This is definitely doable solo on excavation, I just did it myself. There's some obvious strategies such as kiting the enemies around the map and on the upper ledge that leads to the 10k door. Make use of the two traps to take out as many enemies as possible. You should also use an amulet that has a good area of effect attack. And use grenades as much as possible.
Also you might not have noticed but when there's an enemy getting close behind you a zombie hand pops up at the bottom of the screen as a part of the HUD. (I'm not sure if it does this 100% of the time)
I had been using Frank Fairburne in the campaign so I used him here(I like the head explosion perk). The amulet I used was Deadly eye of Horus, which one hit kills 6 enemies if they're close by in front of you. I'm sure there's a bunch of other good combos. Gracie's fast explosive perk would come in handy, and her raging bull amulet move is pretty op, but you can be hit while it's activated so be careful with that one.
Wave 1: just kite and use pistol, traps, and grenade. Might want to save amulet for beginning of wave 2. Only enemies here are basic zombies
Before wave 2 I bought the Chamberlain Auto rifle (700 gold)
Wave 2: kite, traps, grenades. Might want to start using the upper ledge here and funnel enemies to the spinning blade trap.
Enemies: regular zombie, armored sword zombies, the armored ones shoot acid at you sometimes so watch out for that.
Before wave 3 I spent 3000 gold on the random weapon crate that gives you a powerful 3rd weapon, I was lucky and got the scarab launcher.
Wave 3: same strategies as 2
Enemies: regular zombie, armored zombie, mummy The mummies have the underground ranged attack that you have to watch out for. After kiting a bit and using grenades and my amulet ability, I funneled the rest into the area leading up to the upper ledge/walkway, and unloaded my scarab launcher.
At the end of wave 3 the achievement should unlock.
Main thing is to watch out for the ranged attacks. I hope this helped.