02317_Excavation_ _Backfill_Structures.doc

SECTION 02317

EXCAVATION AND BACKFILL FOR STRUCTURES

1. Part 1 - GENERAL

1.01 summary

A. This section specifies excavation and backfill for structures, including excavation; furnishing, hauling and placing of backfill material; disposal of excess or unsuitable backfill material; and grading. Material to be excavated is unclassified.

1.02 related sections A. 01410 – Testing and Quality Control B. 02230 - Clearing and Grubbing

C. 02310 - Grading D. 02336 – Imported Structural Fill

1.03 owner’s instructions

A. Conform to the dimensions and elevations indicated on the Drawings. Suitable bearing may be encountered at different elevations from those on the Drawings. If so, the COR may direct, by written order, that the excavation elevations be changed to the elevation where suitable bearing was encountered. Extend excavation a sufficient distance from walls and footings to allow placing and removal of forms. Undercutting will not be permitted. Prevent surface water from entering the excavation.

2. Part 2 - PRODUCTS

2.01 maTERIALS A. Backfill Materials.

1. Backfill materials shall contain no organic or frozen material.

a. General Backfill Material: Excavated material containing no rock larger than 3 inches.

3. Part 3 - EXECUTION

3.01 – FOUNDATION AND FOOTING EXCAVATION

A. Remove surface material to a depth of 6 inches in areas to be excavated. Stockpile this material separately from other excavated material, for use in grading the site.

B. Footing Keyed into Undisturbed Material: Excavate the foundation to the limits of the footing and compact foundation. Where material does not stand vertically, fill all space between the limits of the footing and the remaining undisturbed material with concrete.

C. Excavation shall be made to the required depth and to a width that will allow installation and bracing of forms REGARDLESS OF THE NATURE OF MATERIAL ENCOUNTERED.permit the D. All soft and yielding material shall be removed and replaced with imported Structural Fill Material.

E. The foundation shall be shaped and compacted to a firm even surface conforming to the section shown in the drawings.

F. Grade areas in vicinity of construction to prevent surface water from running into excavated areas.

3.02 – FOUNDATION AND FOOTING BACKFILL

A. Backfill.

1. Preparation for Backfill.

a. Remove all forms from structure, and clean the excavated area of all debris. Remove any standing water from excavation. Prior to backfill, obtain approval from COR to backfill excavated area.

b. Backfilling all Structures.

1) Do not backfill in a manner to cause structure to become point loaded. Place backfill in uniform lifts around structure.

c. Backfilling of Concrete.

1) Do not backfill until concrete has been in place for 14 days or a strength of 1,000 psi has been reached, unless allowed in writing by COR.

2) Use designated backfill material or crushed rock. Place in layers not greater than 6 inches thick to 6 inches below slab. Compact at or near optimum moisture by hand tamping or mechanical vibrating tamper with 2 passes of the entire lift surface. Finish backfill lift as specified for Overexcavation Backfill Under Slabs.

d. Overexcavation Backfill Under Slabs.

1) Restore grade for slabs as follows:

a) Within 2 inches of slab bottom: Use bedding material.

b) From 2 inches to 6 inches below slab: Use crushed rock.

c) Over 6 inches below slab: Use general backfill material.

e. Placing Backfill Material.

1) Place all backfill material in 8 inch maximum lifts. Compact each lift to 95% maximum dry density.

2) Do not use tracked or wheeled equipment to compact backfill.

f. Topsoil.

1) Deposit original surface material as the final backfill lift and compact with a minimum of 2 passes over the entire surface with mechanical tamper.

B. Grading.

1. Grade surface uniformly between spot elevations or contours to match existing adjacent ground elevations. Slope surface to provide drainage away from structures.

3.03 EXCESS eXCAVATED mATERIAL (SUITABLE AND UNSUITABLE)

A. Remove all unsuitable material from the site for disposal onsite at a location designated by the COR.

4. PART 4 - MEASUREMENT AND PAYMENT

4.01

MEASUREMENT

The work specified herein will not be measured for payment.

4.02

PAYMENT

This work is incidental to pay items 03300(01) and 03300(02).

END OF SECTION

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