Monday, April 15, 2019

Rock Fall Momentum: An Example at Highway 397

The construction of Highway 397 was completed to provide a bypass around Kennewick to the east side of the city and to Finley. The route through the Horse Heaven Hills involved a number of cut and fills to achieve acceptable grades on the highway. One spot where there was excess cut material at the grade down to Zintel Canyon made for a nice illustration of momentum and rock fall run out. 

2004 image of cut and fill work on a portion of 397. 
Cut material was used to fill the side canyon the road was crossing.

2006 image of excess cut material deposited on the slope below the cut area
 
On the ground view looking up at slope

A boulder that traveled well beyond where most of the other rocks stopped

Several rocks traversed the entire slope to the valley bottom

Not a particularly complex concept, but a nice illustration of how the larger boulders with greater mass and thus initial momentum had enough energy to travel well beyond the distance of most of the smaller rocks that had been disposed of at the top of the slope. 

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