Mineral resources are essential to human life and social development and play an important role in national security and economic development. China has huge reserves of metal mineral resources, but the per capita possession is low. Especially, it is difficult for iron, copper, aluminum, and other metal mineral resources to be self-sufficient and heavily dependent on foreign countries.Because of the massive exploitation of metal mineral resources, shallow resources are becoming exhausted, and deep mining will become the main force for the supply of metal mineral resources in the future. “Going deep into the earth” corresponds to the current state of national resource strategy development. It is found that there is still a certain gap between China’s deep metal mining technology and mining depth compared with internationally developed mining countries. The mining depth of foreign mining countries is mostly over 3000 m, with three South African mines having a mining depth of over 4000 m, whereas the mining depth of Chinese mines is mostly below 2000 m, and most of the metal mines have not yet broken through the kilometer depth. Furthermore, the level of mining technology in established mining countries abroad is high, and the degree of mechanization and intelligence is high. Deep mining technology in China is insufficient to meet the need for deep mining. China still has a large gap compared with internationally developed countries; therefore, the related rock mass mechanics theory and mining technology are no longer suitable for deep metal mining. In this paper, we summarize the research status of four major theories and technologies for deep mining of metal mines, namely, deep rock mechanics, deep well building and lifting, green mining, and intelligent mining, and proposes future research emphases. Finally, based on the research status and existing problems of the key technologies and theories of deep metal mining at present,the paper puts forward three strategic ideas:deep-part construction of a super-large intelligent autonomous mine,in-situ fluidized mining,and rock mechanics.With the continuous increase of mining depth,it is urgent to study the related theory and technology of deep mining of metal mines so as to ensure the safe,efficient,economical,and environmentally friendly mining of deep metal mineral resources and ensure the resource security of our country.

Affected by the superposition of working face mining, strong rock pressure phenomena such as rock burst and large deformation easily occur in the gob-side entry when mining extra-thick coal seams. Taking the extra-thick coal seam mining of Caojiatan Coal Mine in Yushen Mining Area as the engineering background, the appearance mechanism of strong mine pressure in gob-side entry is analyzed and a surrounding rock control technology based on deep-hole directional tension blasting and pressure relief is proposed in our study. The effects of the technology are comprehensively studied by numerical simulation and field experiment. It was found that under the condition of fully-mechanized top-coal caving mining in extra-thick coal seam, the large space long cantilever structure of the gob roof breaks and forms a bench rock beam block with a large length. The instability of the long cantilever structure or the roof key layer will cause strong dynamic pressure, which acts on the coal pillar and further transmits to the surrounding rock of the gob-side entry in the advanced mining area, which is the main reason for the large deformation of the floor heave. Numerical study shows that when the directional roof cutting is performed in the gob-side entry, the surrounding rock stress is transferred away from the entry to both sides. The peak stress value is significantly reduced and the stress range is reduced. The engineering test under different roof cutting conditions was carried out in the field. It was found that the deep-hole roof cutting pressure relief technology based on directional tension blasting can effectively reduce the surrounding rock pressure of the gob-side entry at the end of the ultra-thick coal seam working face. The average load of fore support in the entry was reduced by 11% and the average deformation of floor in the serious section of the entry was reduced by 65%after roof cutting. The combined blasting is beneficial to further reduce the deformation of the entry surroundings and improves the stability of the entry. The research results provide an effective method for controlling the deformation of entry induced by strong mining pressure in ultra-thick coal seam mining.

针对厚硬顶板极难破碎垮落,形成的长悬臂梁挤压巷道造成围岩变形破坏的难题,以曹家滩煤矿典型工作面为工程背景开展研究.利用TRIZ理论进行了系统分析,通过因果关系法确定了造成巷道围岩变形的原因,并采用空间分离原理分离采空区顶板与巷道顶板,结合预先作用法"软"化采空区顶板,以达到厚硬顶板及时垮落充填的目的.基于TRIZ理论的思想,提出了一种"定向聚能爆破+非定向加强爆破"组合爆破技术.通过理论分析确定了组合爆破关键参数,并采用数值模拟进行了分析验证.在此基础上,进行了组合爆破方案设计.最后,开展了现场工程试验.现场应用效果表明:采用组合爆破技术后,巷道围岩变形破坏问题得到有效解决.

