Section 252 — Rockery, Special Rock Embankment, and Rock Buttress

AND ROCK BUTTRESS

Description

252.01This work consists of constructing rockeries, special rock embankments, and rock buttresses.

252.02Definitions.

(a)Rockeries. Consists of providing and placing interlocking, dry- stacked rocks without reinforcing steel, mortar, or concrete. (b) Special rock embankments. Consists of providing and placing rock in fill- side sections.

(c)Rock buttresses. Consists of providing and placing rock in cut- side sections.

Material

252.03Conform to the following Subsections : Corrugated polyethylene drainage tubing 708.04 Geotextile 714.01 Granular rock backdrain 703.17 Rock for buttresses 705.05 Rock for rockeries 705.06 Rock for special rock embankments 705.04

Construction Requirements

252.04Qualifications . At least 14 days before starting rockery work, submit a résumé for the on- site supervisor describing experience on at least three projects of similar construction and complexity within the past 5 years. Include project names, a brief description of each pr oject, construction dates and quantities, locations, and contact information for project owners. 252.05 Submittals. At least 14 days before starting rockery, special rock embankment, and rock buttress work, submit the following according to Subsection 104.06:

(a)Start date and schedule;

(b)Description of construction methods and proposed equipment; and

(c)Photos of completed rockeries with narrative descriptions of the rockeries, equipment used, and special or unusual conditions encountered during the construction and how construction methods were adapted.

252.06General. Survey according to Section 152 and verify the limits of installation. Notify the CO if planned lengths, heights, or both are inadequate to intersect with the adjacent slopes. Submit cross -sections verifying intersections for approval. Construct as follows:

(a)Excavation. Perform the work according to Sections 204 and 209. Do not excavate more areas than can be replaced with construction in one shift, except as otherwise noted. The CO may allow excavation beyond the limits that can be completed in one shift provided the Contractor demons trates that the excavation will remain stable until the rock work is completed or provides shoring. Protect backslopes from damage by surface water.

(b)Erection. Place geotextile filter according to Section 207 as shown in the plans . Remove sharp objects from the backslope before installing geotextile filter.

252.07Rockery. Provide and install underdrain systems according to Section 605 as shown in the plans. Seat base rocks f irmly on stable foundation subgrades or leveling pad as shown in the plans. Do not place rocks with shapes that create voids with a linear dimension greater than 12 inches. Place rocks to avoid continuous joints in any direction. Locate at least one bearing point a distance no greater than 6 inches from the face of the rockery. Place each rock to ensure it bears on at least two rocks below. Place incrementally smaller rocks as construction proceeds in successive rows. Slope the top surface of each rock tow ards the back of the rockery at an inclination of at least 5 percent. Choke voids in each successive row. Choke voids greater than 6 inches with a rock large enough to fill the void. Backfill with granular rock backdrain concurrent with rock placement unti l level with the top of rock. Place granular rock backdrain in horizontal lifts no more than 12 inches compacted depth. Compact each lift according to Subsection 204.11. Compact areas not accessible to rollers with other ap proved methods.

252.08Special Rock Embankment and Rock Buttress. Place rocks in a stable orientation with minimal voids to produce a random pattern. Construct the exposed face of the rock mass reasonably uniform with projections beyond the line of the slope that are no greater than 12 inches for mechanically -placed rock or 6 inches for hand-placed rock. Use rock smaller than the minimum rock size to choke the larger rock solidly in position and to fill voids between the large rocks.

252.09Acceptance. Se e Table 252-1 for sampling, testing, and acceptance requirements. Material for rockeries, special rock embankments, and rock buttresses will be evaluated under Subsections 106.02, 106.03, and 106.04. Construction of rockeries, special rock embankments, and rock buttresses will be evaluated under Subsections 106.02 and 106.04. Geotextile filters will be evaluated under Section 207. Roadway excavation will be evaluated under Section 204. Structure excavation and backfill will be evaluated under Section 209. Survey will be evaluated under Section 152. Underdrain systems will be evaluated under Section 605.

Measurement

252.10Measure the Section 252 pay items listed in the bid schedule according to Subsection 109.02 and the following as applicable: When measuring rockeries by the square foot, measure the rockery from the bottom of the base rock elevation to the top of the cap rock elevation. Measure the front face on a plane parallel to the rockery face. When measuring special rock embankments and rock buttresses by the cubic yard, measure in place.

Payment

252.11The accepted quantities will be paid at the contract price per unit of measurement for the Section 252 pay items li sted in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05 . Table 252-1 Sampling, Testing, and Acceptance Requirements

Material or

Product

(Subsection) Type of

Acceptance

(Subsection) Characteristic Category Test Methods

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Source

Rock for

buttresses (705.05 ) Measured & tested for conformance (106.04 & 105) Rock breadth and thickness − Subsection 705.05(a) (1) 1 per rock type Source of material No Before using in work −

Apparent

specific gravity − AASHTO T 85 " " Yes " Not required if using

Government

-furnished source Absorption − " " " " " "

Durability

index (coarse) − AASHTO T 210 " " " " "

Rock for

rockeries (705.06 ) " Apparent specific gravity − " 1 per rock type Source of material Yes Before using in work Not required if using

Government

-furnished source Absorption − " " " " " " LA abrasion − AASHTO T 96 " " " " "

Durability

index (coarse) − AASHTO T 210 " " " " "

Soundness

using sodium sulfate − AASHTO T 104 " " " " " Table 252- 1 (continued) Sampling, Testing, and Acceptance Requirements

Material or

Product

(Subsection) Type of

Acceptance

(Subsection) Characteristic Category Test Methods

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Production

Rock for

special rock embankment (705.04) Process control (153.03 ) Size − (1) 1 per 100 yd3 In-place No 24 hours −

Rock for

buttresses (705.05) " " − " 1 per 100 yd3 " " " −

Rock for

rockeries (705.06) " " − (2) 2 per row of rock per rockery " " " −

(1)For mechanically -placed embankments, verify rock size by confirming that the largest accessible rock has an intermediate dimension greater than the D50 size shown in Table 705-2. Also confirm that the smallest accessible rock has an intermediate dimension within the lower D50 size range shown in Table 705 -2. For hand placed embankments, verify rock size by confirming that the largest accessible rock has an intermediate dimension gr eater than the D75 size shown in Table 705 -3. Also confirm that the smallest accessible rock has an intermediate dimension within the D25 size range shown in Table 705 -3.

(2)Verify rock size by confirming that the largest accessible rock has a width greater than the minimum width shown in the plans.