基于频率步进原理的TDR研制及在土体含水率测试中的应用

Development of TDR based on stepped-frequency principle and its application in measurement of volumetric water content of soils

基于时域无载频脉冲原理的时域反射法(TDR)能够快速准确测试土体含水率,在岩土工程领域有广泛用途。但是目前TDR测定仪器均为进口,国外对中国实行技术封锁。介绍了一套基于频率步进原理的TDR,利用该原理信号源输出的频率分量能够精确获知,接收信号中的噪声有效被抑制;研制了探针转换器,避免在常态测试区域出现测试盲点,提高测试范围和精度。最后通过水、空气及土体3种介质中含水率测试对比试验,验证了新型TDR测试设备的有效性。

The time-domain reflection method (TDR) based on the time-domain carrier-free pulse principle can test volumetric water content of soils timely and accurately and is widely applied in geotechnical engineering. But all the TDR testing instruments are imported at present, and some foreign countries implement blockade on the techniques. A set of TDR system based on the principle of stepped-frequency is recommended. The output frequency component of the signal source can be accurately known and the noise in the received signal can be effectively restrained. A reasonable probe converter is developed to avoid blind spots in normal testing area and to improve testing range and accuracy. Finally, the effectiveness of the new TDR testing equipment is verified by comparing the volumetric water contents of water, air and soil.