Numerical analysis of tunnel reinforcing influences on failure process of surrounding rock under explosive stress waves

Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The results show that the propagation phenomenon of stress wave in the surrounding rock of tunnel and the failure process of surrounding rock under explosive stress waves are reproduced realistically by using numerical code RFPA2O; from the failure process of surrounding rock, the place at which surrounding rock fractures is transferred because of tunnel reinforcing, and the rockfall and collapse caused by failure of surrounding rock are restrained by tunnel reinforcing; furthermore, the absolute values of peak values of major principal stress, and the minimal principal stress and shear stress at center point of tunnel roof are reduced because of tunnel reinforcing, and the displacement at center point of runnel roof is reduced as well, consequently the stability of tunnel increases.

Ti/Al_2O_3 Functionally Gradient Material Prepared by the Explosive Compaction/SHS Process

Ti1Al2O3 Functionally Gradient Material (FGM) was prepared by an explosive compaction/SHS process. Ten sheets of the compounding powder were laminated and pressed to get a green body of FGM. It was then compacted explosively By burying the explosive compaction body into a stoichiometric Al/TiO2 mixture and igniting the combustion of the stoichiometric Al/TiO2 mixture, the SHS reaction of the explosive compaction body was initiated by the heat released from the combustion of the stoichiometric Al/TiO2 mixture. In this way, Ti/Al2O3 FGM was synthesized. The adiabatic temperatures of each gradient layer were calculated when the preheating temperatures were 298 K and 1173 K, respectively The microstructure, composition and properties of Ti/Al2O3 FGM and the reaction mechanism of each gradient layer were studied. It was found that Ti/Al2O3 FGM prepared by the explosive compaction/SHS process had a high density and a high microhardness. Its structure, composition and properties showed apparent gradient distribution. The structure of the standard stoichiometric ratio gradient layer of FGM was a network structure. Its reaction mode could be described as follows: Al powder melted first, then the molten Al penetrated into the TiO2 zone and reacted with TiO2, and big pores were left in the original positions of Al powder. The reaction of gradient layers with the addition of Al3O3 as diluents was similar to that of the standard stoichiometric ratio gradient layer, so were their structure and composition. However, the reaction of gradient layers with the addition of Ti as diluents was more complex and the composition deviated slightly from the designed one

Study on Near Field Dispersal of Fuel Air Explosive

Aim To study fuel dispersion in fuel air explosive(FAE) and computational ways of fuel dispersion velocity in the near area. Methods\ The dispersion process of fuel in FAE was analyzed by the use of results measured with KODAK EKTAPRO EM Motion Analyzer and setting up mechanical models. Results\ Computational methods for fuel dispersion velocity in the acceleration stage is given and taken as a base for the study of fuel dispersion in the intermediate and the far area. Conclusion\ When the fuel flow velocity is higher than that of the explosion gas in the center cavity, the fuel divides with the explosion gas and its velocity of flow reaches a maximum. The acceleration stage ends at that time. The fuel dispersion velocity at this time is the initial conditions for numeral analyses of dispersion process in the intermediate and far areas.

APPLICATION OF HOT-PRESS SINTERING TECHNIQUE TO EXPLOSIVE CHARGE LINER OF PETROLEUM PERFORATION BULLET

A new method for manufacturing explosive charge liner of petroleum perforation bullet, using hot press sintering technique, has been introduced in the paper. The sintering process of making explosive charge liner has been investigated. The mechanical test and SEM analysis indicate that the property of the liner produced by the process is satisfied.

Explosion limits estimation and process optimization of direct propylene epoxidation with H2 and O2

Direct propylene epoxidation with H2 and O2,an attractive process to produce propylene oxide(PO),has a potential explosion danger due to the coexistence of flammable gases(i.e.,C3 H6 and H2)and oxidizer(i.e.,O2).The unknown explosion limits of the multi-component feed gas mixture make it difficult to optimize the reaction process under safe operation conditions.In this work,a distribution method is proposed and verified to be effective by comparing estimated and experimental explosion limits of more than 200 kinds of flammable gas mixture.Then,it is employed to estimate the explosion limits of the feed gas mixture,some results of which are also validated by the classic Le Chatelier’s Rule and flammable resistance method.Based on the estimated explosion limits,process optimization is carried out using commercially high and inherently safe reactant concentrations to enhance reaction performance.The promising results are directly obtained through the interface called gOPT in gPROMS only by using a simple,easy-constructed and mature packed-bed reactor,such as the PO yield of 13.3%,PO selectivity of 85.1%and outlet PO fraction of 1.8%.These results can be rationalized by indepth analyses and discussion about the effects of the decision variables on the operation safety and reaction performance.The insights revealed here could shed new light on the process development of the PO production based on the estimation of the explosion limits of the multi-component feed gas mixture containing flammable gase s,inert gas and O2,followed by process optimization.

