PROJECT: CHINA DEVELOPMENT BANK FUNDED PRIORITY ROAD PROJECT-3(PRP3-PHASE II) REHABILITATION/IMPROVEMENTS OF THIBBUTTA JUNCTION FROM DEMALARAWA-PANANETIPOLA- BATTAGALLA ROAD FROM CH 0+000 TO CH 5+000 KM 2016 OCTOBER ` DETAILED ENGINEERING DESIGNS PAVEMENT DESIGN REPORT THIBBUTTA JUNCTION FROM DEMALARAWA-PANANETIPOLA- BATTAGALLA ROAD FROM CH 0+000-3+219 FROM CH 07+000 TO CH 09+400 KM CLIENT & ENGINEER SUB-CONTRACTOR CONTRACTOR
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THIBBUTTA JUNCTION FROM DEMALARAWA-PANANETIPOLA-BATTAGALLA ROAD
FROM CH 0+000-3+219 FROM CH 07+000 TO CH 09+400 KM
CLIENT & ENGINEER
DESIGN
SUB-CONTRACTOR
CONTRACTOR
1
1 Introduction
Thibbutta Junction from Demalarawa-Pananetipola-Battagalla Road is being rehabilitated and improved by NEM Construction (Pvt) Ltd under China Development Bank Funded project of rehabilitation/improvements Priority Roads Project-Phase II (PRP3-Phase II). This report contains the pavement design of the road section from the Chainage 0+000 to 3+319Km.
Asphalt Concrete Surface with Dense Graded Aggregate Base has been proposed by Road Development Authority. Paved width and earth shoulder width of road are 3.5m and 1.0m respectively.
2 Pavement Condition
The Existing Road Surface consists with the layers as follows.
Table 1- Existing Pavement Condition
Section Pavement Type
Ch 0+000- Ch 0+195 Concrete Section
Ch 0+195- Ch 0+245 6x4 rock Section
Ch 0+245- Ch 0+275 Concrete Section
Ch 0+275- Ch 0+340 6x4 rock Section
Ch 0+340- Ch 0+367 Concrete Section
Ch 0+367- Ch 0+377 6x4 rock Section
Ch 0+377- Ch 0+485 Concrete Section
Ch 0+485- Ch 0+610 6x4 rock Section
Ch 0+610- Ch 0+655 Concrete Section
Ch 0+655 -Ch 0+730 6x4 rock Section
Ch 0+730- Ch 0+895 Concrete Section
Ch 0+895- Ch 1+010 6x4 rock Section
Ch 1+010- Ch 1+122 Concrete Section
Ch 1+122- Ch 1+315 6x4 rock Section
Ch 1+315- Ch 1+535 Asphalt Section
Ch 1+535- Ch 1+665 6x4 rock Section
Ch 1+665- Ch 2+015 Gravel Section
Ch 2+015- Ch 2+055 Concrete Section
Ch 2+055- Ch 2+200 Gravel Section
Ch 2+200- Ch 2+810 6x4 rock Section
Ch 2+810- Ch 3+052 Interlock Section
Ch 3+052- Ch 3+135 6x4 rock Section
Ch 3+135- Ch 3+170 Concrete Section
Ch 3+170- Ch 3+219 6x4 rock Section
2
Since the existing concrete sections have been severely damaged and cracked those were considered as crushed concrete for the design. Furthermore, the existing Interlock Layer too is assumed as a crushed concrete for the design.
3 Pavement Investigation
Due to Existing carriageway width is inadequate for proposed width at certain locations, Dynamic Cone Penetration tests and test pit investigations were carried out on both the existing pavement and the widening section of the road.
The CBR values obtained from DCP tests of the Existing pavement and Widening Sections were summarized in Annex 1A & 1B. Laboratory CBR values and other soil properties of the Existing pavement and Widening Section were summarized in Annex 2.
DCP CBR values were converted to an overall Equivalent DCP CBR value using the following Japanese formula (Japan Road Association, 1989).
DCP CBR is factored by the correlation factor (Lab CBR/Eqv.DCP CBR) that find out for existing pavement and widening section separately. Lab CBR values at 95% MDD under modified conditions of compaction and field dry density were considered for widening sections and existing pavement respectively. Factored DCP CBR values and Lab CBR were used to determine the design Subgrade strength (Design CBR) for the pavement structure.
The Design CBR of the subgrade varies from 1% to 14% for existing pavement section and from 1% to 13% for widening sections. Variation of Design CBR with Chainage is graphically shown in Figure 2 and Figure 3 for carriageway and widening sections respectively. Homogeneous sections were selected based on Design CBR values.
Existing layer thickness & Structural Number Calculation for existing pavement is shown in Annex 3. Considering all data, calculated design structural Number is shown in table 3.
Selected Design Subgrade CBR for Existing pavement and Widening Section were shown in table 02.
