Logs can be great fun and can occur singly, in a pile, or in succession.
Any combination is possible.
One key is to lift up the handlebars either before or during contact with the log. Frequently, your chainring will contact the log as you pedal over. A good one will not bend or be damaged. A rock ring may be used, but I prefer just using the large chainring. Teeth can be damaged on rocks or logs, so maximum ground clearance is important.