极端气候事件触发岩溶塌陷的机理

During recent years, frequent occurrence of extreme weather events, especially prolonged drought or heavy rain, have triggered a series of gigantic sinkhole hazard in China, and gave great influence to citizen life. For example, after rainfall of 469.8mm from the night of May 31 to the noon of June 1, a large scale sinkhole formed in June 3 2010, in Jili village Liangjiang town, Laibin City, Guangxi province. There is tens of sinkhole pits were created, the diameter and depth of the largest is more than 200m and 30m respectively, the area of affected zone is more than 0.4 square kelometers, as results, the most house of whole Jili village were destroyed, and more than 130 families with 600 farmers were influenced. The purpose of this proposal is to establish the approaches and methods for monitoring and early warning of this sinkhole through its mechanism research. Firstly, the applicant selected sinkhole area of Jili village as the typical research site and to take investigation and detection of geological background and dynamic condition. Through systematic analysis of sinkhole development with the action of extreme heavy rains, build the geological mode of sinkhole formation. And then, high resolution piezometers with dataloggers, distributed fiber optic strain sensing system (BOTDR), GPS monitoring system, and Triaxial Broadband Seismometer (CMG-40T) will be introduced to monitoring the precipitation, the pressure of water or gas within karst conduit, ground deformation, and earthquake induced by karst cave collapse. Combine large scale model experiment and numerical simulation, to research the mechanism of sinkhole formation and its development rule, Finally, the relationship between the sinkhole induced by extreme weather and its influence factors will be study to establish the approaches and methods for monitoring and early warning of this sinkhole.

近年来，极端气候事件特别是极端干旱和强降雨事件呈现不断增多增强的趋势，已成为岩溶区诱发大型岩溶塌陷的重要因素。本项目以极端气候事件所引发大型岩溶塌陷的成因机理与监测预警技术为目标，选择2010年发生过特大型岩溶塌陷的广西来宾为研究区、从塌陷发育的基础地质条件和动力学背景调查入手，分析极端气候事件在岩溶塌陷形成演化中的作用，建立极端气候事件影响下岩溶塌陷发育的地质模式。采用高精度孔隙水压力监测系统、分布式光纤传感系统和GPS监测系统、移动地震监测系统等先进技术装备，实时监测典型区降雨量、岩溶管道裂隙系统（地下河）的水气压力、地面变形、隐伏岩溶洞穴变形破坏引发地震活动的过程，结合室内大型物理模拟实验和数值模拟分析，深入剖析极端气候条件下岩溶塌陷成因机理，研究极端气候引发塌陷的演化规律，建立极端气候事件引发塌陷与主要影响因素的关系模型，探索建立通过气象预报和地震监测进行岩溶塌陷预警的途径和方法

近年来，极端气候事件特别是极端干旱和强降雨事件呈现不断增多增强的趋势，已成为岩溶区诱发大型岩溶塌陷的重要因素。本项目以极端气候事件所引发大型岩溶塌陷的成因机理与监测预警技术为目标，选择2010年发生的广西来宾特大型岩溶塌陷的研究区，从塌陷发育的基础地质条件和动力学背景调查入手，通过监测典型区降雨量、岩溶管道裂隙系统（地下河）的水气压力、地面变形、隐伏岩溶洞穴变形破坏引发地震活动的过程，结合室内实验分析，深入剖析极端气候条件下岩溶塌陷成因机理和演化规律，探索建立通过气象预报和地震监测进行岩溶塌陷预警的途径和方法，经过4年的研究，取得以下成果：.一是建立了广西来宾良江极端气候诱发岩溶塌陷的地质模型和动力模式：通过典型区补充调查、探测，获取了该地区历史塌陷发育特点和地质背景条件，建立了岩溶塌陷地质结构模式。指出塌陷区具有“地下河发育、地表岩溶形态发育、历史塌陷发育”等三大特点。.二是明确了极端降雨导致地表径流灌入式补给岩溶含水层，使下伏地下河系统径流速度、水气压力发生急剧变化，进而导致溶洞及充填物发生突发性失稳破坏，产生水击（气爆）、地震等链式效应，最后导致大型溶洞顶板发生大规模垮塌、地面塌陷产生。地下河系统径流速度和水气压力的剧变、水击（气爆）、地震效应是诱发（触发）岩溶塌陷的关键因素。.三是通过典型区岩溶塌陷动力变化过程监测，揭示岩溶系统水气压力对降雨的响应特点发现岩溶溶洞裂隙水对大气降雨反应极为敏感，每一次降雨过程都会导致岩溶系统中水气压力的剧烈、大幅度变化，除显示显示季节性的波动和日波动外，对每一个降雨过程反应都比较敏感，雨季频繁出现大幅、快速变化现象；第四系水位只呈季节性变化和日变化，对单次降雨事件不敏感；裂隙水则介于上述二者之间。.四是研发大型渗透变形实验装置，实现对土体在地下水渗流作用下发生失稳破坏的规律研究和判据测量。