The project “Rolling Dynamic Compaction on Sloping Spoil Heaps” (RoDyCom) was carried out at the University of Applied Sciences Leipzig from 1 April 2019 to 31 March 2023 under the supervision of Prof. Dr.-Ing. Ralf Thiele. Funded by the German Ministry of Education and Research (grant 13FH678IX6), the study addressed the lack of scientific knowledge on how Rolling Dynamic Compaction (RDC) works on the low‑strength, low‑density spoil heaps that have been created by coal mining in the Lausitz region. The spoil heaps are among the largest landscape construction sites in Europe and require compaction to enable agricultural, tourism and economic reuse.
The research was organised into five work modules comprising 15 work packages. Three complementary test tools were used throughout: (1) laboratory model tests in a planar strain state, (2) numerical simulations with ABAQUS, and (3) laboratory and on‑site field experiments. The model tests employed a rigid triaxial roller geometry and a 30 × 10 m soil domain with infinite boundaries. Kinematic boundary conditions were modelled by a constant pulling speed that is initially increased linearly. Soil behaviour was described by a hypoplastic constitutive law that incorporates intergranular strains. A standardised calibration procedure was developed to determine the material parameters with a minimal but sufficiently accurate test programme.
A theoretical framework was established to estimate the energy and impulse transferred to a rigid substrate for arbitrary roller geometries and pulling speeds. The roller kinematics were divided into three phases—lift, drop, and impact—and validated against the three test tools. In the laboratory tests with dry sand, slip of the roller bandage caused difficulties, limiting the analysis to a single roller impact. The results showed that compaction occurs mainly during the impact and lift phases, with the roller generating horizontal and vertical displacement fronts. Field experiments at two pulling speeds and 40 passes confirmed these findings. Contact forces during impact and the start of lift contain critical vertical and horizontal components for compaction. Compared with other impulse compaction devices, the roller impact is a discontinuous impulse that is not decelerated by the soil, suggesting that the increase in vertical force could serve as an indicator for full‑field compaction monitoring.
An adaptive Arbitrary Lagrangian‑Eulerian (ALE) mesh was employed to capture the large soil deformations accurately. The numerical model was calibrated against the laboratory data and subsequently validated with field measurements. The project produced a comprehensive database summarising all known RDC research and data on the spoil heaps in the Lausitz coalfield, together with a catalogue of geotechnical and machine‑specific parameters relevant to RDC.
Beyond the technical outcomes, the project strengthened the young researcher group at HTWK Leipzig. It expanded the research team, promoted a PhD candidate, and improved collaboration with universities and industry partners. The interdisciplinary team developed a new measurement concept for compaction success, including sensors for acceleration and pore‑water pressure, and produced a practical guideline for applying the RDC system on spoil heaps. The results provide a scientific basis for designing efficient compaction strategies and for developing field‑scale monitoring tools, thereby supporting the sustainable redevelopment of large mining landscapes.