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.

Effectiveness analysis of methane-drainage by deep-hole controlled pre-splitting blasting for preventing coal and gas outburst

In the study of the application effectiveness of deep-hole controlled pre-splittingblasting technology,it was found through laboratory micro test and field study on a mine insouth China that under the technology,coal masses produce many irreversible cracks.Afterblasting,the nearer the distance from blasting hole,the larger the BET surface areaand volume ratio of the infiltration pore are;they increased by 11.47%and 5.73%,respectively.The coefficient of air permeability is increased 4 times.After 3 months,the gasdrainage rate was increased by 66%.In the first 15 days,the cumulative pumped gas was1.93 times of blasting before.The average absolute gas emission decreased by 63.46%.Experimental results show that deep-hole controlled pre-splitting blasting not only preventscoal and gas outburst,but also gives good economic results.

CONTROLLED BLASTING RESEARCH FOR SHAPEN CUTTING OF STRUCTURAL DECORATION STONE

This paper analyses the fragmenting principle of static blasting agent (SBA) and the action of its cutting fragmentation. Using SBA for sterming material proved very useful and advantageous. Here we analyse in detail the cutting action of pre- stress and stress wave in pre-stressing force blasting.

ESTIMAING AMOUNT OF EXPLOSIVE FOR FRACTURE PLANE CONTROL BLASTING WITH NOTCHED BOREHOLES

With the development of fracture mechanics,the fracture plane control blasting with notched borcholes hascome into being.This technique is used to create a satisfactory presplit along the contour of an excavation inrock.However,the amount of explosive loaded in each hol usually is determined by trial and error.Because ofthis,two approaches estimating the amount of explosive for the blasting technique are suggested.

Analysis on control technology for collapsing vibration generated by building demolition blasting

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.

Design of cavern blasting based on controllable parameters

After a thorough review of some controllable parameters,which included field investigations,cavern dimensions,explosive,rock strength etc.,cut,contour,lifters and stoping holes were introduced for blasting cavern of nucleus submarine.These design were conducted using a U.Langefors and B.Kihlstrom theory.

Application of Directional Broken Control Blasting in Cutting

Based on experiments in lab, this paper analyzes the mechanism of directional broken controlled blasting and applies the technology to the cutting by utilizing its characteristic. The model cutting experiment and the practical application result show that the cutting blasting technology is an effective way.

Fracture Plane Control in Rock Blasting

Blasting operation dissipates much of the blasting energy in crushing the rock at the borehole and the resulting cracks are randomly oriented. There is very little control of the fracture plane. In order to control the fracture plane, many methods have been applied. This paper discusses a new blasting method in which a high degree of fracture control can be achieved while minimizing the ground shock.

Comprehensive Prevention and Control Technologies of Rice Blast in Disease Nanchong City

The study was conducted to reduce blast damage, the use of pesticides residue, environment pollution and control costs, and to make a significant contribution to the improvement of grain production, quality and agriculture ecological environment. Over these years, by the methods of systematical monitoring, regular surveys, field investigation, rice blast resistance identification, experiments and meteorological data analysis, the study on comprehensive prevention and control of rice blast in Nanchong City was conducted. The results showed that the rice varieties more sensitive to blast had a higher incidence of severe blast disease. Replacing,varieties with different source of resistance every three to five years and reasonable variety distribution can effectively reduce the prevalence of rice blast. Appropriate treatment of infected rice straw and pathogen, seed disinfection, seedling disinfection, and pesticide application at transplanting and etc. can delay blast occurrence and reduce the damage caused by blast. By analyzing the blast control efficiency of pesticides applied at different growth stages, we found that best control efficiency against blast was achieved by spraying pesticide twice during the whole growth stage, once 3 d before transplanting or 10 d after transplanting; and once at initial heading stage. Spraying 525 g/hm^2 75% tricyclazole was proven to be the best dosage for blast control. However, 375-450 g/hm^2 75% tricyclazole is enough if the blast incidence is not severe, or the rice varieties are slightly susceptible to blast.The control efficiency against leaf blast between 4% kasugamycin and 20% tricyclazole had no significant difference, but was significantly higher than that of 100 billion spores/g of Bacillus subtilis. The control efficiency against neck blast had no significant difference among 4% kasugamycin, 20% tricyclazole and 100 billion spores/g of B. subtilis. 450 g/hm^2 75% tricyclazole had better control efficiency against neck blast than 2 250 g/hm^2 2% 800 million spores/g Jinggangmycin-wax bud bacteria SC, 1 050 g/hm^2 41% kasugamycin-isoprothiolane WP and 900 g/hm^2 41%kasugamycin-isoprothiolane WP. The frequency of severe blast incidence in Nanchong City has reached 50% since 1997. The rice blast disease has been effectively controlled by comprehensive prevention and control technology, reducing the production loss to less than 2%, and pesticides by 4 523 t in total. In 2014, 327000 t rice grains were approved as pollution-free, green and organic agricultural products, indicating that the blast control measures produced great economic, social and ecological values.

