Buckling mechanism of pillar rockbursts in underground hard rock mining     

J. Deng  D. S. Gu 《Geomechanics and Geoengineering》2018,13(3):168-183

The objective of this paper is to investigate the buckling mechanism of pillar rockbursts in underground hard rock mines from an innovative point of view. By considering rockbursts as a buckling (instability) problem of structures, rockbursts are classified into three categories: induced rockburst, triggered rockburst and inherent rockburst, in accordance with the magnitude of the dynamic stimulation force from large to null. Rigorous mathematical models are set up for these three rockbursts. For induced and triggered rockbursts, mechanism of parametric resonance is found and perturbation effect is observed. For inherent rockbursts, the condition of critical static loads is obtained. Various examples of rockbursts in Dongguashan Copper Mine are analysed. The limitations of the approach are addressed. Contrary to conventional methods where only rock materials or rock specimens were used for investigation of rockbursts, this study attaches more attention on the structural effect on rockbursts, which may appeal to practising engineers.  相似文献   

Study of 3D Geological Modeling Based on Aeromagnetic Data     

Zheng Hou  Tianyi Wang  Changchun Yu  Shengqing Xiong  Long Di 《地球科学进展》2018,33(3):257-269

With the increasing difficulty of finding the shallow surface deposit and the increasing depth of resources exploration, three-dimensional modeling technology is more apparent in deep prospecting, and its accuracy directly determines the cognitive degree of geological body and metallogenic condition. For this, we put forward a set of the extraction technology of abnormal information combined with aeromagnetic data processing with three-dimensional geological modeling. Inversing the selected profile of the study area and obtaining each profile geological model, we built three-dimensional geological model of geological units by the method of profile linked, using undulating terrain three-dimensional block magnetic field forward techniques to model the three-dimensional geological model of the whole area, and obtained the forward modeling results of the whole three-dimensional geological model and the geological unit. After the comparative analysis with the test result, adding reasonable geological constraints and revising model, through adjusting for many times, we made the model maximum close to the actual situation. The model can well reflect the geological information and make minimum fitting error of observations and theoretical field, with which geologists can use the most of their experience and get more regional geological understanding. Using the thought of main block and secondary block to subdivision modeling of geological body, on the condition of ensuring the accuracy of model, the number of the total model block decreased and the multi-window and multi-geological body parallel computing method were used to improve the modeling speed, effectively solve the limitation problem of the model complexity in the process of the three-dimensional inversion modeling method, and easily form complex and different sizes three-dimensional geological model. We applied this method to the Hubei Daye area, constructed the three-dimensional geological model of Daye Iron Mine, and verified the feasibility and rationality of this method.  相似文献   

Quantifying a realistic,worldwide wind and solar electricity supply     

《Global Environmental Change》2015

Nearly all long-term energy projections rely heavily on renewable energy sources on the assumption of abundance. Yet, already today, wind and solar projects can encounter local objections and competition with other uses. This paper presents the ranges of realistic potential supply for solar and wind electricity, using a 1 km² grid level analysis covering the whole world at country level. In addition, the potential for building-based solar electricity is assessed. We find that long-term combined potentials range between 730 and 3700 EJ/a worldwide, depending crucially on the acceptable share of land—up to 3.5% of total (non-ice covered) land on earth. Realistic potentials account for limitations such as land-use competition and acceptance, together with resource quality and remoteness as proxies for cost. Today's electricity demand (65 EJ/a) is well covered by the range, but constraints may occur in the long run locally. Amongst large countries, Nigeria and India may need imports to meet electricity demand.  相似文献   

A comparative study on the dominant factors responsible for the weaker-than-expected El Niño event in 2014     

