IMO shavings are the most absorbent type of bedding.
How much are you putting down? How big is your stall?
Most my stalls are 12x12, and I put 3-4 bags of shavings in to start as a base, and usually only have to add 1/2 a bag to a bag a day after that. I pick and clean 2/day. First thing in am gets a through cleaning, then later in pm the poos and any big pees are picked out. (my horses are only in overnight from 7pm-7am)
I think The problem is that you have him just on the ground (meaning no base for a stall floor)
I would look into putting a rubber stall mat down. This will allow your ground to stay dry, and not soak up any moisture. Especially if your horse tends to pee in one spot...which alot do. But even then you would need to ensure that your putting ample bedding down to soak up the moisture and for comfort.
My stalls don't have rubber mats, I just have pressure treated wooden planks as a base, with 1/4 down underneath. Have had the barn for 6 years now, and have only had to replace 2 boards due to damage...(but that was from a horse that used to paw in one spot continually)
Horses are like chips...you can never just have one