583RIPRAP

New Hampshire Department of Transportation Standard Specifications – 2016 Description

1.1This work shall consist of furnishing and placing riprap as shown on the plans or ordered. Riprap is typically required for

erosion protection of bridge structures in waterways, for active waterway channel slopes and bottoms, and for intermittent waterway channels where the Engineer determines riprap protection is required to resist expected high water flow velocities. Materials

2.1Riprap shall be quarry stone of approved quality, hard, durable, sub -angular to angular in shape, resistant to weathering and

free from structural defects such as weak seams and cracks. 2.1.1 The suitable shape of the individual stones shall be angular, meeting the gradation in 2.1.1.2 to create interlocking riprap to provide stability of the slope or channel. Round, thin and platy, elongated or needle -like shapes shall not be used. 2.1.1.1 The suitable riprap stone shape is determined by the Length to Thickness ratio, where Length is the longest dimension and Thickness is the shortest dimension, measured in perpendicular axes to each other. The suitable riprap stone shape shall have a length to thickness ratio of no greater than 3. 2.1.1.2 The gradation requirements of the riprap classes in Table 583-1 are based on the stone size Width, the largest dimension perpendicular to the Leng th and Thickness, and the distribution of stone sizes by volume. The volume distribution requires that 15 percent of the stone in the mass shall be no larger than the volume shown in the table (< 15% column), and 1 5 percent of the stone in the mass shall be no smaller than the volume shown in the table (> 85% column). The remaining 70 percent of the stone in the mass shall have a volume between these requirements, averaging to the volume shown in the table (15% - 85% column). None of the stones in the mass shall exceed the maximum volume shown in the table (Maximum column). Table 583-1 Riprap Classes and Sizes Percentage Distribution of Particle Sizes by Volume (cubic feet) Class Nominal Size (in) Maximum Size (in) < 15% 15% – 85% > 85% Maximum I 6 12 0.05 0.14 0.31 1.0 III 12 24 0.4 1.0 2.5 6.5 V 18 36 1.3 3.5 8.5 22 VII 24 48 3 8 19 53 IX 36 72 10 27 65 179 Note: Nominal Size and Maximum Size are based on the Width dimension of the stone. The riprap classes conform to the standard classes described in the FHWA HEC-23 publication. 2.1.2 The sources from which the stone is obtained shall be selected well in advance of the time when the material will be required in the field. The acceptability of the riprap stone shape and grading will be determined by the Engineer. 2.1.3 Control of the gradation will be completed by visual inspection approval by the Engineer of a stockpile at the quarry or other agreed site. Mechanical equipment as needed to assist in checking the stockpile gradation shall be provided by the Contractor. Stockpile replenishment will require re-approval.

2.2Gravel blanket material shall conform to 209.2.1.2.

2.3Geotextile shall conform to 593.2.

Construction Requirements

3.1Preparation of slopes. Slopes that will be covered by riprap shall be free of brush, trees, stumps, and other organic material

and shall be graded to a smooth surface. All soft material shall be removed to the depth shown on the plans or as directed and replaced with approved material per 203.3.6. It is the Contractor’s responsibility to protect embankments and excavated slopes from erosion during construction of the riprap covered slope.

3.2Gravel blanket construction. When called for o n the plans, the gravel blanket shall be placed on the prepared area to the

specified thickness in one operation, using methods which will not cause segregation of particle sizes within the layer. The surface of the finished layer shall be even and free from mounds or windrows.

3.3Geotextile placement. Geotextile shall be placed in accordance with 593.3.

3.4Riprap placement. Riprap shall be constructed to the dimensions shown on the plans or as directed by the Engineer.

New Hampshire Department of Transportation Standard Specifications – 2016 3.4.1 Placement of riprap shall be conducted as soon as possible after gravel blanket or geotextile placement. 3.4.2 Placement of the riprap shall be started at the toe (key trench) and progress up the slope. The key trench at the bottom of the riprap shall be constructed as shown on the plans. If bedrock is encountered at the key trench it shall be brought to the attention of the Engineer to determine if modification to the riprap installation is needed. 3.4.3 Riprap shall be placed over geotextile by methods that do no stretch, tear, puncture or reposition the fabric. Riprap smaller than 1.5 cu. ft. in volume shall be placed with drop heights of less than 3 ft. to the placement surface. Riprap gre ater than 1.5 cu. ft. in volume shall be placed with no free fall height. 3.4.4 Equipment such as a clamshell, orange-peel bucket, skip or hydraulic excavator shall be used to place the riprap so it is well distributed and there is no large accumulations of either the larger or smaller sizes of stone. Dump trucks or front-end loaders tracked or wheeled vehicles shall not be used since they can destroy the interlocking integrity of the stone when driven over previously placed riprap. Placing the riprap by end dumping on the slopes will cause segregation and will not be permitted. 3.4.5 The riprap shall be placed in a manner which produces a well-graded mass. The larger stones shall be well distributed and the entire mass of riprap shall conform approximately to the gradation specified. Hand placing or rearranging of individual stones by mechanical equipment may be required to the extent necessary to secure the uniformity of gradation and surface specified. Fill voids between larger stones with small stones to ensure interlocking between the riprap. 3.4.6 After the riprap is in place, it shall be compacted by impacting (ramming) the exposed surface to produce a tight, locked surface, not varying more than 6” from the elevations shown on the plans. 3.4.7 Riprap placed in water requires close observation and incr eased quality control to ensure the required thickness, gradation and coverage is achieved. Method of Measurement

4.1Riprap will be measured by the cubic yard.

