SECTION PAVEMENT DESIGN

Transcription

1 SECTION GENERAL SUBSURFACE DRAINAGE DETERMINATION OF DESIGN TRAFFIC SUBGRADE EVALUATION PAVEMENT THICKNESS GRANULAR PAVEMENTS WITH THIN BITUMINOUS SURFACING PAVERS AND DECORATIVE CONCRETE PAVEMENT SURFACES ASPHALT SPRAY SEALS MATERIAL PROPERTIES

2 SECTION GENERAL Road pavements shall be designed in accordance with the requirements of the following manuals except as noted otherwise herein.: (a) Unbound Flexible Pavements where Cumulative ESA's Do Not Exceed 5*10 5 i. AUSTROADS A guide to the design of new pavements for light traffic ii. AUSTROADS Pavement Design, A Guide to the Structural Design of Road Pavement (b) Unbound Flexible Pavements where Cumulative ESA's Exceed 5*10 5 AUSTROADS Pavement Design, A Guide to the Structural Design of Road Pavement (Queensland Transport - Pavement Design Manual is a reference manual for all flexible pavements.) (c) Bound Pavements (All Traffic Loadings) Queensland Transport - Pavement Design Manual The use of bound pavements is subject to the approval of the Director. Generally a stabilised subbase with granular base course is preferred for any bound pavement design. (d) A.C. and Seal Surfacing Material design and construction to Queensland Transport standards. (e) Rigid Pavements The use of rigid pavements is subject to the approval of the Director. Rigid pavements shall be designed to the requirements of : i. AUSTROADS A guide to the design of new pavements for light traffic ii. AUSTROADS Pavement Design, A Guide to the Structural Design of Road Pavement "Concrete Pavement Design for Residential Streets" by Standards Australia & Cement and Concrete Association (of Australia) is also a useful guide for the design of rigid pavements: (f) Concrete Segmental Pavements The use of pavers is subject to the approval of the Director. Concrete segmental paving shall be designed and constructed in accordance with Concrete Masonry Association of Australia guidelines for use of Concrete Segmental Pavers in Subdivisional Roadways SUBSURFACE DRAINAGE The design of subsurface drainage shall generally comply with the ARRB publication Subsurface drainage of road structures and Council s standard drawing. The Consultant shall verify the suitability of the subsoil drainage type, and the appropriate filter prior to installation.

3 3.3.3 DETERMINATION OF DESIGN TRAFFIC All traffic loadings shall be based on Equivalent Standard Axles (ESA's, ie. equivalent 80kN axle load passes) for a minimum design life of 20 years. Design Traffic for the various road classifications is defined as indicated below: Table 3.3A Design Traffic ROAD DESCRIPTION Access Places Local Access Access Streets Collector Rural - Access - Collector - Connecting Road Trunk Collector Connecting Road Sub-Arterial Arterial Industrial - Access St - Collector St ESA s 1 x x x x x 10 4 Note 1 3*10 5 Note 1 Note 1: Note 2: ESA s to be confirmed by the Director. In the absence of more specific information, designers shall use the following parameters for the calculation of design ESA s: Design life 25 years. 5-10% CV (Review on basis of Councils available traffic count data.) ESA per CV. (Adopt 0.6 ESA/CV for trunk collector/arterial roads) (Adopt 1 ESA/CV for connecting roads) (Adopt 1.1 ESA/CV for industrial roads) 4% min. annual traffic growth. (Adopt 1% min. annual growth in rural areas.) Figures indicated shall be used as a guide only and may be subject to verification by the Director SUBGRADE EVALUATION Subgrade evaluation shall be undertaken in accordance with AUSTROADS Pavement Design, A Guide to the Structural Design of Road Pavement except as varied herein. Site investigations shall be performed to determine soil types, based on a series of test holes sampled along the job site. Testing should be at a sufficient interval so as to determine soil boundaries. Minimum soil sampling frequencies are outlined in Table 3.3B. Table 3.3B Testing Distance Street Length <120m Street Length >120m 2 test locations Test location every m depending on soil types

