时序SAR数据监测青藏高原多年冻土区铁路/公路沿线的形变灾害

Due to the global warming and frequent human activities, the permafrost on the Qinghai-Tibet plateau is suffering serious degradation, which has caused severe ground settlement and hot-melt disasters, and then threatened the security of human engineering infrastructure including railway and highway. This project will use an advanced multi-temporal differential interferometric synthetic aperture radar (MTInSAR) technique to monitor the long-term surface deformation and thaw-melt hazards along the Qinghai-Tibet railway and highway: First, through analyzing the coherence matrix, constructing temporal attenuation model, and performing the filtering on both the spatial and temporal dimension, we deal with the problem of serious decorrelation which is common over the permafrost environment to amplify the extent and capability of MTInSAR technique; Secondly we would improve the precision of deformation surveying through the construction of seasonal deformation model, with the specific procedure like analyzing the relationships between ground parameters and deformation, confirming the variables as well as their variations, and so on; Then based on the deformation results we would map the potential and existing thaw-melt hazards along the railway and highway, analyze the properties of their spatial distribution and temporal evolution; At last, we study the deformation and damage features of railway and highway, and reveal the mechanism of the impacts of thaw-melt hazards. This research aims to promote the application of MTInSAR technique in permafrost environment, help monitor the thaw-melt hazards and protect the railway and highway.

在全球气候变暖和人类活动的影响下，青藏高原多年冻土退化日益剧烈，随之引发的地表沉降与热融灾害对青藏铁路和公路的安全造成了严重的威胁。本研究拟改进现有的时序差分干涉技术对青藏铁路/公路沿线的地表形变和热融灾害进行监测：首先通过相干性分析、构建衰减模型以及时空滤波的方法解决多年冻土区失相干严重的问题，扩大形变测量的范围和能力；其次通过分析地表参数与形变的关系，确定变量及其变化规律，构建符合地表特征的形变模型以提高测量的精度；然后基于形变结果和其它辅助数据对道路沿线潜在的和已发生的热融灾害进行制图，分析其时空分布特征；最后分析青藏铁路/公路的形变特征和受破坏的现状，揭示热融灾害对它们的影响机制。本项目的研究成果旨在推动时序差分干涉技术在多年冻土区的应用，为热融灾害的监测、铁路/公路的建设与维护提供科学依据。

青藏铁路/公路的修建是我国实施西部大开发战略的重大措施之一，对促进青海与西藏经济快速发展，增进民族团结与社会稳定有着深远的影响。作为世界上海拔最高的交通线，青藏铁路和公路沿线地质结构复杂，断裂层广布，且穿越了550公里的多年连续冻土区，从施工到道路维护都面临着严峻挑战。本项目采用时序干涉SAR技术（multi-temporal differential interferometric synthetic aperture radar, MTInSAR），大范围、快速、高精度地监测多年冻土区铁路/公路沿线的热融灾害。一方面研究时序InSAR技术在多年冻土环境中失相干严重的问题，分析时间失相干特征，建立相干系数衰减模型，并提取分布式散射体和采用时空滤波方法降低噪声影响，提升干涉图质量。另一方面建立季节性的形变模型，提升形变反演的模型精度。然后基于InSAR地表形变反演结果，采用半自动化的形态学GIS方法进行热融灾害解译。本实验选取了青海省北麓河试验区，收集了ASAR、TerraSAR和PALSAR三类数据，测试了改进的时序InSAR算法，成功的监测到了青藏铁路/公路沿线的热融灾害，并分析了热融灾害分布的特征和规律。本项目的研究成果旨在推动时序差分干涉技术在多年冻土区的应 用，为热融灾害的监测、铁路/公路的建设与维护提供科学依据。