1. Project Statement
This project is a newly-built highway of Class I in the city of Hefei. This report mainly solves the issue of asphalt pavement design.
This design was based on the national asphalt pavement design specification (JTG D50-2006) and technical standards of highway engineering (JTGB01-2003) as well as practical highway construction condition. Data pertinent to the pavement design were collected and properly modified after analysis of social and economy conditions. The requirements of safety, serviceability and durability are also taken into serious consideration. 2. Design data 2.1 Data Collection
This task takes 20% of the total grade of the course project. Students should collect data of climate, geology, subgrade, traffic, and other conditions pertinent to the pavement design in their hometowns. For instance, a student is from Xi’an of Shaanxi province, he or she may collect data near Xi’an city. Followed are guidelines for data collection: 1) Climate data
(1) Natural Zoning for Highways: Ⅳ2
In this area, plum rains in summer is obviously harmful to highway. High temperature of ground is easy to cause bleeding of asphalt pavement and increase the curling stress of concrete pavement. The terrain is in general plain so that highway can pass through the geomorphic condition easily.
(2) Temperature
The highest temperature is 30℃～35℃ and the lowest temperature is -9℃～-14℃.
(3) Rainfall
The rainfall is 1000～1600mm. (4) Humidity
This project is located on wet area. 2) Geological and subgrade conditions
(1) Filling materials and thickness
Because construction site is close to Huai river, the filling materials generally adopt gravel or other soil of good property. As for the thickness, it depends on detail conditions of different segments of the highway and ranges from 0.3m to 1.2m.
(2) Water table height
The water table height is over 3m. (3) Other information
There is mainly clay whose strength is good in this area and the subgrade condition is satisfactory. But sometimes digging side slope may bring about land slip and drainage system must be given attention. 3) Traffic data
Traffic data was collected in Hefei city and selected the following seven dominant vehicles to analyze and determine the highway class and traffic loads level. The following is relative data:
Traffic volume forecast fixed number of year: 15 years; Traffic volume forecast increasing ratio: 7%; Design period of asphalt pavement: 15 years; Design traffic volume increasing ratio: 6%;
Lane distribution factor: 0.5 (four lanes in two directions)
Table.2-1-1 Traffic Data
2.2 Traffic Analysis 1). Traffic Prediction
According to the original traffic data, the sum of the converted AADT of each type of vehicle is 11763 vel/d, assume that the increasing rate is 7%, the daily traffic volume after converted into small passenger vehicle in 15 years after construction is as following:
=26595
According to technical standards of highway engineering (JTGB01-2003), the predicted daily traffic volume for highway of Class I with four-lanes in two directions is approximately 15000~30000 vel/d in 15 years. 2). Accumulative ESALs by Surface Deflection or Tensile Stress at the Bottom of Asphalt Layer
The calculation results are shown in the following charts.
Table.2-2-1 Truck Factor
Table.2-2-2 ESALs
3). Accumulative ESALs by Tensile Stress at the Bottom of Semi-rigid Layer
The calculation results are shown in the following charts.
Table.2-2-3 Truck Factor
Table.2-2-4 ESALs
4). Traffic Loads Level
The accumulative ESALs under two different design criteria are respectively: 13.28msa and 22.10msa. The traffic volume of large passenger vehicle and medium or large truck is 11763/4=2941vel/(d*lane)
According to the Asphalt Pavement Design Specification JTG D50-2006(Table 3.1.8), the traffic load level is heavy traffic. 2.2 Subgrade Modulus
1) Subgrade Modulus Using TLU Methods
(1) Critical Height H1, H2 and H3
The distance between water table and roadbed surface: H=3.5m H1=1.6m, H2=1.1m, H3=0.8m (2) Average Roadbed Consistency
As H1 < H, the subgrade humidity is dry and the soil consistency Wc =1.15.
(3) Subgrade MR Design Value Assuming Wc =1.15, MR = 33.0 MPa
Since the TLU methods is 20% to 35% lower, therefore, the final MR 3. Combination Design 3.1 Asphalt surface course
According to the specification, 3 kinds of surface layers are selected as followings:
Case1: 4cm FAC (AC-13) + 5cm MAC (AC-20) + 7cm CAC (AC-25) Case2: 4cm FAC (AC-13) + 4cmMAC (AC-20) + 6cm CAC (AC-25) Case3: 4cm FAC (AC-13) + 8cm MAC (AC-20) + 8cm CAC (AC-25) 3.2 Base and subbase courses
According to the specification, 3 kinds of base and subbase course as follows are selected as followings:
Case1: ? cm HBM (CBM) + 18 cm UGM (Graded Gravel Sands) Case2: 35cm HBM (CBM) + ? cm HBM (Lime Bound Soils) Case3: 22cm AM(ATB-20) + ? cm UGM (Graded Gravel Sands) 3.3 Cushion layer design
Given the influence of plum rains of summer, cushion layer should be provided to meet drainage requirements. Therefore, Graded broken stone of the thickness of 15 cm is selected as cushion layer. 3.4 Summary
Considering seriously all data and requirements of specification, combination design is completed according to experience. They all meet recommendations. Next, the work is to check various index. 4. Material proportion design and properties 4.1 Asphalt surface Materials
Based on the combination design, the corresponding material properties should be determined based on the recommended values in the specification.
