TABLE 1.
ACB Requirements
Criteria
Required Value
Test Method
TABLE 1.
ACB Requirements
Criteria
Required Value
Test Method
Matrix Assembly: Interlocking Blocks / Cabled System
Thickness, minimum
[4 inches]
N/A
[Net Weight/Area, minimum
30 psf
Note a.]
Critical Shear Stress, minimum
[3.5 psf]
FHWA RD-89-199
[Critical Velocity, minimum
15 ft/sec
FHWA RD-89-199]
[Curvature Radius, maximum
3 feet
Note b.]
[Surface Void Area Ratio
25% - 40%
Note c.]
[Drainage Correction Factor (DCF)
20% - 35%
Note d.]
Block/Geotextile Interface
Friction Angle
[35 degrees]
Note e.
a. The weight of the mattress per unit area shall be determined with
the nominal joint spacing, in a non-submerged condition.
b. The curvature radius shall be indicative of the ability of the
assembled mattress to conform to one dimensional subgrade curves
without binding, such as for anchor trenches and swales. The curvature
radius shall be demonstrated, if requested by the Contracting Officer.
c. The surface void area ratio shall be determined at the visible
(with filled voids) surface of the blocks, with the joints spaced in a
neutral position (50%), and shall be expressed as a percentage of the
gross mat area. The void area shall include area between the blocks
and open cells within the block.
d. The drainage correction factor shall be the minimum void area ratio
(usually taken at the base of the blocks), with the joints spaced in a
neutral position (50% freeplay in each direction), and shall be
expressed as a percentage of the gross mat area.
e. The concrete
surface shall be sufficiently rough to prevent sliding
of the blocks on
the geotextile. The interface friction must be
matched with the
selected block and geotextile combination, and shall
be included with
the ACB and Geotextile Data submittal. The
block/geotextile
interface friction angle shall be demonstrated, if
requested by the
Contracting Officer.
2.1.1
Hydraulic Stability
**************************************************************************
NOTE: The velocity and shear stress conditions
derived from this test are critical state
conditions, and do not represent allowable design
values. The surface tolerances for block placement
are generally better in the test than field
conditions.
FHWA RD-89-199 is a research document, not a
standard test method. ASTM committee D18.25.04 has
a draft standard based on a flume test, similar to
FHWA RD-89-199. The flume test is very expensive:
SECTION 02382
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