I have an apk of 80Mb and so am not able to upload it on google play store. I have googled a lot and found that I have to create .obb file as the main expansion
Try this
$ jobb -d /temp/assets/ -o new-obb-file.obb -k secret-key -pn com.my.app.package -pv 11
Where
-d : Set the input directory for creating an OBB file.
-o : Specify the filename for the OBB file.
-k : Specify a password for encrypting a new OBB file
-pn : Specify the package name for the application that mounts the OBB file, which corresponds to the package value specified in your application's manifest.
-pv : Set the minimum version for the application that can mount the OBB file, which corresponds to the android:versionCode value in your application's manifest.
Try this command.
check following link http://developer.android.com/tools/help/jobb.html