Analysis of explosion risk factor potential on coal reclaim tunnel facilities by modified analytical hierarchy process

This study focused on developing a risk assessment method for explosion at a coal reclaim tunnel （CRT） facility. The method was developed based on an analytical hierarchy process （AHP）, which is an expert system that quantifies the factors of explosion incidents, based on events and hierarchies. In this paper, the proposed model was modification from original AHP model, specifically modifying the structure from ＂alternative＇s results＂ to ＂total risk-rating＇s results＂. The total risk-rating is obtained by summing up risk-rating of each factor, where the risk-rating is a multiplication product of the risk value by the AHP weighted value. To support decision-making using the expert system, data on the real conditions of the CRT were collected and analyzed. A physical modeling of the CRT with laboratory-scale experiments was carried out to show the impact of a ventilation system in CRT on diluting the methane gas and coal dust, in order to support the quantification of AHP risk value. The criteria to evaluate the risk of explosion was constructed from six components that are： fuel, oxygen, ignition, confinement, dispersion, and monitoring system. Those components had fifty-two factors that serve as sub-components （root causes）. The main causes of explosion in CRT were found to be： mechanical ventilation failure and abnormal ventilation, breakdown of monitoring system, and coal spontaneous-combustion. Assessments of two CRT facilities at Mine A and Mine B were carried out as a case study in order to check the reliability of the developed AHP method. The results showed that the risk rating of Mine A was classified as high and Mine B was classified as medium, which is in a good agreement with the site conditions.

Experimental investigation of external explosion in the venting process

Experimental investigations were conducted on the process of combustion and explosion vent in a 200 mm (diame- ter)×400 mm (length) vertical cylindrical vessel. When CH4-air mixture gases were used and the vent diameter was 55 mm, conditions of Φ (equivalent ratio)=0.8, Φ=1.0 and Φ=1.3 and two ignition positions (at the cylinder center and bottom) were selected. The venting processes and the correlated factors are discussed in this paper.

Research on Explosive Welding Technology of Railway Connector

Railway signal transmission is the key to ensure the safe and normal operation of the train. The railway connecting line for signal transmission is important equipment to guarantee the railway signal transmission and reduce the imbalance of electric current. In point of engineering application, the explosive welding technology of railway connecting line is studied theoretically, the appearance, tensile strength, micro configuration of welding junction , welding area are detected after explosive welding. Experimental and detecting results show that the connecting quality of explosive welding is reliable, which lays the foundation for the engineering practice of technology.

New Type of Fluidizate-Explosive Rock in Sedimentary Strata (Torgashino Limestone Deposit, Eastern Sayan Mountains, Russia)

The paper provides the results of comprehensive studies of bodies composed of different fluidolite types (psephitic, argillizite) and hydrothermalites found in the carbonate stratum of the Torgashino suite (Eastern Sayan Mountains, Russia). These rocks are the result of post-sedimentation processes imposed on limestones. Argillizites in the carbonate stratum are referred to a new type of fluidizate-explosive rock. Their low-temperature hydrothermal origin and association with the Later Ordovician tectono-magmatic activation of the area have been identified.

Porous NiTi shape memory alloys prepared by thermal explosion method

Thermal explosion method was used to prepare porous NiTi shape memory alloy. The process of thermal explosion was investigated. The effect of process parameters on thermal explosion reaction and properties of products was analyzed. The results showed heating rate, green density, particle size of initial powder strongly affected combustion temperature, porosity and compressive strength of final products. The mechanism of thermal explosion and the microstructure of reacted products were studied by XRD and SEM photographs. The results showed the final products mainly comprised of NiTi, Ti2Ni and TiNi3 phases and their strength decreased with the increase of porosity.

Micro-seeding and soft template effects on the control of polymorph and morphology of HMX micro particles in solvent-antisolvent process

A seeding strategy was developed in the preparation of cyclotetramethylenetetranitramine(HMX)explosive micro-particles by solvent-antisolvent method, to control their polymorphs from dangerous gamma(y) type to the desired and standard beta(β) form with the size distribution of <10.0 μm, by using a low concentration of β-HMX fine particles as micro-seed in the antisolvent medium. All products were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), and dynamic light scattering particle size analyzer. In the next step, the effective factors on the sizes and morphologies of micro-particles in the presence and absence of two soft templates of poly(ethylene glycol)-400(PEG-400) polymer and coconut fatty acid diethanolamide(lauramide) surfactant were investigated. The results of experiments showed that using of water-soluble PEG-400 in the low antisolvent temperatures leads to the production of very spherical particles. Also non-ionic surfactant of lauramide, direct the crystal growth to needle-like structures. The advantages of this method are its capability for the simple production of β-HMX micro-particles in the large scale production process, with the various crystal structures and particles size distributions.

