CHAPTER 6 SMALL ELEMENT PAVEMENTS - TU Delft

development of the characteristic rut depth RD c (30% probability of exceeding) under a1.2 m long straightedge. Similar to figure 6.14 also in figure 6.15 corresponding testpavements or test sections have been combined, because the thickness of theconcrete paving blocks also had no significant influence on the development of therutting on the test pavements.S = sand sub-base onlyCBS = mix granulate base and sand sub-baseCCS = concrete granulate base and sand sub-baseFigure 6.15: Development of the characteristic rut depth RD c (30% probability ofexceeding) on the test pavements Alphen and Rotterdam.A comparison of the rutting behaviour of the test pavements Alphen 1 and 2 clearlydemonstrates the very beneficial effect of the unbound base of 0.25 m concretegranulate in the case of a very weak peat subgrade, The base not only prevented thetest pavement Alphen 2 from instability (shear failure), but also limited the rutting to anacceptable level considering the heavy traffic loadings and very weak subgrade.The rutting behaviour of the test pavements Rotterdam 3 + 4 (base of 0.30 m concretegranulate) and Rotterdam 5 + 6 (base of 0.30 m mix granulate) is about equal. Therutting behaviour of the test pavements Rotterdam 1 + 2 (with a sand sub-base only) isclearly worse although shear failure did not occur.With the exception of the completely failed test pavement Alphen 1 the development ofthe rutting on the remaining stable test pavements is described by the equation:cpb pRD = a . N(6.1)where:RD c = characteristic rut depth (mm), 30% probability of exceeding, under a 1.2 mlong straightedgeN = cumulative number of equivalent 80 kN standard axle load repetitions perlane, taking into account the lateral wander of the traffic (reduction factor1.0 and 0.5 respectively for the test pavements Alphen 2 and Rotterdamrespectively).a p , b p = rutting coefficient with respect to the total pavement structure201