【作者】 王晓川；

【导师】 李晓红；

【作者基本信息】 重庆大学 ， 采矿工程， 2011， 博士

【摘要】 隧道工程及井巷工程掘进中,传统的矿山法爆破出来的隧/巷道轮廓存在平整度差、超欠挖严重以及对保留岩体扰动大、易产生塌方等问题,特别在软弱破碎岩体的开挖掘进过程中,这种问题表现的尤为突出,提高隧/巷道软弱围岩段爆破成型效果,降低爆破对保留岩体的损伤成为亟待解决的关键问题。论文依托国家自然科学创新群体基金项目“高压水射流破岩理论及其在地下工程中的应用基础研究(NO.50621403)”及国家自然科学基金重点项目“高压水射流辅助提高隧道软岩光面爆破成缝率的机理(No.50704039)”,充分考虑软弱围岩工程特点,结合射流切割的特性,提出利用水射流在周边眼切割出导向缝、再进行低损伤光面爆破的新方法。论文采用理论分析、相似实验和数值计算等手段研究了射流割缝对隧道软弱岩体爆破过程中裂纹产生、扩展及岩石的断裂作用机理,设计出适用于隧/巷道软弱围岩周边眼切割导向缝试验设备,并进行了现场试验,得到以下主要结论:①揭示了导向缝对隧道软弱岩体爆破过程中裂纹产生、扩展、断裂的作用机理。在软弱围岩中爆破时,岩石破坏主要是爆炸冲击波和爆炸气体共同作用的结果,而导向缝的存在则削弱了应力波在炮孔周壁其他方向上破岩的效果,同时爆炸气体的气楔作用在导向缝尖端附近产生高度应力集中,促使爆生裂纹沿导向缝方向扩展。②利用断裂力学及爆炸气体准静态理论建立了射流割缝作用下岩石爆破定向断裂分析模型,描述了射流缝中爆炸气体压力与裂隙表面的粗糙程度K、裂缝宽度、裂缝长度等因素的关系,确定了射流割缝孔爆破裂纹发生扩展的断裂条件,研究了割缝几何尺寸以及定向缝的表面的粗糙程度K对爆炸气体促使裂缝扩展的影响规律,得到了爆炸气体产生的动态应力强度因子最大时定向缝长度与宽度的比例关系,即当定向缝长宽比为4K时,爆炸气体在射流缝尖端产生的动态应力强度因子最大。③通过爆炸加载动焦散线测试系统对带有不同尺寸定向缝的有机玻璃板进行了爆破实验,得出射流割缝条件下爆生裂纹分布及扩展规律,即:普通炮孔爆破后,产生的裂纹数目较多且分布较均匀,但分布有一定的随机性,而割缝后的试件裂纹首先沿导向缝起裂扩展,且长度最长,次生裂纹较少,孔壁的损伤较弱;相对普通炮孔,割缝孔爆炸裂纹起裂较容易,爆炸荷载作用时间较长,爆炸能量沿导向缝方向集中程度高。④用ANSYS/LS-DYNA对射流割缝后炮孔的爆炸进行了模拟,模拟结果表明,在爆炸载荷作用下,割缝孔附近的应力场分布和普通圆孔的应力场分布不同,由于射流割缝的作用,沿割缝方向的应力加强,有利于裂纹沿射流缝方向起裂扩展,达到定向断裂的目的,裂纹沿射流缝方向的稳定性扩展有利于相邻炮孔的贯通。⑤通过在某公路穿煤隧道的现场试验,结果表明利用水射流割缝辅助隧道软弱围岩实施光面爆破,可以减少爆破对围岩的扰动及对保留岩体的损伤,有效提高光面爆破周边眼成缝率和爆破后隧道轮廓平整度。本文的创新点:①提出了利用水射流对周边眼预割缝导向软弱围岩光面爆破进行隧道低损伤掘进的新方法。②揭示了射流割缝对软弱岩体爆破过程中裂纹产生、扩展、岩石断裂的作用机理,建立了导向缝作用下岩石爆破定向断裂模型。③利用焦散线实验系统研究射流割缝条件下爆生裂纹分布及扩展规律,得到了爆炸气体产生的动态应力强度因子最大时射流割缝尺寸的比例关系。更多还原

