability to the medium transferred from waste.[Conclusion] The application of waste-transferred medium enjoys a promising marketing future in roof greening.

Evaluation of Ecological Effect of Roof Greening

To evaluate ecological effect of roof greening, AHP and Delphi Technique were adopted to collect qualitative data of roof greening, RS and GIS to collect quantitative data. These techniques greatly promote the rate and precision of data collection and processing, and lay a foundation for quantitative analysis of roof greening analysis. Moreover, weights of all indexes were specified. Exponential weighting statistical evaluation was applied for quantification of single index. On this basis, the collected data were standardized and their role and interaction were analyzed by using multivariate method, integrated and evaluated. Evaluation objects of roof greening ecological effect were appraised comprehensively through qualitative analysis (dominant) and quantitative analysis (secondary).

A New Kind of Roof Greening System in China

With the wider use of green roofs, new technology and new materials are being applied to the field of building roof greening forbuildings. This paper introduces BRGS （built- up roof greening system）, a new type of roof greening system that differs from roofgreening systems currently used in China in that it integrates a main and an auxiliary water storage capacity into the roof greeningsystem. Compared to other systems currently in use, BRGS offers a simpler, quicker, less labor intensive construction process;lighter floor load; and lower long term maintenance requirements and costs. It also makes full use of rainwater and snowmelt,which provides a significant amount of water to plants. This paper also introduces a planting experiment, the results of whichindicate that plants during their early stages of growth tolerate an alkaline environment, and that after a period of time, the pHvalue level of water stored in BRGS approaches 8.3, so we can conclude that BRGS is suitable for construction engineering.