Assessment of Slope Instability and Risk Analysis of Road Cut Slopes in Lashotor Pass, Iran

Table 9

Rockfall hazard rating system parameters and their scores [35].

Category	Rating criteria and score
	Points 3	Points 9	Points 27	Points 81
Slope height	7.5 m	15 m	22.5 m	30 m
Ditch effectiveness	Good catchment	Moderate catchment	Limited catchment	No catchment
Average vehicle risk (% of time)	25%	50%	75%	100%
Percent of decision sight; distance	Adequate sight distance, 100% of low design value	Moderate sight distance, 80% of low design value	Limited sight distance, 60% of low design value	Very limited sight distance, 40% of low design value
Roadway width included paved shoulders	13.20 m	10.80 m	8.40 m	6.00 m
Geologic character
Case 1
Structural condition	Discontinuous joints, favorable orientation	Discontinuous joints, random orientation	Discontinuous joints, adverse orientation	Continuous joints, adverse orientation
Rock friction	Rough, irregular	Undulating	Planar	Clay infilling or slickenside
Case 2
Structural condition	Few differential erosion features	Occasional differential erosion features	Many differential erosion features	Major differential erosion features
Difference in erosion rates	Small	Moderate	Large	Extreme
Block size	30.48 cm	60.96 cm	91.44 cm	121.92 cm
Volume of rockfall per event	2.3 m^3	4.6 m^3	6.9 m^3	9.2 m^3
Climate and presence of water; on slope	Low to moderate precipitation, no freezing periods, no water on slope	Moderate precipitation or short freezing periods intermittent water on slope	High precipitation or long freezing periods or continual water on slope	High precipitation and long freezing periods or continual water on slope and long freezing periods
Rockfall history	Few falls	Occasional falls	Many falls	Constant falls