Hybrid finite-discrete element modelling of dynamic fracture and resultant fragment casting and muck-piling by rock blast

A state-of-the-art review is conducted to highlight the fracture mechanism in rock blast and advantages and limitations of various methods in modelling it. A hybrid finite-discrete element method (FEM-DEM) is implemented to simulate rock fracture and resultant fragment muck-piling in various blasting scenarios. The modelled crushed, cracked and long radial crack zones are compared with those in literatures to calibrate the hybrid FEM-DEM. Moreover, the hybrid modelling reproduces the rock fragmentation process during blasting. It is concluded that the hybrid FEM-DEM is superior to continuous and discontinuous methods in terms of modelling dynamic fracture of rock under blast-induced impact load.     

应用FTIR-SEM研究一类合成欧珀的微结构及其变彩成因机制

近些年来,相关人工合成欧泊的研究工作主要聚焦于天然与合成欧泊的鉴别与筛选,而相关合成欧泊的微结构、变彩机制及其中水的赋存状态的深入研究鲜见报道。本文通过傅里叶变换红外光谱(FTIR)、场发射扫描电镜(FE-SEM)对一类合成欧泊的微结构、结构缺陷进行较系统的研究。同时,结合对样品的热处理就该合成欧泊体色、变彩机制及其中水的赋存状态作了初步探讨。结果表明:该样品的红外光谱中,在约2900 cm~(-1)、1737 cm~(-1)处出现合成欧泊特征吸收,且在4000~6000 cm-1波段,合成欧泊相比天然欧泊的吸收峰更为复杂。合成欧泊的颜色由体色与变彩两者共同构成,该体色与存在于其微结构中准球状、粒径约205 nm的二氧化硅颗粒的间隙填充物直接关联,且在热处理条件下随着间隙物的析出而渐退。同时,该类合成欧泊的变彩归因于结构致色并由其内部SiO_2颗粒周期性排列而构成的三维的光子带隙结构所致。此外,在欧泊的微观结构发生重构前,变彩所呈现的颜色主要由准球状二氧化硅颗粒粒径与间隙填充物决定。     

Active and passive arching stresses in c′-ϕ′ soils: A sensitivity study using computational limit analysis

Vertical soil arching, commonly known as the “trapdoor mechanism,” is a pervasive phenomenon in various geotechnical applications that can be evaluated through a variety of analytical and numerical approaches, most of which exist due to a variety of proposed arching mechanisms, many of which are focused on either purely frictional or cohesive soils. This study investigates the realized arching mechanisms and associated loads for trapdoors under both active and passive arching conditions in c′-ϕ′ soils through a series of dimensionless charts using both upper and lower bound limit analyses. An associated sensitivity analysis demonstrates that arching loads are highly dependent on collapse mechanism, a function of not only geometry, but soil shear strength, with cohesion affecting the realized mechanism and arching loads.     

Influence of single flaw on the failure process and energy mechanics of rock-like material

This paper investigates the influence of a flaw on crack initiation, the failure mode, deformation field and energy mechanism of the rock-like material under uniaxial compression. The results of laboratory test and numerical simulation demonstrate the flaw inclination effect can be classified into three groups: 0–30°, 30–60° and 75–90°. The characteristic stresses increase as the flaw angle increases. The tensile cracks initiate from gentle flaws (α ⩽ 30°) and shear cracks appear at tips of steep flaws (α ⩾ 45°). The input energy, strain energy and dissipation energy of a specimen show approximate increasing trends as the flaw angle increases.     

兰州九州重塑黄土的抗拉变形破坏机理

通过对不同干密度及含水量的重塑黄土进行室内抗拉强度试验,探究轴向压裂法致使试样破坏的机理及一般规律。结果表明,黄土的抗拉变形破坏可分为4种类型：I类,高干密度低含水量（干密度大于1.65 g·cm^-3,含水量小于15%）,抗拉强度介于8~12 kPa;Ⅱ类,低干密度低含水量（干密度小于1.60 g·cm^-3,含水量小于15%）,抗拉强度介于4~8 kPa;Ⅲ类,高干密度高含水量（干密度大于1.65 g·cm^-3,含水量大于17%）,抗拉强度介于4~8 kPa;IV类,低干密度高含水量（干密度小于1.60 g·cm^-3,含水量大于17%）,抗拉强度介于3~4 kPa。I类、Ⅱ类破坏类型属于脆性破坏,Ⅲ类、IV类属于塑性破坏。重塑黄土抵抗变形最弱的含水量为15%。通过对比分析黄土、普通黄黏土、红黏土及膨胀土的抗拉强度发现,在最优含水量处,不同干密度下黄土的抗拉强度均最小。黏性土的持水能力远超过黄土。黏土及膨胀土的抗拉强度均在最优含水量处达到最大值,而黄土的抗拉强度随着含水量的增加持续减小。研究结果对黄土强度特性的理解具有一定的参考意义。     

