Are there any rules for digging out of a grave?

Question

Here is the situation. The villain used a Sleep spell to take out a player.

each creature affected by this spell falls unconscious until the spell ends, the sleeper takes damage, or someone uses an action to shake or slap the sleeper awake.

Then he used Mold Earth to make a 5 foot pit.

If you target an area of loose earth, you can instantaneously excavate it, move it along the ground, and deposit it up to 5 feet away. This movement doesn’t have enough force to cause damage.

Then he used the Gust spell to move the player into the pit (auto fail of saving throw due to being unconscious.)

You seize the air and compel it to create one of the following effects at a point you can see within range:
One Medium or smaller creature that you choose must succeed on a Strength saving throw or be pushed up to 5 feet away from you.

He then quickened another Mold Earth spell to cover the character up with dirt.

My question is, how long will it take for the character to dig through a 5' cube of dirt? Are there any rules for this?

The amount of time matters because the character only has his Constitution modifier in rounds to live without air. The character is asleep when the dirt covers him, so he doesn't get an action to hold his breath.

Time will end up being a plot device to give other characters a chance to save him.

Answer 1

There are no general rules for digging speed

There are no general rules for how quickly characters can dig, whether they're doing a proper excavation from outside the hole or if they're trying to dig themselves out of a grave.

Other answers have fairly pointed out that the realistic effect of being shoved into a hole and having a five foot cube of dirt dropped on you is that you die; the pressure of a couple of tons of earth will squeeze the life out of anyone pretty quickly. So, in the real world, the unfortunate character is dead and there's not much they can do about it.

However, D&D is a system where sufficiently heroic and healthy adventurers can easily survive falling a thousand feet onto rocks and will then stand up and walk it off, so the realistic ruling doesn't strike me as being particularly genre-appropriate. You probably want the unfortunate character to have a reasonable chance of surviving, especially if you don't want this particular trick to become your players' go-to method for defeating any medium size enemy.

A specific example of digging out a buried character

A quick search on D&D Beyond for any similar situations from the published books reveals the Hidden Shrine of Tamoachan adventure, from Tales From the Yawning Portal, in which there is a scenario which can result in an adventurer being buried by rubble:

Cave-In. Attempting to dig upward through the rubble in the west end of the room results only in more detritus falling into the area.

Any further collapse deals 2 (1d4) bludgeoning damage to each digger. Each digger must also succeed on a DC 13 Dexterity saving throw or be buried by the rubble and take another 7 (3d4) bludgeoning damage. If the saving throw fails by 5 or more, the rubble engulfs the digger completely, and the trapped character can’t breathe until dug out. Struggling out on one’s own requires a successful DC 15 Strength (Athletics) check, and doing so takes 1 minute.

So in this case, the adventurer is sufficiently buried that they cannot breathe, and extricating themselves on their own requires an Athletics check and a minute of effort, though it does not specifically clarify how long it would take for another character to dig them out - I'd suggest that would be a minute as well, reduced proportionally if multiple characters work together. You could lift this mechanic directly to use in your own situation.

Personal ruling

If I were adjudicating your situation, then I would rule along these lines:

• When mold earth is used to excavate and move earth, the pile of earth that results is well aerated and very loosely packed, so it is easy to dig through and isn't very dense.
• The character hit by gust will auto-fail their strength save for being asleep and so get shoved five feet, but the shove by the gust would be enough to wake them up, so they should get a dexterity save to avoid falling in the hole in the first place (use the caster's spell save DC, disadvantage for being prone applies); if they succeed, they managed to roll to the side of the hole.
• Dropping the dirt on the character might conceivably do a few d4 of damage with a dex save to avoid (they'll probably be prone when it happens, so that save has disadvantage too) - but move earth doesn't move earth with great force or speed, and it wouldn't be falling far, so it's unlikely to deal an initial bludgeoning injury.
• Once buried, the character cannot breathe, so will start to suffocate in the default 1 + con mod minutes. (I assume they're awake and can see the dirt starting to fall on them, and they have a chance to take a breath before they're buried. If not, the trap is obviously a lot more dangerous.)
• A buried character can make Strength (Athletics) checks as an action to try and extricate themselves from the grave - for consistency's sake, might as well just continue to use the caster's spell save DC to set the DC for that check. For dramatic tension, the character needs to accumulate three successful athletics checks before they finally emerge from the ground.
• Allies outside the grave can use actions to make their own athletics checks to contribute to getting the victim out of the grave. They're flinging armfuls of loose soil away to tunnel down to their ally. If they succeed they manage to get ahold of the creature and pull them up through the dirt.
• A successful extraction doesn't mean somehow digging out the entire five foot cube in less than sixty seconds; the character will manage to get up and out through a narrow tunnel in the earth, so the actual volume that needs to be shifted by the characters involved is quite small.

