This answer explains that this regular grid of concrete posts at Baikonur LC-1 Gagarin's Start is designed to reduce damage to the launch control bunker beneath it in the event of a catastrophic failure soon after launch:
Подземный бункер пуска - самое близкое к старту место. Над ним специальные бетонные столбики, так называемые волнорезы, чтобы ударная сила не повредила этот стратегический объект.
The underground bunker is the closest place to start. Above it are special concrete columns, so-called breakwaters, so that the impact force does not damage this strategic object.
How do these pillars help reduce damage to the bunker?
Clearly such a failure would result in devastating damage to the vehicle and any unprotected surrounding infrastructure.
Grid of pillars with Soyuz MS-09 launching in the background
Annotated map - pillars highlighted in red; background buildings in yellow.
View of launch site showing the grid and the bunker entrance (blue) in the background
Note - this question has changed to reflect the developments in the related question