Simulation of Airblast Load and Its Effect on RC Structures

In the analysis of a structure subjected to an explosion event, the determination of the blast load constitutes a crucial step. The effect of the blast load on the structure depends not only on the peak shock overpressure, but also the impulse (hence the duration). For structures with a regular geometry, the blast load may be fairly well estimated using appropriate empirical formulae; however, for more complex situations, a direct simulation using appropriate computational techniques is necessary. This paper presents a numerical simulation study on the prediction of the blast load in free air using a hydrocode, with focus on the sensitivity of the simulated blast load to the mesh grid size. The simulation results are compared with empirical predictions. It is found that the simulated blast load is sensitive to the mesh size, especially in the close-in range, and with a practically affordable mesh grid density, the blast load tends to be systematically underestimated. The study is extended to internal blast cases. An example concrete slab under internal explosion is analyzed using a coupled analysis scheme. The internal blast load from the simulation is examined and the response of the RC slab is commented.

Experimental Investigation on Shock Wave Characteristics of Aluminized Explosives in Air Blast

To investigate the shock wave characteristics of RDX-based aluminized explosives,air blast tests were conducted for measuring the parameters of 10 kg aluminized explosives which contained 0-40% aluminum.The results showed that with the increasing of aluminum content,the overpressures and impulses increase at first and then decrease within 7 m or 5 m,which reached the maximum when aluminum content was 20% or 30%.Power exponential formulas are used to fit the shock wave parameters vs scaled distance,where an equal weight of TNT is used to calculate the scaled distance.The overpressures of HL0 and TNT in tested locations not only conform to the similar law,but also conform to the same attenuation law after gaining the scaled distances of equal TNT mass.The pre-exponential factors of overpressure and impulse,kp and kI,decrease along with the increasing of Al content and keep the same pace as the calculated PCJ）.The attenuation coefficients a_P and aIincrease at first and decrease later with the increasing of aluminum content,and they reached the maximal values with30% Al containing,which keeps the same pace as the calculated QV.

Optimization of the Air Deck Blasting Parameters on the Basis of the Holmquist-Johnson-Cook Constitutive Model

The present study considers the so-called air deck blasting,one of the most commonly used techniques for the improvement of blasting efficiency in mining applications.In particular,it aims to improve the operating conditions of large-scale equipment,increase the efficiency of the slope enlarging process,and reduce the mining cost.These objectives are implemented through a two-fold approach where,first,a program for slope enlarging based on the middle air-deck charge blasting-loosening technology is proposed,and second,the physical mechanism responsible for the stress wave attenuation in the rock is analyzed in the framework of a Holmquist–Johnson–Cook constitutive model.Field test results verify that the proposed approach is highly efficient and economical when used in medium-hard rock blasting and thus provides a basis for the practical implementation of slope enlargement for high benches in Open-Pit Mines.

Physical Properties of Crushed Air-cooled Blast Furnace Slag and Numerical Representation of Its Morphology Characteristics

Physical properties and geometrical morphologies of crushed air-cooled blast furnace slag （SCR） and crushed limestone （LCR） were comparatively investigated. The shape, angularity, surface texture and internal pore structure of aggregate particles for different size and gradation were numerically represented by sphericity （ψ） and shape index （SI）, angularity number （AN）, index of aggregate particle shape and texture （IAPST）, porosity and pore size, respectively. The results show that SCR is a porous and rough aggregate. Apparent density, void, water absorption and smashing index of SCR are obviously higher than those of LCR with the same gradation, respectively. However, bulk density of SCR is lower than that of LCR with the same gradation. SI, AN, IAPST and porosity of SCR are obviously higher than those of LCR with the same gradation, respectively. The smaller particle size of SCR, the larger of its AN, IAPST and porosity.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Effect of Crushed Air-cooled Blast Furnace Slag on Mechanical Properties of Concrete

Morphology characteristics of mix aggregates with crushed air-cooled blast furnace slag（SCR） and crushed limestone（LCR） with 5-20 mm and 20-40 mm gradation were represented by numerical parameters including angularity number（AN） and index of aggregate particle shape and texture（IAPST）.The effect of mix aggregates containing SCR on compressive strength and splitting tensile strength of concrete was investigated.Fracture characteristics of concrete,interfacial structure between aggregates and matrix were analyzed.The experimental results show that porous and rough SCR increases contact area with matrix in concrete,concave holes and micro-pores on the surface of SCR are filled by mortar and hydrated cement paste,which may increase interlocking and mechanical bond between aggregate and matrix in concrete.SCR can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with LCR.The increase of AN and IAPST of aggregate may enhance mechanical properties of concrete.

