叶巴滩水电站坝址区斜长花岗岩声发射试验研究

发布时间：2018-04-16 15:09

本文选题：斜长花岗岩 + 声发射　；参考：《成都理工大学》2017年硕士论文

【摘要】：通过实地勘察叶巴滩坝址区揭示的深部岩体变形破裂现象,深刻分析深部卸荷发育的应力环境与含水状态,科学的、合理的设计试验方案。本文基于MTS815岩石力学试验机与PAC-II声发射测试系统,开展叶巴滩坝址区斜长花岗岩在不同围压与含水量的循环三轴加卸荷声发射试验研究。根据声发射振铃计数、声发射能量计数、振幅反映岩石变形破坏过程微破裂发育活动性;基于破裂点空间集群分布特征,分析岩石内部潜在危险区域,并揭示岩石主破裂面形成过程与力学机制。论文主要研究成果如下:(1)根据声发射事件率、累计事件数、振铃计数、能量计数随时间的变化关系,可将整个声发射过程划分为5个阶段,能够较好的与岩石变形破坏阶段相对应。(2)由于岩石材料结构、成分差异,以及不均性,岩石变形破坏过程b值变化有所差异,但大体上有如下规律:岩石失稳破坏前b值会出现小幅度波动,表明岩石破裂处在稳定渐进破坏过程;在接近破坏时,b值快速下降或大幅度波动,岩石结构剧烈损伤,裂纹快速扩展、贯通,代表一种突发式失稳破坏。(3)基于以往声发射事件空间分布的统计方法分析,提出一种统计声发射事件空间分布规律的新方法,即时间-距离方法。通过该方法可将岩石变形破坏过程划分为三个阶段,并得到2个明显的特征意义点。这两个点在岩石变形破坏过程中具有重要的意义,可作为岩石变形破坏过程内部结构改变的重要衡量指标。(4)在声发射初期,破裂点之间距离主要以3-6mm为主,且大于8mm的距离比例在10%以上,说明破裂点之间的距离较大,相关性不明显。随着岩石变形破坏进程逐渐发展,距离较大的破裂点数量逐渐减少,破裂点距离集中分布在1-2mm,所占比例约50%。距离在0-1mm的破裂点所占比例,随着岩石变形破坏过程逐渐增加,从最初的1%增加至10~30%。此外,研究发现岩石失稳破坏时空间相关长度最终保持在2mm左右,当空间相关长度下降至2mm时预示着岩石试样即将失稳破坏。(5)围压是改善岩石力学性质的重要因素,随着围压增大饱和试样与天然石的峰值应力、峰值应变都明显增加。相同围压条件下,天然状态岩样峰值应力、应变明显高于饱和状态岩样,说明水的存在降低岩石的强度,弱化岩石抵抗变形的能力。从岩石应变的角度来看,声发射变化规律与轴向残余应变、侧向应变、体积应变具有较好的相关性,能有效的反映岩石变形破坏过程内部结构损伤。(6)声发射技术作为监测岩体稳定性的重要手段,在实践工程中运用广泛。基于本文提出的衡量岩石失稳破坏过程的新指标d值,结合声发射各阶段破裂点的空间分布图,确定破裂点空间集群方位,辨别岩石内部潜在危险区域的位置,建立衡量岩石失稳破坏的新指标。d值的变化趋势与岩石变形破坏过程有较大的相关性,但要实现定量的评价岩石稳定性,还有很多的后续工作需要开展。
[Abstract]:Through field investigation of deformation and fracture phenomena of deep rock mass in Yabatan dam site, the stress environment and water bearing state of deep unloading are deeply analyzed, and scientific and reasonable design and test scheme are designed.Based on MTS815 rock mechanics testing machine and PAC-II acoustic emission testing system, the cyclic triaxial loading and unloading acoustic emission test of the obliquity granites in Yabatan dam area under different confining pressure and water content is carried out.According to the acoustic emission ringing count, the acoustic emission energy count, the amplitude reflect the microfracture development activity during the rock deformation and failure process, based on the spatial cluster distribution characteristics of the fracture points, the potential dangerous areas within the rock are analyzed.The formation process and mechanical mechanism of the main fracture surface of rock are revealed.The main research results are as follows: (1) according to the change of AE event rate, cumulative event number, ringing count and energy count with time, the whole AE process can be divided into five stages.Because of the difference of rock material structure, composition, and unevenness, the change of b value of rock deformation and failure process is different.But there are the following rules: before the rock instability failure, the b value will fluctuate by a small margin, which indicates that the rock fracture is in the process of steady and progressive failure, and when the rock failure is approaching the failure, the b value will decrease rapidly or fluctuate by a large margin, and the rock structure will be severely damaged.Based on the statistical analysis of the spatial distribution of acoustic emission events in the past, a new method, time-distance method, is proposed to calculate the spatial distribution of acoustic emission events.Through this method, the rock deformation and failure process can be divided into three stages, and two distinct characteristic points can be obtained.These two points are of great significance in the process of rock deformation and failure, and can be used as an important index to measure the change of internal structure in the process of rock deformation and failure. In the initial stage of acoustic emission, the distance between the fracture points is mainly 3-6mm.The ratio of distance greater than 8mm is more than 10%, which indicates that the distance between rupture points is large and the correlation is not obvious.With the gradual development of rock deformation and failure process, the number of fracture points with a long distance decreases gradually, and the distance of fracture points is concentrated in 1-2mm, accounting for about 50%.The ratio of distance to the rupture point of 0-1mm increases gradually with the deformation and failure process of rock, from 1% to 1030%.In addition, it is found that the spatial correlation length of rock under instability failure is about 2mm, and when the spatial correlation length decreases to 2mm, it indicates that the confining pressure of rock specimen is an important factor to improve the mechanical properties of rock.With the increase of confining pressure, the peak strain of saturated specimen and natural stone increases obviously.Under the same confining pressure, the peak stress and strain of natural rock samples are obviously higher than that of saturated rock samples, which indicates that the existence of water reduces the strength of rock and weakens the ability of rock to resist deformation.From the point of view of rock strain, acoustic emission variation has a good correlation with axial residual strain, lateral strain and volume strain.Acoustic emission (AE) technology, which can effectively reflect the damage of internal structure in the process of rock deformation and failure, is widely used in practical engineering as an important means to monitor the stability of rock mass.Based on the new index d of rock instability and failure process proposed in this paper, combined with the spatial distribution map of fracture points in each stage of acoustic emission, the location of the space cluster of fracture points is determined, and the location of potential dangerous area inside rock is identified.To establish a new index. D value of rock instability and failure is related to the rock deformation and failure process, but to achieve quantitative evaluation of rock stability, there is still a lot of follow-up work needs to be carried out.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV223

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