Motivated by traffic congestion and air pollution, Beijing is one of several major cities to restrict vehicle ownership by requiring residents to win a lottery for the right to obtain an additional car. We examine the welfare cost of preventing people from owning cars because of misallocation: under a lottery, some individuals with low willingness to pay (WTP) for cars can obtain cars, while other individuals with high WTP cannot. We estimate welfare costs using a new contingent valuation method survey of Beijing lottery participants which we designed and conducted explicitly for this purpose. We find that restricting vehicle ownership reduced private welfare by 26 billion yuan. Back-of-the-envelope calculations suggest that the benefits of lower congestion and pollution roughly equal the costs. Our WTP estimates indicate a net welfare gain of approximately 32 billion yuan if Beijing's lottery were replaced with an auction, which is similar to previous estimates.

Do informal paid transportation services complement or substitute for paid transportation services? We leverage a large set of travel diaries from a government survey to examine the markets for formal and informal taxis in Beijing. We provide a set of stylized facts on the users of each form of transportation, where and when trips take place, and the purposes for trips. In some ways, informal taxis complement formal ones: they are cheaper, and serve passengers with lower incomes than those on regular taxis. In other ways, informal taxis substitute for formal ones: informal taxis overlap with formal ones on where they serve, patron demographic characteristics are very similar, and taxis are taken at the same times of day and for the same purposes. We conclude that informal taxis complement formal taxis in some ways, but substitute for them in others.

轨道交通的运营标志着城市交通网络的初步形成,给交通效率带来飞跃式提升的同时,也加快了大中型城市多中心发展格局的形成.因此,轨道交通会对沿线地产价格产生正面影响.整理归纳已有文献并进行分析,得出轨道交通附近的楼盘价格由自身价值和供求关系决定,并受到轨道交通建设的影响,并且其影响具有时空特征的结论.轨道交通建设阶段、距离最近地铁站距离、与城市中心配套距离、是否为换乘站四个变量对房地产价格影响显著.该研究期望为大型城市地铁沿线地产开发和建设规划提供参考,同时对政府、房地产开发商和购房者三方的决策具有一定指导意义.

矿产资源是发展之基、生产之要.作为世界上矿种最齐全、总量最丰富的矿产资源大国之一,中国在矿产资源总产量、矿业总产值和主要矿产资源消费量等方面均位居世界第一.其中,金属矿行业极大程度地保障了我国现代化建设所需的基本物质与资源,推动我国经济发展和社会进步.然而也应注意到,我国金属矿资源人均占有量较低,主要金属矿资源对外依存度较高,现有资源产量难以满足国家高速发展的需求,供需矛盾较为突出,国家资源安全难以得到保障.此外,我国金属矿资源的生产技术水平与世界先进水平相比还存有一定差距,金属矿资源保护与开发利用水平也亟待提高.

围绕城市轨道交通智慧化建设和运营中开展北斗系统应用的主题,按照基础条件梳理、需求分析、应用前景展望的思路进行研究.首先,在基础条件梳理方面,从北斗系统的建设成就、功能服务与技术水平入手,介绍其应用发展情况,进而识别出北斗系统与智慧城轨融合发展的结合点;然后,根据北斗系统的服务功能,分析智慧城轨在建设和运营中对时空基准、空间数字化、高精度定位与授时3方面的应用需求;最后,以上述2点为基础,对北斗系统在智慧城轨中应用的2方面重点工作,即时空体系网络建设与关键技术突破进行规划,并对其在智慧城轨运行、维修、客服等领域的应用服务进行展望.

铁路信号系统安全证据具有一定的特殊性.在客观性方面,铁路信号系统安全证据除应满足内容和形式客观外,应从科学性和时效性的角度克服其主观性较强的问题.在关联性方面,铁路信号系统安全证据应当从关联性层级决定证明能力层级角度,设定安全证据采纳的最低关联性标准,同时还应注意关联性包含安全证据"证是"和"证否"的双重功能.在合法性方面,铁路信号系统安全证据应当同时满足主体、形式、程序合法的要求.

随着浅部矿物资源日益减少,越来越多的矿井开采向深部推进.开采深度不断增加所引起的软岩大变形、岩爆、高矿压、热害、瓦斯突出和强扰动等工程灾害为深部采矿工程带来了极大的挑战,严重威胁着矿井的生产安全.中外学者针对深部资源开采面临的工程问题进行了大量的理论与试验研究并取得了一定的成果.阐述了引起深部工程灾害的主控因素,总结了深部复杂地质环境灾害现象物理力学机制的研究进展,介绍了深部开采工程实践中防治各类灾害事故的技术装备和理论构想的发展现状,最后提出了未来深部岩体力学理论研究与灾害控制措施研究面临的挑战.