A novel artificial intelligent model for predicting air overpressure using brain inspired emotional neural network

Blasting is the live wire of mining and its operations,with air overpressure(AOp)recognised as an end product of blasting.AOp is known to be one of the most important environmental hazards of mining.Further research in this area of mining is required to help improve on safety of the working environment.Review of previous studies has shown that many empirical and artificial intelligence(AI)methods have been proposed as a forecasting model.As an alternative to the previous methods,this study proposes a new class of advanced artificial neural network known as brain inspired emotional neural network(BIENN)to predict AOp.The proposed BI-ENN approach is compared with two classical AOp predictors(generalised predictor and McKenzie formula)and three established AI methods of backpropagation neural network(BPNN),group method of data handling(GMDH),and support vector machine(SVM).From the analysis of the results,BI-ENN is the best by achieving the least RMSE,MAPE,NRMSE and highest R,VAF and PI values of 1.0941,0.8339%,0.1243%,0.8249,68.0512%and 1.2367 respectively and thus can be used for monitoring and controlling AOp.

Experimental Study on Coal-Breaking Pressure for Compressed Air

Based on lab model experiments and through the limit analysis, the theoretical formula of calculation coal breaking pressure with compressed air was derived. The experimental result shows that blasting pressure must exceed 84.0MPa to break coal with compressive strength of 13.2MPa. The research provides an important theoretical basis for the design of airshooting mining and industrial tests.

Hot Blast Flow Measurement in Blast Furnace in Straight Pipe

This article shows an innovative method to model and validate the hot air flow through the blast furnacés tuyeres. This study will be the basis for flow measurements implementation and safety interlocks for the pulverized coal injection. The flow measurements were taken in the blast furnace down leg pipes by installing refractory Venturi tubes. The system for the calculation of differential pressure takes into consideration the dimension of the Venturi, the air density and compressibility. The objective is to specify the flow transmitters required to automate a control system and implement safety interlocks for the coal injection plant.

基于爆破块度控制的空气间隔装药台阶爆破参数优化

为解决某灰岩建筑石料矿山爆破后小粒径矿石难以与土分离而导致矿石回收率低下的问题,首先基于现场实测数据和数值模拟结果,构建爆破块度与岩体动力损伤关联模型,确定不同岩块粒径对应的动力损伤阈值;其次选用不同空气间隔装药段数和孔网参数开展三维裂隙岩体台阶爆破数值模拟试验,以提高0.3~0.9 m矿石粒径产率为目的,兼顾控制大块率,获取最佳爆破参数;最后,在数值模拟结果的基础上,开展现场爆破试验,优化装药结构和孔网参数。结果表明:灰岩爆破块度尺寸与动力损伤值之间存在负指数函数关系,爆破块度尺寸0.3 m和0.9 m所对应的岩体动力损伤阈值分别为0.793和0.286;仅采用空气间隔装药结构可提高0.3~0.9 m粒径占比,但大块率增幅较大;采用空气间隔装药结构、适当缩小孔网参数可显著提升0.3~0.9 m粒径占比,同时大块率几乎不变;其中采用二段空气间隔装药结构、适当缩小孔网参数,爆破效果最优。矿山现场应用结果表明,0.3~0.9 m矿石粒径占比提高了20.09个百分点,大块率基本不变,炸药单耗降低10.29%。

