Материал: Russian Journal of Building Construction and Architecture

A shift of the phase of oscillations is given by the expression identically to [20]:

The angle of the displacement between movements of the vibratory mill and direction of a constraining force is very important and the only parameter that we have available using which the energy balance for the compaction of the layer of an asphalt concrete mix can be identified, i.e. its power for maintaining the oscillations of the vibratory mill as the data on the angle of the displacement characterize the properties of the layer of an asphalt concrete mix as an energy absorber.

Determining the amplitude of oscillations and the angle of the displacement of the phases between the movements of the vibratory mill and the direction of a constraining force with the formula suggested by S. A. Varganov [3], we can identify the power for maintaining the oscillations:

where N is the power of maintaining the oscillations, Watt; Р2 is a constraining force, N; А is the amplitude of the oscillations of the vibratory mill, m; is the angular frequency of the rotation of misbalances, s-1; is the angle of the displacement of the phases between the movement of the vibratory mill and the direction of a constraining force.

Using the expressions for the amplitude of oscillations, angle of the displacement between the phases of the movement of the vibratory mill and the direction of a constraining force as well as the characteristics of the physical and mechanical properties of a compacted layer, the power for maintaining the oscillations of the vibrator was identified.

The first half of the compaction of a vacuum asphalt concrete mix does not require much power to maintain the oscillations but as the compaction coefficient reaches 0.96, this power gradually increases from one run to another till it goes up to 0.75…0.8 kWatt. According to the calculation, the amplitude of oscillations of the vacuum-type vibratory roller during compaction ranged from 0.17…0.4 mm. The acceleration of the vacuum-type vibratory roller is 1.01…2.27 g depending on the frequency of the oscillations and a constraining force.

There were also calculations of the power of a regular vibratory roller as well. Fig. 2 shows relative capacities for maintaining the oscillations of the vacuum-type vibratory mill compared to a regular vibratory roller for the same parameters and modes of operation.

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Russian journal of building construction and architecture

N Vibration

N Vibration + Vacuum

Fig. 2. Relative power for maintaining oscillations of the vacuum-type vibratory roller depending on the density of an asphalt concrete mix in the process

As Figure suggests, at the initial stage of compaction the power of the vibratory roller is 2.5…3 times higher than that of the vacuum-type vibratory roller. At the final stage of compaction this ratio goes up to 10…12. Thus in the technological process of the compaction of vacuum layers of an asphalt concrete mix using vibratory rollers a considerable amount of energy can be saved for operating the vibrator particularly in the final stage of compaction.

Conclusions

Based on the methods of formalizing dynamic models, a generalized dynamic model of the compaction of road asphalt concrete mixes and foundations was developed considering the major parameters of a compacting machinery as well as rheological parameters of a compacted material to allow a a qualitative as well as a quantitative evaluation of the dynamics of a system. The parameters of a compacted material in the model are presented by means of the physical and mechanical parameters that reflects the deformation modulus per a unit of the thickness of a compacted layer. Depending on the types of compacting machinery, the guidelines for the use of particular elements in a dynamic model are provided.

Mathematical modelling of compaction of road asphalt concrete mixes using vibratory rollers indicated that the first half of the compaction of an asphalt concrete mix does not require much power for maintaining the oscillations of vibratory mills while as the compaction coefficient reaches 0.96, the power gradually goes up from one run to another. At the initial stage of compaction, the power of a vibratory roller is 2.5…3 times higher than of a vacuum-type vibratory roller. At the final stage of compaction this ratio goes up to 10…12. Therefore a considerable amount of power is saved on operating a vibrator during compaction of vacuum layer of an asphalt concrete mixes using vibratory rollers, particularly at the final stage of compaction.

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References

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UDC 624.131.54 : 625.855.3

S. V. Nosov1

DETERMINATION OF RATIONAL CONTACT PRESSURE UNDER A ROLLER WHEN COMPACTING ASPHALT CONCRETE MIXES

Lipetsk State technical University

Russia, Lipetsk, tel.: (4742)55-59-84, e-mаil: nosovsergej@mail.ru

1D. Sc. in Engineering, Prof. of the Dept. of Building Materials and Road Technologies

Statement of the problem. Determining the applicability of rollers of different weight, type and mode of operation when compacting various asphalt mixes should be carried out on the basis of the rheological approach. This allows one you to take into account the exposure time of the seal on the compacted layer of the mixture, as well as the rate of change in operating contact stress under the roller rink. It should be understood that the modulus of deformation and tensile strength of asphalt mixture layer are also a function of these factors expressed implicitly. If there is insufficient contact pressure under the roller rink, sealing effect is reduced. At excessively large contact pressures the structure is destroyed forming mixture during compacting. In this regard, there is a task to develop a method of definition of rational contact pressures under seals rollers when compacting asphalt mixes based on the development of their rheology.

Results. On the basis of experimental and theoretical studies using simulation compaction of asphalt mixes process on a computer obtained regularities that determine the nature of the changes required under the existing roller contact pressure rollers. Thus in addition to the known technologies seal asphalt mixtures are the recommendations of the contact pressure to ensure a roller rink in the application of new advanced compression technology of asphalt mixes with evacuation.

Conclusions. The investigation results allow one to deduce process variables selected by rollers on the optimum operating modes to ensure maximum effect sealing asphalt concrete mixtures and high-quality asphalt.

Keywords: road rollers, contact pressures, rheological approach.

Introduction

Choice and use of a particular roller should be due to the strength characteristics of a compacted layer. Contact pressures occurring under the operating bodies of compactors should not exceed the strength limit of a compacted material [3, 19].

© Nosov S. V., 2017

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