Comparison and Analysis of Data from Flexible Inclination Meters and Total Stations in Monitoring Slope Deformation at the Lianghekou Hydropower Station

1. Overview

The Lianghekou Hydropower Station is located on the main stream of the Yalong River in Yajiang County, Ganzi Prefecture, Sichuan Province, approximately 25 km upstream from Yajiang County. It is a key reservoir project for the Yalong River's middle and lower reaches, significantly impacting the development of the entire Yalong River cascade hydropower system. The main purpose of the station's development is power generation, while also serving to store water and energy, alleviate flood control tasks in the middle and lower reaches of the Yangtze River, and improve navigation conditions during dry seasons. Its economic benefits are substantial. The dam site is located about 1.8 km downstream from the confluence of the Qiangda River with the Yalong River, controlling a drainage area of 65,599 square kilometers.

The Lianghekou Hydropower Station is the largest hydropower project in the Tibetan area of China, featuring the world's largest high slope group and a domestic maximum earth-rock dam height of 295 meters. Therefore, its safe and high-quality operation holds significant economic, social, political, and ecological importance.

Figure 1-1: Site Map of Lianghekou Hydropower Station

2. Layout and Installation of Monitoring Points

Figure 2-1: Site Layout Map

An 80-meter flexible inclination meter was installed at the "Hagda No. 3 Hole" upstream of the Lianghekou Hydropower Station, with a sensor placed every meter, totaling 80 sensors. After completing the installation, the initial values were recorded, and the automatic data collection frequency was set to once every hour.

Refer to the installation flow chart below.

Figure 2-1: Installation Flow Chart of Flexible Inclination Meter

Figure 2-2: Completed Installation of Flexible Inclination Meter

3. Comparison of Monitoring Results

Figure 3-1: Comparison of Equipment Installation Locations

Figure 3-2: Field Equipment Distribution Map

After the installation of the flexible inclination meter at Hagda No. 3 Hole, the initial value was obtained on June 30, 2023. A total station prism observation point, TPHGD-2, was set up 3 meters away from the measurement hole, with the initial value recorded on August 13, 2021. To compare data from the flexible inclination meter and the total station at the same time, the initial value time for the prism observation point was also set to the closest time to the flexible inclination meter (July 1, 2023).

Figure 3-3: Depth Displacement Process Line Profile for Hagda No. 3 Hole (as of December 1, 2023)

Figure 3-4: Displacement Change Process Line for Hagda No. 3 Hole (as of December 1, 2023)

Figure 3-5: Cumulative Displacement Comparison between Total Station and Flexible Inclination Meter (as of December 1, 2023)

From the above charts, it can be seen that the trends and values of changes from the flexible inclination meter and the total station are generally consistent.

4. Conclusion

The cumulative deformation data from the flexible inclination meter at Hagda No. 3 Hole and the nearby total station over five months show consistent trends, and the deformation data is largely in agreement. Additionally, the slope displacement monitoring data from the flexible inclination meter at Hagda No. 3 Hole indicates that there has been varying degrees of displacement since its installation, with deformation trends not converging. This information has been communicated to the relevant management departments. In summary, the proper application of flexible inclination meters in this project is crucial for early detection and warning, significantly helping to mitigate the risk of landslide disasters.