To me this creates a scenario which the character has a reasonable chance to avoid (so doesn't feel totally unfair if they do end up in the hole), is likely survivable (a couple of cantrips shouldn't be able to arbitrarily kill things) and the mechanic of surviving is dramatic enough to be interesting and rewards teamwork by the players. I would, however, be preparing myself for my players to start trying to use the same trick whenever they have the opportunity to prepare a battlefield before a fight.

Answer 2

The fancy unconscious/initial dig is not that important. Arguably the PC was awake after being dropped 5' into a pit, but prone, as being pushed 5' by wind then dropped 5' is a lot more impactful than a slap, and definitely shakes the creature.

So the question becomes, there is a creature prone in a 5' square pit. Someone uses mold earth to bury them. How quickly do they die?

The answer is:

Mold Earth doesn't work that way

Mold Earth cannot be used to do damage. You aren't allowed to grapple someone with mold earth, restrain them with mold earth, or push them around with mold earth. You can make earth flow along the ground, you cannot make it flow over someone.

If you target an area of loose earth, you can instantaneously excavate it, move it along the ground, and deposit it up to 5 feet away. This movement doesn’t have enough force to cause damage.

So the earth fills the hole, and the PC ends up on the surface again, if you allow using Mold Earth to lift someone; or the dirt doesn't end up over the PC. Because the earth you move can only move along the ground, it cannot end up above the PC in the hole. Because in order to be above the PC, it was not moving along the ground.

Now, you could read "along the ground" as "so long as any part of it is touching the ground", but then Mold Earth becomes a way to drop tonnes of matter as an action; this contrived example is just a hard way to do it.

There is a type of rules bending where you do a bunch of contrived things chained together, as if the complexity of the chain makes the result somehow more justified. This just looks like an example of it.

Mold Earth is a powerful utility cantrip, it is not a combat cantrip for killing creatures directly.

But lets assume you are ok with Mold Earth being used as a weapon.

It is my game, Mold Earth works like that

A 5' deep hole with vertical sides is not stable in loose Earth. The angle of loose Earth is about 30' off horizontal (give or take), after which it collapses, and of the Earth wasn't loose Mold Earth cannot have moved it.

As the pit can be no more than 5' wide, that means the bottom is no more than 2.5' down. You then put a 5' cube of Earth above them; this collapses into a cone immediately.

$$(5 feet)^3=2 \pi r^2 \frac{h}{3} - 4 ft^3 $$

The 2 here represents the double cone (from the depression and the pile above it), and the \$ - 4 ft^3\$ term the rough volume of the buried person.

With a 30 degree angle, \$h = \frac{r}{2}\$, so we get

$$(5 feet)^3=h^3 \frac{8 \pi}{3} - 4 ft^3 $$

$$ \frac{363}{8 \pi} feet^3 =h^3$$

$$ h = 2.4 feet $$

Or about 2.4 + 2.4 feet deep.

From NASA male american chests are about 25 cm deep, or about 10 inches. So the total depth the person is buried is about 4 feet in the center.

The person is about 55 cm broad (call it 2 feet) and 160 cm tall (call it 6 feet). Every 2 feet away from center the dirt is 2 feet shorter, as both the top and bottom slope together; assuming centered, the head and feet are about 1 foot down, and the arms are under 1-2 feet of dirt.

1 cubic foot of dirt weighs about 80 lbs. if not crushed to death, they can probably kick their legs free (legs are strong).

Getting even a bit of vibration in your extremities would start making the dirt above shift, giving you more freedom to move. Your lungs wouldn't be emptied by that pressure, just compressed. So you will have some time to attempt to escape.

Someone outside who knows where your face is should have no problem digging off the foot of dirt before you suffocate.

Are you crushed to death?

While the weight of dirt is large, they are in effect a fluid-filled tunnel in it. Some of the force of the dirt will go around the body, and the body will be supported from below and from the sides by more dirt.

If you are 8 feet deep in a pool, you have more mass over you than you would with this dirt pile on top of you, and that mass has less structure than the dirt does. You aren't going to insta-gib just from the weight.

Answer 3

Under the condition that the GM decides that it works as depicted by OP:

He's dead Jim

Sorry to break this to you, but the character will be squished by up to 11.8125 metric tons (~13 US tons) of loose dirt the moment the spell Mold Earth releases the grasp on the ground: That excavated cube is about 3.375 m³. The heaviest rocks have a density of about 3.5 t/m³. That's about the weight of 10 Toyota Yaris or a Peterbilt 389 tractor, or roundabout the weight of a Panzerkampfwagen 35(t). Agricultural soil has a density of 1.1 to 1.6 tons per m³, so our cube weighs only between 3.7 and 5.4 metric tons. Only about 3 Yaris to one Panzerkampfwagen 1.

