Széchenyi István University Faculty of Architecture, Civil Engineering and Transport Sciences Department of Transport Infrastructure.

Transcription

1 Széchenyi István University Faculty of Architecture, Civil Engineering and Transport Sciences Department of Transport Infrastructure Design traffic, Bearing capacity, Falling Weight Deflectometer (FWD)

2 Design traffic Themes of lecture Exposure categories of hot asphalt mixtures. Bearing capacity evaluation methods of layers and soils Empirical relationship between different bearing capacity methods Falling Weight Deflection measurements (LWD, FWD, HWD). Surface modulus. Curvature indexes. Pavement analysis.

3 Design traffic TF (F100)

4 Calculation of design traffic TF (F100) Technical specification with the title of Aszfaltburkolatú útpályaszerkezetek méretezése és megerősítése e-ut [ÚT :2005]. Traffic data to determine the design traffic : Buses and coaches (single and articulated), Heavy trucks (over 7,5 tons), Truck trailers, Semitrailers and Special vehicles. Cars and smaller vans are irrelevant because their damage factor is too low. During the design their numbers will neglect.

5 TF F100 = z 1, t r s f n ÁNF a e a + ÁNF n e n + ÁNF p e p + ÁNF ny e ny TF(F100) design traffic [passing axles, pcs] (equivalent standard axle) z coefficient for extra fatigue effect of single 115 kn, double 180 kn and 190 kn axle, value 1,5 1,25 safety factor, t design period [years], r direction factor, s lane factor, f N growth factor, for t/2 years from the opening date, ÁNF i average flow of traffic of ith vehicle class [vehicle/day], vehicle conversion factor of ith vehicle class. e i Calculation of design traffic TF (F100)

6 Calculation of design traffic TF (F100) Design period (t, year): A time period from the opening of the road when the pavement will be deteriorated insomuch that a renewal is obligate. Highways, important urban main roads: t = 20 years Main roads and urban main roads: t = 15 years Rural roads, lower category roads: t = 10 years

7 Calculation of design traffic TF (F100) r direction factor design traffic can be calculated for one direction in a cross section. r = 1,0 roads with one lane and 5,0 m width pavement or less; r - 0,5 roads with two or more lanes or with one lane and the pavement is wider than 5,0 m, if the heavy traffic ratio between the directions is 50-50%, r = 0,5-1,0 - the heavy traffic ratio between the directions is different than 50-50%; value of direction factor is proportional to the heavy traffic, can be between 0,5 and 1,0.

8 Calculation of design traffic TF (F100) s lane factor, this value depends on the number of one direction running lanes; s = 1,0 one lane roads with two direction traffic, and two lanes roads with two direction traffic (one per direction); s = 1,0 two lanes in one direction; s = 0,9 minimum three lanes in one direction;

9 Calculation of design traffic TF (F100) f N growth factor according e-ut Technical Specification. Growth factor is always calculated for t/2 years after road opening (half of the design period). (etc. t = 15 years the 8th year is counted as the middle of design period)

10 Calculation of design traffic TF (F100) Growth of traffic flow Case of Traffic design: Growth factor for the last year, f(t) -> Case of Pavement design: Growth factor for the f(t/2) -> We need the number of equivalent Standard axle which will be running to the end of lifetime (design period).

11 Calculation of design traffic TF (F100) e i vehicle conversion factor of ith vehicle class, based on damage factor. Vehicle class Buses and coaches (single and articulated) Vehicle conversion factor e a 1,3 Heavy trucks (over 7,5 tons) e n 0,6 Truck trailers e p 1,6 Semi-trailers e ny 1,7 ÁNF i average flow of traffic of ith vehicle class [vehicle/day],

12 Calculation of design traffic TF (F100)

13 Calculation of design traffic TF (F100) Detailed vehicle classes:

14 Calculation of design traffic TF (F100) f N Calculation of growth factor according e-ut Közutak távlati forgalmának meghatározása előrevetítő módszerrel : f = a x 3 + b x 2 + c x + d f calculated growth factor to (x+2000)th years correlate to year 2000, a,b,c variables which are contained in a table, depends on vehicle classes and counties, d constant, its value is 1,0.

