When you have built your retaining wall, then you will need to add some backfill to the hole in order to shore up the wall, and prevent any type of collapse of the underlying structure. When you are ready to add your backfill to the hole, you should make sure that you have enough suitable material to install in the hole, and also take care that you avoid problems such as collapse of the backfill after it has been in the hole for a while.
1. Sift the Backfill
Before you start working, you should ensure that you take the time to sift the backfill. You are looking for lumps of soil that might loosen under pressure, and flatten out, and you are also looking for vegetation and other products that might degrade with time. Rotting vegetation is one of the key reasons why backfill piles collapse, and you need to avoid this, as it can easily damage your wall if there is not enough support to hold it. Remove roots, grass, plant matter, compost and lumps of soil, and anything else which you fear might cause the backfill to fall in upon itself. Once you have sifted the backfill, you can then place it upon a tarp, or a layer of newspaper, or even some old bed sheets, until you are ready to fill it in.
2. Manual Filling
At first, filling the hole manually can seem like a bad idea, particularly if you are not used to working heavy loads. However, there are advantages to doing it this way, including being able to take a good look at what is going into the hole. If you have sifted the backfill properly, then you should be clear of degradable products, but filling by hand allows you to make extra sure. You can also compact the backfill, which you would not be able to do with a simple machine.
Fill the hole starting at one side, and pour it as levelly as you can. Don't try and lift too much when you begin to add the backfill, but work regularly. If you are concerned that you cannot fill all of this without causing some damage to yourself, consider calling in some friends to assist you while you work.
3. Machine Filling
The other option for easy filing is to do it using a machine. Earth movers are the obvious choice, but they may not be suited to the ground around you, or may just be too large. Mechanical shovels, which can be rented from home improvement stores or garden centers, are often the best. These usually run on gas-powered engines. Using these can sometimes mean that you don't get as even a layer on your backfill as you would like, so one option is to work the machine until you have almost reached the top, and then use a manual shovel to fill in the final level of backfill.