Emad Gheibi

Effect of tyre powder penetration on stress and stability of the road embankments

Vehicle tyres are shred due to the friction induced by road surface texture. The shredded tyre particles might then penetrate into the roadside embankment during rain. In this study, the stability of roadside embankment containing 0.25–1.5% of tyre powder is examined. Also the change in extreme stress and displacement is evaluated. Mechanical characteristics of soil–tyre powder mixture are defined through laboratory tests and are used as input parameters needed for PLAXIS software analysis. The results show that the optimum percentage of tyre powder in embankment in terms of stress and displacement is about 0.5%. It is also shown that more penetration of tyre powder in embankment increases the factor of safety against sliding.

Magnitudes of Prehistoric Earthquakes at the Hollywood, South Carolina Site

Pleistocene soil deposits show an increase in liquefaction resistance compared to younger deposits; thus, semi-empirical procedures for evaluating liquefaction potential that are derived from databases of young Holocene soils may not be applicable to aged soils. In this study, the minimum earthquake magnitude and peak ground acceleration required to initiate liquefaction were computed for soils estimated to be about 120,000 to 130,000 years old at the Hollywood site located in the South Carolina Coastal Plain. Discovered sandblows at this site are associated with earthquakes that date back to 11,000 years before present. In-situ geotechnical data, including SPT and CPT with pore water pressure measurements, were used with empirical methods that account for the age of the soil deposit to back analyse the minimum earthquake magnitude and peak ground acceleration at the time of the prehistoric earthquakes. When the age of the earthquake was not considered, the magnitude ranged from 7 to 7.2 and the corresponding acceleration ranged from 0.23 to 0.35g. The earthquake magnitude at the time of earthquake was found to be lower when accounting for age; for the most recent prehistoric earthquake with the age of 546±17, the magnitude was reduced and ranged from 5.7 to 6.7 with corresponding acceleration ranging from 0.17 to 0.30g.

Effect of Parameters on Equivalent Number of Cycles Using Nonlinear Seismic Site Response Analysis

The concept of equivalent number of uniform stress cycles, is essential for assessment of soil liquefaction potential. In this regard, various procedures are used to convert random acceleration time history to uniform cycles having amplitude of 0.65 of peak acceleration. Equivalent number of cycles (Neq) defines equivalent energy generated by harmonic loading as that imposed by irregular motion during an earthquake. Neq is assumed to be a function of earthquake magnitude. Over the past years, in accordance with development in methods of soil liquefaction evaluation, various methods have been proposed to determinate equivalent number of cycles. In particular, parameters like site to source distance (r), have been related directly to Neq. In this study, more than 80 earthquake records have been investigated and their Neqs are assessed using energy approach and nonlinear site response analysis. It is shown that equivalent number of cycles is related to earthquake magnitude (M), r and depth of originated signals. Unlike previous methods which result in scatter in output data, current approach has led to more uniform and consistent results for each earthquake.