Although blast liquefaction studies have shown that vertical drains greatly increase the rate of drainage under field conditions, they have not prevented liquefaction. In addition, it is difficult to compare pore pressure development during blasting and an earthquake. At present, no direct field or laboratory data is available to confirm whether or not the drains have the ability to limit pore pressures and resulting settlement to acceptable levels. However, shaking table tests can be conducted with a large shear box (20 ft high, 9 ft wide, 16 ft long) containing drains at SUNY-Buffalo and compared with identical testing currently underway for another funded study. Tests will be performed at progressively higher acceleration levels and durations to allow comparison of performance (pore pressure & settlement) for earthquake conditions.

Perform shaking table tests on sandy soils with vertical drains installed to confirm whether or not the drains have the ability to limit pore pressures and resulting settlement to acceptable levels during the earthquake event. Three objectives are outlined for this study: 1. Evaluate the ability of vertical drains to prevent liquefaction during an earthquake event as a function of acceleration and duration. 2. Compare settlement of treated sand relative to untreated soil when subjected to shaking and drained with vertical drains. 3. Evaluate the accuracy of simple models and computer models to predict measured behavior.

The scope of work consists of five specific tasks: 1. Prepare test specimen in laminar shear box with vertical drains. 2. Conduct shaking table tests at progressively higher accelerations measuring water pressure, acceleration, and horizontal and vertical displacement. 3. Reduce the test data and compare with previous test on untreated sand 4. Compare measured behavior with behavior computed using computer models and simplified models. 5. Prepare final report on effectiveness of drain technique.

The Principal Investigator for this study will be Dr. Kyle Rollins, of Brigham Young University. Dr. Rollins has extensive experience with liquefaction mitigation studies, the use of vertical drains, and the simulation of earthquake conditions for research. This study promises to yield practical results. Vertical drains offer the potential to deal with liquefaction problems at 30 to 50% of the cost and time required with conventional densification techniques. Drains could also be used in combination with other improvement techniques where it might be difficult or too expensive to completely prevent liquefaction through densification. Drains are particularly attractive for marginal liquefaction problems or for locations where it might be economically difficult to justify the conventional densification procedure.