emacs, unsplit a particular window split

I often want to unsplit window as follows:

+--------------+-------------+			   +--------------+-------------+
|              |             |			   |              |   	       	|
|              |             |			   |              |   	       	|
|              |             |			   |              |   	       	|
+--------------+             |     -->	   |              |   	       	|
|              |             |			   |              |   	       	|
|              |             |			   |              |            	|
|              |             |			   |              |             |
+--------------+-------------+			   +--------------+-------------+



+--------------+--------------+			   +-----------------------------+
|              |              |			   |                             |
|              |              |			   |                             |
|              |              |			   |                             |
+--------------+--------------+    --> 	   +-----------------------------+
|                             |			   |                             |
|                             |			   |                             |
|                             |			   |                             |
+-----------------------------+			   +-----------------------------+

Currently, I start with ctrl-x 1 and then split vertically/horizontally. but my real qustion is how can one remove a particular window split with out disturbing the other window structure? Is there any elisp function in built?

You can use the C-x0 key combination to delete the current window.

Rémi's answer is what you're looking for, but winner mode is also extremely useful for getting you back to previous window configurations after making any arbitrary changes (such as restoring those multiple-splits after typing C-x1).

You can enable it in your init file with:

(winner-mode 1) ;"C-c <left>" and "C-c <right>" undo and re-do window changes.

Also see: http://www.emacswiki.org/emacs/CategoryWindows