【作者】 马长年；

【导师】 徐国元；

【作者基本信息】 中南大学 ， 工程力学， 2011， 博士

【摘要】 金川二矿区是金川集团最大的主力矿山,为了在矿岩稳固性差且地应高的采矿环境下安全有效回收宝贵资源,二矿区采用机械化下向分层水平进路胶结充填采矿法开采。多年的生产实践证明,使用该方法开采二矿区矿体是安全、经济和高效的。随着二矿区开采深度向下延伸,地层中的原岩应力呈随开采深度增加而增大的趋势。进路胶结充填体是采矿生产作业的直接顶板,关乎人员和设备安全、企业效益。然而,在高水平构造应力条件下,充填体的稳定性机制至今仍缺少深入系统的研究,探索下向分层充填法中充填体的力学行为及其作用,具有重要意义。本文通过现场调研,采用理论分析、室内材料试验、基于FLAC3D二次开发的三维力学数值分析相结合的方法,主要根据金川二矿区下向分层充填采矿的生产实践,对充填体力学行为及其作用进行了系统研究,主要研究内容如下：(1)采用结构理论中的三弯矩方程,研究相邻分层进路不同布置条件下,胶结充填形成的人工假顶结构(注：抽象为连续梁)中的内力(M、FQ)状态,得到了相邻分层进路垂直交错布置、相邻分层进路斜交及平行交错布置下,人工假顶结构内力的分布状态方程,为人工假顶设计逐渐由经验设计阶段向定量设计过渡提供了可能。初步揭示了竖向约束(支座)的变化,对人工假顶内力变化产生影响的趋势；建议设计人工假顶时,应采用合理技术措施,如留中间支座、相邻进路充填体采用抗剪连接,以期消除假顶截面中因最大弯矩和最大剪力过度集中而产生的张拉、剪切失效的隐患。(2)目前大多数简化充填体模型没有考虑带筋充填体中的材料构造,难以适应因采动影响产生的复杂加载方式,也无法客观反映加载路径变化产生的影响。针对这些简化模型存在的问题,本文根据金川二矿区生产实际,把进路充填体的主要力学作用,归结由砂浆固结后形成的胶结体和其中的构造钢筋(吊筋和底筋)共同承担,率先提出金川二矿区充填体的基本结构是一种二元结构,也就是,充填体基本结构由砂浆胶结体连续介质(简称“充填体”)和连续介质中的钢筋构件组成；进一步地,根据充填体内钢筋构件主要受拉和受压的力学特点,利用FLAC3D中锚索结构单元,对钢筋构件进行力学数值模拟,进而建立起更接近于实际情况的基于二元结构的充填体FLAC3D数值力学模型。(3)利用Google Earth(GE),通过在线提取二矿区周围地形地表高程的方法,获得了一定网度的地形三维坐标,形成矿山外围地形图及模型地表DTM模型。解决了已收集地表地形数据范围不足以覆盖模型表面的问题,为二矿区大范围全局建模提供了前提条件。利用矿业软件Surpac建立了金川二矿区富矿、贫矿、地表等部分的实体模型、含矿块体单元数据库、地表块体模型及各类约束条件。采用分步建立各部分块体模型的方法,通过坐标变换、数据圆整等措施保证各部分块体模型衔接部分精确对接,再将Surpac含矿块体模型、地表块体模型数据转化FLAC3D数据,加上发散过渡部分最终生成FLAC3D力学模型。克服了直接采用FLAC3D建立复杂地质体模型的困难,为利用FLAC3D程序进行矿山生产过程的力学仿真奠定了基础。(4)应用VC++、数据库技术、Fish语言和FLAC3D相关命令集,开发出FLAC3D力学仿真程序代码生成系统(generating code system for FLAC3D, GCS)。该系统按空间、次序、结构功能及工程地质体属性,对金川二矿区回采、充填等生产过程进行剖分,形成可编程的组件；着重解决了模型单元质心定位、单元捕捉、重组和应用程序变量到FLAC3D变量、函数、语句、数据结构之间映射等问题；开发的GCS应用程序,以模型单元数据库为数据源,通过一系列与用户交互的界面,由用户对回采过程所需步骤和参数进行选择和确认,并将这些步骤和参数传递给仿真代码生成系统,由系统自动完成FLAC3D力学仿真代码的生成,能实现金川二矿区生产顺序、回采过程、充填进路布置、钢筋布设、充填等主要生产过程的三维力学仿真。该系统可大大提高编制FLAC3D三维力学仿真代码的效率,降低程序编制的出错率。(5)基于金川二矿区生产过程的FLAC3D数值模拟,对下向分层充填采矿的采动影响下,采空区中胶结充填体、临时矿柱、近矿围岩等介质的应力重新分布特点、位移规律、地表岩移趋势、充填体破坏状态、钢筋受力状态变化等因素,以及这些因素之间相互作用的力学行为,进行了系统分析和归纳,获得结果初步揭示了维护金川二矿区充填体稳定性的机制。(6)通过室内试验,对比研究不同充填材料在布筋和不布筋两种构造下所形成试件的抗折强度,进一步对比研究了有/无抗剪连接梁拼板试件的抗剪强度,结果表明：①布筋可明显提高试件的抗折强度,加筋试件破坏特征更接近于弹塑性材料,而无配筋试件的破坏特征表现为脆性材料。②同不设置抗剪连接筋的梁拼板试件相比,在梁拼板试件增设抗剪连接筋,明显增加了梁充填体界面之间的抗剪强度；适度施加正压力,对梁充填体界面之间的抗剪强度有一定影响。材料试验结果间接证明：在进路充填体中配筋,以及在同一分层相邻进路充填体界面之间增设抗剪连接筋,对提高用作人工假顶的充填体强度和稳定性,起着积极的重要作用。本文密切结合现场重要技术难题,立足于学科前沿,综合运用结构理论、材料试验、GE和三维矿业软件、基于FLAC3D二次开发的三维力学数值仿真等方法,建立了一整套针对下向分层充填采矿之复杂生产过程的三维力学分析方法,获得了系统性的有益成果,具有重要的理论意义和工程应用价值。更多还原

【Abstract】 Jinchuan No.2Mine was one of underground mines with the hardest mining conditions all over the world. Its rockmass stability was extremely poor, and it was subjected to higher tectonic strata stress. In order to achieve the goal of efficiently extracting mine deposit under safe mining operation, different mining methods including top slicing and caving, cut-and-fill mining and underhand cut-and-fill mining, had been carried out in decades, and the mechanized underhand cut-and-fill mining with drift (MUCFMD) was finally selected as the mine’s primary mining method due to the method’s merit in mining productivity and operation safety.With the mining levels extending downwards, the strata stress increased gradually with the increase in the mining depth. For MUCFMD, the backfilling was the artificial roof of mining drift which was located in the next mining slice, and its stability directly influenced the safety of miners and operation devices. Whereas, there still was lacking in systematic insight into the stability mechanism of backfilling under the mining conditions of higher tectonic strata stress. It was positive that the investigation on the mechanical behaviour and function of backfilling was carried out.Mainly based on the in-site mining engineering situation in Jinchuan No.2mine with MUCFMD in the extremely poor mining conditions, the study on the mechanical behaviour and function of backfilling was systematically carried out in the work by means of comprehensive ways, mainly including field surveying, theoretical analyse, material model test, and3D numerical modelling with FLAC3D and FLAC3D secondary development programmed by the author. The main research contents and conclusions were as follows.