不同环境温度下土体含水率主动加热光纤法监测试验研究  

Experimental study of water content in soils monitored with active heated fiber optic method at different ambient temperatures

作　　者：郭君仪 孙梦雅 施斌[1] 魏广庆 刘洁 GUO Jun-yi;SUN Meng-ya;SHI Bin;WEI Guang-qing;LIU Jie(School of Earth Sciences and Engineering,Nanjing University,Nanjing,Jiangsu 210023,China;Suzhou Nanzee Sensing Co.Ltd.,Suzhou,Jiangsu 215123,China)

机构地区：[1]南京大学地球科学与工程学院,江苏南京210023 [2]苏州南智传感科技有限公司,江苏苏州215123

出　　处：《岩土力学》2020年第12期4137-4144,共8页Rock and Soil Mechanics

基　　金：国家重大科研仪器研制项目(No.41427801);国家自然科学基金重点项目(No.41230636)。

摘　　要：近年来,主动加热光纤(active heated fiber optical,AHFO)法因其具有长距离、耐久性好、分布式等优势,在土体含水率原位监测中不断得到应用。然而,由于我国一些地区土体的温度随四季变化很大,冬季土体温度甚至会达到零下几十度,土体中的水会发生相变,因此,研究不同环境温度对土体含水率AHFO法原位监测结果的影响具有重要意义。采用自主研发的内加热FBG刚玉管传感器,在-20~40℃下对3个不同含水率的试样进行了测试。研究结果表明,在试样含水率不高于8.8%时,不同温度下测得的试样含水率最大误差小于量程的1.5%,测量精度较高,在实际测量中可忽略环境温度的影响。当试样含水率高于8.8%时,正温区含水率测量的最大误差仅为量程的1.34%,测量精度仍较高;而在负温区时,由于自由水和毛细水在低于0℃时发生相变,导致热传递机制和试样结构发生变化,原来的标定公式不再适用,故需重新标定含水率测量的相关参数。研究结果为该技术的进一步完善和推广应用提供了重要依据。In recent years, the active heated fiber optic(AHFO) method has been widely applied in the in-situ soil water content due to its ability to be used in long distance, good durability and distributed monitoring. However, the soil temperature in some areas in China varies greatly with seasons. The soil temperature reaches dozens of degrees below zero in winter, causing the water to freeze. Therefore, it is of great significance to study the influence of different ambient temperatures on the in-situ monitoring results of soil water content using AHFO method. In this paper, the self-developed internally heating alundum tube FBG sensor was used to monitor three loess samples with different water contents at a temperature of -20 to 40 ℃. The results show that when the water content of the loess is not higher than 8.8%, the maximum error of water content measured at different temperatures is less than 1.5% of the range. Since the measurement accuracy is high, the effect of ambient temperature on the monitoring results of water content of soils can be ignored in the actual measurement. When the water content of loess is higher than 8.8%, the maximum error of the measurement of the water content in the positive temperature zone accounts for about 1.34% of the range, and the measurement accuracy is still high. In the negative temperature zone, since free water and capillary water undergo phase transition when the temperature is lower than 0 ℃, the heat transfer mechanism and sample structure change. As a result, the original calibration formula is no longer applicable. Therefore, it is necessary to recalibrate the relevant parameters in water content measurement. The research results provide important reference value for further improvement and application of this technology.

关 键 词：主动加热光纤法 土体 原位含水率 环境温度 误差分析 

分 类 号：TU411.2[建筑科学—岩土工程]