PREMISERI · Preloading to mitigate seismic liquefaction risk

Excessive deformations of level ground caused by earthquakes are of great concern for civil engineering works, human lives and the environment. Such ground deformations are usually associated with liquefaction, i.e., a decrease in strength caused by the increase in pore water pressures in saturated cohesionless materials during earthquake ground motion. Much earthquake damage caused by liquefaction-induced excessive displacements can be mitigated by soil improvement methods, thus limiting the associated economic and social problems. Unfortunately, large scale application of the more common soil improvement methods is often avoided because of excessive costs of deep methods and incomplete understanding of potential benefits of other methods. This leads to potentially catastrophic consequences from earthquakes. For this reason preloading is particularly attractive, because, as it is applied from the surface, it can overcome the restriction of prohibitive costs. The goal of this research is to develop a cost-effective method, based on preloading, to reduce seismic liquefaction susceptibility and the associated risk to buildings that may cause many fatalities. Verify and study the method by a field study and develop procedures to estimate improvement and risk mitigation for new sites. Towards this goal the following major tasks will be performed: 1. Study and verify the method by a field preload test 2. Study of the effect of preloading on the cyclic soil strength by elaborate laboratory testing 3. Collect and analyze in-situ test results before and after the field application of preloading 4. Analyze the effect of preloading on the seismic risk of buildings and other structures on liquefaction-susceptible sites by elaborate numerical analyses 5. Propose rules for new sites based on the above