Design of overlay for flexible pavement civil iitb. Benkelman beam deflection bbd test benkelman beam is less expansive deflection measuring equipment and method of study is simple and easy to carry out. Sample is brought to lab and plasticity index, liquid limit, specific gravity etc. Pavement deflection is measured by the benkelman beam which consists of a slender beam 3. Test method tnz t1 1977 benkelman beam test dear cetanz member, please find attached the results from the benkelman proficiency testing organised by cetanz in may 2008. Tests pits are dug at approximately to m intervals depending on benkelman beam deflection method uniformly in performance of pavement structure in order to determine the pavement details such as, thickness and composition of the pavement layers and the type of sub grade below. Standard guide for general pavement deflection measurements.
Methodology and working of the benkelman beam is as follows. Overlay design by benkelman beam road surface standard. Remaining fatigue and rutting life after and before overlay were. Sudhakar reddy, department of civil engineering, iit kharagpur. Two calibrated modified benkelman beams figure 1 with a data acquisition system and accessories.
Measuring the bearing capacity of forest roads with an. Benkelman beam bb devices should be corrected by a factor of ground water table seasonal factors and temperature correction and a correction factor of the load test if not exact test load of 8. The amount of rebound deflection can be determined by the formula 3 below. By considering the existing pavement as a homogeneous half space, and using the characteristic deflection the modulus value of layer 2 is found out from e2 1.
It was decided that 8 sets of observations of the benkelman beam. With the benkelman beam measurement method, the vertical deflection of the road surface is measured after a defined load of 5 tons has rolled away. For the love of physics walter lewin may 16, 2011 duration. Even though there are many methods for designing of overlays such as, lacroix deflectgraph, dynaflect, falling weight deflectometre fwd and benkelman beam deflection technique among all these bbd technique is the easy and convenient method as mentioned earlier as well. Dimensions a and b must be recorded on form bb1 for each beam together with the benkelman beam no. Evolution of the deflection according to truck overloading. Results of deflection measurement by benkelman beam method and determination of the characteristic deflection the results of the deflection measurements from the fatickkaolack road with modulation of the axle load of 10, and 16 tons are given in table 1. Comparative studies between benkelman beam deflections. Benkelman beam evaluation of structural capacity of existing pavement estimation and design of over lay for strengthening of weak. Benkelman beam test has also been conducted following irc 81 1997on the entire road network to design the overlay. A method for determining allowable spring deflection with the benkelman beam was developed from a literature survey and from a closely related field study. Development correlation between benkelman beam deflection and falling. The following accessories are added to the usual benkelman beam.
The magnitude of rebound deflection of a flexible pavements when a standard wheel load of truck is moved forward is measured. T256standard method of test for pavement deflection measurements. Benkelman beam evaluation of structural capacity of existing pavement estimation and design of over lay for strengthening of weak pavement 5. The method also describes the procedure for the calibration of the deflection data acquisition system ddas and bwl4 manual, queensland. Strength evaluation of flexible pavement of runway using. The entire apparatus, must be sturdy, rigid and without slop. Guidance notes on road testing highways department. The benkelman beam figure 2, developed at the western association of state highway organizations washo road test in 1952, is a simple device that operates on the lever arm principle. The results of the deflection measurements from the fatickkaolack road with modulation of the axle load of 10, and 16 tons are given in table 1 the results showed that the values read on the beam in the case of the load of 10 tons to the axle vary. It should be used to find out the overlay thickness of the. Deflectometer rdd, benkelman beam deflectometer bbd. Comparison study of overlay design for engineering.
Deflection should be find out by benkelman beam deflection test. General a the surface under the beam shall be sound and. Deflection testing of earthwork and pavement layers roads and. The method is suitable for bituminous surface course and concrete pavement surface with texture depth greater than 0. Field density of the subgrade soil using sand replacement method is 2720. Comparison of falling weight deflectometer with other. Collection and interpretation of pavement structural.
Experimental setup of benkelman beam deflection equipment the arrangement was made for benkelman beam deflection test on runway for evaluation of structural capacity of existing flexible pavement. Beams that do not conform must not be used on roads and maritime services projects. Applications the road surface texture can be measured by sand patch method. Possible method of determining structural number for. Portable deflection beams come in a variety of designs and styles, some of which do not conform to roads and maritime services requirements. Rebound deflection using benkelman beam irc 81, 1997. Traffic studies including axle load surveys using portable weigh bridge trl.
Pavement evaluation by benkelman beam of state highway. This method of measurement enables the direct determination of the actual deflection bowl under a slowly moving load, but requires a benkelman beam with the. Related items highlow detector rolling straight edge measures planeness of pavement surfaces, such as highways, airport runways, bridge decks. Operating on a simple lever arm principal, the device consists of a reference beam body, twopart probe beam, and rear zero adjustment assembly.
