Comparative Analysis of Flexible Inclinometer and Manual Inclinometer Data for the Middle Route of the South-to-North Water Diversion Project

1.Overview

The Middle Route of the South-to-North Water Diversion Project diverts water from the Danjiangkou Reservoir on the middle and upper reaches of the Han River, the largest tributary of the Yangtze River (the water source is primarily from the Han River), spanning Hubei and Henan provinces. Starting from the project headworks in Xichuan County, Henan Province, on the eastern bank of the Danjiangkou Reservoir, the main canal is excavated. It passes through the Fangcheng Pass, the watershed divide between the Yangtze River and Huai River basins, then runs along the western edge of the North China Plain. The canal tunnels under the Yellow River, continues northward along the west side of the Beijing-Guangzhou Railway, and finally flows by gravity to the Tuancheng Lake in the Summer Palace, Beijing. The total length of the main water conveyance channel is 1,277 kilometers, with an additional Tianjin branch line extending 155 kilometers.

The Middle Route project primarily addresses water scarcity issues in the four provinces/municipalities of Henan, Hebei, Beijing, and Tianjin. It supplies water for production, domestic use, and agriculture to over a dozen large and medium-sized cities along its route, covering a total water supply area of 155,000 square kilometers.

2.Layout of Flexible Inclinometer Monitoring Points

As of December 2023, approximately 5,000 meters of Huasi Measurement and Control flexible inclinometers have been cumulatively installed in the Middle Route project, enabling automated monitoring in about 213 inclinometer holes. The monitoring points are primarily distributed along the route in high-fill sections, deep-cut sections, and key monitoring areas.

Figure 2-1 Completion of Installation for Some Flexible Inclinometers

3.Comparison of Monitoring Results between Flexible Inclinometers and Manual Inclinometers

To verify the consistency and reliability of monitoring data between flexible inclinometers and manual methods, a data comparison test was conducted in September 2020. Through on-site investigation and consultation with the design and operation management units, five representative inclinometer holes that had undergone automated monitoring were selected within the jurisdiction of the Middle Route Qushou Management Division for this test (see Figure 3-1). By comparing the results from automated monitoring (flexible inclinometers) with manual monitoring (sliding-type inclinometers), the test fully validated the monitoring precision and accuracy of the automated system (flexible inclinometers).

Figure 3-1 On-site of the Manual vs. Automated Monitoring Comparison Test

Theoretically, the difference in displacement measured manually before and after the installation of a flexible inclinometer for automation in an inclinometer hole should match the displacement data recorded by the flexible inclinometer during that same period. The test primarily compared the difference in manual displacement measurements before and after automation within a one-year period with the automated displacement measurements from the flexible inclinometer during that interval. This comparison was used to analyze the accuracy of the automated monitoring results from the flexible inclinometers.

Taking inclinometer hole IN01-9585 as an example, the last manual measurement before automation was on October 18, 2019. The comparative test measurement was taken on September 25, 2020. The flexible inclinometer monitoring results cover the period from December 1, 2019, to September 25, 2020. The monitoring results are shown in Figure 3-1.

Figure 3-1 Process Line of Cumulative Displacement Data for Inclinometer Hole IN01-9585

The results above show that the trends of displacement change from manual monitoring and automated monitoring are consistent in both Direction A and Direction B. This indicates a high degree of agreement between the manual and automated monitoring data for this inclinometer hole.

4.Conclusion

Deformation monitoring of large-scale water diversion projects, especially in high-fill and deep-cut sections, under conditions of water immersion, saturation, and various loads and constraints, is crucial for ensuring the normal operation of this "critical national infrastructure" and the well-being of the people. Current manual monitoring methods struggle to provide round-the-clock tracking of deformation in various hydraulic structures. Through the comparison of manual monitoring and flexible inclinometer automated monitoring for inclinometer hole IN01-9585 within the jurisdiction of the Middle Route Qushou Management Division from October 2019 to September 2020, the results demonstrate not only consistent overall deformation trends but also excellent agreement in details and the total cumulative deformation vector, whether considering the trend of measurements, spatial distribution, or cumulative displacement outcomes. This fully validates the unique advantages of flexible inclinometers in terms of measurement accuracy and their capability to adapt to complex deformation monitoring.