地下洞室围岩体应力波特征与数值模拟

发布时间：2018-03-27 12:51

本文选题：地下洞室　切入点：围岩　出处：《西南石油大学》2015年硕士论文

【摘要】：岩石动力破坏是地下洞室开挖过程中遇到的难题,如何保证洞室围岩稳定取决于对岩石动力学特性和应力调整过程中围岩破坏方式的深入研究,而对岩石破坏过程中的应力波信号特征分析是重要的研究方法。本文采用傅里叶变换、短时傅里叶变换与小波变换等方法分析了应力波的时频特征和能量特性；运用数值模拟方法,建立了爆破荷载对地下洞室的影响的模型,分别从质点波速、振幅以及最大应力三个方面分析了应力波在岩体中的传播特性和规律；结合地下洞室微震监测,分析了微震事件分布规律与硐室稳定关系,获得了监测的多种应力波的波谱及能量特性。主要研究结论如下： (1)地下空间开挖过程中监测到岩体中应力波信号包括直接人为活动产生的,如人工敲击、凿岩、爆破等,也包括岩石破裂、断层错动等产生微震动,这些振动均可以通过傅里叶变换、短时傅里叶变换、小波变换来进行分析。 (2)通过对微震振动和爆破振动的频率分析看出,微震信号一般只有一个主频率,而爆破信号往往有多个主频率,可能是由于开挖过程中微差爆破造成的；通过其能量分布来看,微震信号和爆破信号的主要能量基本集中在低频带,但爆破信号在高频部分也聚集一定的能量,能量分布相对于微震信号较宽。 (3)通过地下洞室爆破施工的数值模拟来看,围岩质点振动速度和振动幅度均是墙脚最大,侧墙次之,拱顶最小,水平方向的速度是垂直方向速度的几倍,这是由于墙脚距爆源最大,受到的冲击作用最为强烈,拱顶位置由于几何形状的影响,加上应力波的反射叠加和衰减,使得应力波对拱顶的作用最小,产生的位移也就最小。从频谱图可以看出,微差爆破产生的应力波有多个主频率,主频范围在80Hz～250Hz,其最大主频率大约在130Hz左右,这与监测到的爆破信号主频率基本一致。 (4)通过对大岗山水电站微震监测事件和微震应力波分析看出,随着分台阶施工从上至下的开展,洞室下部微震事件由于爆破开挖的影响逐步增多,且微震震级较大,在拱顶和两侧墙微震振动相对较小；通过对微震监测数据的综合分析,分析了微震时空分布、震级与能量分布等动力学问题,并总结了微震监测下的地下洞室稳定性评价方法。通过对岩体动力破坏过程中应力波蕴含的大量岩体状态信息来反馈岩体动力破坏过程,为地下洞室围岩稳定性判别、支护设计选择以及设计施工提供了较强的理论和实践基础。
[Abstract]:Dynamic failure of rock is a difficult problem in the excavation of underground cavern. How to ensure the stability of surrounding rock depends on the in-depth study of rock dynamic characteristics and failure mode of surrounding rock during stress adjustment. In this paper, the time-frequency and energy characteristics of stress wave are analyzed by Fourier transform, short-time Fourier transform and wavelet transform. By using numerical simulation method, the model of the influence of blasting load on underground cavern is established. The propagation characteristics and law of stress wave in rock mass are analyzed from three aspects of particle wave velocity, amplitude and maximum stress. Combined with microseismic monitoring of underground caverns, the relationship between microseismic event distribution and chamber stability is analyzed, and the spectrum and energy characteristics of various stress waves are obtained. The main conclusions are as follows:. 1) during the excavation of underground space, the signals of stress waves in rock mass are detected, including those produced by direct human activities, such as artificial percussion, rock drilling, blasting, etc., as well as micro-vibration caused by rock rupture and fault dislocation, etc. These vibrations can be analyzed by Fourier transform, short-time Fourier transform and wavelet transform. 2) by analyzing the frequency of microseismic vibration and blasting vibration, it can be seen that the microseismic signal usually has only one main frequency, and the blasting signal usually has multiple main frequencies, which may be caused by millisecond blasting during excavation. The main energy of the microseismic signal and the blasting signal is concentrated in the low frequency band, but the blasting signal also accumulates some energy in the high frequency part, and the energy distribution is wider than that of the microseismic signal. According to the numerical simulation of blasting construction in underground cavern, the vibration velocity and amplitude of surrounding rock particle are the largest at the foot of the wall, followed by the side wall, and the vault is the smallest, and the velocity in the horizontal direction is several times of the velocity in the vertical direction. This is because the foot of the wall has the largest distance from the detonation source and is most strongly affected by the impact. The position of the vault is affected by the geometry, and the reflection, superposition and attenuation of the stress wave make the stress wave have the least effect on the vault. It can be seen from the spectrum diagram that the stress wave produced by millisecond blasting has several main frequencies, the main frequency range is in the range of 80Hz ~ 250Hz, and its maximum main frequency is about 130Hz, which is basically consistent with the main frequency of the monitored blasting signal. Through the analysis of microseismic monitoring events and microseismic stress waves of Dagangshan Hydropower Station, it is shown that with the development of step construction from top to bottom, the microseismic events in the lower part of the cavern increase gradually due to the influence of blasting excavation, and the magnitude of microearthquakes is larger. The microseismic vibration of the arch roof and the walls on both sides is relatively small, and the dynamic problems such as the spatial and temporal distribution, magnitude and energy distribution of the microearthquakes are analyzed through the comprehensive analysis of the monitoring data of microearthquakes, and the evaluation methods of the stability of underground caverns under the microseismic monitoring are summarized. According to the state information of rock mass contained in stress wave in the process of dynamic rock mass failure, the dynamic failure process of rock mass is feedback, and the stability of surrounding rock in underground cavern can be judged. Support design selection and design and construction provide a strong theoretical and practical basis.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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