Jianying Li  Boqi Liu  Jiandong Li  Jiangyu Mao 《大气科学进展》2015,32(10):1381-1390

Anomalous warming occurred in the equatorial central-eastern Pacific in early May 2014, attracting much attention to the possible occurrence of an extreme El Niño event that year because of its similarity to the situation in early 1997. However, the subsequent variation in sea surface temperature anomalies (SSTAs) during summer 2014 in the tropical Pacific was evidently different to that in 1997, but somewhat similar to the situation of the 1990 aborted El Niño event. Based on NCEP (National Centers for Environmental Prediction) oceanic and atmospheric reanalysis data, the physical processes responsible for the strength of El Niño events are examined by comparing the dominant factors in 2014 in terms of the preceding instability of the coupled ocean-atmosphere system and westerly wind bursts (WWBs) with those in 1997 and 1990, separately. Although the unstable ocean-atmosphere system formed over the tropical Pacific in the preceding winter of 2014, the strength of the preceding instability was relatively weak. Weak oceanic eastward-propagating downwelling Kelvin waves were forced by the weak WWBs over the equatorial western Pacific in March 2014, as in February 1990. The consequent positive upper-oceanic heat content anomalies in the spring of 2014 induced only weak positive SSTAs in the central-eastern Pacific-unfavorable for the subsequent generation of summertime WWB sequences. Moreover, the equatorial western Pacific was not cooled, indicating the absence of positive Bjerknes feedback in early summer 2014. Therefore, the development of El Niño was suspended in summer 2014.  相似文献   

一次纬向暴雨过程的湿对称不稳定与锋生分析     

邓承之  张亚萍  方德贤  翟丹华  吴钲  何跃 《气象》2019,45(11):1527-1538

利用常规观测、加密自动站、NCEP/NCAR(1°×1°)再分析及WRF数值模拟资料,诊断分析了2016年6月27—28日重庆南部大暴雨天气的纬向雨带及湿对称不稳定特征,结果表明:(1)纬向雨带形成并发展于低空湿对称不稳定区,纬向雨带形成前,湿对称不稳定逐渐增强,纬向雨带形成后,湿对称不稳定缓慢释放,湿对称不稳定的持续释放促进了纬向雨带的持续发展。(2)纬向锋生效应的增强,引起低空湿位涡水平分量MPV2的负值增长,为湿对称不稳定的增强及维持提供了有利条件,可能是此次暴雨过程中纬向雨带生成及持续发展的重要机制。  相似文献   

基于大气不稳定参数的广东地区雷暴特征分析     

刘泽  郭凤霞  廉纯皓  曾凡辉  黎奇  甘明骏 《气象科技》2019,47(4):648-654

利用广东省清远地区2011、2012和2014年6—8月地闪定位资料将每天发生的雷暴情况进行分级,并结合对应的探空资料,计算对流有效位能、沙氏指数、K指数等反映大气稳定性或能量关系的参数,分析其在发生时间和强度不同的雷暴发生前的分布情况。结果表明,沙氏指数、抬升指数、K指数、全总指数、强天气威胁指数和对流有效位能与雷暴强度有一定的相关性,而对流抑制能量、粗理查森数与雷暴强度间没有发现较好的相关性。广东地区雷暴发生前沙氏指数小于0℃,抬升指数小于-2℃,K指数大于30℃,对流有效位能大于500J/kg,更容易产生中强雷暴。广东地区的K指数高于青藏高原地区20℃左右,对流有效位能的平均值高于青藏高原及陕甘宁地区约300J/kg,其余参数分布特点与部分地区相似,进一步反映了广东地区雷暴特征的特殊性,加深了对广东地区雷暴特征的认识。  相似文献   

江淮气旋暖锋上多条对流带的组织结构及成因分析          下载免费PDF全文

丁治英  刘瑾  赵向军  王瑾婷 《大气科学学报》2019,42(5):778-789

利用ARW-WRF模式对2014年7月4日12时—5日06时发生在安徽中南部的一次由江淮气旋引发的强降水过程进行模拟,得到暖锋上雨带的雷达回波结构,与实况有较好的一致性。对气旋暖锋上出现的多个小对流带的结构与成因进行了分析,发现暖锋小对流带的高度模拟和实况均在300 hPa以下,其生命史约2～3 h,最长100 km,宽10 km,带与带间距50～100 km,均随高度向东南方向倾斜。其环流特征为对流区东部从低层到高层多对应暖空气上升;对流区西部中上层多为冷区控制;近地面则有类似冷池存在,对流带南部的上升气流有利于对流云的后向新生和形成带状结构。小对流带上,800 hPa有0Ri1和I_(EPV)0区域,稳定层结内出现滚轴状流场分布,有重力波存在的结构特征;600～700 hPa为对流不稳定,对流带间I_(EPV)0。可见暖空气沿暖锋爬升时,在800 hPa附近,由于满足条件性对称不稳定条件,触发条件性对称不稳定和重力波,暖空气继续上升时触发700 hPa之上的对流不稳定,即影响本次暖锋小对流带形成的原因主要为对称-对流不稳定。  相似文献   

