I am new and bought the Bachmann Thunder Chief set and have added to the track layout. Now with more track and 14 DCC controlled turnouts, I was wondering how to individually control those additional turnouts over the first 9 that my controller allows.

Well I'll be,
 Someone has run into the same issue I ran into.   With that, this is how I solved this problem.  It was painful but it works very well now.  For all the DCC turnouts I had, I changed out all the ones that were easy to get to.  That is, I replaced the DCC controlled turnouts with the analog turnouts.  These analog turnouts are now on a separate power supply and therefore do not task the trains power (track power) to perform switching.  The remaining DCC turnouts that were hard to get to were left intact which meant that I didn't need to have more than 9 DCC controlled turnouts.  Currently I use only 5 DCC turnouts that are seldomly used off my mainline.  Plus those are turnouts that are hard to get to.  My 4 x 8 section of the layout, one side of the 4 x 8 is against the wall where the DCC turnouts are located for example.  Kinda hard to get to- reaching over that 4 ft span.

There is another way to control those DCC turnouts but it will task your knowledge while moving trains on your layout.  Again, moving more than one train could cause issues during your switching.  Therefore, program two or three of your DCC switches to the same logic number. This would allow freeing up other numbers of DCC switches for the remaining logic numbers.  For example,   If there is a siding that has an entrance and an exit, program both the exit and entrance to the same logic number, say program button 1.  In other positions double up on those where when you press say logic number 2 two switches would change position.  Do this for the other switches where a switch needs another switch to be repositioned at the same time.   As you will observe it will free up some of the 9 logic positions available.  Of course this method becomes complicated when there are more than 2 locomotives operating at the same time.

Hope this helps.


Additional reference info can be found here:
Simple answer to feeder lines
Decoder-equipped turnouts with the same address - Only one works