Ground pressure is the pressure exerted on the ground by the tiresortracks of a motorized vehicle, and is one measure of its potential mobility,[1] especially over soft ground. It also applies to the feet of a walking person or machine. Pressure is measured in the SI unit of pascals (Pa). Average ground pressure can be calculated using the standard formula for average pressure: P = F/A.[2] In an idealised case, i.e. a static, uniform net force normal to level ground, this is simply the object's weight divided by contact area. The ground pressure of motorized vehicles is often compared with the ground pressure of a human foot, which can be 60 – 80 kPa while walking or as much as 13 MPa for a person in spike heels.[3]
Increasing the size of the contact area on the ground (the footprint) in relation to the weight decreases the unit ground pressure. Ground pressure of 14 kPa (2 psi) or less is recommended for fragile ecosystems like marshes.[4] Decreasing the ground pressure increases the flotation, allowing easier passage of the body over soft terrain. This is exemplified by use of equipment such as snowshoes.
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All examples are approximate, and will vary based on conditions
| Object | Ground pressure (kPa) | (psi) |
|---|---|---|
| Hovercraft | 0.7 | 0.1 |
| Human on snowshoes | 3.5 | 0.5 |
| Rubber-tracked ATV | 5.165 | 0.75 |
| Wheeled ATV | 13.8 | 2 |
| Diedrich D-50 – T2 drilling rig | 26.2 | 3.8 |
| Human male (130 kg, standing on one foot) | 55 | 8 |
| Average human, flat shoes[5] | 17 | 2.5 |
| M1 Abrams tank[6] | 103 | 15 |
| 1993 Toyota 4Runner / Hilux Surf | 170 | 25 |
| Adult horse (550 kg, 1250 lb) | 170 | 25 |
| Bagger 288 excavation machine | 170 | 25 |
| Passenger car | 205 | 30 |
| Adult elephant | 240 | 35 |
| Mountain bicycle | 245 | 40 |
| Road racing bicycle | 620 | 90 |
| Commercial semi truck/Lorrie | 793 | 115 |
| Stiletto heel | 3,250 | 471 |
Note: The pressures for average human and horse are for standing still position.[7] A walking human will exert more than double his standing pressure. A galloping horse will exert up to 3.5 MPa (500 psi). The ground pressure for a pneumatic tire is roughly equal to its inflation pressure.
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