New Method for Static Load Test for Pile Rests in Sandy Soil Underlain by Clay

R. Bakr, M. Elmeligy, A. Ibrahim

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Earth Walls and Foundations

ABSTRACT: for Static Load Test for Pile Rests in Sandy Soil Underlain by Clay Bakr, R., Elmeligy, M., & Ibrahim, A. Department of Structural Engineering, Faculty of Engineering Mansoura University, Mansoura, Egypt ABSTRACT In many cases, there are soil layers with high strength properties exist at shallow depths that can be used as bearing layers for piles especially when there is continuous sand layers at great depths. These layers are either stiff clay layers with high shear strength or sand layers with high friction resistance or mixture of both. Due to the presence of weak soils under the bearing layer, this research focuses on the behavior of pile that rests in sand underlain by clay soil. Two sites were selected for this study, the first is located Mansoura city while the other is in Gamasa and both sites are located in the Nile Delta Region of Egypt. In situ and laboratory tests were carried out to determine soil properties. Static load tests were conducted on a number of piles. Numerical simulation for static load test was then performed for each case. By comparing the results of both the static load tests and the numerical simulation of real-life loading, (RLL), it was found that the pile behavior described by the standard method of static load test, (SSLT), according to ASTM D-1143, is significantly exaggerated. A new method called Modified Quick Load Test (MQLT1.3) is proposed by this study. The new method is validated by numerical simulation and field static load tests. Although the new method is less time-consuming, less expensive, but it's accurately represents the real pile behavior in sand layer underlain by clay. RÉSUMÉ Dans de nombreux cas, il existe des couches de sol avec des propriétés de haute résistance existent à de faibles profondeurs qui peuvent être utilisés comme portant des couches pour les pieux surtout quand il ya des couches de sable continue à de grandes profondeurs. Ces couches sont des couches d'argile rigides avec force de cisaillement ou de sable couches à haute résistance à la friction ou un mélange des deux. En raison de la présence de sols faibles sous la couche de roulement, cette recherche se concentre sur le comportement de la pile qui repose dans le sable reposant sur un sol argileux. Deux sites ont été choisis pour cette étude, la première se trouve Mansoura ville tandis que l'autre est en Gamasa et les deux sites sont situés dans la région du delta du Nil de l'Egypte. In situ et au laboratoire essais ont été réalisés afin de déterminer les propriétés du sol. Essais de charge statique ont été réalisés sur un certain nombre de piles. La simulation numérique pour test de charge statique a ensuite été réalisée pour chaque cas. En comparant les résultats des deux essais de charge statique et la simulation numérique de la vie réelle de la charge (RLL), il a été constaté que le comportement de la pile décrite par la méthode standard de test de charge statique, (SSLT), selon la norme ASTM D -1143, est nettement exagéré. Une nouvelle méthode appelée Modifié test de charge rapide (MQLT1.3) est proposé par cette étude. La nouvelle méthode est validée par des tests de charge statique de simulation et de terrain numériques. Bien que la nouvelle méthode est moins de temps, moins cher, mais ça représente bien le comportement des pieux réel dans la couche de sable reposant sur de l'argile. 1 INTRODUCTION The static load test has been regarded to be the most reliable test method because the true pile-soil behavior can be directly obtained from the test. In delta regions due to its lower level, the subsurface soil consists of successive layers of sand, clay and silt sediments. These deposits are usually built up from mix of these soils. In many cases thick sand or stiff clay layers exist underlain with other soft soils at relatively shallower depths. These layers can be used as bearing soils for pile foundation with careful study of the expected settlement. The authors proved that the pile behavior predicted by the current static load test method in clay soil is extremely exaggerated. A new method was proposed by the authors for the case of pile rests in clay based on numerical and field tests, Bakr, R., et al 2103 and 2014. This study focuses on the evaluation of the standard static load test (SSLT) method as a tool for the prediction of the pile behavior when it rests in sand layer underlain by clay. Field load tests and numerical simulation tools are used to evaluate the standard static load test. 2 TEST SITES Two sites 50 km apart located in Egypt Nile Delta region were selected. The first site is located in Mansoura city where 13 floors building to be constructed while the other site belongs to Delta University which located in Gamasa city on the Medetririan Sea south cost. Figure 1, Shows an image captured from Google earth for both sites. These sites were selected to represent the case of pile rests in sand layer underlain with clay. For site 1 the pile diameter is 0.5m and its length is 14.5m. For site 2 three pile diameters are used 0.5, 0.6, and 0.8m with the same pile length 8.0m.

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R. Bakr; M. Elmeligy; A. Ibrahim (2014) New Method for Static Load Test for Pile Rests in Sandy Soil Underlain by Clay in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper103,author = R. Bakr; M. Elmeligy; A. Ibrahim,title = New Method for Static Load Test for Pile Rests in Sandy Soil Underlain by Clay ,year = 2014}