【作者】 郝兵元；

【导师】 康立勋；

【作者基本信息】 太原理工大学 ， 岩土工程， 2009， 博士

【摘要】 煤矿开采对矿区土地造成的损害由来已久,采用长壁式综放开采的薄基岩厚表土煤层,有其独到的特点,对地面造成的损害较之常规的开采更甚,而对于此类煤田覆岩移动破坏对地面土壤质量影响的研究却鲜见报道。本文在总结已有研究成果的基础之上,结合大型煤炭企业潞安司马矿区的实际情况,通过现场调研与观测、实验室物理模拟、计算机随机模拟、地面现场实测和理论预测、现场取样试验分析、理论分析等大量工作,系统研究了司马矿1101工作面厚表土薄基岩煤层开采的岩层移动规律、地面沉陷特点以及由之引起的土壤质量变异规律,为开采损害的防治和灾后恢复提供理论依据。论文的创新点如下:(1)对厚表土薄基岩开采沉陷区农田土壤破坏规律与煤矿开采过程岩移规律相互关系进行了综合研究,对两者间的相关性进行了探讨。(2)首次分析了开采沉陷预计过程中的相关计算参数的可靠性,对概率积分法预测的参数取值进行了改进,并用随机模拟的原理给出了取值方法的具体实现过程,经实证预测效果良好。(3)针对深部岩层移动难于监测的问题,创造性地设计了一种用于监测岩层移动的传感器,设计了监测系统以及提出系统安装测试方法,并推导出了由微应变量测量大变形量的理论表达,为进一步的实验室及工业试验提供了基础。取得了以下主要成果与结论:(1)对于厚表土浅埋薄基岩,若表土为松散砂土(假设无自承能力),基岩达到一定厚度才能形成自身稳定结构。若基岩上方冲积层有一定厚度的粘土层,由于粘土层有一定的承载能力,基岩承载能力增强。当薄基岩厚度一定,随粘土厚度增加,基岩与粘土组合后能形成稳定结构,承载能力增强,使工作面来压趋于缓和。(2)为了实现对深部基岩和表土层的动态移动进行有效观测,创造性地提出了一种新的位移传感器设计方法。导出由微应变量测得大变形量的理论计算与测量方法,研究设计了一种基于该岩层位移传感器的配套监测方法,论证了其可行性。(3)通过模拟试验发现,薄基岩、厚表土层条件下煤层1101工作面开采后,开采地表下沉盆地更为陡峭,下沉系数偏大,而水平移动系数偏小。具有区别与一般地质采矿条件下的一些独特现象,如下沉曲线在拐点附近变化较快,表现为曲线较陡,同时,边界处收敛很缓慢,表现为边界范围扩展,水平移动系数偏小。岩层以一定的断裂角断裂且向上传递,采空区上方岩层下沉值大于地表下沉值,而煤壁上方岩层下沉值较小。(4)对司马矿区首采工作面进行了地面沉陷监测,得到厚表土薄基岩煤层地面沉陷的规律和特点:地表受采动影响极为敏感,地下开采活动产生的影响很快传递到地表,地表移动的初始期很短,地表快速进入沉降活跃期,移动与变形极为剧烈且集中,采动区地表移动与变形持续时间长,地表裂缝比较发育。煤层开采后,地表移动变形的影响范围变大,采空区边界附近地表下沉盆地陡峭,移动变形显著且分布集中,采空区边界以外地表下沉盆地平缓,即表现为:地表移动变形在拐点内侧下沉值较大,在拐点附近变形发展较为迅速,曲线较陡,而在拐点以外较远区域沉陷变形曲线收敛较慢,但影响范围向外扩展较远。表现在岩移参数上,地表下沉系数较大,达0.94,主要影响角正切tanβ偏大,地表下沉速度偏大,动态变形值大,地表移动剧烈。(5)首次应用可靠性理论分析了概率积分法开采沉陷预测过程中参数的可靠性,针对预测中把具有一定分布规律的随机变量仅取固定值的问题,首次提出了采用随机变量来动态确定预测参数,并用随机模拟的方法改进了开采沉陷预计的参数变量,经检验对1101面的预测结果与实测值具有较好的吻合性。(6)开采沉陷显著影响了农田表层土壤的物理特性;沉陷区农田的上中部有水土流失加剧,养分流失加剧的趋势,而沉陷区低部则积聚了水土侵蚀下移的土壤养分;在土壤物理特性中,在沉陷形成的两年内,受其影响较大的是土壤容重,其次土壤含水量和孔隙度。开采沉陷显著影响沉陷区农田表层土壤的化学特性,在土壤化学特性中,受开采沉陷影响最大的是土壤速效磷,其次是土壤速效钾,再次是土壤全氮和土壤有机质,而土壤酸碱性受其影响小。土壤肥力质量来看,沉陷农田初步稳定后(沉陷1~3年),还可以提供植物生长所需要的土壤条件;从农事操作来看,则仅仅是加大了农事操作工作量。因此,沉陷区农田应在现存破坏的基础上,进行合理的施肥和地表保水措施,继续发挥沉陷区农田的生产潜力。(7)就开采条件和土壤沉陷破坏相关性给出了解释,指出土壤的物理性状变化是由土壤几何变形引起的,水平变形和水平移动引起的土壤拉应力和压应力的变化,导致容重和孔隙度变化;裂缝的发育是导致土壤水份变化的最直接原因,上覆岩层的导水裂隙带的上升高度和发育程度也是土壤水份变化的重要原因。土壤肥力质量的变化是由于土壤宏观形态的改变造成地表径流的不均衡性,导致水土流失,土壤养份随之迁移至盆地底部所致。(8)针对司马矿区的特殊情况,给出了几种适宜选择的农田复垦方式和生态规划建议,供复垦工程参考。更多还原

【Abstract】 Damages to soil caused by mining have long been a problem. The use of fully mechanized long wall caving mining in the coal seam of thin bedrocks and thick surface soil, due to its unique characteristics, causes more severe damages to the soil surface than traditional mining, and yet few reports have been made on the research on the influences of overburden movement destruction on soil quality.On the basis of summing up the existing research results and in combination with the actual situations of Sima Coal Mine of Lu’an Mining Group, a large-sized coal mining enterprise in China, this thesis, through on-the-spot investigation and observation, physical simulation in laboratories, computerized random simulation, surfece measurement , theoretical estimation, test and analysis of site samples, theoretical analysis, studies, in a systematic manner, the law of strata movement, features of surface subsidence, and the law of soil quality variation in Coal Seams # 1101 in Sima Coal Mine, which features thick loess and thin bedrock, so as to provide theoretic bases for .the prevention of mining damages and the afterward restoration.New points of the thesis are as follows:(1) A comprehensive study is carried on the interrelations between the law of soil destruction in mining subsidence area and the law of rock movement in the mining process, and a brief exploration is done between their correlations.