大藤峡水利工程岩溶探测中地球物理方法研究与应用

发布时间：2018-06-14 17:54

本文选题：大藤峡水利工程 + 岩溶　；参考：《吉林大学》2017年硕士论文

【摘要】：由于岩溶发育的不均一性,传统的钻探方法在岩溶调查进行过程中,不仅耗费大量时间与财力,而且由于钻孔数量有限,控制点稀少、信息量小,不易于全面掌握工区岩溶发育情况。为了使岩溶探测工作更加高效、准确、经济、全面,多种地球物理方法在实际探测中得到广泛应用,并取得了良好的探测效果。目前,岩溶探测主要地球物理方法包括瞬变电磁法(TEM)、可控源音频电磁法(CSAMT)、探地雷达法(GPR)、高密度电阻率法、浅层地震波法(折射、反射)、电磁波CT法、地震波CT法、声波CT法及钻孔电视数字成像法等方法。然而,岩溶属于隐蔽灾害地质体,探测起来特别困难和复杂。探测对象的复杂性,即地形条件复杂、边界条件复杂。岩溶多沿地质构造裂面发育,发育强度与水聚集、补给、循环、排泄条件相关,且不同岩性的岩层岩溶发育强度有明显差别。每种方法的适用条件不同、要达到的目的不同,因此如何选择勘察方法显得尤为重要。本文首先依据大藤峡水利工程地质概况、现场情况及物性特征,对不同工程部位选取不同的地球物理方法组合。其中船闸和消力池基础现已开挖至基岩且地形起伏小,选用探地雷达法探测两个工区整体岩溶发育情况,电磁波CT法辅助查明重要工程部位岩溶。泄水闸尾水渠、厂房尾水渠及下引航道工区面积大、地形起伏大、施工干扰大,选用对地面地形条件要求低、探测深度大,探测高阻背景中的低阻地质体效果好的瞬变电磁法探测岩溶发育情况,再根据探测获得异常区进行钻探验证。其次分别介绍三种地球物理方法的理论基础和工作原理基础上,结合大藤峡水利工程工区建立物理参数模型,进行探地雷达和瞬变电磁正演模拟,并对TEM模拟数据进行反演计算,探讨不同工程部位岩溶探测中地球物理方法选择的可行性。根据野外工作实践,确定三种地球物理方法的数据处理流程和异常判别的标准。并完成工程部位探测数据分析,确定施工区覆盖层厚度、地质构造,重点研究岩溶、土洞发育的规模、走向、类别及易塌陷区范围,为岩溶处理提供依据。最后通过本次工程的大量实地工作,以及对其他水利工程岩溶区勘察经验的归纳及总结,建立对于不同工程地质条件下地球物理勘探方法的选择体系:在水库、坝区、帷幕、地下洞室等工程部位前期勘查过程中,根据地形情况可适当的选用瞬变电磁法、EH4、可控音频大地电磁测深法及高密度电法等探测深部岩溶的发育情况,如工区基岩出露,可选用探地雷达探测浅部岩溶的发育情况。同时可以利用已有钻孔布置电磁波CT法、地震波CT法、声波CT法及钻孔电视数字成像法详细探测岩溶的位置、规模、延伸、充填情况。
[Abstract]:Because of the heterogeneity of karst development, the traditional drilling method not only consumes a lot of time and financial resources in the process of karst investigation, but also because of the limited number of boreholes, the few control points and the small amount of information. It is not easy to master the karst development in the working area. In order to make karst exploration more efficient, accurate, economical and comprehensive, a variety of geophysical methods have been widely used in practical exploration, and good results have been obtained. At present, the main geophysical methods for karst exploration include transient electromagnetic method, controllable source audio frequency electromagnetic method, ground penetrating radar method, high density resistivity method, shallow seismic wave method (refraction, reflection, electromagnetic wave CT method, seismic wave CT method). Acoustic CT and borehole TV digital imaging. However, karst is a concealed disaster geological body, which is very difficult and complex to detect. The complexity of detecting object, that is, the terrain condition is complex, the boundary condition is complex. Karst develops along the fracture surface of geological structure, and the development intensity is related to water accumulation, recharge, circulation and discharge condition, and the karst development intensity of different lithology is obviously different. Each method has different applicable conditions and different aims, so how to select the method of investigation is particularly important. In this paper, according to the geological situation, field situation and physical characteristics of Dadengxia water conservancy project, different geophysical methods are selected for different engineering sites. The foundation of shiplock and stilling pool has been excavated to the bedrock and the topography is small. The ground penetrating radar method is used to detect the whole karst development in the two working areas and the electromagnetic wave CT method is used to help identify the karst in the important engineering area. The working area of the tailwater canal, the powerhouse tailwater channel and the lower approach channel are large, the topography fluctuates greatly, the construction interference is large, the selection requires low topographic conditions on the ground, and the detection depth is large. Transient electromagnetic method (TEM), which is effective in detecting low resistivity geological bodies in high resistivity background, is used to detect karst development, and drilling verification is carried out on the basis of abnormal areas. Secondly, on the basis of the theoretical basis and working principle of three geophysical methods, combined with the physical parameter model of Dadengxia water conservancy project area, the ground penetrating radar and transient electromagnetic forward modeling are carried out. The feasibility of geophysical method selection in karst exploration of different engineering sites is discussed by inversion calculation of TEM simulation data. According to the field work practice, the data processing flow of three geophysical methods and the criteria of anomaly discrimination are determined. The data analysis of engineering site detection is completed to determine the overburden thickness and geological structure of the construction area, and to study the scale, trend, category and easy collapse area of karst and soil cave development, which provides the basis for karst treatment. Finally, through a great deal of field work of this project, as well as summing up the exploration experience of other water conservancy projects in karst area, the selection system of geophysical exploration methods under different engineering geological conditions is established: reservoir, dam area, curtain, During the Prophase exploration of underground caverns and other engineering sites, according to the topographic conditions, the transient electromagnetic method (EH4), controllable audio frequency magnetotelluric sounding method and high-density electric method can be used to detect the development of deep karst, such as the outburst of bedrock in the working area. The ground penetrating radar can be used to detect the development of shallow karst. At the same time, the location, scale, extension and filling of karst can be detected in detail by using the existing drilling arrangement electromagnetic wave CT method, seismic wave CT method, acoustic wave CT method and borehole television digital imaging method.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631;TV221.2

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