Surface Movement Regularity of Super-Wide Mining Face With Top-Coal Caving

No.4326 super-wide panel of Wangzhuang Coal Mine ( in which the fully-mechanized top-coal caving longwall mining method was used) was monitored for dynamic characteristic of surface movement. The dynamic surface movement in and after mining was predicted by using the Mining Subsidence Prediction System. The results indicate that after mining, the surface above the super-wide panel reaches a state of full subsidence, making the No.309 national highway above the panel be located on the flat bottom of the subsidence basin so that the influence of mining activity in both sides of 4326 panel on the national highway is the smallest.     

Subsidence control method by inversely-inclined slicing and upward mining for ultra-thick steep seams

Ultra-thick steep coal seam mining will inevitably lead to the increase of greater and violent ground subsidence and deformation. A subsidence control method by inversely-inclined slicing and upward mining is proposed in this paper. By this method, the sequence of collapse of overlying strata and the direction of propagation of strata movement are changed, the extent of roof-side deformation thereby is lessened, and boundary angle of roof-side subsidence is reduced by 5°–10°. The mechanism of this mining method for control of strata movement has been evidenced by numerical simulation and experiments with similarity materials. A subsidence prediction model based on the variation of mining influence propagation angle can be used to evaluate the surface movement and deformation of the mining method. The application of the method in No.3 Mine in Yaojie mining area has yielded the expected result.     

大采深巨厚砾岩综放开采地表沉陷规律

以常村煤矿工程地质资料和地表移动观测站资料为依据,详细分析了2113工作面地表终态下沉、动态下沉和终态水平移动的特征,从机理上研究了大采深巨厚砾岩开采条件下地表形变异常的原因.通过走向方向最大下沉点下沉速度的变化规律和工程实测资料,得出了地表形变与井下冲击地压的关系,确定了地表移动与变形的角量参数.结果表明,受关键层的控制,在整个观测过程中,地表始终处于缓慢下沉状态,且在沉降过程中不存在下沉突变点;下沉速度的反弹可以作为冲击地压危险的预报信息,巨厚砾岩层的运动是发生矿震的主要力源之一.     

Analysis of factors and countermeasures of mining subsidence in Kaiyang Phosphorus Mine

1 INTRODUCTION After useful mineral body has been mined and dragged out, mining goaf is formed and country rocks would probably lose original equivalence. When span of the goaf is long enough, even if the roof is hard and intact, the rock around the goaf would move towards the mining openings, and this movement would pass on to the adjoining rock mass until it reaches the surface and ground displacement can be observed. In other words, underground mining may cause ground cracks and surface…     

Analysis of ARMPS2010 database with La Model and an updated abutment angle equation

The Analysis of Retreat Mining Pillar Stability(ARMPS) program was developed by the National Institute for Occupational Safety and Health(NIOSH) to help the United States coal mining industry to design safe retreat room-and-pillar panels. ARMPS calculates the magnitude of the in-situ and mining-induced loads by using geometrical computations and empirical rules. In particular, the program uses the ‘‘abutment angle" concept in calculating the magnitude of the abutment load on pillars adjacent to a gob. In this paper, stress measurements from United States and Australian mines with different overburden geologies with varying hard rock percentages were back analyzed. The results of the analyses indicated that for depths less than 200 m, the ARMPS empirical derivation of a 21° abutment angle was supported by the case histories; however, at depths greater than 200 m, the abutment angle was found to be significantly less than 21°. In this paper, a new equation employing the panel width to overburden depth ratio is constructed for the calculation of accurate abutment angles for deeper mining cases. The new abutment angle equation was tested using both ARMPS2010 and La Model for the entire case history database of ARMPS2010. The new abutment angle equation to estimate the magnitude of the mining-induced loads used together with the La Model program was found to give good classification accuracies compared to ARMPS2010 for deep cover cases.     

Investigation and characterization of mining subsidence in Kaiyang Phosphorus Mine

In Kaiyang Phosphorus Mine, serious environmental and safety problems are caused by large scale mining activities in the past 40 years. These problems include mining subsidence, low recovery ratio, too much dead ore in pillars, and pollution of phosphorus gypsum. Mining subsidence falls into four categories： curved ground and mesa, ground cracks and collapse hole, spalling and eboulement, slope slide and creeping. Measures to treat the mining subsidence were put forward： finding out and managing abandoned stopes, optimizing mining method （cut and fill mining method）, selecting proper backfilling materials （phosphogypsum mixtures）, avoiding disorder mining operation, and treating highway slopes. These investigations and engineering treatment methods are believed to be able to contribute to the safety extraction of ore and sustainable development in Kaiyang Phosphorus Mine.     

