TUBITAK Project

                                                                                                                                                                                                                                                                                                                                                                                                             

 

 Project Summary:

 

Dynamic Response of Sands Mitigated by IPS (Induced Partial Saturation) under New and Existing Structures

 

The potential vulnerability of existing structures on liquefiable soils continues to be of major concern not only to individual owners but also to the public that faces destruction of their cities, towns, and neighborhoods. This research focuses on the development and implementation of a new liquefaction mitigation technique: Induced Partial Saturation (IPS) that involves generation of gas bubbles in loose saturated sands thus inducing partial saturation leading to not only strength gain against liquefaction, but also potentially eliminating the occurrence of liquefaction under any size earthquake.

IPS intends to prevent the occurrence of liquefaction by increasing the compressibility of the pore fluid with the generation of some amount of gas in the fully saturated sand pores, thus basically by transforming the sand into partially saturated state. This research includes studies for the investigation of the behavior of partially saturated sands in free field and under the foundations during earthquakes. For this purpose, first dynamic simple shear tests with confining pressure (DSS-C) were performed on small samples to understand the effect of vertical effective stresses and pore water pressures on excess pore water pressure generations in partially saturated sands, that has been performed for the first time in the literature. Based on the DSS-C tests and shaking table tests in the literature, numerical model was developped in the software program FLAC3D. The DSS-C tests demonstrated that the excess pore water pressure ratio (ru=Δu/s'v0) reduces as the depth of the sample increases for the same degree of saturation. Also, the effect of degree of saturation in lowering the ru becomes more significant for the samples at deeper levels. The numerical analyses results confirmed the same results for free field models. In addition, the ru generations in fully saturated sand and partially saturated sands under the foundations were found to increase as the depth increases and more ru reduction was observed in partially saturated sands.

 

Outcomes:

  • Seyed Mohsen Seyedi Viand and Ece Eseller-Bayat (2017) "Numerical Modelling of Liquefaction Tests of Partially Saturated Sands in CSSLB" Advances in Laboratory Testing and Modelling of Soils and Shales (ATMSS) Springer Series in Geomechanics and Geoengineering, Ed. Alessio Ferrari and Lyesse Laloui, pp. 139.
  • Derya Burcu Gülen and Ece Eseller-Bayat (2017) "Specimen Preparation Techniques for Testing Fully and Partially Saturated Sands in Dynamic Simple Shear (DSS) Test Device with Confining Pressure" Advances in Laboratory Testing and Modelling of Soils and Shales (ATMSS) Springer Series in Geomechanics and Geoengineering, Ed. Alessio Ferrari and Lyesse Laloui, pp. 139.
  • Ece Eseller-Bayat, Ataollah Nateghi, Seyed Mohsen Seyedi Viand, Navid Jadidoleslam (2016) "Numerical modelling of liquefaction tests of fully saturated sands in CSSLB" 4th International Conference on New Developments in Soil Mechanics and Geotechnical Engineering, Nicosia, North Cyprus.