Sub Grade Drinage

8/10/2019 Sub Grade Drinage

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7.07.17.2

DRAINAGE OF SUBGRADEGeneralAlternative Provisions

7.1 General

7.1.1 On all sites, adequate subgrade drainage shall be provided to ensure that, at all times,the water level is maintained at more than 300mm below formation level. The subgradedrain pipes must be run to an approved outfall. Refer also to Section 1.1 and AppendixB1. Where the sub-soil is gravel, blocky chalk or sand the drainage is not normallynecessary. Where other subsoil materials are encountered it shall be assumed that sub-soil drainage will be required.

7.1.2 Subgrade drainage may not be required when the formation is not rutted and ismaintained free of standing water during construction and when:

a) site investigation has demonstrated that the highest annual ground water level is morethan 300mm (see above) below formation level.Orb) free-draining continuous sand and gravel layers or blocky chalk occur at and belowformation level.

Note:- The requirement for subgrade drainage may only be waived after groundinvestigations have been undertaken which can prove to the Engineer that it is notnecessary.

7.2 Alternative Provision

7.2.1 Where sub-grade drainage has been found to be necessary, but impracticable,separating membranes shall be placed above and below an additional 150mm of Type 1which is to be installed below and extra to the depth of construction required by thePlasticity Index.


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8.08.18.2

CARRIAGEWAY FOUNDATIONGeneralSub-Base Materials

8.1 General8.1.1 Refer to Appendix A for design depths of construction.8.1.2 Sub-base materials shall be spread evenly on the formation in layers of a depth of not

more than 150 mm compacted thickness and compacted in accordance with therequirements of the compaction table Appendix C4, at a moisture content in the rangeoptimum minus 2% or plus 1% and without segregation.

8.1.3 The full thickness of the sub-base shall be continued for a distance of 300 mm beyondthe limits of the kerb beam, the developer should refer to the typical cross-section detailsin Appendix B1.

8.1.4 The Environment Agency shall be consulted over the use of any material that maycontain contaminants and which could generate an unacceptable leachate.

8.2 Sub-Base MaterialsTable 8A - Housing Estate Road Sub-base (HER)

BS sieve size Range of grading % by mass passing

63 mm 100

31.5 mm 74 100

16 mm 44 80

8 mm 30 65

4 mm 18 42

2 mm 13 351 mm 8 28

0.250 mm 0 18

0.063 mm 0 9

8.2.1 The material shall be from Peterborough Local Authorities approved list (drawn up byAtkins Materials Division) of sub base materials and shall be crushed rock, slag, crushedconcrete or other approved material. It shall be well graded and lie within the gradingenvelope in Table 8A.

In the above Table:

a)The particle size shall be determined by the washing and sieving method of BS EN933: Part 1 : 1997b) The material passing the 425 um BS sieve when tested in accordance with BS 1377shall be non-plastic

c) 10% fines value must exceed 40kN tested on a soaked basis in accordance withBS812.

Type 1 Sub-base

Alternatively, SHW Clause 803 Granular Sub-base Material Type 1 may be used.The material shall comply with the full requirements of SHW Clause 803 Granular Sub-base Material Type 1 including acceptable secondary and recycled aggregates. (Only to

be used after engineers approval).


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9.0

9.19.29.39.4

CARRIAGEWAY BASE LAYERS

GeneralMaterialsBase Layer - Hot Rolled AsphaltBase Layer - Dense Bitumen Macadam

9.1 General9.1.1 Refer to Appendix A for design depths of construction.9.1.2 Bituminous materials shall be machine-laid. Where agreed with the Engineer, hand

laid materials may be used but shall be restricted to small areas see clause 1.11.

9.1.3 Where damage resulting from trafficking of bituminous layers occurs, appropriateremedial treatment shall be carried out which shall comply with the requirements ofClause 1.11.3.

9.1.4 Note: - The combined thickness of bound material shown in the relevant

appendices shall be the minimum thickness permitted.

9.2 Materials9.2.1 The Base layer materials shall be either Hot Rolled Asphalt to Clause 9.3 or Dense

BitumenMacadam to Clause 9.4 below. The materials formulation and compactionstandards shall be such as to ensure individual insitu air voids are more than 2% butless than 10%. For the purpose of overall compliance, the following void levels shallbe deemed acceptable.

DBM materials - as per Specification for Highway Works Clause 929

HRA materials - Average of six core measurements to be < or = 5% with no

individual value being > 8%

Note: -Consideration will be given to Developers/Contractors wishing to usematerial containing recycled products such as Glasfalt subject to the conditions seeClause 1.11.7.

9.3 Hot Rolled Asphalt9.3.1 The material shall be 60% 0/20 designation to Column 2/4, Table 2 of BS 594 Part 1,

2003. It shall be placed in two layers and thoroughly compacted, all in accordancewith BS 594 Part 2, 2003 Binder to be 40 - 60 pen.

9.3.2 Where the aggregate is gravel, 2% of Ordinary Portland Cement (OPC) or 2%

hydrated lime must be included in the material passing the 75um sieve or anapproved type and quantity of adhesion agent may be substituted for theOPC/Hydrated Lime.

