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H. Brandl, F. Kopf, D. Adam:
"Continuous Compaction Control (CCC) with differently excited dynamic rollers, ISSN 0379-1491";
Report for Bundesministerium für Verkehr, Innovation und Technologie; 2005; 150 pages.

Continuous Compaction Control (CCC) with differently excited dynamic rollers
In this research project "Continuous Compaction Control" (CCC) is considered in connection
with rollers equipped with different kinds of exciters. The main aim is directed to the oscillatory
roller, the Vario-roller, and the automatically controlled Vario-Control-roller.
The drum of an oscillatory roller oscillates torsionally. The torsional motion is caused by two
opposite, rotating excenter masses, which shafts are arranged excentrically to the axle of the drum.
Thus, the soil is loaded horizontally in addition to the vertical static dead load of the drum and the
contributing roller frame. These horizontal forces result in additional soil shear deformation.
In a Vario-roller two counter-rotating exciter masses, which are concentrically shafted on the
axle of the drum, cause a directed vibration. The direction of excitation can be adjusted by turning
the complete vibrator unit.
A further development of the Vario-roller is the Vario-Control-roller. In this roller type the
direction of excitation is controlled automatically by using defined control criteria, which allow an
optimised compaction process and, furthermore, a highly uniform compaction.
CCC is a roller integrated method in order to optimise compaction and to check continuously
the compaction success during compaction with a dynamic roller. The motion behaviour of the
dynamically excited roller drum indicates soil stiffness properties. Consequently, dynamic compaction
values are calculated from measured drum accelerations. Thus, compaction success
and synchronous increase of soil stiffness can be assessed already during the compaction
process. Furthermore, all data are automatically memorised in a documentation unit.
Two recording systems are available for vibratory rollers and Vario-rollers with vertical or
any inclined excitation direction (except horizontal direction):
Compactometer - dynamic compaction value: CMV
Terrameter - dynamic compaction value: OMEGA
Another recording system has been developed for oscillatory rollers:
Oscillometer - dynamic compaction value: OMV
In the scope of this research project the horizontal motion behaviour of oscillatory rollers
and Vario-rollers with horizontally adjusted exciter units was investigated by simulating the roller
interaction using computer calculations. Therefore, the elastic part of soil could be described by
a physical cone model representing the homogeneous elastic half space, which resulted in a
spring-dashpot system (Kelvin-Voigt element).
Large-scale in-situ tests were carried out to investigate the effect of an oscillatory roller and
a prototype of a Vario-Control-roller both on cohesive and non-cohesive granular material. Each
roller was equipped with adequate CCC-systems and additional transducers. In selected sections
of two test fields static and dynamic deformations, pressures, and accelerations in one or
two directions were measured in different depths. Synchronous measurement of roller and soil
data enabled the investigation of the interaction between roller and soil.
In a special test weak spots were placed and covered with layers of granular fill material.
Each layer was compacted separately with the test rollers and documented with CCC. Thus, the
influence of weak spots in the sub-soil on the motion behaviour of the roller drums, on the CCCvalues,
and on the automatic control system of the Vario-Control-roller could be investigated.
Results of computer simulations and measured data from large-scale in-situ tests were
analysed and interpreted. Revealed effects of the rollers were compared. The comparison of the
theoretical studies and practical investigations resulted in important scientific findings regarding
soil compaction, whereby well-known phenomena could be confirmed. Furthermore relevant
information for practical application was found. To sum up, the comprehensive research work
has lead to a significant improvement of compaction equipment, of compaction technique and of
compaction control.