Characteristics and close-range exploration methods of near- Earth asteroid 2016HO_(3)

The characteristics of asteroids are vital parameters for planning asteroid exploration missions.These characteristics have been explored in close range for some typical asteroids,and are summarized in the article.This allows estimates of the characteristics of asteroid 2016HO_(3),the target of the first Chinese asteroid exploration mission,Tianwen 2.We obtain 80 characteristic parameters in 9 categories and analyze their impacts on the mission.By comparing three close-range exploration modes,we provide advantages and disadvantages of each,and propose suitable methods for the exploration of 2016HO_(3).Owing to the weak gravity and small size of 2016HO_(3),a combination of multiple hovering positions and active orbiting is recommended for scientific exploration.

Application of Roadway Spray Material to Fire Prevention in Goaf Excavation

In order to reduce the risk of spontaneous combustion in goaf during goaf excavation process, polymer modified cement mortar spraying material was used to spray and seal the roadway surface. The experimental application was carried out in the upper channel 2304 of a mine in Henan Province. The test results showed that polymer modified cement mortar spraying material could effectively support the roadway and greatly reduce the deformation rate of the roadway. The best spraying thickness is 5 mm. Through the monitoring of tunnel air leakage, it is concluded that the polymer modified cement mortar spraying material can reduce the tunnel air leakage and play a better sealing effect.

Measurement of Coordinate Parameter by Multi-baseline Digital Close-range Photogrammetry System and Data Analysis for Jujube

[Objective] The aim was to explore the measurement of coordinate parameter by multi-baseline digital close-range photogrammetry system.[Method] The 3-dimensional coordinate of 8-year-old Jujube was measured by using Lensphoto multi-baseline digital close-range photogrammetry system,and through comparing with measured data of Total Station,the error and accuracy of photogrammetry data were analyzed.[Result] The absolute error of X,Y and Z coordinate was 0-0.014,0-0.018 and 0-0.004 m respectively,and the relative error of X,Y and Z coordinate was less than 0.145%.The significance test of pairs for the photogrammetry data and measured data of Total Station indicated that the space coordinate data of stumpage were accurately measured by using the multi-baseline digital close-range photogrammetry method,and the photogrammetry data meet the need of space coordinate measurement for virtual plant growth simulation.[Conclusion] This study had provided theoretical basis for the growth measurement of virtual plant growth simulation.

Research on the feasibility of storage and estimation model of storage capacity of CO_(2)in fissures of coal mine old goaf

The concept of the carbon cycle in the old goaf of a coal mine based on CO_(2)utilization and storage was put forward adhering to the principle of low-carbon development,utilization of space resources in old goafs,and associated gas resources development.Firstly,the evolution characteristics of overburden fissures in the goaf of the case was studied using a two-dimensional physical similarity simulation test,the sealing performance of the caprocks after stabilization was analyzed,and the fissures were counted and classi-fied.Then,the process of gaseous CO_(2)injection in the connected fissure was simulated by Ansys Fluent software,and the migration law and distribution characteristics of CO_(2)under the condition of gaseous CO_(2)injection were analyzed.Finally,the estimation models of free CO_(2)storage capacity in the old goaf were constructed considering the proportion of connected fissure and the effectiveness of CO_(2)injection.The CO_(2)storage capacity in the old goaf of the case coal mine was estimated.The results showed that a caprock group of“hard-thickness low-permeability hard-thickness”was formed after the caprock-fissures system in the goaf of the case tended to be stable vertically.The connected fissure,occlude cracks,and micro-fractures in the goaf accounted for 85.5%,8.5%,and 6%of the total fissures,respectively.Gaseous CO_(2)first migrated to the bottom of the connected fissure after CO_(2)was injected into the goaf,then spread horizontally along the bottom of the connected fissure after reaching the bottom,and finally spread longitudinally after filling the bottom of the entire connected fissure.The theoretical and effective storage capacities of free CO_(2)at normal temperature and pressure in the old goaf of the case were 9757 and 7477 t,respectively.The effective storage capacity of free CO_(2)at normal temperature and pressure in the old goaf after all minefield mined was 193404 t.The research can provide some reference for the coal mining industry to help the goal of“carbon peaking and carbon neutrality”.

