【作者】 代树红；

【导师】 马胜利；

【作者基本信息】 中国地震局地质研究所 ， 固体地球物理学， 2013， 博士

【摘要】 活断层是发生构造地震和引起相关地质灾害的主要原因,其中受第四系松散沉积物覆盖的活断层相对于地表出露的断层更具隐蔽性和危险性。因此,活断层破裂及其在沉积层中的扩展研究是地震地质科学和防震减灾工程中的重要课题。为了深入理解活断层破裂扩展特征和机理,本文基于数字图像相关方法开展了破裂在岩石和断层基岩上覆沉积层扩展的断裂实验和地质力学模型实验研究。为揭示典型性断层破裂在沉积层的扩展规律及地表破裂带的分布特征,研制了针对走滑断层和逆断层破裂扩展研究的模型实验系统和相似材料,通过模型实验系统的模型架可以方便的调整断层构造的几何参数,从而达到研究断层的几何参数对其破裂扩展影响的研究目标,模型实验系统通过由伺服电机控制的加载系统可以精确的实现对断层基岩错动方式的控制；由石英砂和石膏等材料配比而成的相似材料具有成本低、填装方便和强度可调整范围大的优点,能够有效模拟活断层基岩和沉积层的物理力学性质,适合于开展大规模和具可重复性的活断层破裂扩展的实验研究。为观测模型实验中断层的破裂扩展过程,本文基于DICM (Digital image correlation method)的基本原理,讨论了应用DICM观测非连续变形场的技术,系统化了3D-DICM的理论和观测方法,研制了3D-DICM的观测系统,经改进的DICM可以有效的观测模型实验中活断层破裂在沉积层的扩展过程及地表变形场和地表破裂带的演化过程。为解决岩石裂纹扩展过程中测定裂纹尖端断裂参数的难题,论文提出了一种基于DICM测定岩石裂纹扩展过程中,裂纹尖端应力强度因子、裂纹尖端位置和裂纹扩展长度的岩石断裂实验方法,该方法能够直接测定岩石裂纹尖端的断裂参数,为揭示断层基岩破裂扩展特征和力学机理提供了有效的实验方法。文中应用新近提出的DICM研究了半圆盘岩石试件在三点弯曲加载条件下Ⅰ型和Ⅰ-Ⅱ复合型裂纹扩展过程中应力强度因子和裂纹扩展长度的演化过程。研究表明,岩石裂纹扩展过程中具有亚临界扩展阶段,通过裂纹扩展过程中的应力强度因子和裂纹扩展速率的变化特征可以有效的判别裂纹的亚临界扩展阶段,亚临界扩展过程对于断层基岩破裂扩展和地震前兆信息的研究具有重要的地震地质意义。裂纹在辉绿岩中含石英夹层、砂泥岩互层和层状岩石模拟试件扩展过程中,层状岩石中的界面层、界面层滑动效应和界面层两侧的岩石强度差异性,对破裂在界面层两侧的岩体扩展具有止裂和改变扩展方向的作用,该研究有助于揭示断层在不同岩性的层状盖层中扩展的规律和机理。论文基于地质力学模型试验方法和系统,研究了走滑断层破裂在沉积层中的扩展形迹,沉积层厚度和断层错动位移这两个关键参数对地表变形场和地表破裂带演化过程的影响,以及破裂带内的破裂类型。研究表明,破裂在上覆沉积层和地表的扩展受断层基岩的错动位移量控制,地表变形带宽度随断层位移量呈近二次曲线增大,并最终趋于稳定：地表破裂带(变形带)影响范围随沉积层厚度增大而增大,地表破裂带内的破裂是破裂自基岩和沉积层的接触面呈螺旋曲面向地表扩展的结果,扩展至地表后破裂呈间距性分布,破裂间距同沉积层厚度成正比。通过地质力学模型实验,研究了逆冲断层基岩错动条件下,破裂自基岩上断点向沉积层地表扩展过程中,断层倾角、沉积层厚度和断层错动位移量对地表变形场演化过程的影响规律,以及地表破裂带的演化及分布。研究表明,沉积层表面围绕基岩断层上断点的投影线形成垂直位移梯度带(形变带),形变带宽度和带内最大垂直位移随基岩断层位移的增加而线性地增加,但当破裂扩展至沉积层表面后带宽逐渐趋于稳定；随沉积层厚度增加,地表变形带的影响范围增大但带内变形强度减弱,沉积层中分别出现了剪切和拉张破裂带；沉积层表面形变带的宽度将随基岩断层倾角的增加而减小,但同时基岩断层倾角越大,形变带内最大位移量越大在沉积层表面引起的变形破坏的程度越强烈。更多还原