15 Calculation of design traffic TF (F100) f N Calculation of growth factor according e-ut Közutak távlati forgalmának meghatározása előrevetítő módszerrel : Base year (year1): year with the last traffic data. Zero year (year0): the base year of variables: always Forecast year (year2): year to calculated traffic. f y1/y0 = a y 1 y b y 1 y c y 1 y 0 f y2/y0 = a y 2 y b y 2 y c y 2 y 0 + d + d f y2/y1 = f y2/y0 f y1/y0

16 Calculation of design traffic TF (F100)

17 Calculation of design traffic TF (F100) Source: Soós Zoltán: A forgalomfejlődés becslésének módszertana a valós forgalom és a nemzetközigyakorlat tükrében. Manuscript, 2015

18 Calculation of design traffic TF (F100) Source: Soós Zoltán: A forgalomfejlődés becslésének módszertana a valós forgalom és a nemzetközigyakorlat tükrében. Manuscript, 2015

19 Calculation of design traffic TF (F100) Source: Soós Zoltán: A forgalomfejlődés becslésének módszertana a valós forgalom és a nemzetközigyakorlat tükrében. Manuscript, 2015

20 Design traffic categories Sign Design traffic category Design traffic TF (F100, million pcs) A Very light 0,03 0,1 B Light 0,1 0,3 C Average 0,3 1,0 D Heavy 1,0 3,0 E Very heavy 3,0 10,0 K Especially heavy 10,0 30,0 R Extremely heavy > 30,0

21 Exposure categories of hot asphalt mixtures Exposure category: Different types of asphalt (normal (N) or increased, improved (F)) Increased, improved = more resistant against the traffic and weather effects

22 Exposure categories of hot asphalt mixtures Exposure category: Heavy traffic Design traffic TF (F100) Design traffic categories (A-B-C-D-E-K-R) Character of traffic flow Free traffic flow Flow in channel Climbing lane Roundabout Transfer lane Bus lane Urban section of main roads Exposure category Layer Type of asphalt Layer thickness Normal or Increased, improved Surface, Binder of Base course AC, SMA, PA, etc. from the standard in centimetre

23 Exposure categories of hot asphalt mixtures Exposure category:

24 Bearing capacity evaluation methods of soils Bearing capacity: The capacity of soil to support the loads applied to the ground The maximum average contact pressure which should not produce shear failure in the soil E 2 modulus (MPa) CBR% (California Bearing Ratio) Different types of methods by loading: Static (E 2 ) Dynamic(E din )

25 Bearing capacity evaluation methods of soils Plate Load Test: Loading stages (counterweight is needed, ~6-8 tons) Waiting for consolidation (~30 minutes) Bearing capacity based on elastic and permanent strains Evaluate at one point on surface D = 30 cm

26 Bearing capacity evaluation methods of soils Light Falling Weight Deflectometer: No counterweight is needed Background: Boussinesq equation E vd = 22,5 D = 30 cm s 0 N mm 2

27 Bearing capacity evaluation methods of soils B&C Deflectometer: No counterweight is needed Background: Boussinesq equation E d D = 16,3 cm

28 Bearing capacity evaluation methods of soils Bearing capacity evaluation methods: Plate load test E 2 Light Falling Weight Deflectometer (KTI formula) E 2 = (E vd -9,1) / 0,52 Light Falling Weight Deflectometer (Eisenbahn unterbau formula) E 2 = (E vd -5,5) / 0,42 B&C Deflectometer (Tompai) E 2 = 0,89 x E d

29 Bearing capacity evaluation methods of soils CBR %: Static bearing capacity of soil can be calculated with the CBR % value based on the empirical equation: E 2,soil = 10 CBR 2/3 [MN/m 2 ]

30 CBR %: Bearing capacity evaluation methods of soils

31 Bearing capacity evaluation methods of layers Different types of methods: Static (Benkelman beam) Semi-static (Lacroix) Dynamic (KUAB, Dynatest, Carl Bro, JILS)

