【摘要】：在實(shí)際的開采過程中,許多煤礦工作面頂板為堅(jiān)硬的灰?guī)r、砂巖或其他硬度更大的巖層。堅(jiān)硬頂板條件下煤礦開采存在頂板大面積懸露、誘發(fā)沖擊可能性增加等一系列問題,對于堅(jiān)硬頂板采場一般需要采取強(qiáng)制放頂措施來控制頂板的垮落。預(yù)裂爆破強(qiáng)制放頂技術(shù)由于對煤層地質(zhì)的適應(yīng)性強(qiáng),對緩解大面積來壓效果顯著,而被廣泛運(yùn)用。由于開采深度的增加,深部巖體將具有很高的地應(yīng)力,從而使得深部巖體爆破損傷弱化機(jī)理與淺部不同。本文通過理論分析和數(shù)值仿真手段對深部環(huán)境下堅(jiān)硬頂板預(yù)裂爆破弱化機(jī)理進(jìn)行了相關(guān)研究。主要完成的研究工作如下:(1)歸納總結(jié)了堅(jiān)硬頂板所具有的物理特性和破斷特性。根據(jù)堅(jiān)硬頂板采場特點(diǎn),通過對堅(jiān)硬頂板破斷理論的簡單推導(dǎo),分析了堅(jiān)硬頂板初次來壓步距和周期來壓步距的估算方法及相關(guān)破斷位置。(2)綜合各種理論探討了巖體爆破破碎損傷機(jī)理。通過對爆破應(yīng)力波的衰減特點(diǎn)及傳播特點(diǎn)進(jìn)行分析,得到了巖體先發(fā)生拉壓變形,再發(fā)生剪切變形的破壞特征以及通低頻阻高頻的應(yīng)力波傳播特性。(3)運(yùn)用ANSYS/LS-DYNA顯式動(dòng)力學(xué)有限元軟件對巖體在單孔爆破荷載作用下的動(dòng)力響應(yīng)機(jī)理及裂隙發(fā)育規(guī)律做了數(shù)值仿真試驗(yàn),并研究了彈性模量、巖層埋深的變化對巖體裂隙發(fā)育規(guī)律的影響,同時(shí)研究了雙孔爆破巖體動(dòng)力響應(yīng)規(guī)律以及起爆延時(shí)對巖體爆破動(dòng)力破碎效果的影響。分析表明:隨著埋深的增加,爆破后產(chǎn)生的裂隙區(qū)半徑減小,巖體的破碎損傷程度增大;隨著彈性模量的增加,爆破后產(chǎn)生的裂隙區(qū)半徑增大,巖體的破碎損傷程度增大;隨著起爆延時(shí)的增加,爆破應(yīng)力波的疊加作用減弱,爆破孔間形成的貫通裂隙區(qū)減小,巖體的破碎損傷程度降低。(4)以納林河二礦3-1煤層首采工作面為工程背景,運(yùn)用UDEC軟件對堅(jiān)硬頂板預(yù)裂爆破強(qiáng)制放頂過程進(jìn)行了數(shù)值仿真分析。結(jié)果表明:采取預(yù)裂爆破強(qiáng)制放頂措施后,采場頂板初次來壓垮落步距降幅接近50%,周期來壓垮落步距降幅在25%到50%之間,頂板超前集中應(yīng)力峰值減小5.1MPa;隨著預(yù)裂高度的增加,采場初次來壓步距逐漸減小,煤壁處壓力及巖層超前支撐壓力峰值逐漸降低,采場頂板的初次來壓將經(jīng)歷兩次釋放的過程。在一定預(yù)裂高度范圍內(nèi),采場頂板弱化效果明顯,可以達(dá)到人為控制采場頂板破斷垮落步距目的。
[Abstract]:In the actual mining process, the roof of many coal face is hard limestone, sandstone or other rock strata with greater hardness. A series of problems exist in mining under the condition of hard roof, such as large area hanging of roof, increasing possibility of induced impact and so on. For hard roof stope, it is necessary to take forced roof caving measures to control the collapse of roof. Presplit blasting forced caving technology is widely used because of its strong adaptability to coal seam geology and remarkable effect on relieving large area pressure. Because of the increase of mining depth, the deep rock mass will have high in-situ stress, which makes the mechanism of deep rock blasting damage weakening different from that of shallow rock mass. In this paper, the weakening mechanism of hard roof pre-splitting blasting in deep environment is studied by means of theoretical analysis and numerical simulation. The main works are as follows: (1) the physical and fracture characteristics of hard roof are summarized. According to the characteristics of hard roof stope, a simple derivation of breaking theory of hard roof is given. In this paper, the estimation methods of the initial pressure step and periodic pressure step of hard roof and the relative breaking positions are analyzed. (2) the damage mechanism of rock mass blasting breakage is discussed by synthesizing various theories. By analyzing the attenuation and propagation characteristics of blasting stress wave, it is obtained that the first deformation of rock mass occurs under tension and compression. Failure characteristics of secondary shear deformation and propagation of stress wave at low frequency and high frequency. (3) dynamic response mechanism and fracture development of rock mass under single hole blasting load are studied by ANSYS/LS-DYNA explicit dynamic finite element software. Numerical simulation test, The influence of elastic modulus and the change of rock stratum depth on the fracture development of rock mass is studied. The dynamic response law of rock mass and the effect of initiation delay on the dynamic fracture effect of rock mass blasting are also studied. The analysis shows that with the increase of burying depth, the radius of fracture area decreases after blasting, and the degree of fragmentation damage increases, and with the increase of elastic modulus, the radius of fracture zone increases after blasting, and the damage degree of rock mass increases. With the increase of detonation delay, the superposition of blasting stress wave weakens, the through fracture area between blasting holes decreases, and the degree of rock mass fragmentation decreases. (4) taking the first mining face of 3-1 coal seam in Nalinhe No. 2 Mine as the engineering background, UDEC software is used to simulate and analyze the forced caving process of hard roof pre-splitting blasting. The results show that after the presplit blasting forced roof caving, the drop distance of the first roof collapse is close to 50, the periodic collapse step drop is between 25% and 50%, the peak value of the roof leading concentration stress is reduced by 5.1 MPA, and with the increase of the pre-cracking height, the peak value of the roof leading concentration stress decreases by 5.1 MPa, and the peak value of the roof leading concentration stress decreases by 5.1 MPa with the increase of the pre-cracking height. The initial pressure step of stope decreases gradually, the pressure at coal wall and the peak value of rock support pressure gradually decrease, and the initial pressure of stope roof will go through the process of twice releasing. In the range of certain pre-splitting height, the weakening effect of stope roof is obvious, which can achieve the purpose of artificially controlling the stope roof breaking and falling distance.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TD327.2;TD235

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