The BMC Racing rider hit the rocks on his right-hand side and was attended to by medics, who carried him into an ambulance on a stretcher.
Team doctor Max Testa said Porte had suffered a broken collarbone and a fractured pelvis.
“Normally, a fractured clavicle and pelvis would require four to six weeks’ recovery, providing there are no complications, Testa said.
"If everything goes to plan, Richie could be back on the bike at the beginning of August and slowly build his fitness up from there. Based on Richie’s recovery, we will re-evaluate his programme for the rest of the season in consultation with BMC Racing Team management."
Earlier, Geraint Thomas of Team Sky also crashed out of the race.
"I was looking at him, he was in pain," Porte's sports director Fabio Baldato said.
"He was always conscious. He was asking for his helmet and his glasses."
Baldato added that Porte had ridden the descent four times before the Tour, including once in racing conditions during last month's Criterium du Dauphine.
(Editing by Ed Osmond)