棘爪机构伸缩式钻孔水力开采装置的设计与试验

钻孔水力采矿由于安全系数高、工程效益和生态环境保护好等优点在国外一直被研究和使用。我国相关的科研院所也正在开展研究。本文在分析研究国外钻孔水力开采装置的基础上,研制了具有自主知识产权的棘爪机构伸缩式钻孔水力开采装置。该装置利用机械式伸缩水枪的方式扩大水力开采矿层的范围,创新性地采用棘爪机构固定水枪的伸出角度,从而提高单孔开采量,降低开采成本。初步野外实验结果表明,该装置结构设计合理、工作可靠性高,可有效进行开采,达到了预期的目标。     

Characteristics of Ore-controlling Structures and Ore Emplacement Mechanism in the Shihu Gold Deposit,Hebei Province - A Case Study of the No.101 VeinEI北大核心CSCD

The Shihu gold deposit lies in the middle-northern Taihang Mountains and is strictly controlled by faults. The ore-controlling structures in the mining district are not well-documented. Detailed field observation and laboratory investigation of the No.101 vein indicated that the ore-controlling structures of the Shihu gold deposit are the pre-Mesozoic shear joints with SN and NW strike that reactivated during the Yanshanian emerged from. The NNW-SSE left-strike-slip stresses during the main mineralization stage led to the dilation of the NW-strike structural segments along the roof and footwall of the early quartz diorite porphyrite veins, which contributed to the extensive wall-rock alteration, intensive gold mineralization and occur as quartz-vein type ores, and consequently the formation of rich ore pillars. On the contrary, the SN-strike compressive structures correspond to the weak wall-rock alteration and gold mineralization and occur as altered-rock type ores. All the rich ore pillars laterally distributed with high-angle (70°±), and wholly pitched southward with 40° angle. According to the structural ore-controlling regularities, the location between the No.47 and the No.61 exploratory line with elevation below 150 m is an excellent ore-prospecting area. Our prospecting proposal based on the ore-controlling structural analyses in the study area has been proven by the underground works in the Shihu gold deposit. © 2017, Science Press. All right reserved.     

岩溶矿床疏干区地下水位恢复对岩溶塌陷作用机制的研究——以湖南宁乡大成桥为例

截止2016年底,大成桥疏干区在地下水位恢复过程中共发生了17起岩溶塌陷,文章结合地下水动态监测、水文地质钻探成果以及现场调查资料等,研究地下水恢复特征及其对岩溶塌陷的作用机制,为研究区塌陷的预警防治提供科学依据。结果表明:研究区岩溶塌陷集中在河流两岸阶地和麻枣冲沟中;岩溶塌陷发生顺序为先补给区后径流区,与地下水恢复动态过程密切相关;区内地下水恢复过程可分为4个阶段,不同阶段岩溶塌陷机理可分为渗流潜蚀-气爆效应,负压吸蚀效应,软化增荷-挤压-吸蚀效应和软化-崩解效应等4种力学效应组合,不同力学效应作用下的致塌模式有所不同。其中地下水位在基岩面附近4~5 m范围波动更容易引发岩溶塌陷。目前补给区地下水位标高63.95~71.8 m,高于基岩面5~6 m;径流区为42.8~57.7 m,位于基岩面以下4~17 m,因此须密切观测研究区地下水位变化。      

Review of Deep-Penetrating Geochemical Exploration Methods

It is a worldwide challenge to explore the deeply buried deposits. Deep-penetrating geochemical exploration methods were developed to solve the problems of how to get the information of the buried deposits in the covered layer. The methods were successfully used to indicate some buried deposits, but not all kinds of deposits. What is more, a method cannot be used in all kinds of landscapes. In this paper, theories and case studies of deep-penetrating geochemical exploration methods, including mobile metal ions, enzyme leach, leaching of mobile forms of metals in overburden, electro-geochemical extraction method, biogeochemical exploration, nano-metal in geogas were reviewed. Elements migration, unloading mechanism and anomaly models are the most important parts for deep-penetrating geochemistry and need to be further investigated. From the perspective of economic efficiency and applicability, sampling and analyzing procedures should be simplified to improve the stability of all methods.     

贵德盆地热结构及地热成因机制

贵德盆地位于青藏高原东北缘黄河谷地之中, 四周环山, 为新生代断陷盆地, 地貌单元位于青藏块体, 地处祁连、昆仑和秦岭三大褶皱系交汇地带; 新构造活动强烈, 发育一系列NWW向、NW向及NNW向断裂, 为区内高温地热系统提供了较好的地热地质条件。区内地热显示类型多样, 水热活动剧烈, 尤其是盆地西部的扎仓寺热田, 水温高达 93℃, 蕴藏着丰富的地热资源。但是由于客观条件限制, 区内地热资源的开发利用及相关研究尚有不足之处。