Time Dependent Capacity Increase for Driven Pile in Cohesionless Soil

The increase in driven pile capacity with time is termed set-up. The mechanism contributing to this phenomenon is not yet fully understood. Moreover, a rational approach to account for the increase in driven pile capacity with time in design has not yet been developed. In this study, a database comprising of 55 pile load tests (static and dynamic tests) were collected from the current engineering literature. The piles were driven in cohesionless soils with sand relative density varying from loose to dense. The measured capacities of the database piles with time were correlated to pile characteristics and soil properties. Pile set-up was found to be a phenomenon related to an increase in pile shaft friction with time and increases with decreasing pile diameter. On the other hand, pile setup was found to increase with increasing pile penetration depth and thus with pile slenderness ratio. A new approach for the estimation of pile set-up in cohesionless soils is presented in this study. The new approach considers the effects of pile characteristics and soil properties. Comparison of predicted and measured pile set-up using the developed method in this study indicates reasonable agreement. Also, comparison of prediction using the new approach with those made using previously published methods indicates that the developed method in this study yields better results

Determination of Saline Soils Specific Gravity

The existence of salts as part of the solid phase of the soil or dissolved within the pore fluid may cause significant errors in the values of specific gravity of such soils by using conventional determination methods. Errors may arise from effects of wrong measurements of weights or volumes that take place due to dissolution of the salt during testing, precipitation during drying or dehydration of the crystals of certain salts such as gypsum. To overcome this confusion, the standard procedure for specific gravity determination is reconsidered and the calculation methods are reanalyzed. Suggestions for a more adequate procedure for gypseous or other types of saline soils are presented and corrections required for computations are derived

Deaggregation of Probabilistic Ground Motions for Selected Jordanian Cities

Probabilistic Seismic Hazard Analysis (PSHA) approach was adopted to investigate seismic hazard distribution across Jordan. Potential sources of seismic activities in the region were identified, and their earthquake recurrence relationships were developed from instrumental and historical data. Maps of peak ground acceleration and spectral accelerations (T=0.2 and T=1.0 sec.) of 2% and 10% probability of exceedance in 50 years were developed. This study deaggregated the PSHA results of 2% and 10% probability of exceedance in 50 years results of twelve Jordanian cities to help understand the relative control of these sources in terms of distances and magnitudes. Results indicated that seismic hazard across these cities is mainly controlled by area sources located along the Dead Sea Transform (DST) fault system. Cities located at short distances from the DST tend to show close deaggregation behavior. Some discrepancies may exist due to the proximity or remoteness of these cities relative to the DST seismic sources and local seismicity. The modal or most probable distance distribution indicated that the distance to the earthquake which contributes most to the hazard at each city is mainly controlled by shaking along faults associated with near seismic area sources. The influence of adjacent seismic sources to the seismic hazard of each city is more evident for the long period spectral acceleration. Distant sources, such as the eastern Mediterranean, Cyprus, Suez and the southern region of the Gulf of Aqaba are relatively low, but can not be neglected due to the intrinsic uncertainties and incomplete seismic data