A Comparative Experimental Study on the Blast-Resistant Performances of Single and Multi-Layered Thin Plates Under Close-Range Airblast Loading

The performance of multilayered thin steel plates subjected to close-range air blasts has been experimentally studied and compared with that of monolithic plates made of the same material and having equal mass. In present experiments, multilayered plates are in-contact four-layered thin steel plates and two types of deformation/failure modes were observed for them. Comparisons concerning deformation/failure modes, strain distributions and energy absorptions between the multilayered plate and its monolithic counterpart were conducted. It is found that the multilayered plate is much superior to its monolithic counterpart in the ability to deform against blast loading. Furthermore, under intense airblast loading, the multilayered plate can not only absorb much more energy but also effectively reduce the secondary destruction ability of structural fragments in comparison with its monolithic counterpart.

Algorithm for cavity flow in a new-born goaf and experimental verification

Prevention and control measures of spontaneous combustion of coal and gas accumulation in a goaf require an accurate description of its gas flow state.However,the commonly used fluid dynamics in porous media is not suitable for the new-born goaf with fracture cavity combination,multi-scale,and large blocks.In this study,we propose a cavity flow algorithm to accurately describe the gas flow state in the new-born goaf.The genetic algorithm(GA)is used to randomly generate the binary matrix of a goaf caving shape.The difference between the gas flow state calculated by the lattice Boltzmann method(LBM)and the measured data at the boundary or internal measuring points of the real goaf is taken as the GA fitness value,and the real goaf caving shape and the gas flow state are quickly addressed by GA.The experimental model of new-born goaf is established,and the laser Doppler anemometry(LDA)experiment is carried out.The results show that the Jaccard similarity coefficient between the reconstructed caving shape and the real caving shape is 0.7473,the mean square error between the calculated wind speed and the LDA-measured value is 0.0244,and the R2 coefficient is 0.8986,which verify the feasibility of the algorithm.

Digital close-range photogrammetric application to small-scale physical simulation experiment

In order to research the possibility of digital close-range photogrammetric surveying in small scale physical simulation experiment, physical model coinciding with engineering practice was constructed based on similar theory. The datum processing method and surveying precision of digital close-range photogrammetric were analyzed. And the function relationship between overburden subsidence factor qr and the ratio z/H of stratum horizon z and mining depth H was researched. The results show that surveying points position mean error along horizontal direction is ±0.131 mm and vertical direction is ±0.192 mm. Therefore, multi-taking station cross direction digital close-range photogrammetric can completely satisfy the precision need of physical simulation experiment. And the empirical formula can be utilized to represent evolution law of stratum subsidence factor.

Effect of periodic wide atmospheric pressure change on CO emission in closed goaf

Atmospheric pressure fuctuation is one of the most important factors afecting the climate environment and gas emission in the fre area.To obtain the infuence rule of the surface atmospheric pressure change on the gas sampling and abnormal emission in the mine closed goaf,the No.1 coal mine in Dananhu was taken as the research object.Using Fourier transform and Fisher harmonic analysis and other statistical methods,the infuence of the periodic variation of atmospheric pressure on the gas leakage and outfow in the closed goaf was studied.The results showed that there were three atmospheric pressure periods of 15.2 d,1 d and 182.2 d,and the probability was greater than 95%.The time period with the highest number of atmospheric pressure peaks was 7:00–8:00,which accounted for 20.2%of total occurrence number in a day.And the time periods with the highest number of atmospheric pressure trough were 2:00,15:00 and 16:00,accounting for 27.4%.The peak-to-trough transition time was mainly concentrated around 6 h,and the diurnal variation curve of atmospheric pressure was mainly bimodal.The atmospheric pressure change rate was mostly concentrated in 10–50 Pa/h.It was determined that the distance that the gas sampling pipe was pre-laid into the inner side of the closed wall should be greater than 44.4 m,and the CO concentration and atmospheric pressure in the closed goaf were both periodic and negative with atmospheric pressure.The research results have important guiding signifcance for the monitoring,early warning and environmental protection of the goaf.