【Abstract】 Active fault is not only the main cause of tectonic earthquake, but also the intensified cause of geological and earthquake disasters. Active fault covered by the quaternary loose sediment is more covert and dangerous compared to active fault exposed on the ground surface, so the study of active fault propagation in sedimentary layer is a very important topic in the study of seismic geology and earthquake disaster reduction engineering. In order to reveal the active fault propagation characteristics and mechanism, the rock fracture experiments and the fault propagation experiments were carried out based on the digital image correlation method.In order to reveal the rules of typical active fault rupture in sediments and the distribution characteristics of ground surface rupture zone, we developed the modeling test systems and analogue materials to simulate the strike slip fault and thrust fault rupture propagation process in sedimentary layer. The modeling frame of experimental system can easily adjust the geometry parameters of the fault, and the loading system can precisely control the displacement value and model of the fault by servo motor. The analogue material made of quartz sand and plaster has the advantages of low cost, easy-to-use and wide adjustable range of strength. It can effectively simulate the physical and mechanical characters of rock and sediment. So, the analogue material is suitable for large-scale and repeatability modeling test research of active fault rupture propagation process in sedimentary layer. In order to measure the rupture propagation process of active fault, we reviewed the technique of measuring discontinuous deformation field by digital image correlation method (DICM), and developed3D-DICM measuring system. The improved DICM and measurement systems can effectively measure the evolutionary process of the ground surface deformation field and rupture zone. In order to reveal the crack propagation mechanism in bedrock, we developed a new method based on DICM to measure stress intensity factors, crack tip position and crack length during the crack extension process. It shows that the fracture parameters measured by the above method can be used in rock fracture mechanics to analyse the problem of rock fracture.The mode I and mixed-mode Ⅰ-Ⅱ crack propagation characteristics of rock are studied utilizing DICM, and the rock interface layer’s influence on the crack propagation in stratified rock is studied at the same time. The experimental result shows that there is a subcritical crack growth stage in rock fracture process, and the stage can be identified by stress intensity factor and crack extension speed. The study of subcritical crack growth stage has important geological significance in the research of bedrock rupture propagation and earthquake precursor. The experiment of crack propagation in stratified rock was carried out, which shows that the rock interface, interface slip and rock property have influence on the crack propagation.The analogue material and equipment system of geological mechanics modeling test were used to study the strike slip fault propagation process in sedimentary layer, then influence of bedrock displacement and sedimentary thickness on sedimentary fracture are mainly studied. The experimental results indicate that the ground surface deformation and fracture band width are mainly controlled by bedrock movement, the surface deformation band width increases with fault displacement are nearly quadratic curve, which finally tends to be stable width; ground surface rupture zone increases with sedimentary thickness, the crack in rupture zone is formed after the initial crack in bedrock penetrated the sedimentary layer, and the rupture plane in sedimentary is a spiral curved surface, the cracks distributed in spacing mode, sedimentary thickness is proportional to the fracture spacing.The influence rule of bedrock slide displacement, fault dip angle and sedimentary thickness on the fracture propagation process and ground surface deformation is studied in the modeling test of thrust fault propagation. The experiment results indicate that the deformation band width increases with bedrock slide displacement and sedimentary thickness, tends to be a constant value after the rupture appeared on ground surface; the width of deformation band dereases with the fault dip angle, but the fracture degree on ground surface increases with the fault dip angle更多还原