Subgrade And Base Course Pavement Road Procedure

This procedure is used for the job as follows:

1. Preparation of subgrade

2. Preparation of Base Course

1. Preparation of subgrade

Construction

The following procedures are recommended in order to prepare the subgrade for the project.

The work area will first be stripped of vegetation or, in cut areas, excavated to a Design SubgradeElevation as shown on the plans.

1. The subgrade after cut will be proof rolled to verify a stable subgrade as directed by the engineer.

2. A series of test pits may be needed as directed by the soils engineer to verify additional undercutas predicted or estimated by Boring Logs and the Earthwork Undercut Plan.

Proof rolling procedures will be as follows:

a. Two (2) to four (4) passes with a 25 ton rubber tire roller or equivalent; and

b. Concentrate additional passes in areas that exhibit instability as directed by the engineer.

Unstable and unsuitable subgrade materials will be removed to the depth encountered as directed by the Engineer.

1. Materials at undercut subgrade elevation should:

a. Have an unconfined compressive strength (Qu) of 2.0 tsf minimum, or cone index of 250 minimum;

b. Contain no foreign materials or have organic contents in excess of six (6) percent total organic matter as determined by the Wet Combustion Method (AASHTO T-194); or maximum dry densities less than 105 pcf as determined by AASHTO T-180 (ASTM D-1557); 

c. Be able to support necessary construction equipment without severe rutting ordeflection.

At undercut subgrade elevation, the upper eight (8)-inches of soil shall be scarified or disced and recompacted to 95 percent of the maximum dry density as defined by AASHTO T-180 (ASTMD-1557), prior to remedial work fill placement.

Proof rolling of the prepared undercut subgrade will be done if required by the soils engineer to furtherverify a stable subgrade prior to fill placement.

Roadway fill shall be placed in successive horizontal lifts of not more than six (6)-inches in loosedepth (cohesive material), or not more than nine (9)-inches in loose depth (porous granular material.)

The upper eight (8)-inches of subgrade in areas not undercut shall also be scarified and recompacted to 95 percent of the maximum dry density as defined by AASHTO T-180 (ASTM D-1557), prior toplacement of subsequent lift of FILL material.

Once the existing subgrade is stabilized, fill can be placed and compacted in lifts to Design SubgradeElevation. All roadway fill materials shall be compacted to 95 percent of AASHTO T-180(ASTM D-557.)

When the work listed in the steps above has been completed, the subgrade will be checked by proofrolling and approved by the Owner before construction of the subbase, base course, or pavement isstarted. The Owner will make the determination as to whether areas failing this proof roll requireadditional drying and recompaction or whether the soil conditions warrant more extensive treatment.

2. Preparation of Base Course

Material For Sand Gravel roads

Material shall sand + gravel material with minimum compacted thickness 15 cm accordance to ASTM C136 and shall be extended on both sides of the road layer as road shoulder. For sand gravel roads, this sub-base course will also be surface pavement.

Equipment

1) Excavator/Power shovel

2) Dumptruck

3) Water tank

4) Grader/Dozer

5) Tire Roller Compactor 8 ton 

Preparation

1. Contractor shall prepare the following below at least 7 days before the date proposed in the use of any material for the first time as Aggregate Base:

a) Two examples of each 50 kg of material.

b) Statement regarding the origin and composition of each material proposed for Aggregate Base, and laboratory test results prove that the properties of the materials.

2. Contractor must send the following below in writing immediately after the completion of each segment of the work and prior approval is given for the spreading material over the other aggregate base :

• The results of the density and moisture content testing as specified in Item 2.2. Item number 6.

• Test results measurement surface inspection and survey data stating that the tolerances.

Spreading and grading methods

After the sub-grade layer is actually in compliance with the terms of elevation and density we will begin the work of sub-base course.

We must first set its marking again to achieve the desired thickness. Minimum required points: 5 points according to the cross-section (X - section) and with a maximum distance of 25 meters in longitudinal cuts or profile.

After completion of the installation of markers to determine the height / thickness so we can bring this material sub-base spaciousness. The stakes have mounted strong enough, and we protect him with the material sub-base ø ± 30 cm.

Compaction methods

The principle of compaction should start from the edge / of low to middle / high. Once we smooth the surface with a motor grader. We proceed by first compacting road roller Furthermore with Roller Tire where he participated condense on the time / circumstances require while watering. To complete the compaction we should use Compacting road Roller.

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