why does the green knight strikes three blows? is there a symbolic link betewwen the three blows and the three days sir gawain spent at hautdesert?

There is a symbolic link between the number of blows and the time that Gawain spent at the castle. The first two blows represent his first two days at the castle when he KEEPS his part of the bargain and gives his host back what he's won. The blow to the neck (and the slight cut) represent the fact that he broke his promise and did not return what the host's wife had given him; namely the girdle.