This is from a zerg's perspective. Recently it has come to my attention that I have zero clue on how to infiltrate a walled in base. I absolutely love early game harass - in fact I love it so much it probably screws me over for the remainder of the game.
My typical build for ladder is: 10/scout 14/pool 14/gas 16/overlord queen 10 zerglings -> harass
This is where I encounter a walled in base and things start to go completely awry. (sure I could just 6 pool each game but where is the fun in that?)
If I get into the base: cool - I win, destroy workers, kite & profit.
Last night against terran, he completely walled in and went for marines/marauders. I realized my zerglings had no chance - so I built banelings. By the time I had those and was at his base to try and break down the wall/harass, he had a tank or two and my army melted. I pulled away and sat near his nat expo watching for expansion. Then I expanded/fast tech'd to mutalisks (as MM/Tank would destroy zerg t1/1.5 ground army). He moved out with tanks and took out my fast expo just as I was pumping my first mutas, had to let it die. I expanded elsewhere. So did he, I couldn't stop it.
My question: Where do I go from here?
I went for muta harass on mineral lines and hit the front with zerglings for a distraction, but I swear he had so many marines I was rendered useless.
In the end I had my base/3 expansions (two just for gas). I still couldnt keep a muta army big enough to inflict any damage to him. He was riding off base/1 expo and was able to thwart all my attempts at entering. Eventually he had 8 tanks, a bajillion marines, and 3 Thors.
I magic boxed the thors down but died to marines, and then he just walked around the map picking off my expos while I frantically built a pathetic army to try and take out his expo (as stopping his army was impossible at this point).
My only thought is that maybe ultralisks/nydus canal would have worked but really..... it looked bleak and I was tapped for gas just trying to maintain any sort of map control.
(Sorry I couldn't post replay, I am at work; if it is necessary I'll post it later but it is a seriously poor game and boring to watch)
TL;DR - How do I beat someone that deliberately turtles and masses a huge army?
First of all you will need to learn how to beat this; no decent Terran player wont wall against Zerg.
I've had the same issue, Terran definitely has very powerful one base play. As Zerg you have to take control of the map against Terran. Get Mutalisks fast and even if you're not ever attacking keep poking around his base, this does two things. It lets you know what he's doing and what tech he's going and it keeps him in his base - not knowing what you're doing.
Baneling busts will only really work before Tanks, as soon as he has though or if he's close don't bother trying one (but if he's making a bioball still get them as they roflstomp mmm).
To put it extremely simply; expand, control the map, creep everywhere, try to harass him - keeping him on one base, expand more, scout him (send a sacrificial overlord in - or dart in and out with an overseer).
BE READY. When he leaves his base you need to be ready to flank his army on the move. aka without seiged tanks. ultras/hydra at the front, lings/banes from the sides/back throw in some broods and easy peasy.
Also, burrowed banelings somewhere where he'll move through on the way to your base, as he walks over explode them = sad bioball.
The most key thing? Be patient! Your 2-4 base army will beat his 1 base army. But not if you try to attack up his ramp against a wall.
Thank you sir, playing like this has allowed me to win against 3 turtling opponents in a row. I am still waiting to see how I'll do against the bio ball but being patient seems to be the biggest thing that helped me.
I've also started to more aggressively expand my creep, and it honestly makes an entire world of difference.
I have been going for 2 queens early game (around 16-18 food), as it allows me to maintain high larva output and creep really early on.