Evaluation and optimization of blasting approaches to reducing oversize boulders and toes in open-pit mine

A new blasting approach of combined blastholes with different diameters is proposed to solve the problems of oversize boulders and rock toes in open-pit mine. A non-ideal detonation model and a statistical damage constitutive model are implemented in dynamic finite element analysis to investigate the formation mechanism of oversize boulders and toes. The damage distribution and evolution process of rock blasting fragmentation is simulated, and the scheme is further optimized. Numerical analysis results showed that pocket charges and satellite blastholes can only improve bench top fragmentation, but they cannot reduce the oversize in the middle and bottom of bench as well as the toe problem. The new blasting approach of combined blastholes with different diameters can effectively reduce the oversize boulders and toes as well as the production costs.     

改善露天铁矿爆破效果的实践

从分析冯家峪露天铁矿爆破大块根底产生的原因出发,研究了减少大块和克服根底的有效方法.通过生产实践使采矿生产条件得到改善并降低了采矿成本,取得了较好的效益.     

巨石在堰塞湖泄流过程中的影响试验分析

汶川大地震后,在唐家山堰塞湖泄流槽内和稳定的下游河道上,存在很多巨大的石头。这些巨石的存在到底对泄流过程起到怎样的影响,为探索其中的规律,本文设计堰塞湖的泄流试验,通过量测添加巨石情况下河道坡度以及河道地形与无巨石情况下比较,探索巨石对泄流过程造成的影响。     

球状风化孤石对盾构施工的影响及其处理措施

通过对广深地铁隧道所处地层条件的判断,分析了采用盾构法施工遇到孤石产生的影响和危害,提出了直接破碎孤石的条件和复合地层盾构机推进需注意的问题,最后阐述了几种处理球状风化孤石的方法,为复合地层盾构法施工积累了经验。     

带网钻头用于基桩成孔突破卵砾石层获成功

在大口径工程施工中,钻进卵砾石层采用一般方法钻进比较困难,效果不佳。本文所介绍的采用带网钻头钻进工艺技术,能有效地解决施工的难题。     

边滩漂石河流水沙输移及河床响应数值分析

山区流域地表松散破碎,在地震、暴雨等动力条件影响下大量松散碎屑物质进入沟床,使得山区河流的泥沙补给条件发生突变。由于不同河段输沙能力差异明显,泥沙易在局部河段淤堵,河床剧烈调整,水位显著抬升,这给山区河流的水沙灾害防治造成巨大威胁。基于岷江支流白沙河与龙溪河局部河段的野外调查发现,在干支交汇段沿程边滩漂石结构突出,河道主槽冲刷强,边滩淤堵少。在此基础上,为了分析山区河道中边滩交错漂石结构对水沙运动及河床变形的影响,采用CFD-DEM（计算流体力学CFD,离散单元法DEM）耦合模型,针对不同边滩交错漂石结构下的输沙及河床响应过程开展模拟研究,重点分析了流量、沟道来沙量以及边滩漂石结构对河道下游调沙减灾效果的影响。计算结果表明,山区河道中的边滩交错漂石能够有效改变泥沙颗粒运动轨迹,使得绝大部分颗粒从河道中央向下游输移,进而减少颗粒在河道两岸淤积。此外,边滩交错漂石可以调节山区河流下游河段的来沙过程,控制来沙强度和来沙量,减少泥沙在保护河段落淤进而有效降低河道的沿程水位。随着边滩漂石布设间距的减小、流量的降低以及沟道内来沙质量的增大,边滩漂石对松散堆积体的固沙效果越好,对下游河道的削峰调沙及保护河段的防灾减灾作用越明显。     

融冠1号矿中深孔爆破参数优化研究

在内蒙古兴业集团融冠矿业l号矿中深孔爆破之中,存在炸药单耗大、大块产出率高,影响出矿效率的问题.通过对施工管理和设计等方面地分析研究,针对现场情况从加强矿山地质编录工作和爆破施工管理,优化单位炸药消耗量、炮孔密集系数、最小抵抗线、孔底距和爆孔堵塞长度等方面提出解决问题的方法,使矿山单耗减15％左右,大块率减少0.8％,...     

Behavioural responses of juvenile Atlantic salmon (Salmo salar) to presence of boulders

The influence of boulder presence on the behaviour of juvenile Atlantic salmon (Salmo salar) was investigated experimentally in an indoor flume fed by a 16 l s^?1 flow of natural river water. The flume was divided into 16 arenas (each 1 m²) that were landscaped with river gravel and standardized boulders, to represent relative ‘complex’ or ‘simple’ habitats. Each arena housed three wild‐caught fish. In a three‐week trial, the effects of landscape on aspects of individual behaviour were recorded. Food intake was highest in the simple landscape and directly related to social status and time spent in the water column. The fish in the complex chambers actively maintained station in the water column significantly more than fish in simple landscapes and therefore partially compensated for reduced foraging rates associated with complexity. Fish in simple chambers spent more time orientated upstream than those in complex landscapes. There was no evidence that habitat complexity influenced levels of aggression, average aggressive distance, ‘constrained’ territory size, or dominance. Activity and space use varied with social status. Overall, this study illustrates that addition of boulders can result in costs to Atlantic salmon parr, which can be expected to offset to some extent benefits brought about by increased stream complexity. Work is now needed to evaluate the balance of costs and benefits at different life stages and under various environmental conditions. © Crown copyright 2005. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Assessing the effect of visual isolation on the population density of Atlantic salmon (Salmo salar) using GIS

Few studies investigate the behavioural response of organisms to stream enhancement schemes. One behavioural process that is rarely examined in enhancement studies is the visual isolation created by adding boulders on the river bed. The objective of this research is to use a Geographic Information Systems (GIS) viewshed analysis to determine if the increase in density of Atlantic salmon observed in boulder‐added zones is related to visual isolation or, alternatively, the presence of a velocity refuge. Eight study sites were established on Catamaran Brook and Little Southwest Miramichi River (New Brunswick, Canada). Each reach was divided into three quadrats of 3 m × 2 m. In one of the quadrats, 36 boulders (D₅₀ = 0.20 m) were added to increase visual isolation. Boulders were removed from another adjacent quadrat whereas a third quadrat was left in a natural state. A detailed Digital Elevation Model (DEM) was created for all the sites with a total station. Atlantic salmon were observed by snorkelling on several occasions during two summers. Their position was recorded with the total station and the snout and average velocity was measured. A GIS viewshed analysis was performed to determine the visible area for each fish and to verify whether the surrounding fish were visible or not. Results suggest that the primary mechanism responsible for the observed increase in Atlantic salmon population density in the experimental quadrats is a reduction in the field of view of individuals, through an increase in habitat heterogeneity, which is consistent with the visual isolation hypothesis. There was also no change in the snout velocity of salmon among the three treatments, suggesting that the increase in density is not consistent with the velocity‐refuge hypothesis. Copyright © 2007 John Wiley & Sons, Ltd.