The expansion required digging the soil deeper, which was the hardest job to me, since the original soil was so hard that root vegetables like daikon radishes can not grow in soil.
After 2-hour chore, I was able to create new gardening spaces, which are shown with yellow-lines in a photo shown below.
Drainage is always my concern when I think of changing design of my plots. I dug deeper the soil to create drainage to make water run to a main drainage.
I believe the expansion can give me a great hope for harvesting more various kinds of vegetables.
I want to try to grow fruits like strawberry and herbs in the new spaces. I'm looking forward to seeing my plots will be filled with colorful vegetables and fruits in near future.