基于静力水准的采空区地表变形监测及误差分析

目前,采空区上方的地表沉降变形监测主要采用人工水准仪测量,该方法效率低、成本高、周期长,且无法实现自动化实时监测。为解决上述问题,引入静力水准自动化监测技术,在分析静力水准自动化监测工作原理及监测系统构成的基础上,对其可靠性、误差来源及消除方法进行了深入探讨,最后结合条带采空区上方地表监测实例从监测方案、测点布置、数据分析等多个角度进行了系统研究。研究结果表明:该技术能够满足条带采空区上方地表沉降变形自动化监测的要求,可为相关监测工作提供技术支撑。

小断层影响下的采空区瓦斯运移规律研究

在煤矿开采过程中,小断层会导致采空区瓦斯聚集形成瓦斯富集区,对生产安全具有很大威胁,因此有必要研究小断层影响下的采空区瓦斯运移规律。通过UDEC数值模拟采空区上覆岩层破坏过程,从而计算小断层影响下采空区上覆岩层的空隙率,并利用FLUENT软件数值模拟开采过程中考虑小断层影响的采空区瓦斯运移规律。研究表明:①工作面距离小断层20 m远处,小断层从顶部首先出现滑移现象,采空区上覆岩层的位移开始受到断层的影响;工作面到达断层时,由于断层滑移,上盘岩体在断层面滑移产生回转现象,支撑着采空区岩层,覆岩垮落位移量出现大幅度减小,并且岩层垮落出现滞后现象;小断层的影响范围有限,工作面过小断层60 m之后,采空区上覆岩层位移规律逐渐恢复正常。②通过分析含小断层采空区上覆岩层位移特征,得到了采空区上覆岩层位移及其拟合公式,计算得到了三维空隙率分布规律:垮落带范围内,覆岩空隙率在4个隅角位置最大,并且断层靠近进回风巷的位置也出现了空隙率增高;裂隙带范围内,除断层靠近进回风巷的位置空隙率较大,其他位置空隙率相对较低且变化不明显。③获得了小断层影响下的采空区瓦斯运移规律:在工作面距离断层50 m远处,采空区瓦斯运移几乎不受断层的影响;在工作面推进至断层时,瓦斯沿着断层及其附近的高空隙率覆岩产生的优势逃逸通道向采空区深部运移,同时上盘的瓦斯也向深部转移导致大量瓦斯积聚在断层下盘,可能导致瓦斯随漏风流入工作面及回风巷;在工作面过断层50 m时,采空区瓦斯继续向上隅角附近转移;工作面过断层100 m时,采空区上覆岩层瓦斯运移出现回转现象,上隅角和下盘垮落带瓦斯体积分数高。

深部条带老采空区覆岩破坏多参量监测研究

针对深部条带老采空区覆岩移动变形问题,确定了裂隙发育、拉压应变、岩层物性等主要参量指标,采用钻孔电视法、分布式光纤感测法、井间电法CT、微震法构建了采空区覆岩“点-线-面-体”多参量监测模式;运用该监测模式对工程实例进行实测分析,获取了采空区覆岩全方位、多层次的移动破坏特征,得出覆岩裂隙多集中在465 m以下,少量空洞位于垮落带及煤柱上方靠近采空区侧,煤柱塑性区范围约8 m的结论,综合判定采空区覆岩结构可在长时间内保持相对稳定。结果表明:“点-线-面-体”多参量监测模式在内容上能够有效涵盖条带采空区覆岩移动变形的各参量指标,时空上可实现点(静态)、线(动态)、面(静态)、体(动态)相互结合的全过程监测,监测结果间能相互验证,可满足深部条带采空区覆岩移动变形监测要求。

地空瞬变电磁法在煤矿采空区中的应用效果分析

煤矿采空区一直是工程中难以解决的重点难题之一,现工程中一般是结合开采资料及煤层分布进行综合分析。由于大型煤矿多采用自然塌落法来处理采空巷道,而非金属类矿山的填充法,随着时间的推移,会出现非常多的塌陷,导致采空区内部情况非常复杂,难以查清。尤其是在老旧的煤矿当中,由于过去技术落后,矿洞测绘资料存在一定的失真,导致很难明确定义现采空区的具体范围,为工程的顺利开展提出了重大的课题。结合黑龙江依兰煤矿(日伪时期的开采老旧煤矿采空区),在地形地貌条件特别差,人难以攀登的条件下,应用地空瞬变电磁法,初步解决了该采空区的范围和规模。

