✔ 最佳答案
As long as the it goes below the frost line. You did not state what this for . Any time I put in posts for a fence I just used sank a hole deep enough and put in the cement in around the post below the frost line. If you don't put in deep enough the ice in the ground will shift the post. I live southern Ontario so the ground freezes a 6 inches down without a good snow cover. I sank my holes down at least 3 feet down and then added the cement. This way I prevented any shifting of the posts