This has been superseded by Caltrans New Riprap Classes.

D50 Equivalent Spherical Diameter
RSP Class D50Size1 D50Weight
  inches pounds
8 Ton 71 17600
4 Ton 56 8800
2 Ton 45 4400
1 Ton 36 2200
1/2 Ton 28 1100
1/4 Ton 23 550
Light 16 200
Facing 12 75
Backing No 1 12 75
Backing No 2 8 25
Backing No 3 4 2/3 5
Small RSP (7-inch) 3 1 1/3
Small RSP (5-inch) 2 2/5
Small RSP (4-inch) 1 1/20
1Assumes rock density = 165 lb/ft3

Caltrans Standard Specifications

72-2 ROCK SLOPE PROTECTION

72-2.02A Rock

For method A placement and the class of RSP described, comply with the rock grading shown in the following table:

Rock Grading for Method A Placement
Rock size Percentage larger thana
Class
8T 4T 2T 1T 1/2 T
16 Ton 0–5
8 Ton 50–100 0–5
4 Ton 95–100 50–100 0–5
2 Ton 95–100 50–100 0–5
1 Ton 95–100 50–100 0–5
1/2 Ton 95–100 50–100
1/4 Ton 95–100
aFor any class, the percentage of rock smaller than the smallest rock size must be determined on the basis of weight. For all other rock sizes within a class, the percentage must be determined on the basis of the ratio of the number of individual rocks larger than the smallest size shown for that class compared to the total number of rocks.

For method B placement and the class of RSP described, comply with the rock grading shown in the following table:

Rock Grading for Method B Placement
Rock size Percentage larger thana
Class
1 T 1/2 T 1/4 T Light Facing No. 1 No. 2 No. 3
2 Ton 0–5
1 Ton 50–100 0–5
1/2 Ton 50–100 0–5
1/4 Ton 95–100 50–100 0–5
200 lb 95–100 50–100 0–5 0–5
75 lb 95–100 50–100 50–100 0–5
25 lb 95–100 90–100 90–100 25–75 0–5
5 lb 90–100 25–75
1 lb 90–100
aFor any class, the percentage of rock smaller than the smallest rock size must be determined on the basis of weight. For all other rock sizes within a class, the percentage must be determined on the basis of the ratio of the number of individual rocks larger than the smallest size shown for that class compared to the total number of rocks.

Rock must have the values for the material properties shown in the following table:

Rock Material Properties
Property California Test Value
Apparent specific gravity 206 2.5 minimum
Absorption 206 4.2% maximum
Durability index 229 52 minimum

Select rock so that shapes provide a stable structure for the required section. If the slope is steeper than 2:1, do not use rounded boulders and cobbles. Angular shaped rock may be used on any planned slope. Flat or needle shaped rock must not be used unless the individual rock thickness is greater than 0.33 times the length.

72-2.02B Fabric

Fabric must be RSP fabric that complies with the class shown in the following table:

Fabric Class
Class Largest rock grading class used in slope protection
8 1 ton or smaller
10 Larger than 1 ton

72-4 SMALL-ROCK SLOPE PROTECTION

72-4.02 MATERIALS

Rock must be cobble, gravel, crushed gravel, crushed rock, or any combination of these.

If the rock layer is shown as 7 inches thick, comply with grading shown in the following table:

Rock Grading for 7-inch-Thick Layer
Sieve sizes Percentage passing
5 inch 100
4 inch 90–100
3 inch 25–40
2 inch 0–10

If the rock layer is shown as 5 inches thick, comply with the grading shown in the following table:

Rock Grading for 5-inch-Thick Layer
Sieve sizes Percentage passing
4 inch 100
3 inch 90–100
2 inch 25–40
1 inch 0–10

If the rock layer is shown as 4-inches thick, comply with grading shown in the following table:

Rock Grading for 4-inch Thick Layer
Sieve sizes Percentage passing
3 inch 100
2 inch 90–100
1 inch 25–40
3/4 inch 0–10

Granular material must contain at least 90 percent crushed particles when tested under California Test 205.

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