SMITH,
H.R. A deflection survey technique for pavement evaluation in developing countries. Department of the Environment, TRRL ReportLR
525, Crowthorne 1973 (Transport and Road Research Laboratory).BULMAN, J.N. Strengthening of flexible roads in the tropics: the use of deflection measurements. Department of the Environment,
TRRL
ReportLR
444, Crowthorne 1972(Transport and Road Research Laboratory).
SECRETARIAT D'ETAT AUX AFFAIRES £TRANGERES. Contribution to the study of the
strengthening of paved roads in tropical Africa and Madagascar (Contribution a l'etude du renforcement des chaussees revetues en Afrique tropicale et
a
Madagascar).CEBTP Avril 1971.
CEBTP Sept 71 Manual of road design for developing tropical countries (Mamiel de dimensionnement de chaussees pour les pays tropicaux en voie de developpement).
LIAUTAUD,G. Utilisation and effectiveness of deflection measurements on roads in
french speaking Africa and Madagascar (Utilisation et interet deB measures de d{flexion sur chaussees en Afrique francophone et
a
Madagascar). Revue generale des RoutesNo 484 Fe~ 1973.
DURRIEU, J, G. LIAUTAUD and ADAM. Non-destructive testing by deflectometer measurements on paved roads in Senegal, (Auscultation, par la m~thode deflectom{trique de chaussees revetues au Senegal. Revue generale des Routes No 485 Mars 1973.
LABORATCIRE DES TRAVAUX PUBLICS DU CAMEROUN. Waza-Maltam Road: The problem of its strengthening and deflection survey (Route Waza-Maltam; Probl~me de son renforcement et campagne de deflexion). Internal report Feb-March 1973.
LASSALLE, J, and G. LANGUMIER. Considerations of the strengthening design for flexible roads (consideration sur Ie culcul, du renforcement des chaussees souples). ·Revue generale des Routes No 392 1964.
LASSALLE, J, and G. LANGUMIER. Some examples of the application of the Colas
experimental method (Quelques examples d'application de la methode experimentale Colas).
Revue generale des Routes No 413 1966.
CHANTERAU, M, and P. LEXiER. The catalogue of typical road structures of the Department of Roads (Le catalogue de structures types de chauBsees de la Direction des Routes).
Bulletin de liaison du LCPC. No 61 Sept 1972.
LASSALLE.
J.
Strengthening with bituminous materials.(Renforcements en erobes bitumineux. Consid€rations et
Revue generale des Routes No 404 Nov 1968.
Consideration of new applications applications nonvelles).
LABORATOIRE DES TRAVAUX PUBLICS DU CAMEROUN.
Summary Report (ContrOle des travaux; Voieme Internal report June 1973.
Control of works; Roads department;
de Douala; Rapport de synth~se).
13. APPENDIX 1
Standard TllllL method of l18king daflection beam measuremante
1) Load a
5
ton lorry (or similar) fitted with twin rear wheels to give a load of 6350kg (14 OOOlb) on the rear axle (ie 3175kg or 7000lb On each pair of twin rear wheels).2) Inflate the rear tyPres to 585 kN/m2
(85lb/sq in).
3) Mark a point on the road at which the deflection is to be measured, and reverse the lorry until the rear wheels at 1.25m (4ft) behind the marked point.
4) Insert the deflection beam between the twin rear wheels until its point rests on the lllarked point of the road. If required, insert a second beam in a siailar way between the other pair of twin rear wheels.
5) I t is helpful in positioning the lorry and aligning the beSlls parallel to the lorry axis i f a pointer is fixed to the lorry 1.25_ (4ft) in front of each pair of twin rear wheels.
6) Check the beam pivot arms for free movement, adjust the footscrews if necessary, and zero the dial gauges whilst tapping the beams gently with a SJl8ll spanner.
7) Record the dial gauge reading. (Either zero or BOme BJl811 positive or negative reading).
8) Drive the lorry slowly forward and whilst gently tapping the beu note the maximum dial gauge readings and the final readings when the lorry wheels have IIOved 3m (10ft) or more clear of the tips of the beams.
9) For each beam calculate the deflection of the road surface by adding the difference between the first and maximum dial gauge readings to the difference between the lllaximum and final gauge readings.
..
14. APPENDIX 2
Procedure used by the Overseas Unit of TRRL for carrying out deflection surveys for over~ design.
1. Mark out the road at intervals of 100II (330ft) and make deflection ..eaaure..enta in the standard lBanner* in both wheel tracks of both lanes of a two-lane road. or in both slow lanes of a dual carriageway four-lane road.
2. Measure the transverse deformation (using a 2IB long straight edge) in the wheel tracks and note the IIIIIOunt of cracking at each of the II&rked chainages. and at any intermediate points where the surface distress is observed to be exceptional.
Measure the deflections at these intermediate points.
3. If any deflection recorded is greater than 1.... (40 x 10- 3 in) the extent of the area having a deflection of this IBagnitude is then investigated and . .rked out on the road (or on a plan) by taking a series of deflection .easure.ents across the area at 10m (33ft) chainage intervals. The highest deflection in such an area b
then taken as representing that area in subsequent ana!ysis(aaaum!jg that the . .jori~
of the road bas substantially lower deflections than 1l1li (40 x 10 in».
4. Calculate the .ean of the deflection ..eaaured at the first ten consecutive cbainages. including the intermediate 'weak' areas if any, using the highest
deflection measured at each chainage irrespective of the lane or wheel-path it was ..easured in. Repeat the calculation of the .ean of successive blocks of ten consec-utive deflections taken in the deflection at the next cbainage along the road and o..itting the last one in each case. Repeat this process until the whole road under survey bas been traversed.
5.
I f the highest and lowest deflection in any block of ten differs fro.. the aean of that block by ..ore than one third of the .ean value. additional deflectionmeasurements should be made at chainages which exhibited the highest and lowest deflections in that block of ten.
6. Plot the IBaX1mum deflection at each chainage against the chainage, noting on the same sheet the deformation and degree of cracking.
7. Determine the minimum overlay thickness needed for each section of road on the basis of the design life required and the mean deflection plus one standard deviation of each section of road. The length of the sections are chosen so as to conform to
the important variations in the ..ean deflection of the pavement, whilst .iniaising the number of changes in overlay thickness required to achieve this.
* See Appendix 1
Crown Copyright. Aay views expressed in this Paper are not necessarily those of the Department of the Environaent. Extracts from the text may be reproduced.
except for commercial purposes. provided the source is acknowledged.
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