Three-dimensional coordinates test method with uncertain projectile proximity explosion position based on dynamic seven photoelectric detection screen

To objectively obtain the three-dimensional coordinates of the projectile fuze proximity explosion when projectile intersects the head of missile target, we propose a dynamic seven photoelectric detection screen test method, which is made up of six plane detection screens and a flash photoelectric dynamic detection screen. The three-dimensional coordinates calculation model of the projectile proximity explosion position based on seven plane detection screens with dynamic characteristics is established.According to the relation of the dynamic seven photoelectric detection screen planes and the time values,the analytical function of the projectile proximity explosion position parameters under non-linear motion is derived. The projectile signal filtering method based on discrete wavelet transform is explored in this work. Additionally, the projectile signal recognition algorithm using an improved particle swarm is proposed. Based on the characteristics of the time duration and the signal peak error for the projectile passing through the detection screen, the signals attribution of the same projectile passing through six detection screens are analyzed for obtaining precise time values of the same projectile passing through the detection screens. On the basis of the projectile fuze proximity explosion test, the linear motion model and the proposed non-linear motion model are used to calculate and compare the same group of projectiles proximity explosion position parameters. The comparison of test results verifies that the proposed test method and calculation model in this work accurately obtain the actual projectile proximity explosion position parameters.

Mechanism research of gas and coal dust explosion

Combined with the experimental results from the large tunnel of the ChongqingResearch Institute,the mechanism of gas and coal dust explosion was studied.Someconcepts about gas and coal dust explosion were introduced such as the form conditionand influential factors.Gas and coal dust explosion propagation was researched and thelifting process of coal dust was simulated.When an explosion occurred due to great mixtureof gas and air,the maximum explosion pressure appeared in the neighborhood of theexplosion source point.Before it propagated to the tunnel of the deposited coal dust,themaximum explosion pressure appeared to be in declining trend.Part of the energy waslost in the process of raising the deposited coal dust through a shock wave,so the maximumexplosion pressure was smallest on the foreside of the deposited coal dust sector.On the deposited coal dust sector,the explosion pressure rapidly increased and droppedoff after achieving the largest peak value.Because of coal dust participation in the explosion,the flame velocity rose rapidly on the deposited coal dust and achieved a basic stablevalue;coal dust was ignited to explode by initial laminar flame,and the laminar flametransformed into turbulent flame.The turbulence transformed the flame fold into a funnelshape and the shock wave interacted with the flame,so the combustion rate rose and thepressure wave was further enhanced.The regeneration mechanism between the flamecombustion rate and the aerodynamic flowing structure achieved the final critical state forforming the detonation.

Coating processes towards selective laser sintering of energetic material composites

This research aims to contribute to the safe methodology for additive manufacturing(AM)of energetic materials.Coating formulation processes were investigated and evaluated to find a suitable method that may enable selective laser sintering(SLS)as the safe method for fabrication of high explosive(HE)compositions.For safety and co nvenie nce reasons,the co ncept demonstration was conducted using inert explosive simulants with properties quasi-similar to the real HE.Coating processes for simulant RDXbased microparticles by means of PCL and 3,4,5-trimethoxybenzaldehyde(as TNT simulant)are reported.These processes were evaluated for uniformity of coating the HE inert simulant particles with binder materials to facilitate the SLS as the adequate binding and fabrication method.Suspension system and single emulsion methods gave required particle near spherical morphology,size and uniform coating.The suspension process appears to be suitable for the SLS of HE mocks and potential formulation methods for active HE composites.The density is estimated to be comparable with the current HE compositions and plastic bonded explosives(PBXs)such as C4 and PE4,produced from traditional methods.The formulation method developed and understanding of the science behind the processes paves the way toward safe SLS of the active HE compositions and may open avenues for further research and development of munitions of the future.

