Innovations in Ground Improvement: Creating Composite Ground with Drill Displacement Column™ and Auger Cast Column™-Paper

Paper

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The paper presents Auger Cast Columns (ACC) and Drill Displacement Columns (DDC) as rigid-inclusion ground-improvement systems used to create composite ground beneath heavy structures. Both methods drill a cavity and pressure-grout it during withdrawal; DDC uses fuller soil displacement, while ACC uses partial displacement. The resulting grout columns and surrounding soil work together to increase bearing capacity and stiffness, control settlement, and mitigate liquefaction.<br /><br />Design must consider both geotechnical and structural performance. Settlement is commonly assessed in improved and unimproved soil zones, with neutral-plane concepts used to estimate load transfer. Full-scale area load tests verify composite-ground capacity. An aggregate cushion or load-transfer platform between the foundation and columns is essential: it helps accommodate stiffness differences, protects the columns, and provides a seismic break. Reinforcement can increase column ductility or provide uplift resistance.<br /><br />The systems offer low-noise, vibration-free installation and can reduce soil spoil—advantages on constrained, sensitive, or environmentally impacted sites. Their use also presents challenges, including heavy equipment access, grout supply and staging, construction-pad demands, and the need to monitor ground heave.<br /><br />Case histories at Stanford Redwood City, Martin Luther King Hospital, and UC Berkeley demonstrate applications involving settlement and liquefaction control, high bearing capacity, uplift resistance, protection of nearby facilities and utilities, and reduced risk of groundwater cross-contamination. Testing and monitoring supported the designs, which achieved project-specific performance targets.<br /><br />The authors conclude that ACC/DDC provide an alternative between conventional deep foundations and more flexible ground-improvement methods. Successful application depends on coordinated geotechnical, structural, and construction design, with further research and consistent standards needed for seismic performance and broader regulatory acceptance.

Keywords

Auger Cast Columns

Drill Displacement Columns

rigid inclusions

ground improvement

bearing capacity

settlement control

liquefaction mitigation

composite ground

load transfer platform

seismic performance