武钢4号高炉炉缸温度异常升高的机理分析

武钢4号高炉炉缸侧壁温度异常升高,主要原因是炉缸碳砖与炉壳之间存在气隙,煤气串入导致热传导变差,再加上铁口区域渣铁环流加剧,碳砖热面渣铁壳的脱落,使渣铁水直接接触碳砖,导致碳砖温度急剧升高。通过灌浆,治理了串煤气,渣铁凝结层逐渐形成,炉缸温度恢复正常。

间隔装药的殉爆起爆技术在露天矿山爆破中的应用

为了降低西沟露天石料厂的采石爆破成本,提高经济效益;应用空气袋间隔装药装置技术进行了150 mm炮孔和100 mm炮孔的爆破实验对比,同时进行了露天炮孔孔内反向和正向起爆殉爆试验对比。结果表明:采用炮孔中部空气袋间隔装置的露天矿台阶爆破,电子雷管起爆一端装药之后再利用其爆轰波殉爆起爆另一端装药,孔径大的炮孔比孔径小的炮孔殉爆起爆的爆破效果好;采用殉爆起爆技术后,做到了节能减排和提效;反向起爆爆破法与正向起爆爆破法相比,爆破效果更好。

侧面爆破粉尘时空分布模拟分析

从开放性细颗粒物污染治理角度出发,建立建筑物拆除爆破产尘的几何计算模型,运用计算流体力学(CFD)工具,对给定环境风速下的建筑物周围压力场和速度场进行了模拟分析,并对侧面折叠爆破粉尘按R-R(Rosin-Rammler)分布,使用气流-粒子双向耦合的DPM模型研究了爆炸粉尘的时空分布。结果表明,下风侧因建筑物存在导致风速、压力急剧变化而产生涡流,涡流是影响爆破粉尘时空分布的关键因素之一。在时间上,爆破粉尘有气流拖曳运动状态和扩散态;在空间上,因重力作用致下部空间的粉尘浓度较大。

深孔轴向多段间隔装药孔壁冲击压力分布

为确定地下垂直长深孔爆破时合理的空气间隔长度,基于爆轰波理论,分析了多段间隔装药爆破条件下孔壁冲击压力随间隔长度变化的内在分布规律函数;依据Mises准则,得出了不同岩性时合理的间隔长度参考值,并通过数值模拟和现场爆破试验进行了验证。结果表明,空气间隔段孔壁冲击压力沿炮孔轴线从两端向中间骤降,但在中点周围略微增大,压力曲线呈两端大、中间小、中点周围略微凸起的“W”形对称分布。

新钢7^(#)高炉炉凉事故分析与处理

新钢7^(#)高炉在有上部结厚的情况下计划检修,休风期间炉墙西南结厚物整体坍塌,复风过程因结厚物进入炉缸破坏了热平衡,补加净焦量不够,风口自动吹开,使用质量差的烧结开机料,最终造成炉温大凉。本文通过对高炉炉凉事故起因、处理经过及恢复到正常三个阶段进行了分析,为处理高炉炉凉事故快速恢复提供了宝贵经验。

Effects of content and particle size of TiH2 powders on the energy output rules of RDX composite explosives

In order to improve the detonation characteristics of RDX,a RDX-based composite explosive with TiH_(2)powders was prepared.The effects of content and particle size of TiH_(2)powders on thermal safety,shock wave parameters and thermal damage effects of RDX-based composite explosive were studied with the C80 microcalorimeter,air blast experiment system and colorimetric thermometry method.Experimental results showed that TiH_(2)powders could enhance the thermal stability of RDX-based composite explosive and increase its ultimate decomposition heat.The content and particle size of TiH_(2)powders also had significant effects on the thermal safety,detonation velocity,shock wave parameters,fireball temperature and duration of RDX-based composite explosives.Furthermore,the differences of TiH_(2)and Ti powders on the detonation energy output rules of RDX-based composite explosives were also compared,showing that TiH_(2)powders had better influences on improving the explosion power and thermal damage effect of RDX-based composite explosives than Ti powders,for the participation of free H_(2)released by TiH_(2)powders in the detonation process.TiH_(2)powders have important research values as a novel energetic additive in the field of military composite explosives.

