Compaction Grouting Test Program for Liquefaction Control

Following the 1989 Loma Prieta earthquake a detailed analysis of liquefaction risk was carried out for an industrial site near the Pajaro River at Watsonville, Calif. A ground improvement project, by grouting, was proposed to prevent lateral spreading and a compaction grout test program was undertaken to validate and refine the project design. In phase 1 of the test program the grout hole spacing was 2.5 and 1.8 m (8 and 6 ft). In phase 2, a closer hole spacing was used, 1.5 and 1.2 m (5 and 4 ft.) The test program employed cone penetration tests and standard penetration tests measurements for evaluation before and after each phase. The results showed the relationship of ground improvement versus grout hole spacing, grout take, and grout pressure. The test program showed that a zone of susceptible soils at the site could be effectively improved to increase their strength and resistance to liquefaction and thus prevent lateral spreading during severe earthquakes.