What is Tunnel Lining? Any impacts on equipment mounting the Tunnel Walll????

Hi, I am a newbie in this forum. I am an electrical engineer and now require to install a control panel on the tunnel wall, which is a new built tunnel and under construction. When doing the installation detail, my client's representative reminded me to get the Tunnel Lining drawings for reference.

Who can help to tell me what is "Tunnel Lining"? Does it affect the drilling depth of anchor bolt on the tunnel wall? or any impacts on the installation design?!

Thanks!!! 😀