Study on cumulative effects of biological craniocerebral trauma under repeated blast

Repeated blast impacts on personnel in explosive environments can exacerbate craniocerebral trauma.Most existing studies focus on the injury effects of a single blast,lacking in-depth analysis on the injury effects and cumulative effects of repeated blasts.Therefore,rats were used as the experimental samples to suffer from explosion blasts with different peak air overpressures(167 kPa~482 kPa)and varying number of repeated blasts.The cumulative effect of craniocerebral trauma was most pronounced for moderate repeated blast,showing approximately 95%increase of trauma severity with penta blast,and an approximately 85%increase of trauma severity with penta minor blast.The cumulative effect of craniocerebral trauma from severe,repeated blast has a smaller rate of change compared to the other two conditions.The severity of trauma from penta blast increased by approximately 69%compared to a single blast.Comprehensive physiological,pathological and biochemical analysis show that the degree of neurological trauma caused by repeated blasts is higher than that of single blasts,and the pathological trauma to brain tissue is more extensive and severe.The trauma degree remains unchanged after double blast,increases by one grade after triple or quadruple blast,and increases by two grades after penta blast.

Research progress on permeability improvement mechanisms and technologies of coalbed deep-hole cumulative blasting

Coalbed gas extraction is an important means of exploiting and utilizing gas resources,as well as a means of preventing coal mine disasters.In view of the low gas extraction rate from coalbeds with high gas content and low permeability,a method of improving permeability through deep-hole cumulative blasting is applied to develop initial directional fractures using a jet flow.Under the action of the blasting stress wave and detonation gas wedge,the fractures extend over a large range within the coal,thereby improving coalbed permeability.This study focuses on the criteria of cumulative blasting-induced coalbed fracturing based on a literature review of the penetration effect of cumulative blasting.On this basis,we summarize the coal fracturing zone,crack extension process,and the key technologies of charging and hole sealing for cumulative blasting.In addition,the latest research progress in the optimization of field test drilling and blasting parameters for cumulative blasting is introduced.Research findings indicate that the permeability improvement mechanism of cumulative blasting could be further enhanced,and the technology and technical equipment are in urgent need of improvement.Finally,development trends in the cumulative blasting permeability improvement technique are identified.

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.

Application of deep borehole blasting on fully mechanized hard top-coal pre-splitting and gas extraction in the special thick seam

In order to solve the problems of top-coal inadequate destruction and large amounts of gas emission in mining extra thick and hard coal seam,this study investigated the pre-splitting for deep borehole blasting and gas pre-draining technologies on top coal.The mechanism of the technologies was systematically expounded based on hard top-coal cracks development obtained by numerical simulation and theoretical analysis.The results show that explosive blasting in the hard rock results in a large number of cracks and large displacement in the rock mass due to the effect of explosion stress.Meanwhile,the thick top-coal caves,and desorbing gas flows along the cracks improve gas extraction.Finally,the pre-splitting for deep borehole blasting and gas pre-draining technologies was applied in No.3802 working face of Shui Liandong Coal Mine,which increases monthly output in the face to 67.34 kt and the drained gas concentration to 86.2%.The drained gas average concentration from each borehole reaches 40%,and the effect is remarkable.

Blasting cumulative damage effects of underground engineering rock mass based on sonic wave measurement

The principle of sonic wave measurement was introduced, and cumulative damage effects of underground engineering rock mass under blasting load were studied by in situ test, using RSM-SY5 intelligent sonic wave apparatus. The blasting test was carried out for ten times at some tunnels of Changba Lead-Zinc Mine. The damage depth of surrounding rock caused by old blasting excavation （0.8-1.2 m） was confirmed. The relation between the cumulative damage degree and blast times was obtained. The results show that the sonic velocity decreases gradually with increasing blast times, hut the damage degree （D） increases. The damage cumulative law is non-linear. The damage degree caused by blast decreases with increasing distance, and damage effects become indistinct. The blasting damage of rock mass is anisotropic. The damage degree of rock mass within charging range is maximal. And the more the charge is, the more severe the damage degree of rock mass is. The test results provide references for researches of mechanical parameters of rock mass and dynamic stability analysis of underground chambers.