山区双车道公路延误车头时距分析

跟车时间百分比(延误率)是衡量双车道公路服务水平的一个重要指标.我国将一般双车道公路上小于等于6s的车头时距定义为延误,并作为划分道路服务水平的因素之一.在山区双车道公路进行了阻车实验,并对获得的车头时距、车速等数据进行分析,认为山区双车道公路延误车头时距与前后车速度差的关系不同于一般双车道公路,建议不采用跟车时间百分比作为山区双车道公路服务水平的划分指标,从而为我国山区双车道公路通行能力的研究提供数据依据.     

Investigation of overburden behaviour for grout injection to control mine subsidence

This paper describes a field and numerical investigation of the overburden strata response to underground longwall mining, focusing on overburden strata movements and stress concentrations. Subsidence related high stress concentrations are believed to have caused damage to river beds in the Illawarra region, Australia. In the field study, extensometers, stressmeters and piezometers were installed in the overburden strata of a longwall panel at West Cliff Colliery. During longwall mining, a total of 1000 mm tensile deformation was recorded in the overburden strata and as a result bed separation and gaps were formed. Bed separation was observed to start in the roof of the mining seam and gradually propagate toward the surface as the longwall face advanced. A substantial increase in the near-surface horizontal stresses was recorded before the longwall face reached the monitored locations. The stresses continued to increase as mining advanced and they reached a peak at about 200 m behind the longwall face. A numerical modelling study identified that the angle of breakage (i.e., the angle of the boundary of caved zone) behind the longwall face and over the goaf was 22–25° from vertical direction. This is consistent with the monitoring results showing the high gradient of stresses and strains on the surface 150–320 m behind the mining face.     

Simulation of recovery of upper remnant coal pillar while mining the ultra-close lower panel using longwall top coal caving

With the depletion of easily minable coal seams, less favorable reserves under adverse conditions have to be mined out to meet the market demand. Due to some historical reasons, large amount of remnant coal was left unrecovered. One such case history occurred with the remnant rectangular stripe coal pillars using partial extraction method at Guandi Mine, Shanxi Province, China. The challenge that the coal mine was facing was that there is an ultra-close coal seam right under it with an only 0.8–1.5 m sandstone dirt band in between. The simulation study was carried out to investigate the simultaneous recovery of upper remnant coal pillars while mining the ultra-close lower panel using longwall top coal caving(LTCC). The remnant coal pillar was induced to cave in as top coal in LTCC system. Physical modelling shows that the coal pillars are the abutments of the stress arch structure formed within the overburden strata. The stability of overhanging roof strata highly depends on the stability of the remnant coal pillars. And the gob development(roof strata cave-in) is intermittent with the cave-in of these coal pillars and the sandstone dirt band. FLAC3 D numerical modelling shows that the multi-seam interaction has a significant influence on mining-induced stress environment for mining of lower panels. The pattern of the stress evolution on the coal pillars with the advance of the lower working face was found. It is demonstrated that the stress relief of a remnant coal pillar enhances the caveability of the pillars and sandstone dirt band below.     

Impact of geo technical factors on strata behavior in longwall panels of Godavari Valley coal field-a case study

Understanding the cantilevers formed by thick, massive beds in the near-seam overburden above longwall panels and the associated loads and strata fracturing effects developed during caving(main and periodic weightings) are key elements for the successful implementation of longwalls. Such caving mechanisms rely on the geotechnical conditions within the panel. In India, the majority of longwall downtime and/or roof failures were caused by a lack of knowledge on overburden caveability, in particular when the main and periodic weightings will impact the face and longwall support selection to effectively mitigate such weightings. Godavari Valley Coal Fields is no exception as longwall faces were adversely affected due to the presence of thick, massive beds in the near-seam overburden at both Godavarikhani(GDK) 7 and 9 Incline mines. In contrast, overburden weightings were negotiated successfully in GDK10 A and Adriyala Longwall Project(ALP) mines by detailed geotechnical studies, the use of adequate longwall support capacities, and effective operational practices. Thirteen longwall panels with varying face width, at different depths have been extracted under massive sandstone beds of 18 m to28 m thickness at GDK 10 A and ALP mines. This study elucidates that the main roof weighting interval decreases with an increase in face width and attains a constant value with further increases in face width under the same geo-mining conditions. In addition, this study also concludes that with increases in face width, the periodic roof weighting interval decreases and shield loads increase. Similarly with increasing panel width to depth ratio, the main and periodic roof weighting intervals decrease but shield loads again increase. Lastly, the strata behaviour of the longwall face retreated along up-dip direction is demonstrated. The results of this paper improves the mechanistic understanding of the impact of face width,depth and main roof thickness on periodic weighting and associated roof control problems on the longwall face.     

