Presentation on theme: "RIPRAP INSTALLATION n Construction n1n1 Dennis Clute Construction Engineer NDCSMC."— Presentation transcript:
RIPRAP INSTALLATION n Construction n1n1 Dennis Clute Construction Engineer NDCSMC
CONSTRUCTION SPECIFICATIONS CS 21 – Excavation CS 23 – Earthfill CS 24 – Drainfill CS 31 – Concrete for Major Structures CS 32 – Structure Concrete CS 61 - Rock Riprap CS 62 - Grouted Rock Riprap CS 95 - Geotextile n Construction n2n2
STEP BY STEP PROCESS Materials Approval Staking Subgrade Preparation Filter, Bedding, or Geotextile Placement Grouting (where applicable) n Construction n3n3
ROCK MATERIALS APPROVAL Construction Specifications 61 and 62 require the contractor to designate the rock source at least 30 days prior to delivery to the site. When possible the engineer should visit the source before approving the rock. n Construction n4n4
LIST OF MATERIALS Imported fill material where applicable Filter, bedding, or geotextile Rock Grout design and materials where applicable n Construction n5n5
MATERIALS APPROVAL The engineer should notify the inspector once the materials are approved for use. n Construction n6n6 The job diary has a section entitled “Material Certification Record”. Record in this section the date of approval and the date of material delivery.
MATERIALS APPROVAL Quality – Shape – Bulk Specific Gravity – Absorption – Soundness Gradation n Construction n7n7
MATERIALS APPROVAL Quality n Construction n8n8 èShape Shall be angular to sub-rounded. The least dimension of individual rock shall not be less than 1/3 the greatest dimension. D > 1/3 D This Not This
MATERIALS APPROVAL Quality n Construction n9n9 èBulk Specific Gravity is the ratio of the unit weight of a material to the unit weight of water. Rock with a specific gravity of 2.5 would have a unit weight of 2.5 X 62.4 lb/cu. ft. = 156 lb/cu. ft. Shape
MATERIALS APPROVAL Quality n Construction n 10 Bulk Specific Gravity èAbsorption - A dry rock weights 150 pounds. The rock is soaked in water for days, the surface is dried and the rock now weighs 153 pounds. The absorption is computed as follows: (( ) / 150) x 100% = 2%. Shape
MATERIALS APPROVAL Quality n Construction n 11 Bulk Specific Gravity Absorption èSoundness - èSoundness - Rock shall be tested for soundness according to ASTM Method C88. ASTM Method C88 is a method that simulates freeze thaw damage. Shape
MATERIALS APPROVAL Quality Construction n 12
MATERIALS APPROVAL Quality n Construction n 13 Bulk Specific Gravity Absorption Soundness Shape Gradation is generally specified by weight but can be specified by dimension.
EXAMPLE GRADATION n Construction n 14 Particle % Finer Mass (lb.) Than to to to 15
GRADATION Rock that is too large will cause quantity overruns. n Construction n 15 Rock that is too small may become displaced. Rock that is poorly graded may not protect the subgrade as intended. flow Planned limits Exposed subgrade
GRADATION n Construction n 16 ASTM D Standard Practice for Specifying Standard Sizes of Stone for Erosion Control ASTM D Standard Test Method for Particle Size Analysis of Natural and Man- Made Riprap Materials
ASTM D Standard Practice for Specifying Standard Sizes of Stone for Erosion Control n Construction n 17 The standard sizes for rock are: Rock R-20 R-60 R-150 Avg. lbs Rock R-300 R-700 R-1500 Avg. lbs
n Construction n 18 This standard also addresses filter stone to be used for bedding the rock. The standard sizes for filter stone are: Filter Stone FS-1 FS-2 FS-3 Size Range #100 to 3/8” #100 to 2” #16 to 6 1/2” ASTM D Standard Practice for Specifying Standard Sizes of Stone for Erosion Control
STAKING n Construction n 19 H D Set hubs away from the immediate work area. Record station number, H, and D on lathe near hub. Survey rod
STAKING/JOB DIARY n Construction n 20 The job diary is not to be used for recording survey notes, however, you should record information about staking. Record a detail of exactly what was staked, when, and by whom. This could be especially important if the NRCS is the party responsible for staking.
SUBGRADE PREPARATION Surface irregularities, loose material, vegetation, and all foreign matter shall be removed from foundations. Riprap and bedding or geotextiles shall not be placed until the foundation preparation is completed, and the subgrade surfaces have been inspected and approved by the Engineer. The surface of the finished material shall be to grade and free of mounds, dips or windrows. n Construction n 21
LACK OF SUBGRADE PREPARATION n Construction n 22
COMPACTION OF SUBGRADE n Construction n 23 Hardhats? Record results of tests for earthfill placement moisture and density in the job diary.
