Design of flexible pavement JKR method Prepared by

Design of flexible pavement (JKR method) Prepared by : Syakirah Afiza Mohammed

Cross section of flexible pavement (JKR standard)

Definition and Function of Each Layer Subgrade � The uppermost part of the soil, natural or imported, supporting the load transmitted from the overlying layers. Subbase Course � The layer(s) of the specified material built up to the required designed thickness immediately overlaying the subgrade. It serves as an aid to disperse the load from the base course before transmitting it to the subgrade. (This layer may be absent in some designs. Base Course � The layer(s) of specified material built up to the required designed thickness normally overlying the subbase course. This layer plays a prominent role in the support and dispersion of the traffic loads.

Definition…cont’d Surface Course �All the bound layer(s) within the pavement i. e. wearing course, intermediate course and binder course are. embodied under this general terminology. This layer(s) forms an impermeable and flexible lining of high elastic modulus. Binder Course �The bound layer(s) overlying the base course. Apart from supporting and dispersingthe traffic load, it also resists shear. Wearing Course �The topmost layer of the surface course. It is in direct contact with the traffic and consequently, it must resist abrasion and prevent skidding.

Design Period � A design period of ten years shall be used. � The design period refers to the span of time between the initial passing of user traffic until the fatigue limit of the pavement whereby a strengthening overlay is required. � Currently, a design period of twenty years is stipulated in the Road Note 29. � A design period of only ten years is to be specified, however, as an initial study has indicated that it would be economical in terms of initial. capital outlay and also with respect to the total cost. � The calculation for the traffic estimation for the ten year design period shall be based from the expected year of completion of construction, onwards.

Traffic Estimation �The initial annual commercial traffic for one direction, Vo is obtained by : Vo = ADT x 0. 5 x 365 Pc/100 �where ADT = Average Daily Traffic PC= Percentage of commercial vehicles

Traffic Estimation…. cont’d � The total number of commercial vehicles for one direction (Vc ) is obtained by Vc = Vo[(1+r)^x-1] r � Where Vc = total number of commercial vehicles for x years Vo = initial yearly commercial traffic r = rate of annual traffic growth

Traffic Estimation…. cont’d � The total equivalent Standard Axles (ESA) applications is given by : ESA = Vc x e � The maximum hourly traffic volume, as per 3. 3. 6 is calculated as follows: c=Ix. Rx. T Where c is the maximum one way hourly capacity I is the ideal hourly capacity as in Table 3. 2 R is the roadway factor as in Table 3. 3 T is the traffic reduction factor (Table 3. 4)

Traffic Estimation…. cont’d �Assuming that maximum hourly capacity, c as per 3. 3. 12 reflects 10% of the 24 hrs. capacity, then the one way daily capacity is as follows: C = 10 x c �where C is the 24 hrs. one way traffic capacity c is the maximum one way hourly capacity

Design �The thickness of the various layers shall be obtained using TA = a 1 D 1 + a 2 D 2 +. . . + an. Dn �where al, a 2. . . an are the structural coefficients of each layer as shown in Table 3. 5 �D 1 D 2. . . Dn are thickness of each layer as shown in Table 3. 6