This website shows some hikes and other outdoor activities organized by individuals as well as groups, with the possibility to sign up. You can filter by province(TJ/BJ/Hebei)/date/etc. The website is in Chinese (google chrome translator could help you out with that).
I haven't joined these yet, so can't comment on it, but from what I read through the web-translator it seems quite cool.
--> click on "活动" (Activities) near the airplane icon
8264 is that cool as i've known.. short hike nearby i would like to participate during the weekend.