Case study: a 13-meter high single berm reinforced soil slope with wicking reinforced geotextile at the Nanning pumped storage substation in Guangxi, China

AUTHORS: CHU Jingying, ZHOU Yunhui, and JONG Ching Joo

Heading towards a more sustainable future with lower carbon emissions, China has progressively built more pumped storage hydropower (PSH) facilities, which provide clean energy. PSH systems absorb surplus energy during times of low demand and release it when demand is high. This case study focuses on the Qiushan District, located about 30 km east of the urban center of Wuming District, Nanning City, Guangxi Zhuang Autonomous Region. The Nanning pumped storage substation is constructed on natural terrain, featuring a reinforced soil slope approximately 50 m in length with a 45-degree gradient on the west side of the substation and a height of about 13 meters.

The climate in this area is considered a subtropical humid monsoon climate, characterized by abundant sunshine and rainfall throughout the year. Continuous rainfall, coupled with a shallow groundwater level, is expected to weaken the strength of the in-situ soil. Additionally, the area is subject to earthquakes, prompting the client to prefer a more flexible system compared to the conventional reinforced concrete structure.

After careful consideration, the client decided to adopt a reinforced soil slope system with wicking reinforced geotextile. The wicking reinforced geotextile, with a tensile strength of 100 kN/m, is laid at a vertical spacing of 50 cm throughout the height of the slope. The wicking reinforced geotextile satisfies the long-term design strength requirements as mandated by the design code and is hydrophilic, meaning it can move water in-plane and draw water away from the soil slope, thus providing additional stability. Construction of the reinforced soil slope began in November 2023 and was completed by February 2024. To date, the reinforced soil slope has performed well.