207SUBGRADE

207.01Description

This work shall consist of the construction of the subgrade in accordance with

105.03

MATERIALS

207.02Materials

Materials shall be in acco rdance with the following: 10

Coarse Aggregate, Class D or Higher, Size No. 5, 8, 43, 53, or 73 ................................... 904.03 207.01

Fly Ash, Class C .......................................................... 901.02 Geocell Confinement System ...................................... 918.04 Geogrid, Type IB ......................................................... 918.05 Geotextile Properties for Pavement or Subgrade Stabilizations ....................................... 918.02(c) Geotextile .................................................................... 918.02 Lime ............................................................................ 913.04(b) 20 Portland Cement, Type 1 ............................................. 901.01(b) Water ........................................................................... 913.01

Air-cooled blast furnace slag shall not be used for subgrade treatment Type ID, Type IV, and Type IVA.

Soil Property Test Method Requirements Dry Weight Organic Material AASHTO T 267 ” 3% Max Dry Density AASHTO T 99 • 100 pcf Liquid Limit AASHTO T 89 ” 50 Soluble Sulfate ITM 510 ” 1000 ppm Notes: Only soils meeting these requirements will be allowed within the specified thickness of the subgrade treatment in cut sections.

Only soils meeting these requirements will be allowed within 24 in. of the finished subgrade elevation in fill sections.

Recycled concrete pavement processed in to aggregate-sized material shall not be used as coarse aggregate in any subgrade treatment types.

CONSTRUCTION REQUIREMENTS

207.03Construction Requirements

The subgrade shall be constructed uniformly transversely across the width of the pavement including shoulders or curbs unless shown otherwise on the plans, by one of the following methods:

aggregate in accordance with 301, or

207.03

Longitudinally, the treatment may vary depending on the method of construction.

All rock greater than 3 in. shall be rem oved or broken off and placed at least 6 in. below the specified subgrade. Holes or depressions resulting from the removal of unsuitable material shall be filled with soils in accordance with 207.02 or B borrow and compacted in accordance with 203.23.

Coal within the specified thickness of the subgrade shall be excavated if directed, and disposed of in accordance with 202.02.

During subgrade preparation, adequate drainage shall be provided at all times to 60 prevent water from standing on the subgrade. The grade and cross-section of the subgrade shall be finished within a tolerance of 1/2 in. from the subgrade elevation shown on the plans.

Even though the subgrade has been pr eviously accepted, the condition of the subgrade shall be in accordance with 105.03 and 207.04 at the time paving material is placed.

Finishing within this tolerance by blading or other mechanical means without the use of side forms will be allowed. If these methods do not finish within this tolerance, 70 side forms shall be used.

207.04Subgrade Treatment Types

The subgrade treatment type shall be as specified on the contract plans. If required, the subgrade foundation shall be corrected as directed by the Engineer prior to subgrade treatment.

Type Subgrade Description I 24 in. of soil compacted in accordance with 203.23 IA [blank] IBC 14 in. chemical soil modification using cement IBL 14 in. chemical soil modification using lime IC 12 in. coarse aggregate No . 53 in accordance with 301 ID 12 in. coarse aggregate with Type 2B geotextile in accordance with 918.02(c) II 6 in. coarse aggregate No. 53 in accordance with 301 III In-place compaction in accordance with 203.23 IV 12 in. coarse aggregate No. 53 with Type IB geogrid in accordance with 214 IVA 12 in. coarse aggregate with geocell co nfinement system in accordance with 214 V 3 in. of subgrade excavated and replaced with 3 in. coarse aggregate No. 53

Type ID subgrade treatment shall be constructed with 9 in. of coarse aggregate 207.04

No. 53 over 3 in. of coarse aggregate No. 5 or No. 8. Geotextile Type 2B in accordance 80 with 918.02(c) shall be placed above and below the layer of No. 5 or No. 8 coarse aggregate.

In areas where shallow u tilities are encountered or chemical modification is not allowed, the Contractor may submit a request to the Engineer to substitute Type IC for Type IBC or Type IBL.

Where the strength or density and moisture control option is used, compaction of embankment areas shall be in accordance with 203.23. In cut and transition areas, the top lifts shall be removed, and the bottom 6 in. compacted in-place in accordance with 90

203.23. The excavated material shall then be replaced and compacted in 6 in. lifts in

accordance with 203.23. Removal of the lif ts may be waived and only the upper 6 in. compacted in accordance with 203.23 when it is determined, through testing in accordance with 203.24, that the lower lifts comply with 203.23.

In sections where rock, shale, sandstone or its mixtures are encountered, these materials shall be undercut 24 in. belo w the subgrade elevation and replaced with coarse aggregate No. 53 or No. 73 and compacted in accordance with 301.06. Geotextiles used shall be in accordance with 918.02.

All irregularities and holes shall be graded with either coarse aggregate No. 53 or No. 73. If an aggregate base is part of the HMA pavement structure, the 24 in. excavation depth shall be reduced by the thickness of the aggregate base.

The 3 in. compacted aggregate as part of the subgrade treatment Type V shall be compacted to 100% prior to the placement of the pavement.

When conditions are encountered below the specified subgrade treatment depth that prevent achieving the specified subgrade compaction, such conditions shall be corrected in accordance with 203.09, or as directed. 110

Proofrolling shall be performed in accordance with 203.26.

207.05Method of Measurement

Subgrade treatment will be measured in both cut and fill areas by the square yard per type.

Geosynthetic specified for use in addition to that required for the specified subgrade treatment will be measured in accordance with 214.05.

The undercutting of rock, where encount ered, will be measured in accordance with 203.27(b).

Testing, sampling, coarse aggregates , chemicals for modification, water, excavation, geogrid, geotextile, and geocell confining system for specified subgrade treatment types will not be measured. 207.05

207.06Basis of Payment

The accepted quantities of subgrade treatment will be paid for at the contract unit price per square yard per type, complete in place. In areas where shallow utilities are 130 encountered or the Contractor elects to use Type IC for Type IBC or Type IBL, payment will be made at the price of Type IBC or Type IBL.

The undercutting of rock, where encountered, will be paid for in accordance with

203.28

Payment will be made under:

Pay Item Pay Unit Symbol

Subgrade Treatment, Type _____ ............................................. SYS

The cost of subgrade treatments including testing, sampling, coarse aggregates, chemicals for soil modification with cement or lime, water, excavation, geogrid, geotextile and geocell confinement system for specified subgrade treatment types shall be included in the cost of the pay item.

The cost of excavation and grading of existing railroad ballast and railroad bed material shall be included in the cost of subgrade treatment, Type V.

Geosynthetic specified for use in addition to that required for the specified subgrade treatment will be paid for in accordance with 214.06.

Where conditions exist below the specified subgrade compaction depth that prevent achieving the specified compaction, payment for correcting such conditions will be made based on the directed method of treatment.