4 Samples should be taken in order of running chainages and extend 500mm below the proposed subgrade level. Where the depth of fill will exceeds 500mm, testing at natural surface is not required and testing will be carried out on the fill material. At each test location the testing shall include both field and laboratory testing. (a) Field Testing - Visual description of sample including the material type and colour. The Unified Soil Classification system can be used for this. - Dynamic Cone Penetrometer test to a depth of 1.0m. (Main Roads Test Method Q114B to provide equivalent CBR results.) - Field moisture content. (b) Laboratory Testing - Gradings of the subgrade - Atterberg limits - Linear shrinkage (LS) - 4 Day Soaked CBR testing (Refer to Note 1) Note 1: Following classification of each different material, a minimum of two soaked CBR tests shall be undertaken on each material type. Testing shall be in accordance with Method Q113C. The single point CBR test shall be carried out at OMC and at the density that will occur in service. Refer clause of Austroads Pavement Design Manual. (Eg for subgrades of embankments, test at 97% RDD standard compactive effort). Note 2: Note 3: Note 4: Where directed by Council, additional testing may be required beneath adjoining roads to verify insitu subgrade densities and moisture contents. Such testing could be required if the adjoining road is a minimum of 3 years old and has been built on the same subgrade material, with identical pavement materials and drainage conditions. Unfortunately many of the natural soils in the Shire show rapid drop off in CBR strength for slight moisture variations from OMC. Subsoil drainage has not always been effective and insitu moisture contents at some pavements failures have been higher than OMC. Note 5: Test methods shall be in accordance with the latest amendments to AS1289 (or the equivalent Main Roads Method) except in the case of the CBR and DCP tests which shall only be in accordance with Main Roads Methods as stated herein. The design subgrade CBR of each material type shall take into account the general sensitivity of the material to moisture variations and shall generally be determined as follows: (a) (b) Where there are fewer than 5 CBR test results on the same material Design CBR = the lowest 4 day soaked CBR value (This situation would normally apply.) Where there are more than 4 CBR results on the same material Design CBR = the 10th percentile of all 4 day results on the same material. Design CBR = C - (1.3 x S) where C = the mean of all 4 day soaked CBR values S = standard deviation of all 4 day soaked CBR values

5 The above method is the same as that outlined in Local Sealed Roads Manual for F = 0.9. The method outlined in clause 2.2.3(b) of the above mentioned manual may also be used. Subgrade test results including a drawing showing the locations of tests; and proposed pavement thicknesses shall be submitted to the Director for approval after basic site earthworks have been completed. For silty soils, SM, SC or ML, small fluctuations in moisture content may produce large changes in strength/stiffness while for CL or CH clay, small fluctuations in moisture may produce large variations in both volume and in strength/stiffness. If soaked CBR results for these material types exhibit CBR values in excess of 5, such values shall only be used with the approval of the Director PAVEMENT THICKNESS GRANULAR PAVEMENTS WITH THIN BITUMINOUS SURFACING For roads with kerbing or kerb and channel and design ESA s < 5*10 5 the attached Figure 3.3a shall be used for the determination of pavement thickness. (Figure 3.3a shall also be used for roads incorporating flush kerb profiles.) For roads without kerbing and design ESA s < 5*10 5 the attached Figure 3.3b shall be used for the determination of pavement thickness. For roads with thin bituminous surfacing and design ESA s > 5*10 5 the attached Figure 3.3c shall be used for the determination of pavement thickness. Total pavement depths as read from the appropriate Figure 3.3a or 3.3b or 3.3c shall be rounded up to the nearest 20mm. For those road classifications with ESA s specified in Table 3.3A, the following Table 3.3C shall be used for the determination of pavement thickness.

