Got a 10×10 concrete pad in front of house entry way,one end has sunk about 4 in.If i dig underneath both sides could i jack it up with 2 hydraulic jacks or would it break. Slab is 3 in. thick,i dont think it has any rebar in it.I heard about mudjacking,whats the deal on that.
You might be able to tip the slab up, but it is difficult to brace it and get it to stay up. And you are right; it may crack.
Mudjacking is a better way, but it must be done by a pro with the proper equipment. Basically, it is pumping concrete mix under the slab and forcing it up in place. This applies a fairly uniform pressure that should not harm the slab, and when the pumped mud cures, it will stay in place.