(1) Under change in the layout of mining drifts in conjunctive mining slices, the internal forces(M, FQ) state in the artificial roofs, which were supposed as continuous beam structure, was studied according to the ’three-moment equation’of the structural theory. The equations of internal forces were derived. Further, the quantitative distribution of internal forces for three types of artificial roofs, which respectively corresponded to the three drifts layout (the drifts in upper slice perpendicular to those in next slice, the drifts in upper slice parallel to those in next slice, and the drifts in upper slice oblique with those in next slice), were given. The tension or shear failure in artificial roof adjacent to intermediate supports, which actually were temporary ore ribs or artificial ribs made of backfilling, might be controlled or eliminated by optimizing the span among the supports.(2) As most simplified backfilling models did not consider construction of steel in thin reinforced backfilling, it was difficult for the simplified models to resolve and reflect the change in both stress state and loading paths of steel parts in backfilling resulting from mining operation in extreme geological conditions. For Jinchuan No.2mine, its basic mechanical structure of backfilling was abstracted as a dualistic structural model by author. That is, the backfilling consisted of continuous-homogeneous cemented motar and steel rod, and both of them together undertook the loading. The "cable" element of FLAC3D Platform was acted as steel parts in the mine’s backfilling, and the change in both stress state and loading paths of the steel parts was numerically simulated. The numerical modelling result for steel parts in backfilling was basically proved by the steel deformation or failure found from the in-site survey.(3) Using Google Earth(GE), the three-dimensional coordinates of topography had been obtained by extracting the elevation of surface around the Jinchuan No.2mine in term of a certain degree of flat networknet on line. Further, topographic map and DTM model of surface around the mine were established. These works addressed the problem that the range of data collected were insufficient to cover the surface of model, and provided the preconditions for global modeling of Jinchuan No.2mine.Utilizing mining software Surpac established rich ore model, lean ore model of Jinchuan No.2mine, and other parts of the solid model surface, the ore-bearing block unit database, and various constraints. Using step modeling approach, by coordinate transformation, round of data and other measures to ensure the various parts of the whole block some accurate docking model of convergence, then transforming Surpac ore-bearing block model, surface block model data into Flac3D, adding some of the resulting divergent transition, final the Flac3D mechanical model was established. These methods overcame the difficulties using Flac3D to establish complex geological models directly, and make the foundation to apply Flac3D to simulate the production process of mine.