What you need are sticks stuck in the ground to keep the log from falling over, like this. http://www.mydirttime.com/050717/050717-14.html
There are plenty of good sized rocks in the woods aroung here but logs work good too. I have not had trouble with deadfalls but I have practices alot, so dont get fusterated and keep at it.

Here is a tip for all of you who set deadfalls. I found this trick out a wile back. When setting a deadfall sit down and hold the rock or log or what ever up with your foot and slowly releas presure onto the trigger. This is much more safe and plus you can use both hands to set the deadfall which helps alot.
I only use one foot but for a very heavy rock maybe it would be best to use two.
Good luck

Translation?

Would it steady if I tied 2 or 3 logs together?

If this is the right translation of your question the answer is:
Yes, likely.
If you tie your logs so that you have a flat surface for them to lay on while working.

The string or rope you tie with should be string enough, and the knots should be such that the logs do not have any space to move apart from each other after you tied them. That is, if you lift any of the logs the other should move as if they are one. Not easy to do unless you have straight logs.

If you really want to do this I will help you to find the knots needed.

Willeke