The process of mix proportion design is not required in this course project, but bonus will be given to students who have done proportion design…. 4.2 Base and subbase materials
Based on the combination design, the corresponding material properties should be determined based on the recommended values in the specification. The process of mix proportion design is not required in this course project, but bonus will be given to students who have done proportion design…. 4.3 Cushion layer materials
Based on the combination design, the corresponding material properties should be determined based on the recommended values in the specification. The process of mix proportion design is not required in this course project, but bonus will be given to students who have done proportion design…. 4.4 Summary
The properties is shown in Table.4-4-1.
Table.4-4-1 Properties
MR at 20C (MPa) Material Ep variance σ Fine grained asphalt concrete Medium grained asphalt concrete Course grained asphalt concrete Ep-2σ Eps Ep ．MR at 15C (MPa) variance σ Ep-2σ Ep+2σ Ep代 Ne(time) 。1991 1425 978 201 105 55 Surface course 2681589 344 0 2171215 187 5 132868 60 0 1992 1801 1200 3368 2549 1440 1.46E+07 1.46E+07 1.46E+07 Deflection check Tensile stress check 1.22E+07 1.22E+07 Base or subbase Cement stabilized macadam Cement lime sand soil Graded macadam Graded sand 400 250 3188 1591 782 250 1624 1091 4752 2091 1.46E+07 1.46E+07 5. Thickness Design
5.1 Determine design criteria
According to specifications, surface deflection and tensile stress at the bottom of each layer should satisfy the requirements. 5.2 Determine calculated criteria 1) Calculation of Case 1
Assuming the thickness of subbase (CBM) is 30cm, input the thickness, resilient modulus and passion ratio of each layer into BISAR to obtain the surface deflection and tensile stress at the bottom of each layer which are attached in the APPENDIX. The resilient modulus of each layer is derived from the following table based on specification.
(1) Check of Surface Deflection
Knowing that Ne = 22.10msa, thus the design deflection:
The calculated deflection from BISAR is =10.10(0.01mm) <
The surface deflection satisfied the requirement. (2) Check of Tensile Stress at the Bottom of Each Layer
Table.5-2-1 Case 1
1) Calculation of Case 2
Assuming the thickness of subbase (Lime Bound Soil) is 18cm, input the thickness, resilient modulus and passion ratio of each layer into BISAR to obtain the surface deflection and tensile stress at the bottom of each layer which are attached in the APPENDIX. The resilient modulus of each layer is derived from the following table based on specification.
(1) Check of Surface Deflection
Knowing that Ne = 22.10msa, thus the design deflection:
The calculated deflection from BISAR is =9.49(0.01mm) <
The surface deflection satisfied the requirement. (2) Check of Tensile Stress at the Bottom of Each Layer
Table.5-2-2 Case 2
1) Calculation of Case 3
Assuming the thickness of subbase (Lime Bound Soil) is 18cm, input the thickness, resilient modulus and passion ratio of each layer into BISAR to obtain the surface deflection and tensile stress at the bottom of each layer which are attached in the APPENDIX. The resilient modulus of each layer is derived from the following table based on specification.
(3) Check of Surface Deflection
Knowing that Ne = 22.10msa, thus the design deflection:
The calculated deflection from BISAR is =13.53(0.01mm) <
The surface deflection satisfied the requirement. (3) Check of Tensile Stress at the Bottom of Each Layer
Table.5-2-3 Case 3
5.3 Finalize the thickness design
Through the above calculation and comparison, thickness design of the 3 cases meets the requirement: ls Table 6-1 Link layers Links Tack coat Primer coat Upper seal coat Lower seal coat Locations Interface among upper surface, mid-surface and lower surface Interface between lower seal coat and base Above the upper surface Interface between lower surface and primer coat Material Emulsified asphalt (praying quantity: 0.3 and 0.6 L/m2; asphalt content: 0.15-0.3L/ m2) Emulsified asphalt Emulsified asphalt slurry seal Emulsified asphalt surface treatment Seal coat 7. Finalize the design Cases are summarized as following: Table 1-1 Summary sheet of 3 cases Case Course Surface course Case 1 Base Subbase Cushion layer Surface course Case 2 Base Subbase Cushion layer Surface course Case 3 Base Subbase Cushion layer Material AC13 AC20 AC25 Cement stabilized macadam Graded Gravel Sands Graded sand AC13 AC20 AC25 Cement stabilized macadam Lime Bound Soils Graded sand AC13 AC20 AC25 Asphalt macadam Graded Gravel Sands Graded sand Thickness(cm) 4 5 7 30 18 15 4 4 6 35 18 15 4 8 8 22 35 15 Part II Cement Concrete Pavement Design 1. Project Statement This project is a newly-built highway of Class I in the city of Hefei. This report mainly solves the issue of asphalt pavement design. This design was based on Ministry of Transport of the People's Republic of China, Specification for Design of Highway Cement Concrete Pavement (JTG D40-2011) as well as practical highway construction condition. Data pertinent to the pavement design were collected and properly modified after analysis of social and economy conditions. The requirements of safety, serviceability and durability are also taken into serious consideration. 