瞬变电磁法在煤矿灾害勘察评价的应用案例分析

为进一步明确某现状矿区内易发生地下水危害的区域,采用瞬变电磁法对煤矿地下环境进行勘察,勘察结果表明矿区内可能存在一含水构造带,该构造带纵向基本贯穿标高550~-200 m,可能会对采空区或者巷道的开发使用带来危害。此外在瞬变电磁法对矿区进行勘察时,采空区往往表现为低阻包围着的中高阻特征,而含水裂隙往往表现为低阻特征。本文研究内容对于指导后续矿产资源的开发具有一定指导意义。

基于层次分析法与频率比模型的采空塌陷危险性评价

采空塌陷危险性评价是编制地质灾害防治规划、开展地质灾害防治与监测预警工作的重要依据。本文采用层次分析法与频率比模型相结合构建了采空塌陷危险性评价模型(AHP-PF组合模型)。以沈阳市蒲河-清水矿区为例,考虑了地质条件、地表特征、开采条件等3方面影响因素,选取了第四纪覆盖类型、第四纪松散层厚度、地质构造复杂程度、可采煤层顶板强度指标、煤层倾角、地表沉陷速率、采深采厚比、采空区叠置层数等8个评价指标,利用AHP-PF组合模型计算各指标权重及频率比,最后进行采空塌陷危险性分区。评价结果表明,采空塌陷危险性高区主要集中在采深采厚比小、沉陷速率大及目前仍在开采的区域,该区域是地质灾害防治、搬迁避让的重点区域。

采空区治理用尾矿砂注浆材料的制备及性能研究

为了解决常用的矿山采空区治理用注浆材料凝结时间长、析水率高、结石率低、水下浇筑时水泥流失量大、硬化后易脱空等问题,制备了一种尾矿砂注浆材料,并通过添加性能调节剂CA-Ⅳ、调整原材料配比对其性能进行了优化。结果表明:优化后的尾矿砂注浆材料工作性得到明显改善,凝结时间大幅缩短,24 h竖向膨胀率、结石率和28 d抗压强度均有大幅提高,水泥流失量显著降低。

弹−塑性基础边界两侧采空(留煤柱)基本顶板结构初次破断特征

为了研究两侧采空留煤柱工程条件下基本顶板结构的断裂位态及工程指导意义,构建考虑实体煤弹塑性变形与两侧煤柱宽度及支撑能力弱化的基本顶板结构双塑化基础边界力学模型,基于有限差分算法与主弯矩破断准则系统计算了在非对称煤柱区和长边实体煤区的断裂线形态、区位属性及整体位态特征,并从7个层面、横纵向4对区域与传统模型对比,阐明新模型所得新结论及工程意义。结论如下:(1)两侧非对称煤柱参数对长边实体煤区域的基本顶主弯矩及破断位置影响小,但分别显著影响煤柱区的主弯矩大小、位置及断裂形态。两侧煤柱区(较强/宽煤柱区+较弱/窄煤柱区)基本顶断裂线形态有3类演化模式,随基本顶厚度及弹模增大而煤柱宽度、支撑能力及悬顶跨度减小,其变化规律为:非对称的“连续单弧形+连续单弧形”→“连续单弧形+开口间断双短弧形”→非对称的“开口间断双短弧形+开口间断双短弧形”。(2)长边实体煤区基本顶的断裂线主要有3类区位属性,随基本顶厚度及弹模增大而实体煤的塑性区宽度、塑化程度及悬顶跨度减小,其演变规律为:断裂线在塑性煤体区(C-S式)→弹塑性煤体分界区(C-TS式)→弹性煤体区(C-T式);(3)考虑断裂线区位属性,随基本顶厚度和弹模增大而煤柱宽度、支撑能力及悬顶跨度减小的基本顶全区域破断模式及演变规律为:C-S式的■→C-TS式的■→C-T式的■→C-T式的■→C-T式的■。针对研究两侧采空(煤柱)基本顶板结构破断的3类力学模型,从7个层面对比了3类模型的重要区别,从横向4个区域(开采区域的前方与后方、两侧煤柱区)与纵向4个区域(非对称遗留煤柱下伏、下伏开采空间出/进煤柱/体)阐明了其重要工程作用。