Incidence Law and Disease Symptom of Rice Blast and Its Control Technique

The article systematically summarizes the pathogen, incidence law and disease symptom of rice blast, and raises the integrated control technique for the disease, which will provide the certain theoretical basis for the control of the disease, being benefit for the actual production of rice in field.

Vibration response and safety control for blasting vibration of the existing tunnel with defects

Current studies on blasting construction of small clear-distance tunnels have not considered the impact of existing tunnel lining defects when establishing safety controls.This paper offers a series of study results based on the blasting project of a new tunnel adjacent to the existing defect Xinling tunnel to thoroughly examine the dynamic response,safety control standards,and measures of the existing defect tunnel.First,structural models were developed to investigate the influence of the presence or absence of specific defects(like lining cracks and cavities behind the lining)on the dynamic response of the current tunnel lining to identify the most unfavorable defect distribution.Then,establish safety control standards for intact linings and those with the most unfavorable defects.Eventually,two types of control measures,single safe charge and reasonable delay time,were studied based on the established safety control standards.In particular,the most adverse position of cracks was the wall facing the explosion,the rise in depth was more unfavorable for vibration response,and the impact of the longitudinal crack was restricted to the vicinity of the crack.While the vault was the most adverse cavity position,the rise in cavity area was more damaging,and the influence range varied with longitudinal cavity length.Moreover,the impact of cracks was mainly evident in the amplification effect of stress at the crack region.In contrast,cavities had varied degrees of amplification effects on the vibration velocity and stress response and a relatively extensive influence range.Safety control research was conducted,when the tunnel was intact,with a right wall crack,a vault cavity,and both vault cavity and crack for this project,the peak particle velocity(PPV)of the safety control standard for vibration velocity was 13,10,13,and 8 cm/s,respectively,and the respective single safe charge could be adjusted at 64,53,37,and 25 kg.However,the presence of different defects had a relatively negligible effect on the reasonable delay time;25 ms was recommended for existing tunnel lining with and without the defect.

Blast-induced rock damage control in Fangchenggang nuclear power station, China

In the process of blasting excavation, stress wave propagation and gas expansion can basically induce damage to surrounding rocks, which is detrimental to rock mass integrity and engineering safety. In this case, evaluation and control of blast-induced effects are essential to the safety of nearby buildings and integrity of bedrock in blasting field. In Fangchenggang nuclear power station of China, the drill-and- blast method was employed for bedrock excavation. In order to reduce the blast-induced damage zone, the wave propagation and associated damage to rock mass should be carefully investigated. In this paper, the wave propagation regressively obtained from field monitoring data was presented based on empirical formula （e.g. Sadovsloj formula）. The relationship between the peak particle velocity （PPV） at a distance of 30 m away from the charge hole and charge per delay in blast design was derived. Meanwhile, the acoustic tests before and after blasting were conducted to determine the damage depth of rock mass. The charge per delay in blast design was then calibrated based on the blast-induced wave propagation regularity. The results showed that a satisfactory effect was achieved on blast-induced damage control of rock mass. This could be helpful to rock damage control in similar blasting projects.

