LIQUEFACTION · Effects of permeability and compressibility on liquefaction assessment of silty soils using cone penetration resistance

Effects of permeability and compressibility on liquefaction assessment of silty soils using cone penetration resistance

Earthquakes are among the most catastrophic natural phenomena that mankind has to contend with. Nowadays, most evaluations of earthquake hazards include an assessment of liquefaction potential because liquefaction is a major cause of foundation failures (causing damage or collapse of buildings, bridges and other structures), distribution of transport infrastructure, as well as on ports and buried lifelines during large earthquakes. Liquefaction problem had been studied worldwide for more than four decades since the alarm rung in 1964, when two devastating earthquakes in Niigata (Japan) and Alaska (USA) showed the dramatic disaster that soil liquefaction can cause. Since the beginning of this century, significant progress has been made. Initially, it was thought to be mainly a problem with clean sand, and most of the research focused on these soils. However, as the years passed and earthquakes continued to provide lessons and information, it has become apparent that non-plastic silty sands are commonly involved in liquefaction, and in some cases even silts. The current liquefaction screening method based on cone penetration test (CPT) includes the effects of fines on the liquefaction resistance, which obtained from the field liquefaction observations, and normalized cone penetration resistance, qc1N. Uncertainties prevail at this method whether the existence of fines increase the liquefaction resistance or decrease the penetration resistance. The primary objective of this study was to gain a rational understanding on the effects of non/low plastic fines content on cone penetration resistance and liquefaction resistance by using the field based data. For this reason, twenty different test locations at the Northern coast of Izmir Gulf, situated in the western coast of Turkey were selected according to their non/low plastic fines content and liquefaction susceptibility. At each of these test locations, five high quality field tests; (1) standard penetration (SPT), (2) seismic piezocone penetration (SCPTu), (3) piezocone penetration (CPTu), (4) pore pressure dissipation and (5) direct push permeability tests were performed side-by-side soundings up to about 15m depth. As a result of these intensive in-situ test program first, effects of the coefficient of consolidation or drainage characteristics of soils containing fines on excess pore water pressure and the cone penetration resistance were examined. Second, the contribution of the fines on the liquefaction resistance of soils at different relative density was investigated. Another important objective of this study was to provide the geotechnical literature with well instrumented test data. For this reason, the 1.4 m deep, 1.8m and 0.6m wide large scale flexible laminar box on the shake table was constructed. This 1-g laminar box was filled with silty sands and clean sands and instrumented with accelerometers and pore pressure transducers, to monitor the soil during and after the shaking table tests. The design and preliminary results of these tests can provide the geotechnical literature highly instrumented test data. As a result of the above mentioned in-situ and laboratory test program, engineers will have a better understanding on the behavior of soils with non/low fines under seismic conditions. The soil liquefaction is a major cause of damage during earthquakes occurring in most of the European countries, therefore this study will be a valuable contribution to the European Union. This research attracted new generations of students to earthquake engineering, and brought these results and this way of doing geotechnical earthquake engineering studies to a wide audience of engineers and researchers in Europe and overseas. Fast-track dissemination and transfer of findings to the research community as well as to the engineering community will bring a rapid growth and impact to the profession and benefits to the economy. This research also helped the fellow initiate impact research in the host institution and train graduate students, in the area, who will supply the shortage of engineers and researchers needed in Europe.

Data: CORDIS, © European Union