西部地区环境特点与公路建设可持续发展的探讨

文章论述了西部地区自然环境与公路可持续发展的关系,分析了影响公路可持续发展的因素,提出了实施西部公路可持续发展的几点建议。     

Mining pressure monitoring and analysis in fully mechanized backfilling coal mining face-A case study in Zhai Zhen Coal Mine

Fully mechanized solid backfill mining(FMSBM) technology adopts dense backfill body to support the roof. Based on the distinguishing characteristics and mine pressure control principle in this technology, the basic principles and methods for mining pressure monitoring were analyzed and established. And the characteristics of overburden strata movement were analyzed by monitoring the support resistance of hydraulic support, the dynamic subsidence of immediate roof, the stress of backfill body, the front abutment pressure, and the mass ratio of cut coal to backfilled materials. On-site strata behavior measurements of 7403 W solid backfilling working face in Zhai Zhen Coal Mine show that the backfill body can effectively support the overburden load, obviously control the overburden strata movement, and weaken the strata behaviors distinctly. Specific performances are as follows. The support resistance decreases obviously; the dynamic subsidence of immediate roof keeps consistent to the variation of backfill body stress, and tends to be stable after the face retreating to 120-150 m away from the cut. The peak value of front abutment pressure arises at 5-12 m before the operating face, and mass ratio is greater than the designed value of 1.15, which effectively ensures the control of strata movement. The research results are bases for intensively studying basic theories of solid backfill mining strata behaviors and its control, and provide theoretical guidance for engineering design in FMSBM.     

基于DEA模型的天津市公路网综合评价研究

通过建立一套现代化公路网综合评价指标体系,利用DEA模型将北京市、上海市、天津市、重庆市、江苏省、浙江省、河北省、广东省、四川省等9个省市的公路网现有情况进行综合比较,重点分析天津市公路网存在的问题并提出相应的改进措施.结果表明,该方法用于公路网综合评价是可行有效的,为天津市公路建设管理部门科学决策提供有力的理论依据和实践指导.     

聚氨酯、挤塑夹芯板力学性能的有限元分析

为解决金属面聚氨酯夹芯板、挤塑板(XPS Expanded Polystyrene)被广泛应用却没有统一的设计公式,影响此类新型材料在实际工程中应用的情况.在36个抗拉、抗压、抗剪材性试验和72个构件试验的基础上,采用有限元方法得到聚氨酯、挤塑板夹芯屋面板和墙面板的抗弯承载力及弯曲变形,并分析其受力变形机理.最终给出聚氨酯、挤塑板夹芯屋面板和墙面板的承载力设计公式.通过对试验结果和承载设计公式计算结果的比较,说明了承载力设计公式的有效性.     

Design concerns of room and pillar retreat panels

Why do some room and pillar retreat panels encounter abnormal conditions? What factors deserve the most consideration during the planning and execution phases of mining and what can be done to mitigate those abnormal conditions when they are encountered? To help answer these questions, and to determine some of the relevant factors influencing the conditions of room and pillar (R &; P) retreat mining entries, four consecutive R &; P retreat panels were evaluated. This evaluation was intended to reinforce the influence of topographic changes, depth of cover, multiple-seam interactions, geological conditions, and mining geometry. This paper details observations were made in four consecutive R &; P retreat panels and the data were collected from an instrumentation site during retreat mining. The primary focus was on the differences observed among the four panels and within the panels themselves. The instrumentation study was initially planned to evaluate the interactions between primary and secondary support, but produced rather interesting results relating to the loading encountered under the current mining conditions. In addition to the observation and instrumentation, numerical modeling was performed to evaluate the stress conditions. Both the LaModel 3.0 and Rocscience Phase 2 programs were used to evaluate these four panels. The results of both models indicated a drastic reduction in the vertical stresses experienced in these panels due to the full extraction mining in overlying seams when compared to the full overburden load. Both models showed a higher level of stress associated with the outside entries of the panels. These results agree quite well with the observations and instrumentation studies performed at the mine. These efforts provided two overarching conclusions concerning R &; P retreat mine planning and execution. The first was that there are four areas that should not be overlooked during R &; P retreat mining: topographic relief, multiple-seam stress relief, stress concentrations near the gob edge, and geologic changes in the immediate roof. The second is that in order to successfully retreat an R &; P panel, a three-phased approach to the design and analysis of the panel should be conducted: the planning phase, evaluation phase, and monitoring phase.     