Experimental study and theoretical analysis on the effect of electric field on gas explosion and its propagation

The effect of the electric field with different intensity on explosion wave pressure and flame propagation velocity of gas explosion was experimentally studied, and the effect of electric field on gas explosion and its propagation was theoretically analyzed from heat transportation, mass transportation, and reaction process of gas explosion. The results show that the electric field can affect gas explosion by enhancing explosion intensity and explosion pressure, thus increasing flame velocity. The electric field can offer energy to the gas explosion reaction; the effect of the electric field on gas explosion increases with the increase of electric field intensity. The electric field can increase mass transfer action, heat transfer action, convection effects, diffusion coefficient, and the reaction system entropy, which make the turbulence of gas explosion in electric field increase; therefore, the electric field can improve flame combustion velocity and flame propagation velocity, release more energy, increase shock wave energy, and then promote the gas explosion and its propagation.

地下矿山非爆机械化智能采掘

非爆机械化采掘是替代传统钻爆法进行深部硬岩开挖的一种新方法,其智能化升级包括智能感知、智能决策和智能控制。在综合分析岩石采掘工程涉及的两大问题(破碎和稳定)和三大要素(环境条件、岩体特性、采掘参数)的基础上,建立包括岩体及环境特性原位监测、硬岩可切割性改善、采掘参数智能控制和采掘表现性能评价在内的非爆机械化智能采掘工艺,以实现岩石采掘装备的机械化、自动化、无人化,采掘工艺的连续化、精细化、协同化,以及采掘管理的信息化、数字化、智能化。此外,建立非爆机械化智能采掘PDCA循环管理模式,通过深部高应力诱导利用和能量调控、硬岩诱变改性降危增割和多源载荷联合破岩3个子循环的协同,实现地下矿山安全高效采掘。

多脉冲飞秒激光切割加工炸药装药过程的热响应

为分析多脉冲飞秒激光切割加工炸药过程的安全性,建立多脉冲飞秒激光切割加工炸药装药的二维数值计算模型,对飞秒激光切割加工HMX、TATB、RDX和TNT 4种炸药装药的情况进行数值计算,获得不同加工状况下炸药装药的热响应规律。实验结果表明:飞秒激光切割加工炸药装药过程中,当激光光斑的移动速度为80~300 mm/min时,4种炸药均未发生点火,反应光斑移动速度越慢,热累积效应越明显,且HMX相比其他3种炸药,动态分析区内HMX的热累积效应最明显;当激光重复频率和能量分别为0.1~200 kHz和50~200μJ/pulse时,提高飞秒激光的重复频率和能量对切割速率提升效果呈先上升后降低趋势;飞秒激光对炸药装药的切割加工速率和安全性,会受到炸药的性能参数的影响,切割速率与炸药的激光吸收系数呈正相关,切割安全性与炸药的热感度呈负相关。

飞机火焰抑制器阻火测试中混合气体的适用性研究

文章对典型民用飞机油箱通气口飞机火焰抑制器火焰传播特性开展试验研究。根据SAEARP5416中规定的H_(2)、O_(2)、Ar3种混合气体的燃爆方案,借鉴ISO16852标准下的试验方法,自建燃爆试验台,并分别在不同H_(2)体积分数、阻火芯体内部孔径和芯体长度的情况下开展系列试验,并与现行商用阻火器特性进行对比,同时使用高速摄像机获得爆燃阻火现象及规律并开展仿真对比。试验结果表明,使用体积分数为5.0%~10.0%的H_(2)进行飞机火焰抑制器火焰传播试验时,试验阻火成功率极低,并得到H_(2)体积分数升高对火焰传播速度的影响规律。研究表明,H_(2)与航空煤油蒸气的特性差异是阻火失效的关键因素。该文对此次试验的混合气体局限性进行分析,试验结果也为H2类阻火器的研究提供一定的参考。

我国民爆物品爆炸事故统计分析及防范对策

为分析我国民爆物品爆炸事故一般性规律与事故原因,对2006—2023年全国民爆物品爆炸事故的发生时间、地区分布、事故等级等维度进行事故统计与分析,使用层次分析法构建了包含人、机、环、制度4个一级指标和安全意识、技术培训、监管力度、安全教育、标准化作业、生产设备、生产工艺、天气气候、仓储条件、安全管理体制、应急管理制度共11个二级指标的层次结构模型,通过分析得到各指标权重进而对爆炸事故影响因素做出重要性排序。研究结果表明:爆炸事故发生次数逐年降低,安全形势转好,时间上集中于每年的第2、3季度,空间上以“南北高低交错”特征分布于各省份,事故等级中一般事故、较大事故占据主导地位;基于层次分析法得知一级指标中人是造成事故的最主要因素,二级指标中标准化作业、生产工艺、监管力度和安全管理体制是比较重要的几项因素,最后针对事故影响因素重要度提出了严格标准化作业、增加安全投入、加强监管力度和完善安全管理体制的预防措施。