断层面库仑应力变化监测方法的力学机理实验研究

Nowadays, the lack of means of direct observation of Coulomb stress changes on the fault plane and support from observation data limit the in-depth exploration of the widely-accepted Coulomb stress theory on faults. Through theoretical and experimental research, this study presents a new experimental method for the observations of the Coulomb stress change utilizing the Brillouin scattering (BOTDR) distributed fiber optic sensing technology. This method is developed based upon the classical theoretical models under different fault conditions, and a finite element numerical model is established to simulate the Coulomb stress distribution and variations under different scenarios, which can provide a better insight on the physical-mechanical model. Then the mechanical strain transfer model between the measured substrate (thin anchor) and the BOTDR fiber sensor is established, and the strain transfer relationship between the thin anchor and the optical fiber sensor under normal stress and shear stress is examined. Meanwhile, the research on the placement and installation of distributed BOTDR optical fiber sensing group is also investigated to ensure the experiment can directly and continuously measure the Coulomb stress changes in the fault plane. At last we explores the calculation method of Coulomb stress changes using optical fiber sensing on flauts, and this research aims to realize the observation and optimization of observational data on the Coulomb stress observation experimental mechanics model, and the final findings establishes a theoretical and experimental foundation for the development of crossing fault distributed Coulomb stress monitoring technology.

目前断层面库仑应力变化直接观测手段匮乏，缺乏观测数据支撑，从而限制对现有断层面库仑应力模型深入探索。本研究通过理论和实验研究，提出一种基于布里渊散射（BOTDR）分布式光纤传感技术的断层面库仑应力实验观测方法。首先根据不同断层面工况条件下的经典理论模型，建立库仑应力观测的实验力学模型，同时建立精细有限元数值模型分析模拟在不同工况条件下的断层面库仑应力分布和变化规律，为后续物理力学模型提供数值分析依据。然后建立被测基体（细锚杆）与BOTDR光纤传感器应变传递的力学模型，研究在断层面正应力和剪应力作用下细锚杆与光纤传感器之间的应变传递关系，同时开展BOTDR光纤传感组件研制、布设及安装工艺研究，从而开展直接、连续地获取断层面库仑应力变化的力学机理实验，探索光纤应力应变对应库伦应力变化的解算算法，实现观测数据对实验力学模型的检验与优化，为后续研发跨断层分布式库仑应力监测技术奠定理论和实验基础。

针对断层面库仑应力变化监测手段匮乏、缺乏数据支撑等问题，本项目发展一种基于光纤应变传感技术的断层面库仑应力实验观测方法，结合典型断层类型数值模拟及理论分析验证，探索跨断层的光纤应变传感器对应库仑应力变化的解算算法，实现观测数据对拟建立的库仑应力观测实验力学模型的检验与优化。本项目研究的主要成果有：1）根据不同断层面工况条件下建立库仑应力精细有限元数值模型，推导跨断层准分布式光纤应力变化解算库仑应力算法；2）针对断层面库仑应力变化规律的数值模拟技术，解决传统库仑应力变化计算功能单一、半空间或球分层的基本假设不符合真实地球的局限性，设计一种横向非均匀椭球形地球地震和地表载荷引起的库仑应力变化计算方法；3）开展基于光纤光栅应变传感的库仑应力观测实验研究，设计铝块+锚杆的断层面摩擦室内实验，定量分析断层面的分布式库仑应力变化，初步构建能够直接、连续地获取断层面上的库仑应力变化应力监测光纤传感系统。本项目研究建立了库仑应力变化理论和实际观测量的联系，优化断层面库仑应力变化观测的理论力学模型和实验力学模型，促进地球动力学领域的库仑应力模型理论研究工作；同时，本研究使用准分布式光纤传感技术观测断层面库仑应力变化，较好地弥补断层面库仑应力变化直接、连续观测手段的不足，对地震重点防御区内活动断层的长期应力应变监测具有较好的应用价值。