3.2.1. Fact tables
Fact tables store physical information to describe a factual event.
In this metro tunnel project, the instrumentation data is considered
in the safety diagnosis of the site and is a good reference for safety decisions.
Therefore, all the instrumentation data including the ground
settlement, displacement of the tunnel crown, convergence of the
tunnel, settlement of the adjacent facilities, etc. are stored as factual
data in different fact tables.