深埋高温硐室围岩开挖损伤规律研究

深部工程的高地应力与高地温问题将对地下资源开采和空间利用构成严峻挑战。通过建立深埋高温硐室爆破–卸荷–降温全过程的数值模型,并嵌入率相关岩石本构关系反映钻爆开挖和通风降温过程中的岩体动静态力学响应,分析了不同地应力条件下围岩开挖损伤的时空演化规律。计算结果表明:围岩在动态开挖过程中会由于爆破、卸荷或两者的共同作用产生初始动力损伤,而硐室通风冷却过程所诱发的热应力将在保留岩体中造成额外的热力损伤。在静水应力条件下,围岩动力损伤随地应力量级的提高表现出先减弱后增强的演化趋势,降温损伤则随地应力的上升而单调增大。在非静水应力条件下,硐室拱顶和拱腰附近岩体的动力损伤将随侧压力系数的增大而分别表现出先减小后增大和单调增大的演化趋势;在通风冷却阶段,应力水平较低的拱腰附近未产生显著的热力损伤,而拱顶围岩的热力损伤则随侧压力系数的提升而逐渐增强。

基于动爆冲击波演化规律的超压计算模型

为建立动爆冲击波超压的工程计算模型,开展了球形装药动爆试验和数值模拟研究,获取了动爆冲击波场演化历程图像,定量分析了装药速度对冲击波波阵面传播速度的影响。结果表明:在装药速度影响下爆轰产物各向膨胀速度不再相同,爆轰产物膨胀速度的变化使得冲击波强度和空间位置分布发生了相应的变化,正向冲击波强度更高,更早与爆轰产物相分离。在静爆冲击波演化模型的基础上,通过引入含有角度和传播时间的修正因子,建立了静动爆关联的球形装药动爆冲击波超压计算模型。采用该模型计算得到的不同速度、不同药量球形装药冲击波压力与试验结果吻合较好,模型具有一定普适性。

连接方式对蜂窝夹芯结构抗爆性能的影响规律研究

目的旨在探究近场空爆载荷作用下蜂窝夹芯结构面板与芯层的连接方式对抗爆性能的影响。方法分别设计了由激光选区熔化技术打印制备的316L不锈钢一体式蜂窝夹芯结构和分离式蜂窝夹芯结构2种构型,并进行了50 mm爆距的爆炸冲击实验。后又结合数值模拟方法对比分析了一体式、分离式、胶接式和焊接式4种连接方式在爆炸载荷作用下的动态响应过程,并分别从各层结构变形失效、背板最大残余挠度及吸能等角度联合揭示了抗爆性能差异及其影响规律。结果一体式蜂窝夹芯结构背板最大残余挠度为17.5mm,相比分离式、胶接式和焊接式,分别减少了47.3%、43.0%、28.3%。爆炸冲击结束后,一体式蜂窝夹芯结构的总塑性应变能和背板应变能占比分别为866.9J、13.3%,与焊接式蜂窝夹芯结构的相近,但其总塑性应变能较分离式、胶接式分别低4.1%、16.6%,而背板应变能占比则较二者分别低13.8%、14.3%。结论通过实验与仿真研究,证明了连接强度对蜂窝夹芯结构抗爆性能具有显著的影响,其中一体式结构抗爆性能表现最佳,且连接强度越高,其运动速度越小,响应时间也越短,对其提升防护结构的减震效果具有重要作用。

钻爆法施工隧道风流场及CO运移规律研究

为探究压入式通风下隧道钻爆法施工产生的CO运移情况,以卡拉水电站绕坝交通洞工程为依托,根据计算流体力学理论,通过Fluent软件建立隧道CO组分运输模型,并使用现场监测数据对模型准确性进行验证。结果表明,压入式通风产生远离风筒一侧的回流区提供了CO运移的主要动力,风流卷吸纠缠的涡流区对CO运移具有较强的阻碍作用;对比直立呼吸带高度1.5 m和坐立呼吸带高度0.3 m两者的CO浓度变化情况,发现高度越低,CO浓度越低,CO浓度降低速率越慢。可见建立的CO运移模型能够准确地反映CO扩散运移规律,可以为实际工程的通风设计提供参考。