Table 2– Design Subgrade CBR Values
As per investigations carried out, following locations were identified as having low subgrade
CBR values less than design CBR values.
Chainage Location CBR
Ch 0+000 to Ch 3+219 Carriageway 5 %
Widening 3 %
3
Table 3– Improvement location as per Investigation
These locations shall be confirmed and improved by removing soft soil layers and using rock
filling or other suitable filling material.
The engineer, after inspection of road shall decide the exact extent to be widened at the site.
He shall confirm that the subgrade CBR is greater than value given in table 01 at 95% of MDD
under modified conditions of compaction and at Field density in widening and existing
pavement sections respectively. Locations having less than design CBR shall be improved by
removing soft soil layers and or using rock filling. Also after inspection of the road, the failure
sections of the existing road to be re-constructed shall be identified.
4 Traffic Forecast
As per the instructions given by the Letter RDA/RNIP/PRP3PhaseII/C24/09/01 dated on 1st August 2016 sent by Road Development Authority (RDA) considering future traffic demand, design traffic class was taken as T2 class (Refer Annex 5)
5 Pavement Design
Pavement Design was carried out as per the guidelines given in TRL Overseas Road Note 31, Transport & Road Research Laboratory, United Kingdom.
But The Overseas Road Note 31 does not provide semi structural surface/granular road base pavement type for T2 traffic class (refer Chart 1). Hence design layer thicknesses for the pavement were calculated based on surface dressing / granular road base pavement type. (Refer Chart 3)
The design thicknesses of the road pavement are calculated and presented in the Table 4 based on the design sub-grade CBR value, Remaining Structure number, condition of existing pavement and the Traffic class. Design calculations are shown in Annex 4.
Chainage Location CBR
Ch 0+015 Carriageway 1 %
Ch 0+250 Carriageway 4 %
Ch 2+250 Carriageway 3%
Ch 0+100 Widening 1 %
Ch 0+250 Widening 2 %
Ch 0+400 Widening 2 %
Ch 0+600 Widening 1 %
Ch 0+800 Widening 2 %
Ch 0+900 Widening 1 %
Ch 1+000 Widening 1 %
Ch 1+300 Widening 2 %
Ch 2+200 Widening 2 %
4
Layer thicknesses according to the pavement design
Table 4– Design Layer thicknesses
Chainage Section Design
CBR (%)
Structural Number
Asphalt Concrete
Dense Graded Aggregate
Base * (CBR>=110)
Soil Sub Base
Type I (CBR>=30)
Ch 0+000 to Ch 1+665, Ch 2+015 to Ch 2+055 &Ch 2+200 to Ch
3+319 (Concrete**,
6x4 Rock and Interlock Sections)
Carriageway 5% 9.9 50 150 -
Widening 3% -
50 150 250
Ch 1+665 to Ch 2+015 & Ch 2+055 to
2+200 (Gravel
Sections)
Carriageway 5% - 50 150 150
Widening 3% - 50 150 250
* CBR of DGAB consider as more than 110%
**Existing pavement is recommended to be crushed before overlaying DBAB
Locations where highly deteriorated or damaged existing pavement, should be reconstructed with layers given for widening by scarify the existing pavement and compacting formed subgrade to achieve 95% MDD at modified Procter compaction.
Pavement widening Soft Shoulder
Figure.1 –Typical cross section for Overlay & Widening
Figure.2 –Typical cross section of a Gravel Section
Shoulder Material (CBR≥20%)
Soil Sub Base Type-I (CBR≥30%)
Dense Graded Aggregate Base (CBR≥110%)
5
6 Drainage
It is very essential to provide an efficient system of drainage throughout this road by way of cross drainage structures; side drains lead-away drains etc.
7 Materials and Method of Construction
Material and method of construction has to be selected according to the references given in Table 4.
Table 5- Reference for Materials and Method of Construction
8 References
Yang H. Huang - Pavement Analysis and Design, 2nd Edition Transport & Road Research Laboratory, United Kingdom Road Note 31, 1977 RDA Pavement Design Guide, 1999 Guide to Pavement Technology, Part 2: Pavement Structural Design, Austroads-Sydney-2010 AASHTO Pavement Guide for Design of Pavement Structure, 1993 Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-1989) Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-2009)
Materials Reference
Embankment Type I Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-2009) ,Cl:304 and Table 1708-1
Embankment Type II Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-2009) ,Cl:304 and Table 1708
Sub Bases Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-2009) ,Cl:401.2 and Table 1708.2 ,1708.3
Dense Graded Aggregate Base (DGAB)
Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-2009) ,Cl:405 and Sub Cl:1701.3(Base course Aggregates) & Table 1701-5
Asphalt Concrete Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-2009) ,Cl:506
Shoulders Standard Specification for Construction and Maintenance of Road and Bridges (SSCM-2009) ,Cl-409.2