4.1.1 If the Engineer determines that in-place measurement is impracticable, the quantity for payment will be determined by loose measure in the hauling vehicle on the basis that 1 cubic yard vehicle measure is equivalent to 0.7 cubic yard in place. Basis of Payment

5.1The accepted quantity of riprap will be paid for at the Contract unit price per cubic yard (cubic meter) complete in place.

5.1.1 Only when the stone is examined in accordance with 2.1 and examination proves the gradation to be acceptable will payment be made as provided in 109.04. 5.1.2 Gravel blanket material specified or ordered will be paid for under Section 2 09. 5.1.3 Geotextile specified or ordered will be paid for under Section 593. 5.1.4 The accepted quantity of excavation required for placing riprap and for placing any underlying gravel blanket will be paid for under the item of excavation being performed. Excavation above refers only to excavation of original ground or to material ordered removed not shown on the plans. 5.1.5 Free borrow will not be required to replace the accepted quantity of stone obtained from the excavation. However, when the plans do not call for borrow but the quantity of material removed from excavation for us e under this item requires the Contractor to furnish borrow to complete the work, such borrow will be subsidiary. 5.1.6 Replacement slope material resulting from the requirements of 3.1 will be paid in accordance with 203.5.1.9. Pay item and unit:

583.1Riprap, Class I Cubic Yard

583.3 583.5 583.7 583.9 Riprap, Class III Riprap, Class V Riprap, Class VII Riprap, Class IX

Cubic Yard Cubic Yard Cubic Yard Cubic Yard

New Hampshire Department of Transportation Standard Specifications – 2016

Description

This work shall consist of furnishing and placing a dense stone fill at the locations shown on the plans or ordered. Stone Fill

is typically required for stability of embankment fill and soil cut slopes steeper than 2 horizontal to 1 vertical, although slopes at a flatter grade with water seepage or subject to submergence, such as in water quality treatment basins, could require stone fill. Stone fill is also used for erosion protection at pipe outlets, in drainage channels and for other drainage structures where expected water flows and velocities may require it. Materials

Stone for stone fill shall be approved quarry stone, or broken rock of a hard, sound, and durable quality. The stones and

spalls shall be so graded as to produce a dense fill with a minimum of voids. 2.1.1 Class A stone shall be irregular in shape with approximately 50 percent of the mass having a minimum volume of 12 ft3, approximately 30 percent of the mass ranging between 3 and 12 ft 3, approximately 10 percent of the mass ranging between 1 and 3 ft3, and the remainder of the mass composed of spalls. 2.1.2 Class B stone shall be irregular in shape with approximately 50 percent of the mass having a minimum volume of 3 ft3, approximately 40 percent of the mass ranging between 1 and 3 ft3, and the remainder of the mass composed of spalls. 2.1.3 Class C stone shall consist of clean, durable fragments of ledge rock of uniform quality, reasonably free from thin or elongated pieces. The stone shall be made from rock which is free from topsoil an d other organic material. The stone shall be graded as follows: Sieve Size Percentage by Weight Passing 12 in 100 4 in 50 - 90 1-1/2 in 0 - 30 3/4 in 0 - 10

2.1.4 Class D stone shall conform to Table 520-3 - Coarse Aggregate, Standard Stone Size No. 467. 2.1.5 Spalls for filling voids shall be stones or broken rock ranging downward from a maximum size of 1 ft3.

Gravel blanket material shall conform to 209.2.1.2.

Geotextile shall conform to Section 593.

Construction Requirements

Stones and spalls for stone fill shall be deposited and graded to eliminate voids and obtain a dense mass throughout the

course. The spalls shall be tamped into place using an equipment bucket or other approved method. 3.1.1 When stone fill is placed on a slope, the stones shall be deposited in such a manner as not to dislodge the underlying material unnecessarily. 3.1.2 When stone fill is placed on a geotextile, it shall be deposited in a manner to maintain the integrity of the geotextile.

When gravel blanket is shown or ordered, the gravel shall be placed in layers not exceeding 12 ” in depth unless otherwise

ordered.

The completed surface shall approximate the lines and grades shown or ordered. When ordered, stone placed over 1 ft.

outside or above such lines and grades shall be removed.

Stone fill (Bridge) shall be placed within the limits shown on the plans.

Method of Measurement

Stone fill will be measured by the cubic yard and in accordance with 109.01.

Basis of Payment

The accepted quantity of stone fill of the class specified will be paid for at the Contract unit price per cubic yard complete

in place.

5.2Gravel blanket material specified or ordered will be paid for under Section 2 09.

5.3Geotextile specified or ordered will be paid for under Section 593.