CONSTRUCTION OF ROADS
Learning outcomes of the course unit
he course aims to give the basis for the geometric design of road structures and the choice of materials an realization of road construction.
Course contents summary
1) ROADS AND VEHICLE.
Resistances to motion.
Locomotion mechanic and general equation for traction.
Friction: coefficient of friction fa. Lamm-Herring relationship.
Stopping sight distance.
Overtaking sight distance.
Road vehicles performances.
Perception of road environment.
2) ROAD DESIGN IN HORIZONTAL PLAN.
Vehicle stability on curve.
Visibility in curve.
Superelevation in curve: maximum transversal friction criterion, maximum transversal gradient criterion, proportionality criterion.
Definition of Nomogramma of CNR (curvilinear method).
Calculation of horizontal radius by mean of optical criteria: horizontal sight distance along the inside of a curve.
Stopping sight distance and passing sight distance.
Spiral (transition curve): intrinsic equation, Cartesian coordinates equation: Fresnel integrals, series expansions.
Analytical calculation of shifting R.
Geometric formula of parameter A, unitary spiral, minimum value of parameter A: dynamic criterion, constructive criterion, optic criterion.
Spiral insertion in road axis: straight-curve (preserved radius, preserved centre, preserved vertex). Flex spiral, continuity spiral: rigorous calculation and approximated relationships (Osterloch abacum).
Composition of horizontal axis.
Asymmetrical spirals (CNR).
3) vertical alignment of road.
Maximum grade of vertical alignment.
Vertical circular and parabolic curves.
Horizontal and vertical coordination.
4) ROAD CROSS SECTION.
Road cross section according to CNR.
Characteristics of road cross section.
Particular road cross section.
Road cross section in curve.
Variation of road cross section in curve.
Definition of relative minimum slope “i”.
6) Road structure construction.
Definition of soils as material for embankments.
7) Elements of road geotechnics.
Fundamental parameters of soils: grading analysis, compressibility, shear strength.Water susceptivity, Atterberg limits: LL, LP, LR, IP.
Soils classification: Index group, HRB, FAA. Soils compaction. Soils compaction in (s,W) chart. Proctor and AASHTO test. Control of in situ density.
Embankments construction and plant equipments. Subgrade load bearing capacity. Load bearing capacity test: plate, repeated cycles, McLeod relationship, CBR test, CBR Index. Definition of CBR in situ. Compressibility modulus M.
Subgrade water protection. Ice action in road embankments.
8) Stone aggregates.
Classification of stone aggregates. Required characteristics. Shape characteristics. Test on aggregates: grading analysis, Deval, microdeval, Los Angeles, dynamic crushing , CPA, sand equivalent, ice susceptivity. Aggregate characteristic referred to its employment: subbase, base, binder, wearing course. Sand and filler characteristics.
Binders: bitumen, coal tar, asphalt. Organic binders with polymers, oxidized bitumen, cut-back asphalt, bituminous emulsions. Controls on bituminous binders: penetration, ring and ball temperature, Frass temperature, viscosity. Heukelom abaci. Thermal susceptivity. Stiffness modulus. Bitumen-aggregate adhesion.
10) MIXTURES FOR ROAD STRUCTURES.
Mechanical characteristics of mixtures. Granular mixes subbase. Soil stabilisation for subbase. Bounded and non-bounded for base layers. Bituminous mixtures. Design of optimum grading curve: Fuller curve and grading distribution. Percentage of filler. Determination of binder percentage: English method (voids method), French method (specific surface or Duriez).
Stability of bituminous mixture: Marshall test.
Determination of bitumen percentage by mean of Marshall method.
P. FERRARI, F. GIannINI: "Geometria e progetto di strade", Vol. I, ISEDI.
P. FERRARI, F. GIannINI: "Corpo stradale e pavimentazione ", Vol. II, ISEDI.
G. TESORIERE: "Strade ferrovie e aeroporti: il progetto e le opere d'arte", Vol. I, UTET.
G. TESORIERE: "Strade ferrovie e aeroporti : opere in terra e soprastrutture", Vol. II, UTET.
F. GIannINI, F. LA CAMERA, A. MARCHIONNA: "Appunti di costruzione di strade ferrovie ed aeroporti", ESA.
Oral examination about course subjects and exercise.
Road Design: type F1 DM 5/11/2001.