斑竹垄隧道不良地质体电磁特性及响应特征研究

发布时间：2018-07-12 14:51

本文选题：斑竹垄隧道 + 不良地质体　；参考：《湖南科技大学》2017年硕士论文

【摘要】：随着我国社会经济的飞速发展和隧道工程技术的进步,隧道修建长度和埋深越来越大,工程中遇到的地质问题越来越复杂,给隧道施工带来极大的安全隐患,必须采用各种方法对掌子面前方地质条件进行及时、准确的预报。探地雷达法具有准确、无损、快速、成本低的特点,被广泛采用,但其解译成果的可靠性和精度客观上取决于对围岩物理性质的掌握程度。福建南龙铁路斑竹垄隧道全长约2.7km,地质条件复杂,围岩稳定性差,设计要求采用探地雷达法进行短期超前地质预报。因此,深入研究斑竹垄隧道围岩特别是不良地质体的地球物理特性,对提高探测成果的可靠性和解译精度、确保隧道施工安全具有十分重要的意义。本文在研究分析岩土体材料和不良地质体的地球物理特征的基础上,讨论了围岩含水性对其介电性和导电性的影响,建立了不同类型的不良地质体模型,应用基于时域有限差分法的GPRMAX软件,模拟分析了反射电磁波的相位、振幅和双层走时等响应特征;通过对斑竹垄隧道地质雷达法探测成果与实际开挖情况的对比,从定性和定量两个方面找出预报成果的影响因素,应用反射波波幅法计算围岩的相对介电常数,综合分析了斑竹垄隧道不良地质体的电磁传播特性及其响应特征。研究表明,斑竹垄隧道围岩中微风化花岗岩、微风化花岗闪长岩的平均相对介电常数为7.4、7.8;强风化炭质粉砂岩、强风化炭质石英砂岩、中风化炭质石英砂岩、微风化炭质粉砂岩的平均相对介电常数为17.9、13.9、8.8、7.7;微风化凝灰岩的平均相对介电常数为8.0。同类围岩风化程度越严重,其相对介电常数越大。围岩含水性增强,则相对介电常数和电导率增大,电磁波波速变小;相对介电常数差异越大,反射波振幅越大;相对介电常数的相对大小决定了反射波与直达波相位的正反关系,反射系数为负值时,多次反射明显。充水和充泥溶洞上界面反射波与直达波相位相反,多次反射波相位正反交替。断层破碎带雷达反射波波形杂乱,同相轴错断,能量衰减较快,可见弧形反射波同相轴组;雷达波主频明显减小,中心频率相对分散。节理裂隙密集发育带反射波波形杂乱,且能量衰减严重。软弱夹层界面反射波同相轴平直、清晰,连续性好,下界面反射波一般较清晰,界面反射波与直达波相位相反。
[Abstract]:With the rapid development of our country's social economy and the progress of tunnel engineering technology, the length and depth of tunnel construction are becoming larger and larger, and the geological problems encountered in the project are becoming more and more complicated, which brings great hidden dangers to the tunnel construction. All kinds of methods must be used to forecast the geological conditions in time and accurately. Ground penetrating radar (GPR) is widely used because of its characteristics of accuracy, nondestructive, fast and low cost, but the reliability and accuracy of its interpretation results depend on the degree of mastery of the physical properties of surrounding rock. Due to the complex geological conditions and poor stability of surrounding rock, the tunnel of zebra-ridge in Nanlong railway of Fujian province is about 2.7 km in length. The design requirement is to use the method of ground penetrating radar to carry out short-term geological forecast ahead of time. Therefore, it is of great significance to study the geophysical characteristics of the surrounding rock of zezhulong tunnel, especially the bad geological body, to improve the reliability and interpretation accuracy of the exploration results and to ensure the safety of the tunnel construction. On the basis of studying and analyzing the geophysical characteristics of rock and soil materials and poor geological bodies, this paper discusses the influence of the water content of surrounding rock on its dielectric property and conductivity, and sets up different kinds of bad geological body models. Using GPRMAX software based on finite-difference time-domain method, the response characteristics of reflected electromagnetic wave such as phase, amplitude and double-layer travel time are simulated and analyzed. The influencing factors of prediction results are found out from qualitative and quantitative aspects. The relative dielectric constant of surrounding rock is calculated by means of reflection wave amplitude method. The electromagnetic propagation characteristics and response characteristics of bad geological bodies in porphyry ridge tunnel are comprehensively analyzed. The results show that the average relative permittivity of weathered granite in the surrounding rock of zezhulong tunnel is 7.4 ~ 7.8, that of strongly weathered carbonaceous siltstone, strongly weathered carbonaceous quartz sandstone, medium-weathered carbonaceous quartz sandstone, and that of moderately weathered carbonaceous quartz sandstone. The average relative dielectric constant of aeolian carbonaceous siltstone is 17.9 ~ 13.9m ~ 8.8m ~ 7.7and that of breezy tuff is 8.0. The more serious the weathering degree of the surrounding rock of the same kind, the greater the relative dielectric constant. The relative dielectric constant and conductivity increase, the velocity of electromagnetic wave becomes smaller, the greater the difference of relative dielectric constant, the larger the amplitude of reflected wave. The relative dielectric constant determines the positive and negative relationship between the phase of reflection wave and direct wave. When the reflection coefficient is negative, the multiple reflection is obvious. The phase of the interface reflection wave is opposite to that of the direct wave, and the phase of multiple reflection wave is positive and negative. In fault fracture zone, the radar reflection wave waveform is chaotic, the cophase axis is broken, the energy attenuation is fast, the visible arc reflection wave is in the same phase axis group, the main frequency of radar wave is obviously reduced, and the center frequency is relatively dispersed. The reflected wave waveforms of the dense fracture zone are chaotic and the energy attenuation is serious. The reflection wave of the interface of weak intercalation is straight, clear and continuous in the same phase. The reflection wave of the lower interface is generally clear, and the phase of the reflection wave of the interface is opposite to that of the direct wave.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U452.11

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