Optimization of drilling and blasting operations in an open pit mine——the SOMAIR experience

Drilling and blasting play vital roles in opencast mining. These operations not only affect the cost of production directly but as well and significantly, the overall operational costs. This research was carried out to find a possible way of optimizing the drilling and blasting operations in an open pit mine of Somair (Société des Mines de l’Air), in the Niger Republic. In order to optimize the drilling operation, the time taken by two drilling machines to accomplish the same task was analyzed statistically. The result indicates that the Down the Hole Hammer Drilling Rig (DMNo406) is more efficient than the Drill Master (DM405). The relative unit consumption of two explosives (Explus and Nitram 9), when used under the same operating conditions, were also considered and the results indicate Explus to be more economical per unit consumption with a range of 0.15 g/t–0.183 g/t, when compared with Nitram 9 with a unit consumption range of 0.19 g/t-0.24 g/t in the study area.

Application of slotting-pipe shaped blasting for hard-rock rapid driving

The cumulative blasting using PVC slotting pipe was tested for rapid driving in hard-rock roadway construction. First, the outhors optimized blasting parameters on 2.2 m scheme, and did both-sides comparative experiment of the surrounding holes after the blasting success. The results show that the application of slotting tube obtains four more cut contours than the case without it. Finally we did full-section control and non-control blasting comparative experiment, the results show that the rates of half-hole marks and the non-smooth grades of the cut contours can reach 95%, hole spacing is expanded to larger than 550 mm, and 550 mm is the best under the K2 limestone conditions.

V-BLAST OFDM信号调制识别算法

提出了基于高阶累积量的V-BLASTOFDM信号识别算法,用以区分频率选择性衰落信道条件下V-BLAST结构的多载波信号(OFDM)和单载波信号(MFSK、MPSK、MQAM)。该算法不需要预先知道信号的载波频率、波特率以及信道的先验信息,直接在中频对信号进行识别处理。仿真结果表明该算法具有良好的识别性能。

基于蒙特卡罗方法的煤矿爆破作业风险评估

为量化分析煤矿爆破作业各作业步骤造成的风险以及全面客观地对其进行风险评估,借助蒙特卡罗方法建立煤矿爆破作业步骤风险评估模型,对作业流程的行为风险后果值进行累积概率分布,最终依据蒙特卡罗方法模拟的均值结果和作业流程总体风险结果判定各作业步骤的风险大小和风险等级,并提出控制此类不安全行为发生的措施。结果表明:爆破作业流程风险大小顺序依次为清退物品入库、装药、连线、警戒、起爆后安全检查、领取并检查爆破物品、起爆、运送爆破物品、接受爆破任务、作业前安全检查、起爆前安全检查、封孔。

赵官矿切顶卸压沿空留巷爆破参数研究

以赵官矿2707W工作面为工程背景,对切顶卸压沿空留巷爆破参数进行研究。结合现场工程地质条件,选用双向聚能拉伸爆破技术对试验段顶板进行预裂。综合运用理论分析计算、现场爆破试验等手段,得到了合理的爆破参数:爆破钻孔深度8.0 m,切顶角度10°,炮孔间距600 mm,装药结构为5+4+3。通过现场钻孔窥视和矿压监测等手段验证了切顶爆破效果良好,在丰富切顶卸压沿空留巷爆破技术理论的同时,也为类似工况提供一定的工程借鉴意义。

铁路隧道初期支护混凝土爆破累积损伤特征

依托京张高铁草帽山隧道工程,开展爆破振动监测及声波测试。爆破振动监测结果表明:隧道初期支护对应的质点峰值振动速度满足萨道夫斯基公式。声波测试结果表明:随着爆破次数的增多,爆破累积损伤逐渐增大。但随着爆破距离的增大,累积损伤的增量却呈逐渐减小的趋势。通过数据分析及曲线拟合的方式分别得到爆破施工对应的累积损伤范围(R_(cr))及临界爆破振动速度(PPV_(cr))。数值分析结果显示,累积损伤范围(R_(cr))与对应的临界爆破振动速度(PPV_(cr))之间存在良好的指数函数关系,通过设定相应的爆破振动速度阈值可以达到定量控制爆破损伤范围的目的。