河南栾川钼矿复杂地层探测工艺研究与试验          下载免费PDF全文

陈勇  韦昭杰 《探矿工程》2021,48(10):70-75

洛阳栾川钼矿存在的多层采空区以及大量的矿渣堆积地层,导致钻进过程中孔壁极易失稳,一般表现为坍塌、掉块等;同时导致探测设备无法下放至孔底、延误工期。针对这一现状,本文研究了2种新的勘探工艺方法：（1）使用黄土加固孔壁新工艺,使黄土在孔壁上形成一层保护层,即利用挤密加固后的黄土保护孔壁。（2）设计了新型锥形钻头,使用重锤将锥形钻头砸落至采空区底板,利用中空钻杆保护井下电机等探测设备。将2种方法投入实践证明方法可行,并且随着工期的进行,孔壁保持稳定不再出现失稳的情况,为后续对采空区的地质探测提供了安全保障。在经济、安全的前提下保证了施工的顺利实施,并为今后复杂地层的探测积累了一定的经验。  相似文献   

系统维度对变密度溶质运移的影响研究          下载免费PDF全文

叶逾  蔡芳敏  谢一凡  井淼  鲁春辉 《水文地质工程地质》2022,49(1):146-153

关于地下水变密度流与溶质运移的研究通常局限于二维系统中,三维系统中的研究非常有限。然而,仍有零星研究表明,三维系统中的对流过程与二维系统不同。文章通过SEAWAT-2000进行数值模拟,系统研究了二维和三维系统中的变密度溶质运移过程,利用舍伍德数、空间矩和稀释指数量化了系统的不稳定性和溶质扩散、稀释程度。结果表明:二维系统产生分散指流,而三维系统中因扩散程度的增强使得分散指流的产生受到抑制,但是,三维系统的不稳定性比二维系统更强,对流入渗更快,与指流的产生与否并无直接关联。另外,三维系统中溶质的稀释程度大于二维系统,但溶质在二维系统中将更快接近稀释的最大值,传统二阶中心矩可能会造成自由对流和不稳定性溶质运移过程中溶质扩散和稀释程度的错误估计。研究结果将有助于正确预测三维自然含水层中的自由对流和溶质运移。  相似文献   

城市洪涝中人体失稳机理与判别标准研究进展          下载免费PDF全文

夏军强  董柏良  周美蓉  王小杰  夏军 《水科学进展》2022,33(1):153-163

受全球气候变化和人类活动影响,近年来极端降水事件增多,由此引发的城市洪涝灾害频发。行人在洪水作用下易失去稳定,威胁生命安全,研究洪水中人体的失稳机理与判别标准,能为城市洪涝灾害的风险评估与管理提供科学依据。本文首先总结了国内外城市洪涝中人体失稳机理研究的相关成果,评估了现有人体失稳判别标准的适用范围及优缺点。基于力学分析和实测数据率定的计算公式虽然在推导过程中有一定的简化,但能较好地反映洪水中人体失稳的动力学机理,可以评估不同人群与不同洪水条件下的人体稳定性。针对当前城市洪涝中人体稳定性研究存在的不足,需要开展真实洪水中行人逃生以及沿漫水楼梯行走时的失稳机理与判别标准研究,并深入研究行人站立姿势调整对洪水中人体稳定性的影响;还需基于大数据等手段获取互联网上洪水中人体失稳的影像资料,构建洪水中人体失稳的实测数据库;同时还需推动人体失稳判别标准在洪水风险管理中的具体应用,最大程度地降低城市洪涝灾害带来的不利影响。  相似文献