Located at the junction of Baiyu county in southwest China's Sichuan province and Konjo county in Xizang autonomous region, a world-renowned ultra-high arch dam project — the Yebatan Hydropower Station — is currently buzzing with construction fervor on the upper reaches of the Jinsha River.

"Cracks are a tricky problem in the process of concrete dam pouring," said Du Guangyuan, director of the engineering management department at Yebatan Branch of the Huadian Jinsha River Upstream Hydropower Development Co., Ltd. He added that even the tiniest cracks can compromise the durability of a dam and shorten its service life.

However, the Yebatan Hydropower Station dam has not shown any signs of cracks so far. The massive challenge of temperature control to prevent cracks during winter concrete pouring in cold, high-altitude areas has been overcome by their construction team.

Overcoming a perennial challenge

"Casting a concrete dam is more like baking a cake. Initially, raw materials are poured into a mold first, then the structure is allowed to take shape within that mold," said Du.

However, pouring a concrete dam is more complex due to natural constraints. During the process, the exterior cools rapidly while internal heat from cement hydration accumulates, causing stress due to temperature differences. Once the stress exceeds the endurance limit of the concrete, cracks will form.

Notably, renowned projects such as the Hoover Dam, Aswan Dam, and Itaipu hydropower station, all have the experience of forming cracks during construction. These cracks not only weaken structural integrity but also reduce the dam's capacity to bear pressure.

The construction of the Yebatan Hydropower Station faces a multitude of challenges, including extreme cold, high altitude, significant day-night temperature fluctuations, steep slopes, the complexities associated with building a high arch dam, elevated ground stress, and a climate characterized by long winters and brief transitional seasons between spring and autumn. These conditions make it far more difficult to avoid cracks altogether.

Temperature-controlled dam

The construction team knew that controlling the temperature was the key to building a dam with no cracks in the area.

The hyperbolic arch dam design increased the difficulty of controlling the temperature.

This kind of structure makes the dam subject to many constraints, so that the temperature change is easy to cause cracks to Appear.

"Traditional concrete crack prevention methods are almost ineffective. The low temperature causes the concrete to freeze quickly, seriously affecting the overall quality of the dam," said Zhong Fulin, one of Du's assistants.

After numerous tests and discussions, they produced an imaginative solution to build a controlled temperature area in the dam.

Zhong explained that in order to control temperature, they introduced Inflated Membrane Structure technology, which sprayed polyurethane, a coating material, on the upstream and downstream dam surfaces, and laid plastic films on the deck and cross peak surfaces to effectively maintain a wet environment. They also set up three layers of "insulation blankets" and added heating facilities such as hot heaters to ensure that the concrete can maintain a suitable temperature after pouring.

Self-monitoring operation

Other technologies are also needed to ensure that cracks don't appear in the dam.

"In the past, we relied on our experience to control the temperature, which is time-consuming and not accurate," said Liu Qiang, executive director of the Yebatan Branch.

Now, they rely on the intelligent temperature-control system to set up a "monitor" for the dam, which improves the efficiency of temperature control.The system can monitor the temperature change inside the dam in real-time. Once an anomaly is detected, it responds quickly and adjusts the state of the facility to ensure that the concrete that has been poured is always at the optimal temperature.

Besides, monitoring is also applied to the intelligent management of engineering construction. Through real-time integration of data, it realizes intelligent monitoring of the whole process from concrete production to vibration operation. In addition, it has set up a one-click operation and unmanned control of the grouting operation.

"These technologies allow the dam to remain crack free in extreme weather conditions," said Liu.