(2) For the first time, the reliability of the interrelated calculated parameter is analyzed in the mining subsidence prediction process, and the choosing methods are improved. The specific choosing methods are given based on random simulation theory, which have been proved to be good through practice.(3) For the problem of deep rock movement being difficult to be monitored, a sensor, monitoring system and system installation and measuring method are creatively designed to monitor rock movement; meanwhile, a theoretical description of measuring large-scale strain via micro strain is deduced,so that foundation is laid for further laboratory and industrial tests.The following main results and conclusions have been achieved:(1) For the shallowly-buried thin bedrock with thick loess, if the surface sand is loose(without self loading capacity), the bedrock will not form self stable structure until it reaches certain thickness. If the clay layer of certain thickness exists above the upper shock ply of the bedrock, its loading capacity is increased because the clay layer is possessed with certain loading capacity. The combination of bedrock of fixed thickness and increased thickness of clay layer will form stable structure with increased loading capacity and reduced and smooth pressure to the surface.(2) A new displacement sensor is innovatively designed to effectively monitor the dynamic movement of the deep bedrock and surface soil. Theoretical calculating and measuring methods are deduced to measure large-scale strain via micro strain; a monitoring method is studied based o the sensor of movement in that layer, and its feasibility is expounded on. (3) Simulated tests have discovered a steeper surface subsidence basin, a larger subsidence coefficient, yet a smaller horizontal movement coefficient after the Coal Seam 1101 is mined under the condition of thin rock and thin loess. Some unique features are observed, which are different from the features under the normal geological conditions: subsidence curves changes rapidly around the拐点with a steep curve; meanwhile, the convergence takes place in a very slow manner at he boundaries, which is shown in extended boundaries and smaller horizontal movement coefficient. The rock layers cracks with certain angles and is spread upward. The upper rock layer subsidence value is bigger than the surface value with a relatively small rock layer subsidence value above the coal wall.(4) Through monitoring the surface subsidence of the primary mining phase of Sima Coal Mine, the laws and characteristics of the surface subsidence of coal seam of thick loess and thin bedrock is discovered:Surface is very sensitive to mining influence in that the influence of underground mining activities are soon spread to the surface, and, due to a short initial surface movement period, surface in a very short time enters the subsidence-active period with severe and centralized movement and deformation, long-lasting surface moving and deforming span of the mining area, and relatively developed surface cracks. When the seam is mined, the influencing area of the surface movement and deformation is expended, the surface subsidence basins become steep surrounding mined boundaries with obvious and centralzedly-distrubited movement and