A common policy response to severe air pollution and traffic congestion in developing-country megacities is to ban the driving of vehicles with license plates ending in certain numbers on certain days. We use the contingent valuation method to estimate the costs to drivers of Beijing’s driving restrictions program, one of the world’s largest. Our study generates three main findings. First, costs are substantial: RMB 356 to 709 (US $54 to $107) per driver per year, which represents 0.5 to 1 percent of annual income, and RMB 1.6 billion to 3.3 billion (US $247 million to $493 million) per year for all drivers. Second, comparison of our cost estimates with estimates of the benefits of Beijing’s program from other studies suggests that the benefits exceed the costs. Finally, the costs per driver are significantly smaller than the costs (estimated using the same methods) of Mexico City’s program, which by most accounts has had zero benefits. These findings provide some of the strongest evidence to date that driving restrictions programs can, given certain conditions, have net benefits. They also suggest that relatively high program costs are not a necessary condition for significant program benefits—in fact, the opposite may be true.

Earlier studies that evaluated the impact of vehicular emissions on urban air quality often reached mixed conclusions, providing little guidance to city planners seeking solutions to the ever-growing problem of air pollution. In this paper, we combine the strengths of earlier studies with hourly-level data to reexamine the causal relationship between traffic congestion and ambient air quality in Beijing. We find that around 33% to 57% of ambient air pollution in Beijing can be attributed to vehicular emissions. However, this average figure is masked by nonlinearity, suggesting that policy makers should focus their efforts on alleviating areas with heaviest congestion to improve air quality. (JEL Q53, Q58)

To combat traffic congestion and air pollution, many cities restrict vehicle ownership, but little is known about how these policies actually affect vehicle ownership, use, or travel time. Leveraging the randomization created by Beijing's vehicle license plate lottery, we estimate the effects of the policy on travel behavior. We find that the policy reduces the total stock of cars in Beijing by 14%. It also causes large reductions in vehicle distance traveled, morning rush hour driving, and evening rush hour driving.

巷道安全关系到煤矿的高产高效,深部矿井的巷道稳定性控制尤为重要.以红庆河煤矿3-1101工作面为工程背景,分析深井高应力巷道围岩变形机制,提出一种深部巷道定向拉张爆破切顶卸压围岩控制技术,并运用数值模拟及现场试验等方法对该技术的作用效果开展综合研究.研究发现,定向拉张爆破切项卸压技术可保证在不破坏本工作面巷道稳定性的前提下,通过人为主动控制覆岩结构垮断位置,达到优化巷道应力环境的目的.但是,不同切项效果下,围岩垮落形态、应力分布及变形特征有所差别.数值模拟发现,在一定范围内,增大切项高度有利于促进采空区顶板岩层垮落,减少悬项空间,并减小传递至实体煤上的采空区覆岩荷载.增强切顶效果可减小巷道变形,加快巷道围岩稳定.现场试验发现,随着切顶效果增强,煤体内应力峰值和应力稳定值均会下降,应力达到稳定后的滞后工作面距离会缩短,控制巷道的围岩变形量及变形速率会减小.实践证明,采用该技术后,深井高应力巷道的围岩大变形问题得以有效解决.

OBJECTIVE:To determine the implications of car ownership for physical activity and weight in a global city. DESIGN:Quasi-experimental cross sectional study. SETTING:Beijing, China, 2011-15. PARTICIPANTS:People aged 18 and older from a random sample of households who had entered a permit lottery to purchase a vehicle between January 2011 and November 2015. INTERVENTIONS:Permit allowing purchase of a vehicle within six months of permit issuance. MAIN OUTCOME MEASURES:Transit use (number of subway and bus rides each week), physical activity (minutes of walking or bicycling each day), and weight, measured once in early 2016. RESULTS:Of 937 people analysed in total, 180 had won a permit to purchase a new vehicle. Winning the permit lottery resulted in the purchase of an additional vehicle 91% of the time (95% confidence interval 89% to 94%; P<0.001). About five years after winning, winners took significantly fewer weekly transit rides (-2.9 rides (-5.1 to -0.7); P=0.01) and walked and cycled significantly less (-24.2 minutes (-40.3 to -8.1); P=0.003) than those who did not win the lottery. Average weight did not change significantly between lottery winners and losers. Among those aged 50 and older, however, winners' weight had increased relative to that of losers (10.3 kg (0.5 to 20.2); P=0.04) 5.1 years after winning. CONCLUSIONS:These data indicate that vehicle ownership in a rapidly growing global city led to long term reductions in physical activity and increase in weight. Continuing increases in car use and ownership in developing and middle income countries could adversely affect physical health and obesity rates.

