أنشئ حسابًا أو سجّل الدخول للانضمام إلى مجتمعك المهني.
Yes it can be overlapped .
The two activities can be overlapped as in certain locations eg. in case of tunneling, etc while excavation is being done in one part, previously excavated portion may need shoring. So basically, in our planning procedure, the two activities may overlap