Structural Design of Pavements PART VI Structural ... - TU Delft

More documents

Recommendations

Info

17 One should realise that the influence of temperature always has to be taken into account and that the deflections measured always should be corrected to a reference temperature. The temperature correction procedure will be presented in an other chapter.
18 5. Statistical treatment of raw deflection data and selection of a location representative for the (sub)section: Statistical treatment of the data as measured is always needed in order to be able to recognise trends and in order to limit the amount of work that should be done in the evaluation process. It is e.g. not necessary and even not useful to back calculate the layer moduli for each measurement location simply because of the fact that it is impossible to obtain accurate layer thickness information for each and every location. It is therefore much more effective to concentrate the analysis on locations which can be taken as representative for a particular section or sub-section. Simple statistical procedures have shown to be very effective to discriminate homogeneous sub-sections within a larger section. A homogeneous sub-section is defined as a section where the deflections and so the flexural stiffness are more or less constant. When such homogeneous sub-sections have been determined, one has to take a point which can be taken as being representative for that sub-section. That point can be the location where the measured deflection bowl comes closest to e.g. the average deflection profile or the 85% deflection profile. The 85% profile is the profile that is exceeded by 15% of all the measured profiles. The so-called homogeneous sub-sections can be determined by means of the method of the cumulative sums. The cumulative sums are calculated in the following way. First of all the mean of a variable over the entire section is calculated (e.g. the mean of the maximum deflection). Then the difference between the actual value of the variable and the mean is calculated. Next these differences are summed. In formula the cumulative sums are calculated using: S 1 = x 1 - µ S 2 = x 2 - µ + S 1 S n = x n - µ + S n-1 Where: S n = cumulative sum at location n, x n = value of the variable considered at location n, µ = mean of variable x over entire section. The method is illustrated by means of an example. Table 2 shows the deflections that were measured by means of a FWD on a particular road in the Netherlands. The load applied was 50 kN, the diameter of the loading plate was 300 mm. The table gives values for d 0 , d 300 , etc.; these are the deflections measured at a distance of 0 and 300 mm etc.. An important value is the surface curvature index SCI, which is the difference between the maximum deflection d0 and the deflection, measured at 600 mm from the loading centre (d 600 ). Also the logarithm of the SCI values is reported. Also this is an important characteristic as will be shown later on. As one will observe from the table, high deflections are measured and the amount of variation in the measured deflections is very high. It should be noted that the pavement considered was a polder road on a very weak subgrade and showed a significant amount of damage. It should be noted that the example presented is a rather extreme one; normally such large variations in deflections are not observed. Figure 10 is a graphical representation of the measured deflections, while figure 11 shows the variation of the SCI over the section. Figure 12 shows in a graphical form the variation of the cumsum (cumulative sum) as determined for the SCI. The SCI is selected as parameter decisive in the determination of the homogeneous subsections since the SCI can be considered to be the most important deflection parameter. Homogeneous sub-sections can easily be recognised from figure 12 since by definition an area over which the slope of the cumulative sums plot is more or less constant indicates an area where the differences between the actual measured values and the overall mean value are approximately the same.
Page 1 and 2: CT 4860 Structural Design of Paveme
Page 3 and 4: 2 Table of contents: Preface 3 1. I
Page 5 and 6: 4 1. Introduction: These lecture no
Page 7 and 8: 6 2. Usage and condition dependent
Page 9 and 10: 8 When a swimmer makes a nice dive
Page 11 and 12: 10 Figure 5: Principle of the autom
Page 13 and 14: 12 From the text given above it is
Page 15 and 16: 14 As shown in figure 7, 3 zones ca
Page 17: 16 Figure 9: Placement of loading p
Page 21 and 22: 20 Figure 10: Results of a deflecti
Page 23 and 24: 22 Figure 12: Cumulative sum of the
Page 25 and 26: 24 Section Locations Mean SCI SD SC
Page 27 and 28: 26 6. Back calculation of layer mod
Page 29 and 30: 28 The drawn line indicates a pavem
Page 31 and 32: 30 The clayey subgrade was covered
Page 33 and 34: 32 Section I Temp Force Layer E-mod
Page 35 and 36: 34 [N] [mm] [mm] [MPa] [N] [mm] [mm
Page 37 and 38: 36 Based on these calculations, eva
Page 39 and 40: 38 8. Estimation of the remaining p
Page 41 and 42: 40 Figure 25: Load configuration us
Page 43 and 44: 42 If we assume e.g. that the defle
Page 45 and 46: 44 Figure 27: Relationship between
Page 47 and 48: 46 resistance, some parts of the pa
Page 49 and 50: 48 Log ε = 0.481 + 0.881 log SCI 3
Page 51 and 52: 50 b 3 = 1.0153 b 4 = -7.73 x 10 -6
Page 53 and 54: 52 10. Extension of the simplified
Page 55 and 56: 54 Compressive vertical strain at t
Page 57 and 58: 56 This relationship opens possibil
Page 59 and 60: 58 The remaining pavement life can
Page 61 and 62: 60 estimation of the bitumen and mi
Page 63 and 64: 62 the composition and the degree o
Page 65 and 66: 64 The life of the overlay N can si
Page 67 and 68: 66 Table 7b: Relationship between K
Page 69 and 70:
68 Figure 41: Relationship between
Page 71 and 72:
70 From the nature of the equation
Page 73 and 74:
72 σ σ t Γ ε Figure 43: Strengt
Page 75 and 76:
74 14. Effects of pavement roughnes
Page 77:
76 16. Bekker, P.C.F. Pavement perf
show all

Structural Design of Pavements PART VI Structural ... - TU Delft

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?