起爆方式对爆轰波传播特性的影响研究

为探究爆轰波碰撞对爆轰压力分布规律的影响,采用理论推导、数值模拟和现场试验相结合的方法,分析了不同起爆方式下炸药内部和外部爆轰压力的变化规律。研究结果表明:爆轰波发生碰撞后,依次产生正碰撞、斜碰撞及马赫反射现象,最大爆轰压力可达到稳定爆轰压力的3倍以上;采用对称双线性起爆方式时,土体聚能侧所受爆轰压力是起爆侧的2.74倍,轴向所受爆轰压力较单侧线性起爆方式提升了75%。基坑爆破试验结果表明:采用对称双线性起爆方式时,沿爆轰波碰撞聚能方向呈一字型布置起爆,炮孔间的贯通效果相较于单侧线性起爆方式得到了明显提升。

厚煤层软岩定向预裂切顶自成巷技术

为解决厚煤层软岩巷道沿空留巷巷道变形量大,不能满足施工要求的问题,通过对工作面地质条件分析,采用类比法,确定预裂爆破采用双向聚能管,装药结构采用4-2-2-1-0方式,钻孔设计倾角15°,孔间距1 m,孔深9 m。通过矿压监测,在采用顶板定向预裂切顶等技术后,16011工作面周期来压平均压力减小1 490 kN,降低25.9%,沿空留巷段巷道成型较好,变形量较小,能够满足巷道施工要求。

Study on influencing factors and prediction of peak particle velocity induced by roof pre-split blasting in underground

Blasting technology is widely used to prevent coal bursts by presplitting the overburden in underground coal mines.The control of blasting intensity is important in achieving the optimal pre-split effectiveness and reducing the damage to roadway structures that are subjected to blasting vibrations.As a critical parameter to measure the blasting intensity,the peak particle velocity(PPV)of vibration induced by blasting,should be accurately predicted,and can provide a useful guideline for the design of blasting parameters and the evaluation of the damage.In this paper,various factors that influence PPV,induced by roof pre-split blasting,were analyzed using engineering blasting experiments and numerical simulations.The results showed that PPV was affected by many factors,including charge distribution design(total charge and maximum charge per hole),spacing of explosive centers,as well as propagation distance and path.Two parameters,average charge coefficient and spatial discretization coefficient were used to quantitatively characterize the influences of charge distribution and spacing of explosive centers on the PPV induced by roof pre-split blasting.Then,a model consisting of the combination of artificial neural network(ANN)and genetic algorithm(GA)was adopted to predict the PPV that was induced by roof presplit blasting.A total of 24 rounds of roof pre-split blasting experiments were carried out in a coal mine,and vibration signals were collected using a microseismic(MS)monitoring system to construct the neural network datasets.To verify the efficiency of the proposed GA-ANN model,empirical correlations were applied to predict PPV for the same datasets.The results showed that the GA-ANN model had superiority in predicting PPV compared to empirical correlations.Finally,sensitivity analysis was performed to evaluate the impacts of input parameters on PPV.The research results are of great significance to improve the prediction accuracy of PPV induced by roof pre-splitting blasting.

爆破地震作用下的老旧砌体结构动力特性分析

城市内老旧砌体结构多但抗震性能较差,在爆破作用下可能产生破坏。为研究爆破作用下老旧砌体的动力特性,在爆破现场附近的老旧砌体结构上布设强震仪,以观测爆破地震波对结构的瞬时作用以及长期爆破作用下的累积损伤效应。通过对爆破加速度和速度记录进行时域和频域分析比较,认为爆破速度记录相比爆破加速度记录可以更好地识别出砌体结构的动力特性,且爆破地震速度对砌体结构横向的共振影响最大。采用对比分析法,分别用爆破地震速度和地脉动加速度记录识别老旧砌体结构的动力特性,发现两种方法都能近似地识别出砌体结构的低阶平动和扭转频率,但采用爆破速度计算的自振频率比地脉动法要小1.8%~3.4%,这主要是因为爆破振动更能反映在较大振动作用下结构的响应,频繁的爆破可能导致老旧砌体结构出现非线性反应。通过监测结构自振频率在长期爆破作用下的变化,发现虽然单个爆破振动能满足《爆破安全规程》的安全要求,但在长期爆破作用下,结构1阶扭转频率、2阶横向和纵向频率随爆破次数的增加分别减少了4%、3.6%和5.2%,因此在爆破安全监测中应考虑长期爆破作用对老旧砌体结构等抗震能力较差建筑的累积损伤效应。

