ITEM 505 – RIPRAP AND GROUTED RIPRAP
505.1 Description
This Item shall consist of the furnishing and placing of riprap with or
without grout as the case may be, with or without filter backing, furnished
and constructed in accordance with this Specification and to the lines and
grades and dimensions shown on the Plans.
505.2 Material Requirements
505.2.1 Stones
Stones for riprap shall consist of rock as nearly as rectangular in section
as is practical, except that riprap of Class A may consist of round natural
stones. The stones shall be sound, tough, durable, dense, resistant to the
action of air and water, and suitable in all respects for the purpose
intended.
Stones for riprap shall be one of the following classes as shown on the
Plans or determined by the Engineer.
Class A - Stones ranging from a minimum of 15kg to a maximum of 25kg with
at least 50 percent of the stones weighing more than 20kg
Class B - Stones ranging from minimum of 30kg to a maximum of 70kg with at
least 50 percent of the stones weighing more than 50kg
Class C - Stones ranging from minimum of 60kg to a maximum of 100kg with at
least 50 percent of the stones weighing more than 80kg
Class D - Stones ranging from minimum of 100kg to a maximum of 200kg with
at least 50 percent of the stones weighing more than 150kgSound pieces of
broken concrete obtained from the removal of bridges, culverts and other
structures may be substituted for stone with the approval of the Engineer.
505.2.2 Filter Materials
When required, the riprap shall be placed on a filter layer to prevent fine
embankment materials to be washed out through the voids of the face stones.
The grading of the filter material shall be as specified on the Plans, or
in the Special Provisions. If not so specified, it will be required that D 15 of the filter is at least 4 times the size D85 for
the embankment material, where D15 percent and 85 percent,
respectively, passing (by mass) in a grain size analysis. Fine aggregate
passing grading requirements for Item 405, Structural Concrete, will
satisfy foregoing requirements.
505.2.3 Mortar
Mortar for grouted riprap shall consist of sand, cement and water
conforming to the requirements given under Item 405, Structural Concrete,
mixed in the proportion of one part cement to three parts sand by volume,
and sufficient water to obtain the required consistency.
The horizontal and vertical contact surface between stones shall be
embedded by cement mortar having a minimum thickness of 20 mm. Sufficient
mortar shall be used to completely fill all voids leaving the face of the
stones exposed.
505.3 Construction Requirements
505.3.1 Excavation
The bed for riprap shall be excavated to the required depths and properly
compacted, trimmed and shaped.
The riprap shall be founded in a toe trench dug below the depth of scour as
shown on the Plans or as ordered by the Engineer. The toe trench shall be
filled with stone of the same class as that specified for the riprap,
unless otherwise specified.
505.3.2 Placing
Stones placed below the water line shall be distributed so that the minimum
thickness of the riprap is not less than that specified.
Stones above the water line shall be placed by hand or individually by
machines. They shall be laid with close, broken joints and shall be firmly
bedded into the slope and against the adjoining stones. Each stone shall be
laid with its longest axis perpendicular to the slope in close contact with
each adjacent stone. The riprap shall be thoroughly rammed into place as
construction progresses and the finished surface shall present an even,
tight surface. Interstices between stones shall be filled with small broken
fragments firmly rammed into place.
Unless otherwise provided, riprap shall have the following minimum
thickness, measured perpendicular to the slope:
Class A – 300 mm
Class B – 500 mm
Class C – 600 mm
Class D – 800 mm
The surface of riprap shall not vary from the theoretical surface by more
than 100 mm at any point.
505.3.3 Grouting
When grouted riprap is specified, stones shall be placed by hand, or
individually by machine as specified for riprap placed above the water
line. The spaces between the stones shall then be filled with cement mortar
throughout the thickness of the riprap as specified in Subsection 504.2.3,
mortar. Sufficient mortar shall be used to completely fill all voids,
except that the face surface of the stones shall be left exposed.
Grout shall be placed from bottom to top of the surface swept with a stiff
broom. After grouting is completed, the surface shall be cured as specified
in Item405, Structural Concrete for a period of at least three days.
The stones shall also be laid in a manner that the vertical and horizontal
alignments of the exposed face shall, as possible be maintained in a
straight line.
505.3.4 Weepholes
All walls and abutments shall be provided with weepholes. Unless otherwise
shown on the Plans or directed by the Engineer, the weepholes shall be
placed horizontally at the lowest points where free outlets for water can
be obtained and shall be spaced at not more than 2 m center to center in a
staggered manner. The length of the weepholes shall not be less than the
thickness of the walls of the abutment and shall be at least 50 mm diameter
PVC or other pipe materials accepted by the Engineer. Weepholes must be
provided with filter bags as specified in special provision or as directed
by the Engineer, and shall be incidental to Pay Item 505.
505.4 Method of Measurement
The quantities to be measured for payment shall be the number of cubic
meters of riprap or grouted riprap, as the case may be, including stones
placed in the toe trench laid in position and accepted.
Filter layer of granular material, when required, shall be measured
separately by the cubic meter in place and accepted.
The computation of the quantities will be based on the volume within the
limiting dimensions designated on the Plans or as determined by the
Engineer.
505.5 Basis of Payment
The quantities measured as provided under Subsection 505.4 shall be paid
for at the contract unit price, respectively, for each of the Pay Items
listed below and shown in the Bid Schedule, which price and payment shall
be full compensation for excavation and preparation of the bed, for
furnishing and placing all materials including backfill and all additional
fill to bring the riprap bed up to the lines, grades and dimensions shown
on the plans, and all labor, equipment, tools and incidentals necessary to
complete the Item.
Payment will be made under:
Pay Item Number
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Description
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Unit of Measurement
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505 (1)
505 (2)
505 (3)
505 (4)
505 (5)
505 (6)
505 (7)
505 (8)
505 (9)
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Riprap, Class A
Riprap, Class B Riprap, Class C Riprap, Class D Grouted Riprap, Class A Grouted Riprap, Class B Grouted Riprap, Class C Grouted Riprap, Class D Filter layer of granular material |
Cubic Meter
Cubic Meter
Cubic Meter
Cubic Meter
Cubic Meter
Cubic Meter
Cubic Meter
Cubic Meter
Cubic Meter
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