6 Figure 3.3a Design Chart for Granular Pavements with Thin Bituminous Surfacing (with kerb) Source Austroads APRG Report No. 21

7 Figure 3.3b Design Chart for Granular Pavement with Thin Bituminous Surfacing (without kerb) Source Austroads APRG Report No. 21 Figure 3.3c Design Chart for Granular Pavement with Thin Bituminous Surfacing for roads with > 5 x 10 5 ESA - Source Austroads, 1992

8 Soaked CBR % Table 3.3C - Total Pavement Thickness Access PIace Minor Street Pavement with Kerbing Local Access TOTAL PAVEMENT THICKNESS (mm) Access St Collector St Industrial Access Subgrade treatment required Then treat as CBR 3 material (See Note) Soaked CBR % Minor Street Pavement without Kerbing R.R. Access Place Access Street Collector Rural Access (4m seal) Subgrade treatment required Then treat as CBR 3 material (See Note) / / Note 1 In cases where the 4 day soaked CBR value is less than 3%, 50mm of material having a 4 day soaked CBR of 15% shall be added to the design depth of pavement for each 0.5% or part thereof the CBR is below 3%. For example, if the CBR is 2.5%, add 50mm; if it is 2%, add 100mm. Approved subgrade stabilisation may be used in lieu of subgrade replacement procedures when subgrade CBR is less than 3%.

9 Notwithstanding the pavement results from the above figures, total pavement thickness shall not be less than indicated in Table 3.3D. Where the design pavement depth exceeds the minimum depths in Table 3.3D, the pavement material below subbase level shall have a minimum soaked CBR of 15. Table 3.3D - Minimum Total Pavement Thickness ROAD CLASSIFICATION MIN. TOTAL PAVEMENT (mm) MIN. BASE COURSE (mm) (min CBR) MIN. SUBBASE COURSE (mm) (min CBR) Roads < 10 6 cum. ESA Roads > 10 6 cum. ESA (CBR 60) 125(CBR 80) 100 (CBR 35) 125 (CBR 45) Where asphalt is used as the wearing course of a pavement, the total pavement thickness required shall not include the thickness of the asphalt surfacing unless the asphalt thickness is greater than 50mm. Refer Queensland Transport Pavement Design Manual Section Asphaltic concrete will be considered as a structural course when designed in accordance with Queensland Main Roads standards. The pavement thicknesses shall be subject to confirmation by the Director, following site inspection and further testing of the subgrade if required by Council prior to placement of pavement material. The Director may require either local or general variation of the pavement thickness, dependent upon the actual subgrade conditions encountered PAVERS AND DECORATIVE CONCRETE Pavers shall be designed as for a gravel pavement, but the depth of pavers and bedding sand may be subtracted from the total pavement depth provided that the gravel pavement depth is not less than the minimum requirement (ie 250mm). Decorative concrete shall be designed as specified in this Manual for rigid pavements. Skid resistance of concrete or segmentally paved surfaces shall exceed the values recommended by QT when tested in accordance with the QT test No. Q PAVEMENT SURFACES ASPHALT Section outlines the roads for which asphalt shall be used as the wearing course of the pavement. The usage of asphalt surfacing in any other location will be subject to the approval of the Director. A single coat bitumen seal with 7mm aggregate shall be applied to the surface of all flexible pavements prior to placement of the asphalt wearing course. Asphalt shall comply with Queensland Transport s specifications for dense graded asphalt Refer MRS11.30 Interim 5/97. SMA (Stone Mastic Asphalt) will be permitted to be used and shall be in accordance with MRS11.33 Interim 5/97.

10 SPRAY SEALS Except as indicated in Section 2.4.7,all roads shall have a wearing course of a 16/10 mm aggregate 2 coat spray seal. Refer also Section MATERIAL PROPERTIES Pavement materials shall be in accordance with Queensland Transport Specifications. Sufficient testing of supplied pavement material shall be undertaken to ensure that the material meets grading, plasticity and strength requirements. Refer also Section 3.4 and Appendix H.