I would like to know if it’s permissible to tear down a Sukkah on Chol Hamoed?
For a few reasons.
1. Travel away for the second days, and the Sukka could get blown away or could get stolen.
2. I probably need the place because of the traveling .
Essentially tearing down a succah is doing melacha on Chol hamoed, which is not needed for the chag, and is also preparing (hachanah) for after Yom Tov. Regarding the reasons you are giving, it is hard for me to answer you, becaue I don’t know the extent of the chances that it will indeed get blown down and blown away. If the succah is so flimsy that this is a real fear, that it won’t last for seven days, that might invalidate the succah, (see Tractate Succah 23a). Besides, if it will last for the almost the whole succos, why would it get blown away specifically on the second days?
Regarding your second reason, I don’t understand why you need the place because you are traveling, you aren’t going to be there.