寒区大坝心墙土料冻融监测技术及误差分析

寒区心墙堆石坝冬季施工过程中,快速判断大面积心墙施工区防渗土料的冻融情况,是保证工程质量和快速施工的重要前提。研究发现,红外热成像测温技术可实现对心墙施工现场远距离、大范围、全仓面(超过10 000 m²)地表温度、土料冻融状况的快速检测和判定,但在现场不同环境条件下检测结果存在2 ~ 8 ℃的误差。针对该问题,基于辐射理论及红外测温原理,结合现场红外测温方式,分析得到影响心墙红外热成像仪测温误差的主要因素为心墙区的环境辐射和地表发射率。其中,环境辐射主要受气温控制。地表发射率受防渗土料压实状态(松铺、密实)以及土工布覆盖等不同地表结构形式的影响。结合现场试验数据,建立了地表辐射温度与地表接触式温度之间的修正关系。该研究为寒区工程土料冻融判别技术有重要的指导意义。

Monitoring Technology and Its Error Analysis for Freeze-Thaw of Dam Core Soil in Cold Regions

During the construction of core rockfill dam in cold regions in winter, it is an important precondition to quickly judge the freeze-thaw state of filled soil in the core to ensure the project's quality and the rapid construction. According to field tests, the infrared thermometric technique can be used to quickly detect the surface temperature and the freeze-thaw status of the core at long distance with a large area (more than 10 000 m²). However, under different ambient conditions, the error of surface radiometric temperature measured by infrared thermometric technique was 2-8 °C compared with contact temperature. In view of this, we conclude that environmental radiation and the surface emissivity are major factors that affect the error of infrared temperature measurement, of which the environmental radiation is mainly controlled by air temperature, while surface emissivity is affected by soil surface shapes caused by compaction patterns and geotextile covering. In association with field test data, we established the correction relationship between surface radiometric temperature and contact surface temperature. The research achievement provides important guidance for freeze-thaw detection technique of soil in engineering construction in cold regions.