EARTHWORK AND EXCAVATION

AKSHAYA KRISHNARAGA SANDYAPREETHI ALMA FRANCIS

Earthworks are engineering works created through the moving or processing of parts of the earth's surface involving quantities of soil or unformed rock . The earth may be moved to another location and formed into a desired shape for a purpose.Much of earthworks involves machine excavation and fill or backfill.EXCAVATION•All excavation work shall be carried out by mechanical equipment's unless, in the opinion of Engineer, thework involved and time schedule permit manual work.•Excavation for permanent work shall be taken out to such widths, lengths, depths and profiles as are shown onthe drawings or such other lines and grades as may be specified by Engineer. Rough excavation shall becarried out to a depth 150 mm above the final level. The balance shall be excavated with special care. Softpockets shall be removed even below the final level and extra excavation filled up as directed by Engineershould be carried out just prior to laying the mud-mat.

EARTH WORK AND EXCAVATION

Classification of SoilAll materials to be excavated shall be classified into one of the classes listed below. The engineer’s decision regarding classification of excavated material is binding on thecontractors. Soft/Loose/Hard/Dense Soil and MudGenerally any soil which yields to the application of pick and shovel or to phawra, rake or other ordinary digging equipment such as vegetable or organic soil, turf, gravel, sand, silt,loam, clay, peat, cobble stone, mud etc. It shall include embedded rock boulders of size less than 1 metre in any dimension & not more than 200 mm in any of the other two dimensions.Soft/Disintegrated/Weathered Rock (Not Requiring Blasting)Rock or boulder which may be quarried or split with crowbar. This will also include murrum laterite and hard conglomerate. For this type of soil the core sample recovery is less than or equal to 0.50. This shall also include rock boulder not bigger than 1 metre in any dimension & not more than 500 mm in anyone of other 2 dimension.Hard Rock (Requiring Blasting)The type of strata which cannot be excavated with pick-axes, crowbars etc. Any rock or boulder for the excavation of which blasting is required. For this type of soil the core sample recovery is more than 0.50.

GENERALAll fill materials will be subject to Engineer’s approval. If Engineer rejects any materials, Contractor shall remove the same forthwith from the site at no extra cost to the Owner. Surplus fill material shall be deposited/disposed off as directed by Engineer after the fill work is completed.No earth fill shall commence until surface water discharges and streams have been properly intercepted or otherwise dealt with as directed by Engineer.

FILL, BACK FILLING AND SITE GRADING

MATERIALTo the extent available, selected surplus spoils from excavated materials shall be used as backfill. Fill materials shall be free from clods, salts, sulphates, and organic or other foreign material. All clods of earth shall be broken into pieces not larger than 150-mm size mixed with properly graded fine materials consistingof murrum or earth to fill up the voids and the mixture used for filling.

If any selected fill material is required to be borrowed; Contractor shall make arrangements for bringing such material form outside borrow pits. The material and source shall be

subject to prior approval of Engineer. Theapproved borrow pit area shall be cleared of all bushes, roots of trees, plants, rubbish etc. top soil containing A-1/4 salts/ sulphates and other foreign materials shall be removed. The materials so removed shall be burnt or disposal off as

directed by Engineer. Contractor shall make necessary access roads to borrow areas andmaintain the same, if such access road does not exist, at his cost.

The Contractor shall furnish, place, and compact AASHTO Class A-3 soil, free of organic or other suitable material for backfill or bedding as specified herein, in authorized excavation above or below normal grade and in other locations as indicated on the drawings, or as specified, and where ordered by the Engineer for miscellaneous backfill.

AASHTO CLASS A-3 SOIL BACKFILL

•Where the trenches are excavated in soil, the filling from the bottom of the trench to the level of the centerlineof the pipe shall be done by hand compaction with selected approved earth in layers, backfilling above the levelof the centre line of the pipe shall be done with selected earth by hand compaction or other approved means inlayers.

FILLING IN TRENCHES•Filling in trenches for pipes and drains shall be commenced as soon as the joints of pipe and drains have beentested and passed. The backfilling materials shall be properly consolidated by watering and ramming, takingdue care that no damage is caused to the pipes.

•In case of excavation of trenches in rock, the filling up to a level 30 cm. above the top of the pipe shall be donewith fine materials, such as earth, murrum etc. The filling up of the level of the centerline of the pipe shall bedone by hand compaction in layers.

•The filling from a level 30-cm above the top ofthe pipe to the trench shall be done by hand or other approved mechanical methods with broken rock fillingmixed with fine material as available to fill up the voids.Filling of the trenches shall be carried simultaneously on both sides of the pipe to avoid unequal pressure onthe pipe.

•Whereas the filling above the centerline of the pipe shall be done by handcompaction or approved means in layer not exceeding 45 cms.

BACKFILL – STRUCTURESBackfilling shall be accomplished as soon as practical afterunderground work on the structure is completed. No trash shall beallowed to accumulate in the space to be backfilled. Particular careshall be taken to avoid leaving wood where it will be buried.

COMPACTION AND DENSITYBackfill and compaction shall be conducted to achieve densities asspecified herein. Methods for backfill placement and compaction shall besubject to approval by the Engineer. Compaction “under paving” shallrefer to installations immediately under paving and also to installationswithin a plane described as 1 (horizontal) to 1 (vertical) slope downwardfrom the edge of roadway or back of curb.

The space to be backfilled shall be well cleaned before backfillingcommences.Ground surface shall be restored to the elevation shown on theplans, which generally will conform to the undisturbed surface