多频次爆破扰动对倾倒式危岩体稳定性影响分析

危岩体主控结构面岩桥段岩石有效发挥其抗拉或抗剪性能是维系倾倒式危岩体稳定的关键,而岩桥段岩石力学性能常因工程爆破扰动而劣化,导致危岩体稳定性持续降低。首先,基于极限平衡理论考虑衰减后的爆炸应力波对危岩体稳定性影响,构建倾倒式危岩体稳定性评价方法;其次,通过Lemaitre等效原理得到爆破荷载作用下岩桥段岩石细观累积损伤变量,根据岩石有效抗拉面积弱化得到抗拉强度劣化方程并通过试验结果进行验证;最后,根据抗拉强度劣化方程对危岩体稳定性评价方法进行修正,依托工程算例分析相关敏感参数对危岩体稳定性的影响。研究结果表明:频繁的爆破扰动会使主控面的力学性能劣化,危岩体随爆破强度的增大、爆炸应力波传播距离的减小,岩桥段岩石力学性能劣化加剧,其自身的稳定性系数衰减趋势增大且爆炸产生对危岩体的倾倒荷载相较于岩体力学性能劣化更为敏感。

累积爆破作用下露天矿山边坡稳定性变化研究

为研究多次开挖爆破作用对露天矿山边坡岩体的累计损伤及其对边坡稳定性的影响,提高生产的安全性,根据岩石室内物理力学试验结果,基于颗粒流离散元方法(PFC)和有限元分析软件MidasGTS,模拟研究了边坡岩体在多次爆破荷载作用下的累计损伤,探明了边坡岩体抗剪强度随岩体累计损伤的变化规律,建立典型露天矿山边坡岩体模型,研究了多次爆破荷载作用下边坡安全系数的变化情况。结果表明,随爆破次数的增加,边坡岩体的裂隙增多,岩体受扰动程度增大,爆破动荷载对边坡岩体的累计损伤效应持续增强;边坡岩体抗剪强度随岩体损伤的累积呈类似指数型下降;每次爆破动荷载作用使边坡安全系数降低16.2%~30.3%,8次爆破累积损伤作用使边坡安全系数降低约40.8%。

隧道施工爆破诱发的围岩累积损伤规律研究

隧道钻爆法推进式爆破过程会不可避免地对岩体造成损伤,岩体累积损伤源于持续的岩体动力响应。然而,目前尚缺乏量化隧道各分段炸药陆续爆破、隧道推进式重复爆破对围岩造成累积损伤值的计算方法。文章以某隧道工程为研究背景,提出一种模拟隧道各分段炸药陆续爆破、推进式重复爆破的方法,并量化了各个工况对围岩造成的累积损伤程度,最终结合现场测试数据佐证了该方法的可靠性。结果表明:(1)计算大规模起爆引起的损伤时,采用等效荷载方式模拟爆破具有优势;(2)隧道单循环进尺开挖诱发的围岩损伤是多段炸药延期爆破叠加引起的,主要受邻近辅助眼爆破的影响;(3)多循环进尺的爆破开挖会诱发围岩损伤的累积,且累积过程主要受当前爆破进尺和上一个爆破进尺影响;相比于单循环进尺,多循环进尺对隧道中间侧墙的损伤累积程度增大26.7%。

切顶卸压沿空留巷技术在四老沟矿的应用

针对综采工作面之间留设护巷煤柱造成煤柱区域应力集中、煤炭资源浪费等问题,四老沟矿结合矿井地质条件,试验切顶卸压沿空留巷技术。通过运用关键层理论及双向聚能爆破致裂技术,实现工作面采空区顶板顺利切落成巷,通过进行矿压观测分析,达到预期的留巷效果。

综采面复用留巷爆破预裂卸压护巷技术应用

王坡煤矿3306运输顺槽为复用留巷,受采动影响,出现了两帮强烈挤压、顶板破碎下沉和底板底鼓的全断面变形。为了减小或消除临近留用巷道的有害变形,保证围岩的完整性,避免留用巷道二次维修甚至多次巷修,拟在3308回风顺槽顶板采用深孔聚能爆破预裂卸压技术。卸压爆破后,利用钻孔窥视仪对3308回风顺槽顶板预留空孔观察,其岩体向上10 m至25 m范围内均产生较为明显的纵向爆破裂隙,达到切顶预期目标。预裂实施后,3308回风顺槽顶底板累计移近量206 mm,与未采取切顶措施相比,降低60%,其中顶板下沉量51 mm,仅占25%。