That's a good question and I don't know anything RAW.
We did have a similar situation a while back.
Our Mystic was trying to push some orcs into a crevasse. I thought the Blocking skill would be appropriate, even though it's normally used just to prevent people from crossing a line; ie. American football.
This character is a big guy, very strong and had a spear to help push them back. This gave a few bonuses.. a DR mod might be easier.
Since he opposed a group, I (think I) gave them the Coordinated Efforts bonus (SoHK, pg 6).
Then it was a MM vs MM. He won and % of the chart was how far he pushed them back that round based on 1/10th his BMR. IIRC, he had to roll twice (2 rnds total) to push them into the hole.