The cube has 2.25 m² that actually press down, the human only exposes about 1 square meter of crosssection upwards, so our human laying in there is technically only pressed together by sitting between a weight of 5.25 tons for our heavy rock (actually a metal-ore) and a hard place. Or in more figurative terms: a whole Panzerkampfwagen 1 is parking on him and him alone. For dirt, it's only 1.6 to 2.4 tons. Or about one and a half to two and a half Toyota Yaris. All stacked onto your body.

Or, if we calculate for different body parts using the 9-percent-rule, we have a minimum of 144 kilos placed on the head and 576 kilos on the chest. Yes, more than half a Toyota Yaris ends up on the chest alone. And the weight of two 1-liter 1KR-FE engines (that are used in the Yaris) ends on the head. Or if you prefer: a Panda. Sure, the human body can withstand a lot, and getting squished by a weight of 340 kg on the torso takes about 15 minutes while 180 kilos isn't lethal to a human usually. So, just the crushing alone on the torso is rather lethal - and since the weight is not put down gently like in the judicial crushing, it comes down like a rock. You won't survive more than moments.

With that kind of weight, the crushing damage incoming the moment the spell releases the earth is so ludicrously high, that any GM should refuse to even calculate damage extrapolations from falling roofs... Ok, well, I did: if you assume 4d10 per 100 kilos striking someone with a piece of roof (that's the collapsing roof), I expect between 64d10 to 96d10 damage per round for loose dirt just sitting there on the body and continuing to squeeze.

That's enough damage that I wouldn't even allow any death-saving rolls. He's Dead Jim. Dig him out and then pay someone for a Resurrection spell.

The good news

The crushing damage will be so swift, that suffocation doesn't matter. And neither does the depth of the hole: it takes 10 feet to inflict 1d6 damage.

The bad news

The crushing damage will be so swift, that anything short of magic to try and dig him out or teleport him out of the 5-feet deep hole doesn't matter.

What if... I had a coffin?

If you have a coffin, GOOD NEWS! The coffin can take all the weight off your chest and you won't get crushed. Also, you now have (for a typical coffin and human) about 820 liters of air around you in your box, enough to last you roundabout 5 hours and 30 minutes, if you stay calm. That's enough time for the other heroes to get shovels and dig you out - because Kill-Bill punching your way out will just get you buried with a small crater above you. Ask the Mythbusters, Season 1, Episode 8. Or to quote a professor:

“There’s nothing someone [buried alive] could do. Once you’re in there, you’re in there,” says Alan R. Leff, professor emeritus at University of Chicago in the pulmonary and critical care department.

Word of Advice

Please, dear GM don't let the poor lad wake up from falling down there, or at least don't ever describe whatever he sees last when the earth literally swallows him and puts the equivalent of half a tank over the body. The more I researched into what happens in this trap you proposed, the more it becomes apparent that a character that witnesses such should be deeply scarred emotionally, and should the character swallowed this way somehow survive or be resurrected, he better not remember the last 6 seconds of his life.

Luckily...

Mold Earth moves earth along the ground and should float our victim back up the hole, as he is not part of the ground.

Answer 4

The character is dead.

Based on this reference, the lower end for the weight of a cubic foot of soil is 74 pounds. The character is buried under 125 cubic feet of soil, or at least 9250 pounds of soil. But let's be more conservative - the character is not 5 feet by 5 feet. Suppose the soil directly above the characters body is more like 2 x 5 x 5 feet, or 50 cubic feet: 3700 pounds. The rules for lifting weight state:

You can push, drag, or lift a weight in pounds up to twice your carrying capacity (or 30 times your Strength score).

Now, suppose we are a Goliath:

You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift.

Counting as Large for the purposes of lifting:

For each size category above Medium, double the creature's carrying capacity and the amount it can push, drag, or lift.

Putting it all together, a 30 Strength Goliath can lift 1800 pounds. Less than half the weight of the dirt on top of this character.

He ded.

Answer 5

You’ve asked for digging rules. Other answers have explained whether or not the situation works as you plan, but if you go for it (or find another way to engineer the situation) and want digging rules: The closest I can find are in Dragon of Icespire Peak, which I presume counts as fairly official?

I can’t remember how to mark a spoiler on my phone, so I’m not going to say which encounter this is from. The encounter expects that someone gets buried behind 25’ of earth. When my party ran this, they had no problems digging out a buried creature before they died, but it was suitably tense, which is I assume what you’re wanting.

Note that the buried creature can’t do anything to save themselves.

“A buried creature is blinded and restrained, has total cover against attacks, and begins to suffocate when it runs out of breath (see "Suffocation" in the rulebook). Only a creature that is not trapped in the tunnel can clear away the collapse, using an action to open up the 5-foot-deep section of tunnel closest to it. A creature in that space is no longer buried.”

This gives a horizontal digging speed of 5’ per (6-second) round.