What does the tank road in the park mean?

You should be talking about the bouncing stone road, which is also called "tank stone road" in some places.

It is to spread coarse sand and gravel on the road surface first, and level the ground one by one with stones larger than fists. With manpower and hammer as tools, the yards are neat and compact, and the gaps between stones are filled with sand and compacted.

As shown in the figure below: