Automated Monitoring of Deep Displacement at the Dunhua Pumped Storage Power Station

1.Project Overview

Figure 1-1: Site Map of Dunhua Pumped Storage Power Station

The Dunhua Pumped Storage Power Station is located in the northern part of Dunhua City, Jilin Province. The station has convenient access, being 111 km from Dunhua City, allowing for the transportation of materials and large components to the site via road, rail, or water transport during construction. The station consists of an upper reservoir, water conveyance system, underground powerhouse, surface switch station, and lower reservoir. The underground powerhouse is equipped with four reversible Francis turbine generator units, each with a capacity of 350 MW, for a total installed capacity of 1,400 MW. The upper reservoir is an asphalt-concrete core rockfill dam with a maximum height of 54 m and a total storage capacity of approximately 7.81 million m³; the lower reservoir has a total capacity of about 8.64 million m³. The overall layout of the project includes the upper reservoir, lower reservoir, waterway system, and underground powerhouse. The upper reservoir is constructed in the Yingtaogou area at the headwaters of the Hailang River using excavation and damming methods. The reservoir is bordered by three rounded hills and two passes, with an asphalt-concrete core rockfill dam built at the eastern entrance of the reservoir basin using excavated materials. The dam site features strong hills on both banks, providing good conditions for dam construction. The upper reservoir project includes the asphalt-concrete core rockfill dam, reservoir excavation, seepage prevention works, and access roads. The lower reservoir is situated at the source area of the Dongbei Chao River, creating the lower reservoir by damming the river. An asphalt-concrete core rockfill dam is constructed in a narrower section of the river valley, utilizing excavated materials. The dam site also has strong hills on both banks, providing good construction conditions. The lower reservoir project includes the asphalt-concrete core rockfill dam, right bank spillway, right bank flood discharge tunnel, reservoir excavation, and seepage prevention works. To monitor the condition of the dam in real-time and ensure the safe operation of the Dunhua Hydropower Station, as well as to provide a scientific basis for emergency operations, the safety monitoring unit has employed Huasu flexible inclination meters for automated monitoring of the landslide.

2 .Overview of Equipment Layout

A 29-meter flexible inclination meter is installed on the slope of the Dunhua Pumped Storage Power Station powerhouse, with a total of 29 monitoring points. The flexible inclination meter has a resolution better than ±1.08″, a measurement accuracy of 0.02 mm/500 mm, and system stability better than ±0.5 mm/32 m.

3 .Twist Correction

The direction of the measuring guide slot of the inclination meter did not align with the main direction of deformation to be measured, forming a 37° angle that could lead to measurement errors. During the installation of the Huasu flexible inclination meter, the twist correction function was utilized to align the installation direction with the monitoring direction, ensuring measurement accuracy. The initial value for this monitoring point was obtained on September 18, 2021. As of December 2023, the instrument has been operating stably, with good continuity and integrity of monitoring data, none of which has exceeded the threshold. The cumulative displacement curve before the twist correction is shown in Figure 1, with a maximum cumulative displacement of 4.2 mm at the hole. The cumulative displacement curve after correction is shown in Figure 2, with a corrected maximum cumulative displacement of 8 mm in the positive direction.

Figure 3-2: Cumulative Displacement Curve Before Twist Correction

Figure 3-3: Cumulative Displacement Curve After Twist Correction

4.Conclusion

This monitoring project demonstrates the unique advantages of the Huasu flexible inclination meter in such monitoring projects through its twist correction function, even when the measuring guide slot direction does not align with the main direction of deformation.