32 Bearing capacity evaluation methods of layers Benkelman beam: Simple device, operates on the lever arm principle Load truck typically 80 kn on a single axle with dual tires Measurement is made by placing the tip of the beam between the dual tires and measuring the pavement surface rebound as the truck is moved away. Low cost but slow method Not provide a deflection basin

33 Bearing capacity evaluation methods of layers Benkelman beam:

34 Bearing capacity evaluation methods of layers Benkelman beam:

35 Bearing capacity evaluation methods of layers Lacroix Deflectograph: The vertical deformation of a surface under the action of a heavy weight moving at constant speed. Correlation with the static deflection measurements (by means of sensors embedded in the road surface) is of very good quality, even for very slight road surface deformation. Measurement speed: 3 km/h +/- 0,5 km/h Distance between measurement increments: 3 to 6 m depending on the vehicle used and the testing speed

36 Bearing capacity evaluation methods of layers Lacroix Deflectograph:

37 Bearing capacity evaluation methods of layers Falling Weight Deflectometer (FWD): Dynamical test Load impact on the pavement surface with a plate Determine the physical properties of pavement The machine is usually contained within a trailer

38 Bearing capacity evaluation methods of layers Falling Weight Deflectometer (FWD): Input data to the maintenance or reconstruction Result: Deflection basin

39 Bearing capacity evaluation methods of layers Falling Weight Deflectometer (FWD): Scheme of FWD:

40 Bearing capacity evaluation methods of layers Falling Weight Deflectometer (FWD): In a single-mass system, a weight is dropped onto a single buffer connected to a load plate, which rests on the surface being tested. In the double-mass system, the weight drops onto a doublebuffer system, which includes a first buffer, a second weight, and a second buffer. The double-mass system essentially produces a longer loading duration that more precisely represents a wheel load. The double-mass system has higher reproducibility and gives a more accurate result on pavements built on soft soils. The single-mass system will seriously overestimate the capacity of pavements built on soft soils. However, single-mass FWDs are smaller, cheaper and faster. Single-mass system: Dynatest,JILS, Carl Bro Double-mass system: KUAB

41 Data analysis of FWD CALCULATION OF SURFACE MODULUS E 2 a= 0,15 radius of loading plate [m]; µ=0,40 Poisson coefficient [-]; 2 1 a [MPa] 0(z 0), d0 σ d r E 0(z=0) stress [MPa]; corrected deflection in the distance r from the middle of the plate [m]; Surface modulus on the surface of the pavement [MPa]

42 Data analysis of FWD CALCULATION OF SURFACE MODULUS E a 0(z r), dr r 2 1 [MPa] a= 0,15 radius of loading plate [m]; µ=0,40 Poisson coefficient [-]; 2 σ d r r stress [MPa]; corrected deflection in the distance r from the middle of the plate [m]; distance of the deflection sensor (geophone) from the middle of the plate [m]; E 0(z=r) Surface modulus in the depth r surface [MPa]

43 Data analysis of FWD CALCULATION OF SURFACE CURVATURE INDEX (AFTER TEMPERATURE AND LOADING CORRECTION) C SCI Ce ( d0 d300 ) BDI C ( ) e d300 d600 BCI C ( d d ) 900 C e d i SCI BDI BCI ,80665 e, F[kgf] e 600 [-]; Loading force correction; Corrected deflection [m]; Surface curvature index [µm]; Base damage index [µm]; Base curvature index [µm];

44 Data analysis of FWD Base layer Base layer with granulated soil Hydraulically bounded base layer Asphalt base layer Condition level E 0(0) [MPa] SCI [µm] BDI [µm] BCI [µm] Good > 350 < 200 < 100 < 50 Warning Bad < 250 >400 >200 >100 Good > 900 < 100 < 50 < 40 Warning Bad < 450 >300 >100 >80 Good > 450 < 150 < 100 < 50 Warning Bad > 300 >300 >150 >80

45 Bearing capacity evaluation methods of layers

46 Thank you for your attention! Any question?