The h3220a benkelman beam apparatus is a convenient and accurate device. Referenced documents purchase separately the documents listed below are referenced within the subject standard but are not provided as part of the standard aashto standard. The h3220a benkelman beam apparatus is a convenient and accurate device used for measuring the deflection of flexible pavements under moving wheel loads. Benkelman beam adalah revisi dari sni 0324161991,metode pengujian lendutan perkerasan lentur alat benkelman beam. It should be used to find out the overlay thickness of the flexible over flexible pavement as per irc81 1997. Benkelman beams shall be calibrated in accordance with appendix a of this method.
To verify the correct performance of the apparatus. Pdf mechanistic design of overlay based on benkelman beam. The requirements of a typical benkelman beam as shown in figure 4 are listed in test methods t160 and t199. The a e dimension can be determined from the following a e 4 recommends that the deflection. Benkelman devised the simple deflection beam in 1953 for measurement of pavement surface deflection. It is widely used all over the world evaluation of the requirements of strengthening of flexible pavements.
It was decided that 8 sets of observations of the benkelman beam deflection test may be taken. The benkelman beam is used with a loaded truck typically 80 kn 18,000 lb on a single axle with dual tires inflated to 480 to 550 kpa 70 to 80 psi. Deflection beam has been in use in india for more than two decades by different organizations. Benkelman beamauxiliary instrument of the maintenance engineer. Results of deflection measurement by benkelman beam method and determination of the characteristic deflection. Deflections by fwd with guidelines of irc115 and by benkelman beam with guidelines of irc81 were measured on selected sections. Working the readings are taken at every 50m interval. Pddx pavement deflection data exchangetechnical data guide, version 1. The vertical deflection is recorded by a special measuring beam, which is mounted on a.
The beam test shall be as per nzta specification t1 except that the recordings for bowl deflection shall not be recorded or used in. Pavement composition from trial pits and core cutter method. Part ii of this report presents the recommended testing procedures, equipment, and personnel requirements for conducting the benkelman beam test. Using fwd data with me design and analysis, volume iii. Accurate sand patch testing cannot be carried out when road. Adjustable feet for benkelman beam, complete with two spirit level calibration device 80b01803 calibration device for 80b0180 benkelman beam apparatus. By suitably placing the probe between the dual wheels of a loaded truck, it is possible to measure the rebound and residual deflections of the pavement structure. The correlation between the heavy vibrator and members of the benkelman beam family is poor. Standard test procedure for benkelman beam deflection.
Pdf on jan 1, 2018, fatou samb and others published evolution of the deflection according to truck overloadingcomparison between benkelman beam method and fem of lateritic pavements find. Measures the deflection of a flexible pavement under moving wheel loads. Data acquisition system qtdas capable of logging test data at every 50mm travel of the test. Pdf evolution of the deflection according to truck. Pdf conventionally in india overlay of flexible pavement design is carried. Benkelman beam deflection bbd part 1 tre highway engg. The original deflection measuring method, using the benkelman beam adopted on washo road test fig. Both the fwd and instrumented benkelman beam are used in new zealand to measure the deflection bowl. Rebound deflections are measured with the help of a benkelman beam. The fact that most test methods result in about the same measure of bearing capacity. E benkelman beam a benkelman beam is shown in figure 2. Lwd deflectometer devices are dynamic nondestructive testing tools commonly used in the field of pavement systems to meas. Aashto t 25601, standard method of test for pavement deflection measurement 3 istilah dan definisi istilah dan definisi yang digunakan dalam standar ini sebagai berikut.
This test method sets out the procedure for measuring the rebound deflection of a flexible pavement or road formation using a portable deflection beam under both a standard wheel load and tyre pressure. Nine laboratories took part in the benkelman beam proficiency test. The beam pivot bearing and the dial gauge must move freely without friction or slop. Ai deflection method the overlaid pavement is considered as a two layer system with ac overlay as layer 1 and the existing pavement as layer 2. Texture depth using sand patch method bs 598 part 105, 1990. The design results obtained from both the methods are compared. History of benkelman beam deflection technique2 development of methods such as benkelman beam deflection method for evaluation of structural capacity of existing flexible pavements and also for estimation and design of overlays for strengthening of any. Flexible road pavement using benkelman beam deflection bbd technique. Benkelman beam apparatus, asphaltbituminous mixture. Introduction the structural number sn is an index providing an indication of the strength of the pavement layers and of the total pavement structure. To lay down a uniform procedure for the design of flexible overlays using the benkelman beam deflection technique tentative guidelines of flexible road pavements using benkelman beam deflection technique irc. Cara uji lendutan perkerasan lentur dengan alat benkelman. Lecture series on introduction to transportation engineering by prof.
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