What is the story of the "intercepting stone" of Sanmenxia water control project?

Story: In the summer of 1958, Sanmenxia Dam of the Yellow River entered the substantive construction stage. Because the Yellow River is famous for its fierceness, the river is even fiercer, and the pier prepared in the middle is washed down, which has caused great difficulties in river closure. After many efforts, Soviet experts and China engineers and technicians who participated in the construction finally designed a tetrahedral triangular concrete block weighing 15-25 tons. The river closure was originally planned to take 12 days, but it actually took less than 6 days to successfully intercept the river, and the task was completed ahead of schedule. Finally, the whole Yellow River was successfully intercepted.

The meaning of tetrahedron:

Tetrahedron became a hero in the history of river closure in China. Because it was used for the first time in the construction of Sanmenxia Dam, in order to commemorate its achievements, Sanmenxia City decided to set up an unused "tetrahedron" as a monument in the leisure square of the Economic and Technological Development Zone in the 1990s, so that more people can understand the construction history of Sanmenxia.