See page 91 of the TRS2004 Content Creator's Guide, version 1.04, for information about a dighole.
From looking at the picture you provided, does the track entering the ground use a tunnel spline to go under the industry? if you don't want to use a tunnel which has a build-in dighole, you can use the track smooth function to create a slot in the ground where the track will go and then cover the resulting gap with some ground plates, concrete slabs or other large objects.
And that's it from me, any more questions - RTFM, search for previous Q&A or start your own thread.
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Now for a tip.
When placing many of the same objects to preserve the local frame rate, vary their heights to avoid that cookie cutter look. You can also overlap and rotate objects like buildings to create different looks.