为了探究断层构造对切顶卸压无煤柱自成巷技术的影响,采用力学分析、数值模拟和现场工程试验相结合的研究方法,对切顶卸压自动成巷工作面过正断层过程中的应力演化特征及围岩运动规律进行了深入研究.研究表明:在正断层作用下,工作面于上盘开采并靠近断层时,上覆岩层呈倒楔状,工作面前方应力及留巷实体煤帮侧应力逐渐增大,留巷围岩变形剧烈.在断层处时,上覆倒楔状覆岩应力传递至下盘和工作面端头留巷煤帮侧,断层带易活化、破碎及易滑移的特性导致断层处留巷围岩变形最大.工作面过断层后,上覆岩层呈正楔状,此时工作面前方和留巷实体煤帮侧应力变小,但由于此时留巷位于断层破碎带下方,上盘倒楔状岩层应力向下盘传递,导致留巷变形依然较大.断层带影响范围约为其前后70 m,该范围内成巷围岩需重点控制.

为研究无煤柱自成巷开采条件下基本顶不同断裂位置对巷道变形的影响,分析顶板岩层运动特征,建立基本顶不同断裂位态力学模型,分别推导出基本顶在不同断裂位置时的巷内临时支护强度计算公式,得出巷内临时支护强度临界值.采用离散元数值软件UDEC对基本顶不同断裂位态下的岩层运动进行模拟分析.结果表明:基本顶在实体煤侧及采空区侧发生断裂,巷道变形较小,而在巷道上方发生断裂时变形破坏严重;通过调整切顶护帮支架对巷道顶板支撑力控制下位顶板的变形,使基本顶在较为有利的位置发生断裂;通过切顶护帮支架、恒阻大变形锚索支护等技术可以有效控制巷道变形,并在柠条塔煤矿S1201-Ⅱ工作面成功应用.

In light of the problems of cockamamie construction technology and high cost of constructing roadway existing in traditional gob-side entry retaining technology,an innovative no coal pillar mining technology by cutting roof to release pressure was proposed.Based on the movement laws of overlying strata in traditional gob-side entry retaining technology,the mechanism of pressure relief of gob-side roof was studied.In addition,several "surrounding rock structure-roadside support body" mechanical models were established considering different types of roof state,and the design formula of each roadway-side supporting resistance was obtained.The results show that the lower basic roof fall enough and then support the upper roof better by presplitting blasting,thereby limiting the rotational deformation of upper roof and reducing the impact load of roof break.The frature location of roof is shifted to the gob side,the length of the roof cantilever beam is reduced and the short cantilever beam is formed by roof cut,thus reducing the additional load of roadside support.Apart from that,some surrounding rock control technologies such as directional pre-splitting roof cutting technology,the constant resistance large deformation (CRLD) bolt and roadside intensive individual props were proposed.These technologies have been used in 12201 working face of Halagou coal mine and a good effect of field application was achieved.

为了探索无煤柱自成巷开采条件下“短臂梁”顶板结构及变形特征,建立了顶板变形计算模型,运用能量理论与位移变分方法对顶板变形及其影响因素进行了分析.结果表明:留巷宽度、断裂岩块回转运动对顶板变形影响较为显著;而巷内锚索支护、临时支护对顶板变形控制作用有限.顶板变形的主要影响因素按其影响程度由大到小依次为:留巷宽度、岩体泊松比、断裂岩块回转角度、岩体弹性模量、临时支护强度、锚索支护强度.据此提出应严格控制留巷宽度,合理设计顶板切缝高度的围岩控制思路,可降低上覆岩层断裂岩块回转下沉空间,减小“短臂梁”顶板变形,有利于提高巷道稳定性.

针对大采高综放工作面煤壁片帮严重问题,建立了综放工作面围岩力学模型,分析了影响煤壁片帮的3个方面:顶板压力大小、Ⅳ1区和Ⅳ2区的特性.提出通过弱化Ⅳ1区力学参数减缓大采高综放工作面片帮的想法,基于注水弱化理论和散体吸能防冲原理阐述了上述想法的可行性,并对不连沟煤矿F6202工作面煤壁片帮问题提出了注水弱化Ⅳ1区的实施方案,最后通过FLAC3D数值模拟软件模拟了不同弱化参数下的支承压力分布特点,得到了注水弱化煤岩体能使支承压力峰值向后上方移动,支承压力峰值减小,机采高度范围内受高应力影响减小,从而得到弱化煤岩体能有效控制综放工作面的煤壁片帮的结论.