The soil response beneath the ground due to impact rolling

What is it about?

Rolling Dynamic Compaction (RDC) imparts energy to the ground via the use of a heavy non-circular module that impacts the ground. To quantify the effects of RDC, testing is typically undertaken pre- and/or post-compaction to determine if a project specification has been met (or otherwise). However, such testing methods fail to capture the dynamic effects of a single module impact. This study involved conducting a full-scale research trial where an 8-tonne 4-sided impact roller (shown in Figure 1) compacted homogeneous fill material in which buried earth pressure cells and accelerometers were placed at a depth of 0.7 m to capture the real-time ground response to RDC beneath the surface.

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Photo by Ermelinda Martín on Unsplash

Photo by Ermelinda Martín on Unsplash

Why is it important?

Key findings or contributions to knowledge from this paper include: • Pressures up to 1100 kPa were measured at a depth of 0.7 m below the ground surface. • Quantified that the dynamic loading and unloading of soil occurs over a duration of approximately 0.05 seconds. • The acceleration response due to impact was measured in three orthogonal directions with vertical accelerations dominant (peak accelerations up to 21g were measured). • The accelerometer response indicated that the direction of travel of the roller influences the ground response; an expected result given the module is not just falling vertically onto the ground. • Uneven module geometry results in some passes imparting much greater pressures than others. This was quantified by measuring the force-displacement response for consecutive passes. • Force was quantified from measurements of the pressure imparted into the soil using buried earth pressure cells of known cross-sectional area. Displacement was inferred from double-integration of the accelerometer data, and quantified both recoverable (elastic) and permanent (plastic) components of soil settlement.

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