96M03/29/06

S251-96M.doc

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  Use on projects as appropriate. Also include SCR for Subsection 705.02.

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**Section 251. - RIPRAP**

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**Description**

**251.01** This work consists of furnishing and placing riprap for bank
protection, slope protection, drainage structures, and erosion control.

Riprap classes are designated as shown in Table 705-1.

**Material**

**251.02** Conform to the following Subsections:

> Geotextile type IV 714.01
>
> Grout 725.22(e)
>
> Riprap rock 705.02

**Construction Requirements**

**251.03 General.** Perform the work under Section 209. Dress the slope
to produce a smooth surface. If earthwork geotextile is required, place
according to Section 207.

**251.04 Placed Riprap.** Placed riprap is rock placed on a prepared
surface to form a well-graded mass.

Place riprap to its full thickness in one operation to avoid displacing
the underlying material. Do not place riprap material by methods that
cause segregation or damage to the prepared surface. Place or rearrange
individual rocks by mechanical or hand methods to obtain a dense uniform
blanket with a reasonably smooth surface.

**251.05 Keyed Riprap.** Keyed riprap is rock placed on a prepared
surface and set into place by impact pressure.

Place rock for keyed riprap according to Subsection 251.04. Set the
riprap into place by exerting impact pressure with a hydraulic powered
bucket or an approximately 2000 kilograms flat-faced mass. Repeated
impacts should be made until the rock is firmly seated and forms a
reasonably uniform surface, without reducing the effective sizes of the
rocks. Do not use impact pressure on riprap below the water surface.

**251.06 Grouted Riprap.** Grouted riprap is rock placed or keyed on a
prepared surface and with the voids filled with grout.

Place rock for grouted riprap according to Section 251.04 or 251.05.
Thoroughly moisten the rocks and wash excess fines from the riprap or to
the undersides of the riprap. Place grout only when the air temperature
is no less than 1°C within the near-surface voids of the riprap. Also,
place grout only when the air temperature 300 mm above the riprap
surface is above 2°C. Place the grout in a manner to prevent
segregation. Begin placing grout at the lowest elevation of the riprap.
Fill all voids without unseating the rocks. Do not exceed 1.5 meter
thickness for each layer of grouted riprap. Allow 3 days curing time
before adding the next layer of riprap and grout. Provide weep holes
through the grouted riprap as required. Keep the grouted riprap moist
for 3 days after the work is completed and protect it from freezing for
a minimum of 7 days after grouting.

**251.07 Acceptance.** Rock for riprap will be evaluated under
Subsections 106.02 and 106.03.

Rock placement for riprap will be evaluated under Subsections 106.02 and
106.04.

Structure excavation and backfill will be evaluated under Section 209.

Geotextile will be evaluated under Section 207.

Material for grout will be evaluated under Subsections 106.02 and
106.03. Grout will be evaluated under Subsections 106.02 and 106.04.
Grout placement will be evaluated under Subsection 106.02. See Table
251-1 for minimum sampling and testing requirements.

**Measurement**

**251.08** Measure riprap by the metric ton or by the cubic meter in
place.

**Payment**

**251.09** The accepted quantities, measured as provided above, will be
paid at the contract price per unit of measurement for the pay items
listed below that are shown in the bid schedule. Payment will be full
compensation for the work prescribed in this Section. See Subsection
109.05.

Payment will be made under:

**Pay Item** **Pay Unit**

25101 Placed riprap class\_\_\_\_\_\_ Cubic meter

25102 Placed riprap class\_\_\_\_\_\_ Metric ton

25103 Keyed riprap class\_\_\_\_\_\_ Cubic meter

25104 Keyed riprap class\_\_\_\_\_\_ Metric ton

25105 Grouted riprap class\_\_\_\_\_ Cubic meter

**Table 251-1**

**Sampling and Testing**

  ------------ ------------------ ------------------ --------------- ------------
  **Material   **Property or      **Test Methods or  **Frequency**   **Sampling
  or Product** Characteristic**   Specifications**                   Point**

  Grout        Making test        AASHTO T 23 AASHTO 1 sample per    Job site
               specimens          T 22               installation    
               compressive                           ^(1)^           
               strength ^(2)^                                        
  ------------ ------------------ ------------------ --------------- ------------

^(1)^ Sample consists of 2 test specimens.

^(2)^ The compressive strength will be the average of two test
specimens.