"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in
. 3.70:
They make twist on, gel filled wire nuts for that kind of repair.

They're absolutely, positively a total scam, if the soil under which
they're buried is the least bit moist.

They shouldn't be direct burried. Hence Bruce's suggestion for a handhole.
If the spot isn't naturally low and prone to flooding the splice should be
dry and fairly reliable under a handhole cover at grade.