The serviceability limit state (SLS) design of foundations typically proceeds by limiting the total settlement of individual foundations and restricting the differential settlement between pairs of foundations. In fact, it is often the differential settlement which is more important to the performance of the supported structure. Unfortunately, due to the random nature of the supporting ground, the magnitude of differential settlement is also random, and is typically much more difficult to characterize than is the total settlement of individual foundations. This paper investigates the distribution of the maximum differential settlement between pairs of foundations as a function of the spacing between foundations and the number of foundations. The effects of the correlation lengths between the elastic properties of the ground under each foundation as well as the loads applied to the foundations on the distribution of the maximum differential settlement are investigated. Groups of 4, 9, and 16 foundations arranged in a regular grid pattern are considered and the maximum differential settlement between all possible pairs are studied. Since SLS limits are often expressed in terms of differential slopes, the distribution of the maximum differential slopes between foundations are also investigated. The overall goal is to establish design requirements on the total settlement of individual piles which simultaneously achieves acceptable performance with respect to differential settlement.

This thesis analyzes seven static load tests conducted on helical piles installed in clay till at a site in Northern Manitoba, Canada. Four methods, the Davisson Offset Limit, the Hansen Ultimate Load, the Chin-Kondner Extrapolation, and the Decourt Extrapolation are used to determine the ultimate capacity using the pile load test results. The ultimate capacities obtained were then used to determine the empirical parameter Kt for helical piles in clay tills, this parameter relates the pile capacity of helical piles to the installation torque of the pile. The Davisson Offset Limit and the Hansen Ultimate Load provided consistent and conservative ultimate capacities based on the pile load test results and showed lesser variability in results compared with the Chin-Kondner Extrapolation and Decourt Extrapolation methods. The ultimate loads based from the Hansen and Davisson methods were used to calculate a Kt value. It was determined that a Kt value ranging from 9 m-1 to 11 m-1 is appropriate for evaluating the capacity of a helical pile in clay tills using the installation torque of the pile.

Circular foundations are mainly used in projects such as crude oil storage tanks, cylindrical water tanks, bridge piers, and silos. One of the main challenges in the designing of circular foundations is to control the settlement and uplift, especially when the foundation is resting on loose granular soils and subjected to seismic loads which may undergo large elastic settlements. One way to reduce the settlements of the foundation as well as its uplift is to use stone-columns below the foundation. The main objective of this study is to investigate the seismic performance of circular foundations resting on stone columns through a parametric numerical study. Abaqus software is used to simulate the interactions between structure, foundation, soil and stone columns. The effects of several parameters are investigated on the settlement and uplift of the foundations. These parameters include the diameter of the circular foundation, diameter and length of the stone-columns, and center to center distance of the stone columns. The settlement and uplift of the foundations in the both presence and absence of the stone-columns under seismic loads are discussed. The results revealed that increasing the length of the stone columns up to a threshold value decreases the settlements and after that, the increase will not cause significant changes in the performance of the foundation. In addition, stone columns diameter and distance play more important role than stone columns length in decreasing settlement and uplift due to seismic loads. Moreover, stone columns cannot have the same effect on reducing settlement as they do on decreasing uplift.

Dynamic pile load testing was performed during the driving of 610 mm displacement prestressed concrete piles into sandy soils, and actual pile capacity was determined during end-of-drive (EOID) and at beginning of restrike (BOR) using CAPWAP procedures. The load test provided an opportunity to compare pile design techniques to measured pile performance. The soils at this site prevent the pile driving process from being completed and the required pile length and capacity were not achieved due to early refusal.

An evaluation was carried out to evaluate nine Cone Penetration Test (CPT) methods based on their ability, to which predictive method would be best suited for estimating the pile capacity at a site where such soils may encountered. The study also compared the CPT methods to the results of the bearing capacity obtained from Standard Penetration Test (SPT) based methods presented in the literature for the same pile.

The ratio of predicted total capacity, Qp, to measured total capacity, Qm, is presented, along with the absolute percent difference between the predicted and measured capacities.

Four methods included Philipponnat (1980), De Ruiter and Beringen (1979), Price & Wardle (1982), Zhou Etal (1982) had slightly over predicted the capacities for test pile within 50% to 63% of the capacities determined by the 1-day BOR dynamic loading test. The Qp and Qm ratio was between 1.5 to 1.9 which showed good agreement between predicted and measured capacities.

Keywords- Driving piles, CPT, bearing capacity, large displacement piles

In geotechnical engineering, in-situ penetration tests have been widely used for site investigation in support of analysis and design. The Standard Penetration Test (SPT) is the most common in situ test for soil investigations in sandy soils. On the other hand, The Dynamic Cone Penetration Tests (DCPT) is a rapid inexpensive field test that can be used to assess the engineering properties of soils. However, correlation between the results of DCPT and soil properties or any other trusted field test is not well established yet.

This study presents an evaluation of predictions SPT blow counts using Dynamic Cone Penetrometer Test. Database consisting of 39 SPT and 21 DCPT data sets was utilized to develop a correlation. Data of this study was drawn from 14 different sites located in north costal of Libya (City of Tripoli), served as the subject of SPT-DCPT correlations. The soil investigation program for each site included SPT borehole and adjacent DCPT tests.

The validity of the proposed correlation was verified using test results on similar soils from five new sites. The developed correlation indicates that the relation between the results of the two penetration tests is linear for sandy soils. Positive linear relationships were found between NSPT and NDCPT for sandy soils. To demonstrate the differences between the proposed and previous deterministic equations, comparative studies were performed. The suggested correlations may guide future more detailed correlations between these two in situ tests. N predicted versus N actual showed high correlation coefficients of 0.70.

In summary, direct correlations between SPT and DCPT were produced, showed that the light DCPT is suitable for sandy soils with low density NSPT 30 blows/0.3 m or less, and allowing estimation of NSPT from DCPT