Firstly, we must begin by finding out the surface gravity of such a planet as surface gravity is not dependent only on mass but distance from the center, hence the planet's radius, because
$$
g=G\frac{M}{R^2}
$$
$g$ = surface,
$G$ = Gravitational Constant($\approx 6.67408 × 10^{-11}\,m^3\,kg^{-1}\,s^{-2}$),
$M$ = Mass of object,
$R$ = Radius of object
Utilizing NASA's Exoplanet Archive and filtering for planets with the mass of 2.5-3.5 Earth masses (no planet will have exactly 3 Earth masses), we get 20 planets. That is a low figure. So we add more data from exoplanets.org to get to a grand total of 289 planets (9 excluded as they were discovered by microlensing and hence, we don't know their radii).
The average mass is $2.996925319\,M_\oplus$(Earth masses) (basically 3), and the average radii is $1.395256824\,R_\oplus$(Earth radius) OR $1.71541\times10^{25}\,kg$ and $8457.431881\,km$.
This gives us a final surface gravity of
$$
(6.67408 × 10^{-11}\,m^3\,kg^{-1}\,s^{-2})\times\frac{1.71541\times10^{25}\,kg}{(8457431.881\,m)^2}=16.00542\,m\,s^{-2}
$$
which is around $1.62956\,g$ (Halo rings from Halo have a measured acceleration of $1.55\,g$).
And frankly, as discussions of hypergravity go, this is pretty low. Comparable to reentry acceleration of 1.8 g. This planet would, on a list, come between Jupiter's $24.92\,m\,s^{-2}$ and Neptune's $11.15\,m\,s^{-2}$.
The effects on humans in the long term will be more than noticeable, but not anything critically dangerous or too awesome of a spectacle. The average of 69.2 kg on earth would now weigh 101.03 kg, so not very comfortable, but survivable for a healthy 20-year-old adult. Falling would be a huge problem now as you will fall harder, but the bones and muscles and/or fat that would normally be pushing the weighing scales further would not be there to reduce the impact force. Hunting would much more difficult so would avoiding being hunted (assuming there is local fauna and flora) due to the increased stress on the heart while running. Sitting down would also be very tiring and would be forgotten in favor of lying down as then there is no vertical displacement of blood required. People will want to lose weight and go down to much more tolerable 75-80 kg range, but there actual mass would be between 46.8 and 50, meaning they would need to have a lot of there body to be pure muscle. Fasting, due to lack of food or just exhaustion, would be difficult as there would be little to no fat in the body.
Though there is some hope as long as there are blood-thirsty man eaters out there, as the new citizens just lie down continuously for a day or two with minimal movement, acclimating to the new environment as the heart and skeletal muscles increase in size and strength. No place for flabs here. Except when they are starving and only flabs survive.
Long term survival:-
Reproduction wouldn't be impossible, and pregnancy wouldn't not kill (atleast in mice). But the babies would be lighter, and much more suited to the environment they were born into. The original survivors would also be much stronger and comfortable than before, but leagues behind their children and grandchildren. This is all assuming the original survivors didn't die out, had a guide book of some kind, built some sort of shelter (which may crush them in an earthquake) and had a food source with a decent availability.
Sooo, yeah.
- Have the sudden stress and environment kill some 40% of the initial 100, maybe feed the corpses to the survivors to sustain them.
- Get used to the new environment.
- Get food.
- Get defenses.
- Get shelter.
- Get it on.
Then humanity will do what it does, conquering lands and messing up habitats.
In between, you may accidentally end up ripping off some survival show.