# How would ground pressure effect cyborgs of varying weight?

In the world I'm working on human civilization is mostly dead and the planet is gripped in nuclear winter. Most of the people who've survived are cyborgs. While these cyborgs are still humanoid they vary in weight. A cyborg with the size and proportions of an average human can vary in weight from 30 to 250 KG. Under which terrain would these cyborgs have to worry about ground pressure?

The main terrain I'm interested in are: snow, road/highways, concrete.

### Snow

I want to use this to introduce people to the concept of ground pressure. There would be a scene where a lighter civilian cyborg walks on top of the snow while a heavier military/sports/luxury cyborg has to march through the snow. My main question on this is how light would someone need to be in order to walk on top of snow assuming average surface area of human male feet?

Without human maintenance the quality of the highways deteriorated quickly. Before the war period would society need to set laws preventing cyborgs from running at super human speeds (>45kmh) to prevent them from destroying the roads?

### Concrete

How high would pressure need to be in order to leave foot prints on concrete? How much force could they exert unto the ground before it breaks. Would they benefit from jumping on all fours in order to avoid losing energy to the concrete breaking underneath them?

### Ice covered lakes

Due to the nuclear winter many bodies of water have frozen over. My question for this is how would smaller holes effect the stability of the surrounding ice. i.e. if a cyborg decided to balance on one toe which led to a small hole, would this cause the ice to no longer be able to hold the cyborg up?

Any other scenarios that I'm missing?

Also where can I get relevant data like: surface area of different body parts, max pressure of different materials, formulas for calculating this stuff?

• You are asking a lot of questions in one post. Sep 27, 2020 at 20:18
• @TheDaleks they're closely related, I think it's fine. The same physics formula can answer each of the questions, just with different values. Sep 27, 2020 at 20:27
• Side note: 150kg is not really that much; you could compare it (as in The Daleks's answer) to one 75kg person carrying another. There are many and sundry factors to carrying someone but I've never heard of floors breaking as a potential hazard, even indoors. Sep 27, 2020 at 20:48
• @Cadence true I should probably tack on another 100 kg to the max weight Sep 27, 2020 at 21:03
• It's not really the weight, it's the sturdiness and agility of cyborgs that would affect the pavement. 250 kg man walking on asphalt is nothing. 250 kg man running at 45 mph and hard landing on it after jumping off 3 story buildings would bring cracks. Sep 28, 2020 at 16:28

Provided that your cyborgs follow the basic humanoid bodyplan, here's a list of steps (derived from the owner's manual for the Panzerkampfwagen VI) to acquire accurate data on this.

1. Find a strong buddy who's willing to give you piggyback rides.
2. Go to the various types of terrain.
3. Have your friend give you a piggyback ride across it.
4. If you sink in, you have a problem.

Here's some educated guesses.

Snow:

• Thickness < 2 feet: They should be fine, although it'll slow them down a bit.
• More than 2 feet: Forget about it. They'll end up uselessly floundering the moment they encounter a drift.

Highways: Yes, the pre-war era would need regulatory laws. Post-bellum, it'll be at least a little better than bare ground, but they'll be slick.

Concrete: They won't leave footprints in it, although it will wear out.

Ice-Covered Lakes: If it's anything like North Dakota (I've lived there; it's practically a nuclear-winter-stricken wasteland anyway), they'll be fine. I can attest from experience that people drive pickup trucks on that stuff to get to good icefishing spots. That being said, they probably wouldn't be jumping up and down on it.

• I'm not sure cyborgs would actually damage a road surface that badly, but going up to highway speeds is such a bad idea for other reasons (low visibility, poor braking ability) that it's better for them to stick to surface streets anyway. Sep 27, 2020 at 20:28
• @Cadence I was sure that cyborgs would bang up roads. Think about how your foot hits the ground when you sprint. It's a lot of force concentrated unto one point. Then multiply it several times over since the cyborgs are heavier and stronger. Sep 27, 2020 at 20:32
• @Cubedspartan Sure, it's more than a regular human by a fair bit. I'm just not sure how it compares to, e.g. motorcycles, or racing bikes with high-pressure tires. Sep 27, 2020 at 20:39
• @Cadence For a sense of scale I just found an article about horses damaging highways with their studded shoes. Horses are much heavier then the max weight that I mentioned but these horses were probably walking not sprinting. Sep 27, 2020 at 20:45
• @Cadence there's a difference between static load and impact and the way and amout of force both put on a surface. That said cars are over 300kg per tire, and the contact pach is smaller than the average foot. That'd more than make up the difference from impact. Oct 5, 2020 at 17:19