deformation, and the surface subsidence basins become smooth outside mined boundaries, which is reflected in the following: the subsidence value is relatively large in the internal side of the inflection of the surface movement and deformation; in the area surrounding the inflection, the curve develops more rapidly, thus a steep cure, while in the areas further away from the inflection, the subsidence deforming curves convergence slowly but with further extending area. Reflected in the rock movement index, the surface subsidence index is relatively large, reaching 0.94, with a large tangent B, subsidence speeds, and dynamic deforming values, resulting in severe surface movement.(5)Reliability of the parameter in the calculating process of mining subsidence is analyzed for the first time by adopting the Theory of Reliability, and the dynamic determination of expected parameter by random variable is for the first time put forward in connection with only fixed value being chosen for random variables with certain distribution laws. In addition, the estimated parameter variables for mining subsidence is improved by adopting random simulation method, which has been proved to be in relatively good in accordance with the real value of Seam 1101.(6)Mining subsidence has significantly influenced the physical features of the surface soil; Water and nutrition losses become severe in the upper and middle parts of the farmlands in the subsidence area, while soil nutrition is centralized in the low subsidence area; Regarding physical properties of the soil, within two years after the formation of subsidence, soil bulk density is affected the most, followed by water contained in the soil and its porosity. Regarding the chemical features of the soil, soil available p is most affected, followed by available potassium, and total soil nitrogen and organic matter, with acidity and basicity least being affected. As far as the soil fertility is concerned, after the stabilization of subsidence(1-3 years), necessary soil conditions are able to be provided for the growth of plants; with regard to farming operation, only operational load is added Therefore, for the farmlands in the subsidence area, proper fertilizing and water protecting measures should be taken despite the existing destruction, so as to continuously bring into play the potential productivity of the farmland.(7)Interrelation between the mining conditions and soil subsidence destruction is interpreted, and the law is pointed that physical changes in the soil is resulted from its geometrical deformation in that horizontal deformation and movement may result in the change in the tensile stress and compressive stress of soil, which, in turn, results in the change in volume weight and extent of porosity. Development of cracks constitutes the most direct reason for the change of water in the soil, besides which, rising height and developing level of the water flowing fractured zone in the upper rocks are also important. The change in the soil fertilizing quality due to the imbalance of surface runoff, resulted from soil macro formation change, brings about water losses, thus leading to the movement of nutrition to the basin bottom.(8)In consideration of the specific conditions of Sima Coal Mine, several suitable reclaiming modes and ecological designing suggestions are raised for project references.更多还原