Games officials have been racing to complete preparations in time but as Britain's Billy Morgan, the first athlete out of the gate, slid into the finish zone volunteers were still hammering poles into the ground to secure crash barriers.
All eyes were on the course following Wednesday's withdrawal of American Shaun White, citing safety concerns.
Australian Scotty James was left clutching his ribs after a heavy fall, but competitors were generally pleased with the course as they sought to make it through to Saturday's final.
"It's demanding, but it works. It's not a bad course," Norway's Torgeir Bergrem, who suffered slips in both his runs, told Reuters in the finish zone
"They're not the most 'poppy' jumps - we're used to getting a little help with our tricks - but you have to do everything on your own here, so I guess that's the main difference that people are struggling with."
Bergrem said that doubts over course safety expressed earlier in the week had been dealt with after organisers trimmed the height of some of the jumps.
"It's not dangerous at all, it's a regular course," he said. "The jumps are regular size, the rails are good, it's fine."
Peetu Piiroinen of Finland, who led after the first run, said that the only problem he had was the light.
"The light is pretty bad, you can't see the takeoffs, there is a shadow on the takeoffs," he said.
Qualifying for three events are taking place on Thursday - a day before the opening ceremony for the February 7-23 games.
(Editing by Ossian Shine)