9.3.3 Guidelines for delivery and rolling temperatures for Hot Rolled Asphalt Baselayerare given in Appendix D.

9.3.4 The combined thickness of bound material shown in the relevant appendices shallbe the minimum thickness permitted.

9.4 Dense Bitumen Macadam9.4.1 The material shall be 0/20 mm Nominal Size to Clause 6.5 of BS 4987, 2003. It shall

be placed in two layers and thoroughly compacted all in accordance with BS 4987,Part 2, 2003. Binder to be either 100 150 pen or 40 60 pen if requested.


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9.4.2 Where the aggregate is gravel, 2% of Ordinary Portland Cement (OPC) or 2%hydrated lime shall be included in the material passing the 75um sieve or anapproved type and quantity of adhesion agent may be substituted for theOPC/Hydrated Lime.

9.4.3 If Gravel is to be used proof shall be provided to show that the mixture has beensubject to the SHW Clause 929 design process and that it has been successfully laid

and trafficked elsewhere.9.4.4 Guidelines for delivery and rolling temperatures for Dense Bitumen Macadam Baselayer are given in Appendix D.


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10.0 CARRIAGEWAY BINDER LAYER

10.110.210.310.4

10.5

10.1

GeneralBinder Course Layer Hot Rolled AsphaltBinder Course Layer Dense Bitumen MacadamPermitted Variations

Substitution of Materials

General10.1.1 Refer to Appendix A for design depths of construction. Where the Binder course

layer is to be trafficked, the binder content shall be enhanced.

10.1.2 The only materials permitted on housing estate and distributor roads are Hot RolledAsphalt or Dense Bitumen Macadam as specified in clause 10.2 and 10.3.

10.1.3 For major spine estate roads the Design Bulletin 32 (DB32) shall be used for theoverall design. Only Dense Bitumen Macadam to clause 9.4 shall be used, unlessthe laying contractor is able to prove through site testing that adequate standardsare in-built with the use of any alternative materials. Such testing should beproposed and agreed by the Engineer prior to the commencement of the works. Allsuch testing to be at the developers cost.

10.1.4 Bituminous materials shall be machine-laid. Where agreed with the Engineer, handlaid materials may be used but shall be restricted to small areas. See clause 1.11.2

10.1.5 Where damage resulting from trafficking of bituminous layers occurs, appropriateremedial treatment shall be carried out which shall comply with the requirements ofClause 1.11.3.

10.1.6 Note: The combined thickness of bound material shown in the relevantappendices shall be the minimum thickness permitted.

10.2 Binder Course Layer - Hot Rolled Asphalt

10.2.1 The material shall be 60% 0/20mm designation to Column 2/4 of Table 2 of BS 594,Part 1, 2003 and laid 60mm thick. Coarse aggregate shall be crushed rock only. Thematerial shall be laid and thoroughly compacted all in accordance with BS 594, Part2, 2003. Binder to be 50 pen.

10.2.2 Guidelines for delivery and rolling temperatures for Hot Rolled Asphalt BinderCourse layer are given in Appendix D.

10.3

10.3.1

10.3.2

Binder Course Layer - Dense Bitumen Macadam

The material shall be 0/20 mm Nominal Size to Clause 6.5 of BS 4987, 2003 andlaid 60mm thick. It shall be laid and thoroughly compacted all in accordance with BS4987, Part 2, 2003. Binder to be either 125 pen or 50 pen if requested.

Guidelines for delivery and rolling temperatures for Dense Bitumen Macadam Binder

Course layer are given in Appendix D.


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10.4

10.4.1

Permitted Variations

Where the permitted variations are not used all materials for Base and BinderCourse layers shall comply with Clauses 9.3 or 9.4 or 10.2 and 10.3 respectively.

10.4.2 For Housing Estate Roads and Distributor Roads only (designed to Appendix A1

and A2). Where the Binder and Base layers are to comprise of the same materiali.e. Hot Rolled Asphalt to Clause 9.3 or Dense Bitumen Macadam to Clause 9.4, thelayers may be combined and laid in two lifts. (See Diagrams 10.6 and 10.7 below)

Note:Consideration will be given to Developers/Contractors wishing to usematerials containing recycled products such as Glasfalt subject to the conditions seeClause 1.11.7

10.6 Hot Rolled Asphalt - Binder and Base

a) Housing Estate Roads

40 mm surface course 80 mm binder course 80 mm base layer

b) Distributor Roads (See Appendix A2)

No Permitted Alternatives

c) Industrial Roads (See Appendix A3)


Note: Tack/bond coats to be applied in accord with Clause 1.11.3 for all layers.Cold applied bitumen or Hot pitch to be applied to all vertical joints i.e. Kerbs,Ironwork and joints.


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10.7 Dense Bitumen Macadam - Binder and Base

a) Housing Estate Roads


b) Distributor Roads


c) Industrial Roads (See Appendix A3)


Note: The combined thickness of bound material shown in the relevantappendices shall be the minimum thickness permitted.

10.5 Substitution of Materials

10.5.1 Where the overall design pavement thickness exceeds the 450mm minimumrequired in Appendices A1, A2 and A3 the depth of sub-base material may bereduced by increasing the bituminous Base thickness in the proportion of 1 partbituminous to 3 parts granular, subject to:

overall construction thickness not being less than 450mm and

sub-base thickness not to be less than 200mm

Geotextile must be used at formation level.

Sub Grade Drinage

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