Prologue: arrival

So this is how we will do stone removing: you roll strength check for ever 10 minutes of your work
Result less than 5: you become tired and have to rest next 10 minutes (i.e. spend 20 minutes instead of 10)
Result 5-9 : you work at half speed
Result 10-14: you work normal speed
Result 15-19: twice the speed
Result 20: speed tripled

It takes 200 person-minutes to remove all stones from one pile. You could work together and your effort will sum. i.e. assuming you roll 10 all the time you need to roll it 20 times, 10 times each and it will take you 100 minutes.
As noted previously - you don't know if you will need to remove all of them, perhaps you could dig some hole to squeeze through.

P.S. You will not be able to benefit from short rest if you work this hard.

So it will take Thorem by himself 2 hours to clear the way to the door.

Result 5-9 : you work at half speed
Result 10-14: you work normal speed
Result 15-19: twice the speed
Result 20: speed tripled

1d20+3 : (6) + 3 = 9 = .5
1d20+3 : (7) + 3 = 10 = 1
1d20+3 : (10) + 3 = 13 = 1
1d20+3 : (10) + 3 = 13 = 1
1d20+3 : (20) + 3 = 23 =3

Total = 6.5 or 65/200 needed for the first 50 minutes.

1d20+3 : (11) + 3 = 14 = 1
1d20+3 : (20) + 3 = 23 = 3
1d20+3 : (17) + 3 = 20 = 3
1d20+3 : (12) + 3 = 15 = 2
1d20+3 : (18) + 3 = 21 = 3

Total = 12 or 120/200 needed for the second 50 minutes.

so that is 185/200 now



do another 5o minutes

After you have spend some hour working you suddenly hear a sound like someone is chopping a wood behind the doors... or is he chopping the door? Then you hear a crack and when stones stop shaking you hear from the other side of the doors someone ends the sentence
...set the thing aflame? and just wait until they either burn out or collapse..