This is the first of the Konkan Railways tunnels – the 290 meter long Dasgaon tunnel. There are other tunnels between this location and Mumbai, but those are on the Central Railways, hence this is T1.
This is the North end portal of the tunnel. Note the rock nets on the side walls of the tunnel entry. The purpose of the laterite blocks and sandbags are explained on this page on the KR website. Also note the communications tower – probably from the Anti Collision Device (ACD) network.
Here is a satellite image of the Dasgaon tunnel.
(Apurva)