FILTERS, BEDDING, OR GEOTEXTILE n Construction n 24 Filters are required where riprap alone will not protect against base soil erosion. These filters will likely be two stage filters in order to safely transition from the small base soil particles to the rock riprap. Base Soil Sand Gravel Riprap
FILTERS, BEDDING, OR GEOTEXTILE n Construction n 25 Base Soil Geotextile Geotextile is often used to filter base soil. There is a potential for plugging of the geotextile in some cases. Filter compatibility may be important. Direction of lap splice is critical. Water
PLACEMENT Equipment-Placed – Install full course thickness in one operation. – Should result in reasonably homogeneous rock fill with large rocks evenly distributed and small rocks filling voids between large rocks. Hand-Placed – Large rocks should be firmly in contact with one another. – Spaces between large rocks filled with small rocks. – Slab rock laid on vertical edge. n Construction n 26
SECTION VIEW of PROPER vs. IMPROPER PLACEMENT n Construction n 27 PROPER PLACEMENT Large rocks evenly distributed and small rocks filling voids between large rocks. IMPROPER PLACEMENT Large rocks distributed unevenly with pockets of small rock in between.
PLAN VIEW OF PROPER PLACEMENT n Construction n 28 You want the the large rocks touching, the small rocks filling the voids between the large rocks. You shouldn’t see much ground when you look down through the rocks.
AVOID DOUBLE DECKING n Construction n 29 Double decking usually occurs when hand placing is involved. It is where smaller rocks are placed on top of the rock fill to bring it up to the specified grade. Looks good, works bad.
GROUTED ROCK RIPRAP n Construction n 30 Grouted rock riprap is often used if larger rock is not economically available and heavy-duty protection is needed. Sometimes it is designed with oversize rocks placed in a variable pattern to produce a rough surface that will retard the water velocity or wave runup in a protected area. Normally the grout should not be so deep that the mass will not crack to allow the riprap to maintain contact with the subgrade if settlement occurs.
GROUT PLACEMENT n Construction n 31 Ideal grout placement would bind the individual rocks together but would leave the rock exposed for energy dissipation. We are not trying to pour a concrete slab here, we still want the riprap to be able to move some so that it can continue to conform to the subgrade should subgrade settlement occur. Good grout placement begins with good rock placement. Poor grout placement
GROUT QUANTITY n Construction n 32 Expect the grout quantity to be 0.25 to 0.35 times the volume of rock. Quantity of grout is dependent on the gradation and size of the rock and the grout depth. Well graded rock – less voids -less grout Gap graded rock – more voids - more grout
PLACING Grout mix shall not be dropped over 5 feet. Grout shall not be placed until the rock riprap has been inspected and approved. Rock shall be kept wet for at least 2 hours immediately prior to grouting. Rock shall be washed with water to remove fines prior to placing grout. Rock shall be kept moist just ahead of grouting. n Construction n 33
PLACING Grout placed on nearly level areas may be placed in one course. On slopes, grout shall be placed in two courses approximately 10 feet wide starting at the toe and working upward. Grout shall be discharged directly to the rock surface using a splash guard to guard against displacing rock. Bars and concrete vibrators shall be used to loosen tight pockets of rock and aid grout penetration. n Construction n 34
PLACING Brooming shall be uphill. After grout has stiffened the entire surface shall be rebroomed to eliminate runs and fill voids caused by sloughing. Curing shall begin immediately. A strip or panel is considered complete only after curing has begun. After completion of any strip or panel, no workman or load shall be allowed on the grouted surface for 24 hours. n Construction n 35
CURING The surface shall be kept moist for 7 days or until approved curing compound is applied. On large jobs this means start the wetting or apply the curing compound before all the grout is placed. Spray curing compound on the moist surface as soon as free water disappears. Do not spray areas requiring bond to subsequently placed grout or concrete. n Construction n 36
INSPECTION CHECKLIST Check materials against approval documentation. – rock riprap – bedding material and/or geotextile – grout design – curing compound Check assembly and installation. – subgrade compacted to line and grade – bedding or geotextile properly installed – geotextile not punctured – in-place rock gradation as specified – approved grout mix supplied including air content and temperature of grout – grout installed to specified limits without segregation – proper grout curing n Construction n 37
JOB DIARY Record material certification for: – rock riprap – grout design – bedding material and/or geotextile – curing compound Record time of delivery and status of materials. Record results of tests for earthfill placement moisture and density, gradation tests on bedding, filter, and/or rock riprap, air content and temperature of grout. Record interim, cumulative, and final quantities on a daily basis. Record day to day activities relating to the installation of rock riprap and/or grouted rock riprap. n Construction n 38