采空区地表沉陷计算预测方法研究

本文以某煤矿开采形成的采空区范围为研究区,在搜集煤层赋存情况、现有采空区分布情况的基础上,选取岩层合理的物理力学指标,利用比较常用的概率积分法、数值模拟法对采空区的下沉值、水平变形、最大地表竖向变形等进行预测模拟,从而预测研究区地表变形情况。煤矿采空区地表变形的预测,是工程建设场地适宜性预测评估结论的重要依据。

采空区场地高速铁路路基动力响应离散元数值模拟分析

目的高速铁路穿越采空区场地存在重大安全隐患,为探讨采空区场地高速铁路路基的动力响应规律,方法利用3DEC离散元软件建立17组采空区场地高速铁路路基数值模型,分析不同列车荷载作用下路基内部的沉降变形和动应力分布规律,对比分析无砟轨道和有砟轨道路基内部动力响应的分布差异,分析采空区开采宽度、厚度对动力响应分布规律的影响。结果与无砟轨道相比,有砟轨道路基内部的动应力幅值明显更高,但其动应力的衰减速率也更高;动应力、动位移的时程曲线沿着路基深度方向出现不断增大的相位差;路基内部动位移幅值随着荷载作用时间增加而逐渐增大,但增大的速度不断降低,动应力幅值基本保持不变;动应力、动位移幅值与列车轴重存在明显的线性关系,随着轴重增加而线性增大;采空区开采宽度、厚度越大,列车荷载造成的动位移幅值也越大,但当开采宽度大于一定数值后,动位移幅值反而出现减小趋势。结论列车荷载、路基轨道类型和采空区场地的差异都会对路基内部的动力响应分布情况产生影响,研究结果可为采空区场地高速铁路的安全运行提供理论参考。

基于Mathews稳定图法的采空区稳定性分析

采空区稳定性关系到矿山生产安全。为了方便准确地对采空区稳定性进行分析,以指导矿山安全生产。以某铅锌矿的某采空区为例,获取了采场的RQD值、节理组数、节理粗糙度、节理蚀变度等采空区力学指标或结构参数,分别计算出采空区的修正的岩石Q值、应力系数、节理方位系数、重力调整系数,进而计算得到采场的稳定数;统计了采空区的长度、高度和宽度等形状参数,以此为基础计算得到采空区的壁面积和壁周长,进而计算得到采空区的形状因子,以采空区的稳定数和形状因子为依据,在Mathews稳定图确定采空区所在的点,根据落点位置确定采空区稳定性,进而指导矿山安全生产。实践证明,Mathews稳定图法对采场稳定性分析是准确的。

岩块尺度对采空区煤自燃区域的影响研究

为探究综放采空区岩块尺度对煤自然发火的影响,采用Fluent软件数值模拟不同直径岩块条件下采空区的煤自燃规律,分析采空区氧浓度场和风速场,分别以氧气体积分数和风速为指标,确定采空区氧化带面积并以二场叠加场作为采空区煤自燃危险区划分标准,研究煤自燃危险区域与岩块直径的关系。研究结果表明:当岩块直径由0增加到10 m时,以氧气体积分数为指标,氧化带宽度变小,面积由5563.84 m^(2)减至2602.69 m^(2);以风速为指标,氧化带面积由3376.60 m^(2)减至1262.95 m^(2);将2种指标确定的氧化带进行叠加得到煤自燃危险区,随着岩块直径的增加,其面积由1854.04 m^(2)减至552.91 m^(2),煤自燃危险区最大宽度由20.40 m缩减至9.06 m。研究结果可为采空区煤自燃发火区域的确定提供参考。