山区双车道公路尾随相撞事故与道路线形的关系

为了改善我国山区双车道公路的安全状况,选取负二项分布作为回归分析的模型基础,应用同向纵坡的概念将甘肃省某山区双车道公路长为139 km的路段划分成94个同向纵坡单元,运用Stata 9.0统计软件对该路段内2003—2005年所发生的100起尾随相撞事故与8个反映道路设计要素的线形变量进行了广义的负二项回归分析.结果表明,山区双车道公路上的尾随相撞事故与累计坡长呈很强的正相关关系,累计坡长越长,尾随相撞的事故数越多.     

太阳翼基板的构型分析

针对太阳翼基板构型设计方法缺乏系统性和普适性问题,提出太阳翼基板构型的基本几何模型——可展曲面.利用类比的方法,将可展曲面上的直母线当作基板间的转动副,将直母线之间的曲面当作基板,建立可展曲面与基板构型之间的对应关系.从几何学和机构构型的角度研究太阳翼基板的折展原理,建立不同基板构型的几何特征约束方程.阐述太阳翼基板构型基本组成单元的概念并找到各基本单元,对现有的太阳翼基板构型进行分类,并对不同的构型进行分析,验证了可展曲面与基板构型的对应关系.对新型太阳翼基板构型进行分析,并建立了对应的几何模型.     

生态公路与景观的研究

公路建设的迅速发展使其对自然生态环境的影响越来越突出,这使公路设计者不得不考虑生态环境对公路建设及运营的重要意义,将人与自然、生存与发展、改造自然与尊重自然的协调关系融入到公路设计中。生态公路概念的提出正是人类生态价值意识加强的体现,对公路可持续发展的实现具有重要推动作用。在介绍生态美与生态伦理的基础上,从公路与生态环境的相互关系出发,界定了生态公路的内涵与特征,论述了公路生态景观的特点,并就生态公路设计的原则和要求进行了分析,以使生态理念渗透到包括设计、施工及运营的各个阶段,以实现公路的可持续发展,并作为生态公路和景观设计的依据。     

公路泥石流防治结构内泥石流体运动规律研究

泥石流是一种典型的公路水毁病害,也是公路水毁时主要破坏动荷载,遵循泥石流的运动规律和道路破坏特点,建立泥石流防治技术是治理公路水毁病害的关键。文章通过分析泥石流体的运动特点,提出了合理的速流槽泥石流防治结构剖面形状,根据能量守恒原理建立的泥石流体运动方程和根据平抛理论建立的泥石流体抛程计算公式,解决了泥石流防治结构受泥石流体作用力大小的计算和泥石流防治与公路水毁病害治理效果的理论判断问题,为同类型的特大型公路泥石流防治结构设计与公路水毁病害治理提供了理论依据。     

钢筋混凝土墙板内置无粘结钢支撑抗冲切研究

为了改善钢筋混凝土墙板内置单斜形无粘结钢板支撑中墙板的抗冲切性能,用开孔槽钢来抗冲切,并将钢板支撑端部的加劲肋立放设置．采用拟静力试验研究了构造对试件滞回性能的影响,基于试验结果探讨了墙板的抗冲切设计方法．试验表明:与支撑周围采用加密拉结筋的抗冲切构造相比,采用开孔槽钢可避免墙板局部冲切破坏,墙板局部冲切开裂程度大幅降低;与支撑端部加劲肋平放设置相比,加劲肋立放时可减小加劲肋端墙板与支撑间空隙的宽度,从而减小端部钢板支撑对墙板的冲切作用力;试件最终发生了墙板局部冲切破坏或支撑受拉断裂,破坏前试件滞回曲线饱满稳定;依据墙板可能的冲切破坏模式,给出了抗冲切验算方法．