近松散层煤层开采突水溃砂试验研究

发布时间：2018-02-02 23:56

本文关键词： 采煤突水溃砂假粘聚力启动含水量质量流量孔隙水压力土压力　出处：《中国矿业大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文以西部高强度开采条件下小纪汗煤矿覆岩(土)的工程地质条件、水文地质条件为背景,以颗粒流动理论、水砂运移理论为指导,通过试验研究开采引起的松散砂溃砂流动运移规律及机理。在分析总结陕北煤矿区溃砂特性、研究小纪汗矿区覆岩(土)的工程地质、水文地质特征基础上,采用室内模型试验探究突水溃砂过程中因素及机理。取得的主要研究成果如下:(1)结合煤矿溃砂案例,概括了陕北矿区溃砂的基本特性,即:水量大、含砂比高、波及地表等。详细研究了小纪汗井田的工程地质条件和水文地质条件,从水砂物源、溃砂通道和水动力条件分析了影响溃砂的因素,得出:溃砂的砂源主要来自风积砂和第四系萨拉乌苏组的冲积砂;水源主要来自萨拉乌苏组孔隙含水层;溃砂通道主要是基岩风化带薄的区域的天然溃砂通道和开采引起的覆岩破坏带。(2)对溃砂流动过程的分析表明,干砂具备较好的流动性,饱和水砂也具备较好流动性形成水砂混合流;而当砂土中具有较小的含水量时,由于毛细作用,具有一定的假粘聚力,呈现出一定的稳定性。当含水量从0过渡到饱和时,存在一个含水量,在大于该含水量后,砂土的假粘聚力变为0,水砂混合物容易形成流动。本文将假粘聚力为0时的含水量定义为溃砂启动含水量:即水砂混合物在自重应力下由稳态转变为流态的含水量。模型试验结果验证了溃砂启动含水量的存在。(3)对砂土的直接剪切试验表明,内摩擦角随着含水量的增加先减小后增加,在10%的含水量时存在最小值;假粘聚力随着含水量增加呈二次曲线先增加后减小。最大假粘聚力时,含水量随着粒径增大呈指数递减;同一含水量下的假粘聚力随着粒径有减小的趋势。(4)研究了溃砂的质量流量变化特征。水砂混合物质量流量先增大后降低后分阶段周期性降低。砂厚/水头高度的值越小,所形成的漏斗开口越大,越近似于锥形。淹没于水面以下,漏斗表面砂颗粒是在重力和动水冲力共同作用沿着坡面进行坡面流。当裂隙开启溃砂发生,裂隙周围底板孔压会瞬时响应,都会呈现不同程度的孔压降低和震荡变化。土压力增大比例约在15%-20%。底板上的土压力存在明显的土拱效应。(5)结合溃砂剖面特征二维溃砂剖面概化了溃砂概念模型,发现裂隙开启瞬时整个溃砂剖面竖直方向首先流动响应,从溃砂剖面结合孔压变化,提出通道开启后的基岩面孔压分布范围,并给出了分布计算式。参考地下水井流影响半径的分析思路,提出瞬时孔压影响半径这一概念,并得出了半经验公式。孔压引起的水力坡度比水位变化引起的水力坡度响应要早,这一改变将促进溃砂的形成。
[Abstract]:In this paper, the engineering geological conditions and hydrogeological conditions of overburden rock (soil) in Xiao-Jihan coal mine under the condition of high-strength mining in the west of China are taken as the background, and the theory of particle flow and the theory of water-sand migration are taken as the guidance. On the basis of analyzing and summarizing the characteristics of sand collapse in North Shaanxi coal mine and studying the engineering geology and hydrogeological characteristics of overburden rock (soil) in Xiaojihan mining area, this paper studies the law and mechanism of loose sand flow and migration caused by mining. The main research results are as follows: (1) combined with the case of coal mine, the basic characteristics of sand bursting in North Shaanxi mining area are summarized, that is, large amount of water. The engineering geological conditions and hydrogeological conditions of Xiaojihan well are studied in detail, and the factors influencing the sand bursting are analyzed from the sources of water sand, sand crashing passage and hydrodynamic conditions. The results show that the sand source of burst sand mainly comes from the aeolian sand and the alluvial sand of the Quaternary Salawusu formation; The source of water mainly comes from the pore aquifer of the Sarawusu formation; The analysis of the flow process of overburden sand flow in the area with thin weathering zone of bedrock and rock overburden caused by mining shows that dry sand has good fluidity. Saturated water and sand also have good fluidity to form mixed flow of water and sand; However, when the sand has a small water content, it has a certain pseudocohesive force due to the capillary effect, showing a certain stability. When the water content from 0 to saturation, there is a water content. When the water content is greater than the water content, the pseudo-cohesive force of sand becomes 0. The water and sand mixture is easy to flow. In this paper, the water content of the pseudo-cohesive force of 0:00 is defined as the initial water content of the burst sand. That is, the water content of the mixture of water and sand changed from steady state to flowing state under the self-gravity stress. The model test results verified the existence of water content at the start of sand burst. 3) the direct shear test of sand shows that. The internal friction angle decreases first and then increases with the increase of water content, and there is a minimum value when the water content is 10%. The pseudo-cohesive force increases first and then decreases with the increase of water content. When the maximum pseudo-cohesive force increases, the water content decreases exponentially with the increase of particle size. Under the same water content, the pseudo-cohesion tends to decrease with the particle size. The characteristics of mass flow change of crushed sand are studied. The mass flow rate of water-sand mixture first increases and then decreases periodically, and the value of sand thickness / head height is smaller. The larger the opening of the funnel is, the closer it is to the cone. The sand particles on the surface of the funnel flow along the slope under the interaction of gravity and hydrodynamic forces. The pore pressure of the bottom plate around the crack will be instantaneous response. The proportion of the increase of earth pressure is about 15 to 20. The earth pressure on the bottom plate has obvious soil arch effect. Combined with the characteristics of sand bursting profile, the conceptual model of sand bursting is generalized in two-dimensional sand bursting section. It is found that the vertical direction of the whole sand burst section is the first flow response, and the distribution range of the bedrock face pressure after the opening of the channel is put forward from the break sand profile combined with the pore pressure change. The concept of instantaneous pore pressure influence radius is put forward with reference to the analysis of the influence radius of water well flow under the ground. The semi-empirical formula is obtained. The response of hydraulic slope caused by pore pressure is earlier than that of hydraulic gradient caused by water level change, which will promote the formation of sand rout.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD745

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