The Use of Rice Varietal Diversity for Rice Blast Control

Field experiments of mixed- (intercropping) and pure-planting (monoculture) of four rice varieties, representing improved hybrid varieties (Shanyou63 and Shanyou22) and high-quality traditional varieties (Huangkenuo and Zigu) from Yunnan Province, were conducted based on their differences in genetic background and agro-economical characteristics. The results demonstrated that the mixed-planting of the hybrid rice and high-quality traditional rice varieties had a significantly greater effect on controlling rice blast disease than the monoculture of these varieties, particularly the traditional ones. It is evident for the highly susceptible traditional varieties in mixed-planting to achieve disease control, with significant decreases in blast incidences and severity indexes. The blast control efficiency reached up to 83-98% under such planting model. This suggests that an appropriate mixed-planting of rice varieties with diverse genetic background and agro-economical characteristics is an effective approach for rice blast control. In addition, resistance of the traditional rice varieties to lodging was considerably increased in the plots with mixed-planting, compared with the plots with monoculture. The average rate of grain-yield increase ranged from 6. 5 to 9.7% in the plots with mixed-planting.

Understanding the connection between blasting and highwall stability

Surface mines continue to implement highwalls for several reasons, such as increasing recovery, improving margins, and justifying higher stripping ratios. Highwall stability is a complex issue that is dependent upon a variety of mining and geologic factors, and a safe design is necessary for a successful surface operation. To improve highwall stability, it is important to understand the connection between local geology and blasting. Explosives are employed throughout the mining industry for primary rock breakage. There are a number of controlled blasting techniques that can be implemented to improve highwall stability.These include line drilling, smooth wall blasting, trim blasting, buffer blasting, air decking, and presplitting. Each of these techniques have associated advantages and disadvantages. Understanding local geology is necessary for selecting the appropriate controlled blasting technique. Furthermore, understanding the limitations and conditions for successful implementation of each technique is necessary. A discussion of the impact of geologic conditions on highwall stability is provided. Additionally, discussion is provided for the successful incorporation of the controlled blasting techniques listed above, and the associated mining and geologic factors that influence the selection and design of controlled blasting plans.Finally, a new methodology is proposed.

Key technologies of precision demolition blasting of ultra-long urban viaduct in complicated surroundings

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.

THEORETICAL AND EXPERIMENTAL STUDIES ON FRACTURE PLANE CONTROL BLAST WITH NOTCHED BOREHOLES

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A Blast Shock Isolation System with MRFD and Its Semi-Active Control Analysis

To effectively reduce the damage to people and devices in civil defense engineering subjected to blast shock, a blast shock isolation system with magnetorheological fluid dampers (MRFD) is proposed. MRFD can provide continuously adjustable Coulomb friction and has many advantages for semi-active control. Numerical simulation of this isolation system is finished using Matlab simulink toolbox. General semi-active control algorithms are consided based on instantaneous optimal active control algorithm. And the results indicate that the shock isolation system can work efficiently, decreasing about 93% of the peak acceleration of the isolation floor.

Liquid Jet Blasting Using Ultra-High Frequency Supersonic Pulsed Air Jet

This paper reports an experimental study on a liquid injector assembly integrated with an ultra-high frequency pulsed air jet that operates at 21 kHz. The active air-blasting assembly steadily injects a liquid through four micro-nozzles of 0.4 mm diameters each, positioned around a 1 mm nozzle through which the pulsed actuation jet flows out at supersonic velocity. High-frequency compressible air vortexes and shock waves generated by the injector atomize the liquid stream into finer droplets and distribute them to a larger area to improve mixing with the ambiance. The paper presents the design details and preliminary studies on the flow field characteristics of this novel injection scheme, which is a potential candidate for high-speed flow mixing and control applications.

Advances in Integrated Control Techniques of Rice Blast

Rice blast is the most devastating disease in rice,and it seriously threatens the safety of rice production.Improving the ability of integrated prevention and control of rice blast has always been an important part of ensuring food production safety.In the past decade,scientists have made great progress in the prevention and control techniques of rice blast,which paves the way for the green controlling of rice diseases.In this article,the advances in the intelligentization of rice blast field monitoring techniques,the optimization of prediction and forecast modeling system,the research and development of low-toxic and high-efficiency chemical pesticides,biogenic pesticides and inducers and the regulation of multiple ecological factors including variety and cultivation are reviewed,and the new strategies for green controlling of rice blast based on these techniques are summarized.Further,the problems such as high pesticide prices and pesticide residue faced by rice blast prevention and control and the challenge of slow research and development of low-toxic and economical biogenic pesticides are discussed.Finally,the development direction of green controlling of rice blast based on molecular targets,small interfering RNA(siRNA)and CRISPR/Cas9 technologies is predicted,with a view to guaranteeing the safety of rice production.