【Abstract】 During the tunnel and roadway excavation process, the tunnel profile by blasting has the problems of poor flatness, serious excess under-excavation, great disturbance to the remaining rock, as well as easy collapse. Those problems are particularly prominent in the soft and broken rock excavation and tunneling process. Therefore, how to improve the shaping effect of soft surrounding rock in the tunnel under blasting and reduce the damage of blasting on the remaining rock is currently the urgent problem to be solved.To settle problem above, referring to Science Fund for Creative Research Groups of High-pressure Water Jets Rock Blasting Theory and Its Basic Application Research in Underground Engineering (50621403) and the National Natural Science Foundation of China of High-pressure Water Jet Assisting to Improve the Mechanism of Blasting the Soft Rock of the Tunnel to be the Joint Rate (No.50704039), combined with the characteristics of jet slotting and considering the characteristics of the soft rock engineering of tunnel, this paper introduces the directional jet slotting technology and put forwards the new method of slotting and blasting along the around eyes to achieve low-damage tunneling. This paper studies the cracking ,expansion and fracturing mechanism of soft rocks under the jet slotting from the perspectives of theory, similarity experiment and numerical calculation, preliminarily designs the experimental equipment which is suitable for low-damage tunneling of the soft surrounding rock and makes the on-site testing, achieving results.①Reveals the cracking and fracturing mechanism of rocks under the blasting after the jet slotting .In the soft rock blasting, the damage of rock is mainly the result of blast wave and explosive gas, Because of the jet slot, rock breaking efficiency of stress wave is weakened in the other direction. The wedging of the blasting gas results in high degree of stress concentration near the tip of the jet slot, force the rocks to fracture mainly along the jet direction.②Build the directed fracture model of the jet slot by the application of fracture mechanics and the blasting gas quasi-static theory, describe the pressure of the blasting gas is affected by several factors like the roughness on the fracture surface, crack width, crack length and other factors. Determine the fracture conditions of jet slotting hole and study the effect law of slotted geometry and the roughness(K) on the fracture surface for the blasting crack extension on the jet slotting holes. Point out an optimum the dynamic stress intensity factor of slot length to slot width: when the ratio factor is 4K, the dynamic stress intensity factor produced by the blasting gas in peak reaches a maximum.③Make blasting tests on the plexiglass plates after different size jetting and slotting with the dynamic caustics test system under blasting loading. The results show the law of distribution and extension: the cracks are more and distributed evenly after the blasting of the ordinary holes. However, the distribution is somewhat random. For the blasting effect of the test pieces after slotting, the main crack extension shows strong directional properties and is concentrated on the slot direction in a longest length. It has little short cracks and low damage on the wall of holes; compared with the ordinary hole, the slotted hole is easy to crack with long blasting loading effect and high degree of energy concentration.④Simulate the blasting after the jet slotted hole with ANSYS / LS-DYNA. The simulation analysis shows that under the effect of blasting and loading, the stress distribution near the slotted hole is different from that of the general holes. Due to the role of the jet slotting, the stress along the slot direction is strengthened, which is beneficial to the directed extension of cracks along the jet slot direction, realizing the purpose of directional cracking. At the same time, the directed extension of cracks along the jet slot direction is beneficial to the perforation of adjacent charge holes.⑤Through the field test of a highway tunnel through the coal seam, it shows that the application of water jet slotting in the smooth blasting of the soft surrounding rock in the tunnel can reduce the disturbance of the surrounding rocks and the damage on the remaining rocks by blasting, effectively increase the slotting rate of the eyes around by the smooth blasting and the flatness of the tunnel profile after blasting.The innovations of this paper:①It proposes a new method of assisting the soft surrounding rocks in the tunnel for the smooth blasting by water jet slotting, thus realizing the low-damage tunneling.②It reveals the mechanisms of rock fracture and cracks, extension of soft rock during blasting under jet slot. The directed fracture model of rock blasting under the jet slot is established.③Make a study on the distribution and extension principles of the blasting crack under the jet slotting with the caustics experimental system and obtain the proportional relationship between jet length and jet width when the dynamic stress intensity factor produced by the blasting gas reaches a maximum.更多还原