土洞气体运移机理及对岩溶塌陷指征作用研究

The recent characteristics of sudden, high and frequent occurrence of Sinkhole collapse indicate that the existing monitoring and early warning theories and techniques are still inadequate. This study starts with the gas anomalies generated during the development of Sinkhole collapse (soil hole), and comprehensively uses gas sampling, gas tracer, isotope testing, model tests, and numerical simulations to analyze the different Sinkhole collapses (soil hole). At the development stage, the spatio-temporal variation characteristics and migration laws of the cavern gas and the corresponding relationships between the gas eigenvalues and the different development stages of the Sinkhole collapse (soil hole) are established, and then the monitoring and warning of the Sinkhole collapse using the monitoring cavern gas is realized. The specific work of the project is centered on the following four aspects. First is the study of the formation conditions of the gas in the caverns; the second is the study of the storage and migration laws of the cavern gas; the third is the research on the indications of the cave gas to the Sinkhole collapse; and the fourth is based on the Research on Theory and Method of Sinkhole Collapse Early Warning Technology Monitored by Soil Caverns. The innovation of this project is to start the monitoring and early warning research of Sinkhole collapse from the anomalous phenomena of gas generated during the development of Sinkhole collapse (soil holes), which is similar to the use of groundwater monitoring for early warning. The advantage is that the gas is diffusive and indirect. To reflect the degree of structural damage such as soil gaps, surface monitoring and early warning can be performed early in the collapse.

近期岩溶塌陷突发、高发、频发的特征表明，现有的监测预警理论和技术方法尚有不足。本项研究从岩溶塌陷（土洞）发育过程中产生的气体异常现象入手，综合运用气体取样、气体示踪、同位素测试、模型试验和数值模拟等技术方法手段，分析岩溶塌陷（土洞）不同发育阶段土洞气体的时空变化特征和运移规律，建立气体特征值与岩溶塌陷（土洞）不同发育阶段的对应关系，进而实现利用监测土洞气体进行岩溶塌陷预测预警。项目具体的工作围绕以下四个方面开展，一是土洞气体的形成条件研究；二是土洞气体的存储和迁移规律研究；三是土洞气体对岩溶塌陷的指征作用研究；四是基于土洞气体监测的岩溶塌陷预警技术理论方法研究。本项目的创新之处是从岩溶塌陷（土洞）发育过程中产生的气体异常现象入手进行岩溶塌陷监测预警研究，与利用地下水监测进行预警有异曲同工之效，其优点是气体具有扩散性，间接反映土体缝隙等结构破坏程度，可在塌陷早期进行地表直接监测预警。

项目针对我国岩溶塌陷地质灾害防治面临的监测方法不足和预警精度偏低等问题，从土洞气体形成背景、运移规律和预警作用三个方面探索性开展了利用土洞气体进行岩溶塌陷监测预警的相关研究工作，取得了三个方面的主要成果，完成了预期目标。一是完成了土洞气体示踪试验装置和岩溶塌陷多参数监测预警试验系统的设计和制作，为项目以及后期开展相关研究工作提供了基础试验平台；二是明确了岩溶区典型土洞内、外气体的主要特征和形成条件，分析了其在土洞不同发育阶段的运移规律，建立了土洞不同发育阶段与气体浓度特征变化的对应关系，为通过利用气体浓度监测进行岩溶塌陷预警提供了理论基础；二是成功将气体示踪技术引入到岩溶塌陷监测预警工作中，并开展了实际应用探索和技术方法总结，丰富完善了岩溶塌陷监测预警技术体系。