2. Design data 2.1 Traffic Analysis The calculation formula of equivalent standard axle loads is: Highway Cement Concrete Pavement, we calculate for concrete pavement design with design period of 30 years, results are shown in the following tables: Table. 2-1-1 Design data Table. 2-1-2 Average Truck Factor Table. 2-1-3 ESALs = times/lane So the traffic load is heavy. 2.2 Subgrade Modulus On account of JTG D40-2011 Specifications for Design of Highway Cement Concrete Pavement, the range of MR is 80-120 MPa and the representative value is 100 MPa. In terms of relationship between humidity adjustment coefficient and distance from water table to roadbed top, the value of adjustment coefficient can be selected as 0.95. So the final value of MR is: . 3. Combination Design 3.1 Concrete Surface course Based on the specification, as the traffic level is heavy and highway is class I. Since the variance level is middle level and then the surface thickness reference value is ranged from 260mm~220mm. So assume the thickness of surface course is 240mm as the trial design. 3.2 Base and subbase courses Due to the large traffic load, the base is made of inorganic binder stabilized aggregate or asphalt stabilized macadam with relatively higher modulus. The subbase is formed by granular material or inorganic binder stabilized aggregate because minor load is transmitted to the course. 3.3 Cushion layer design Considering the impact of plum rains, drainage cushion layer should be set for soil cutting with adverse hydrogeological conditions and great humidity of subgrade soil. 3.4 Summary According to the specification, 3 cases are selected as followings: Case 1: Jointed plain concrete pavement + Cement stabilized macadam + Granular material. Case 2: Jointed plain concrete pavement + Cement stabilized macadam + Lime and fly ash stabilized macadam. Case 3: Jointed plain concrete pavement + Graded Crushed Stones. 4. Joint Design 4.1 Transverse Joints Base on the specification, transverse joint spacing is 5 m (between 4~6m) and the type is dummy joint (contraction joint) without dowel bar. 4.2 Longitudinal Joints Base on the specification, longitudinal joint spacing is 4 m (between 3~4.5m) and the type is butt joint (contraction joint) with dowel bar. 5. Material proportion design and properties 5.1 Concrete Materials According to the specification, the bending-tension strength should be taken as 5 MPa as the moderate traffic level. Besides, the elastic modulus should be 31Gpa, Poisson’ ratio is 0.15 and thermal coefficient is 1 . 5.2 Base and subbase materials According to the specification, Case I and Case II can be considered as the model of the double layer slab and Case III as the model of the single layer slab. In Case 1, the MR of granular material is 300MPa; in Case 2, the MR of lime and fly ash stabilized macadam is 1500MPa; in Case 3, the MR of graded crushed stones is 300MPa. 5.3 Cushion layer materials The width of cushion layer is same as the width of subgrade and is made of gravel. Its thickness is 160mm. 5.4 Summary Assume the thickness of each layer in each case: Case 1: Jointed plain concrete pavement (26cm) + Cement stabilized macadam (20cm) + Granular material (22cm). Case 2: Jointed plain concrete pavement (25cm) + Cement stabilized macadam (18cm) + Lime and fly ash stabilized macadam (20cm). Case 3: Jointed plain concrete pavement (26cm) + Graded Crushed Stones (20cm). Therefore, according to Ex1 = 300MPa, Ex2 = 1500MPa, Ex3 = 300MPa 6. Calculation and analysis of load-induced stress According to the different models of concrete slabs of each case, select diverse equations to calculate relative results. The following is the detailed process of double layer model. Other models are the similar process. The results are shown in the following table. Table.6-1-1 Calculation data 6.1 Load-induced fatigue stress Through the equation We get the results shown in the table. Table.6-2-1 Calculation results of load-induced fatigue stress 6.2 Load-induced ultimate stress Through the equation We get the results shown in the table. Table7-1-1 Calculation results 7. Calculation and analysis of thermal stress 7.1 Thermal fatigue stress Through the equation We get the results shown in the table. Table.7-2-1 Calculation data and results of thermal ultimate stress 7.2 Thermal ultimate stress Through the equation ] We get the results shown in the table. Table 7-2-1 Calculation data of thermal fatigue stress of surface plate 8. Finalize the design The criteria to verify whether the thickness of the trial design is ok or not is: Through looking the table in the specification, we can determine =1.10. Table. 8-1 Comparison between calculation stress and tensile strength From the results, we can clearly conclude that the cases of design all can satisfy the requirements. 因篇幅问题不能全部显示，请点此查看更多更全内容