【作者】 索永录；

【导师】 石平五；

【作者基本信息】 西安科技大学 ， 安全技术及工程， 2004， 博士

【摘要】 坚硬特厚煤层采用综采放顶煤方法开采时,顶煤在矿山压力作用下得不到充分破坏,造成资源采出率低,并会使工作面出现比较剧烈的矿压显现而严重威胁工作面的安全。坚硬煤层综放工作面安全、高效开采的关键问题就是要有效调控顶煤的破坏过程,顶煤预先爆破弱化技术是解决这一问题的有效方法。坚硬煤层综放采场顶煤系统在时间和空间上具有连续动态性,顶煤预先弱化是坚硬顶煤破坏全过程的重要组成部分,顶煤预先弱化的实质就是人为地预先使其整体强度降低。坚硬顶煤是指在不对顶煤进行专门处理时,其放出回收存在明显困难的一类顶煤,通过对坚硬顶煤破坏和垮冒特性的分析,给出了顶煤放出的必要条件,提出了坚硬顶煤模糊综合评价的识别方法和考虑宏观结构弱面影响的顶煤初始损伤的计算方法。 坚硬顶煤预先弱化爆破是一种井下特殊爆破形式。实验研究表明,坚硬煤体爆破时应力波峰值压力按幂函数形式衰减,煤体爆破的波耗损大于一般岩体的波耗损。在此基础上,结合现场试验观测,提出了可适用于现场工程实际的坚硬顶煤弱化爆破粉碎区、裂隙发育区和裂隙区范围的计算方法;利用岩石爆破裂纹密度weibull分布假设和等效应变原理,提出了坚硬煤体弱化爆破应变波峰值体积应变随比例距离具有幂函数衰减规律的推断,导出了坚硬顶煤弱化爆破损伤破坏程度函数的表达式。改变顶煤的整体结构力学特征是坚硬顶煤预先爆破的主要弱化作用形式,由此建立了综放开采坚硬顶煤弱化爆破后顶煤的整体结构力学模型和破坏条件,通过顶煤整体刚度变化的分析,证明了按排布孔的科学合理性,推导出了支承压力作用下顶煤体统计损伤变量的表达式。在坚硬煤层综放采场,一般中位岩层中形成“悬臂”式小结构,高位岩层中形成“砌体梁”一类的大结构,采场上覆岩层活动由中位和高位两个关<WP=5>键层所共同控制,剧烈周期来压是两个关键层的复合效应引起的,但来压显现的剧烈程度一般主要取决于工作面上方顶煤的整体力学性态。比较普遍的存在剧烈的周期来压现象是坚硬煤层综放面矿压显现最显著的特点,顶煤预先爆破弱化由于降低了顶煤的整体刚度和强度而明显影响工作面的矿压显现,由此提出了采用顶煤顶板预先弱化爆破来预防坚硬煤层综放面发生顶板灾害的方法。现场试验进一步证明综放开采坚硬顶煤预先爆破弱化方法的实际可行性,表明综放开采坚硬顶煤预先爆破弱化理论分析结果符合生产实际,取得了良好的技术经济效益。更多还原

【Abstract】 When the fully mechanized top-coal caving is used in hard thick coal seam, the top-coal cannot be broken fully by ground pressure, and this will cause the coal recovery is lower and the violent ground behaviors threatened safety appear in working face. The key of fully mechanized caving safely and efficiently in hard thick seam is to control the top-coal breaking process effectively, the technology of the top-coal pre-blast weakening is a valid method to resolve this problem. The top-coal system of fully mechanized caving face in hard thick seam is a continuous and dynamic system on time and space, the pre-weakening is a important part composing the whole breaking process of the top-coal, and the essential to pre-weakening the hard top-coal is artificially and beforehand to make its whole strength lower. The hard top-coal is defined as a kind of the top-coal that its outflow and recovery exists obvious trouble when it did not be processed specially. The necessary conditions to put out the top-coal are presented, and a hard top-coal identifying method with the fuzzy appraisal as well a calculating method of the top-coal original damage including the macroscopic structure face strength influence is proposed out.The hard top-coal pre-weakening blast is an especial kind of the mine underground blast. The experiments indicate that the peak pressure of the blasting stress wave within the coal attenuates as the power function, and the loss of the wave energy in it exceeds that in the <WP=7>general rocks. According to the experiment and the site-testing, the methods to calculate the crushed area, the tensile failure area and the cracked area of the weakening blast in hard top-coal are put forward, and more, using the Weibull distribution of the rock blasting crack density and the equivalent strain principle, it is concluded that the attenuation law of the peak cubage strain of the blasting strain wave with the proportion distance is the power function and the damage degree function of the weakening blast is derived in hard top-coal.To change the characteristic of the whole structural mechanics of the top-coal is the main pre-blast weakening form, thereby the whole structural mechanics model and its breakage condition of the hard top-coal after pre-weakening blast in fully mechanized caving are set up. By the analysis of the whole rigidity change of the top-coal, the rationality that the blast hole must be arranged in row is proved and the statistical damage variable expression of it under the action of the abutment pressure is deduced.In the fully mechanized caving face of hard thick seam, the small structure in “cantilever” type is formed in the middle roof strata and the big structure in “voussoir” type is formed in the high roof strata generally, the overlying strata movement of the face is controlled by the two key strata in middle and high, the violent periodic weightings are arose by the composite effect of the two key strata movements, but the violent degree of the weighting behaviors rests with whole mechanics capability of the top-coal above the faces generally. It is the most remarkable characteristic of the ground behavior in hard seam fully mechanized caving face that there are the violent periodic weighting phenomena. The pre-blast weakening obviously influences the ground behavior of the face because of lowering the whole rigidity and strength of the top-coal, thereby the way that to use the beforehand weakening blast of the top-coal and the roof prevents the roof disaster accident is proposed.The site tests further testify the hard top-coal pre-weakening blasting method in fully mechanized caving is actual workable, show off the results from the hard top-coal pre-blast weakening theory <WP=8>accord with the actual situation in practice, and the good technological and economical benefits have be won.更多还原