Liquefaction Mitigation by Chemical Grouting-PPT Presentation

PPT Presentation

Pdf Summary

The project addressed liquefaction risk beneath an expansion of the Newport Beach Sailing School in California. The new two-story concrete building was planned partly above an existing garage, only a few feet from the seawall and one foot from a neighboring building. With groundwater at approximately 0.9 m, a design earthquake magnitude of 6.9, and peak ground acceleration of up to 0.5 g, analyses estimated 6.4 cm of liquefaction-induced settlement.<br /><br />Conventional cement-based permeation grouts were unsuitable for the site’s fine and silty sands. Colloidal silica was selected because it can permeate these soils at low pressure, gel in the presence of salt water, and minimize environmental impacts, ground heave, and disturbance to nearby structures. The grout was designed to form interconnected, sandstone-like soil grids that increase resistance to cyclic loading. Design targets included an unconfined compressive strength of 172 kPa and a shear modulus of 16 MPa.<br /><br />The treatment covered approximately 53% of the liquefiable sand volume, creating equivalent grout columns 1.52–1.83 m in diameter. Quality controls included injection refusal criteria and monitoring of surface levels, utilities, and seawall movement. In total, 154 holes were grouted using 466 m³ of chemicals, with no building heave or seawall movement reported.<br /><br />The project demonstrated the first industrial-scale, permanent application of colloidal silica for soil liquefaction mitigation in an operating building with restricted access. The treated soil grids mitigated liquefaction and supported static and seismic building loads while meeting stringent environmental requirements.

Keywords

liquefaction mitigation

colloidal silica

Newport Beach

soil grouting

seismic settlement

fine sandy soil

groundwater

seawall

ground improvement

California