(4) Through the secondary development of Flac3D, the Generating Code System for Flac3D, GCS, had been developed. The programmable components formed by dividing the mining&filling process of Jinchuan No.2mine according space position, order, structural function and attribution of engineering geological body were researched. The problem of the model unit centroid localization, unit capture, restructure, application variables, Flac3D variables, function, sentence, the mapping between data structure etc were resolved.Developed by VC++, This application program used the database of cell model as a data resource, through a series of steps, the process and parameters of excavation process necessary can been selected and confirmed, which can been transferred to the simulation code generation system, and then the Flac3D codes would be generated by the application program. By the system, the three-dimensional mechanical simulation for the main production process of Jinchuan No.2mine, such as production order, mining process, layout of mining drifts, layout of reinforcement, filling etc., can be realized. The system can greatly improve the efficiency and reduce the error rate of programming the3D mechanical simulation code.(5) Through the more accurate simulation by Flac3D for the production process of Jinchuan No.2mine, the mechanical behaviours associated with the backfilling of No. mine, such as the features of the stress redistribution and the law of the displacement movement in the backfilling, pillar and near-ore rock, the law of the rock movement on the surface, the destructive state of backfilling, the stress state and changes of force in the reinforcement, were fully described and induced, and the backfill stable mechanism was revealed.(6) Two sorts of comparative investigation into mechanical performance of physical models made of different backfill motars, including beam models (BM) and slab models (SM) formed with joining three pieces of beam together, was carried out by indoor model test. In BM sort investigation, the flexural strength of beam models, including reinforced beam models (RBM) and plain beam models (PBM), was comparatively tested and analysed. The results of BM sort showed that the flexural strength of RBM was obviously bigger than that of PBM the failure characteristics of RBM was closer to that of elastic-plastic materials, and the failure of PBM was characterized in brittle fracture. In SM sort investigation, the shear strength of weak interfaces existing in slab models, including the slab models with reinforced interfaces by shear connecting element (RSM) and other slab models with plain interfaces existing naturally (PSM), was comparatively tested and analysed as well. The results of SM sort showed that, under like conditions, the shear strength of RSM was bigger than that of PSM. It was good for backfilling stability to be improved by suitably reinforcing drift backfilling and by suitably installing shear connecting elements along interfaces between drift backfill.This paper closely combines the important technical problems of the engineering practice, stands on subject frontier, comprehensively uses the means of material model tests,3D mining software, secondary development of Flac3D and3D numerical simulation of mechanics, establishes a set of3D mechanical analysis method for the complex production process of mine, obtains systematic beneficial results, has important theoretical significance and engineering value.更多还原