Interstate 5 through the Sacramento River canyon north of Lakehead became an obstacle course Thursday after at least 3 separate big rig crashes between Lakehead and Vollmers. One involved a UPS semi that jackknifed at around 11:30. Another involved a big rig versus a motor home. No injuries were reported. The most serious was the one just south of Sims Road shortly after 10am. A tractor-trailer came around a curve in heavy rain and jackknifed, with the cab hanging up on the center wall and blocking the northbound fast lane and the trailer blocking both southbound lanes. It was very similar to a crash that happened nearby on Monday. Traffic initially got by on the shoulder until the southbound slow lane was cleared about 2 hours later. The other southbound lane was closed until well after dark as the wreckage was picked up and repairs were made to the wall.