Engineering and Technology Journal

Comparison of the Behavior for Free Standing Pile Group and Piles of Piled Raft

Awf Al-Kaisi; Falah H. Rahil; Mohanned Waheed

Volume 36, 4A , April 2018, , Page 373-380

https://doi.org/10.30684/etj.36.4A.3

Abstract

The intended task of this paper is studying the behavior of free standing pile groups and piles of piled raft driven in clayey soil under axial loading. The raft-piles interaction is ... Read More ... The intended task of this paper is studying the behavior of free standing pile groups and piles of piled raft driven in clayey soil under axial loading. The raft-piles interaction is investigated as well through the two series of tests. Each one of these series includes twelve tests, the two series are conducted with the same configuration, spacing, size of piles and undrained shear strength of soil except that in the free standing group there is a gap of about (20-25 mm) between the raft and the soil surface to have the applied load transferred to the piles only in order to compare the behavior of piles in the two cases. Three grades of undrained shear strength (cu) of clayey soil are selected which are (20 or 40 or 60 kPa) and the configuration of the pile groups used in all tests is (2 x 2). Two different pile lengths (L) are selected (300 and 450 mm). These lengths represent the slenderness ratio (L/D) of (10) and (15) respectively, so that the center-to-center spacing between the piles (S) used are (3D) and (5D). It is observed that piles exhibited a very high stiffness at initial loading stages till the settlement is about 0.5mm, beyond this level, even for a small increment in the load, the pile settled rapidly, which means that once the friction is overcome the piles failed instantaneously. In addition, most of the load capacity of piles is mobilized at settlement of around (1 – 2 mm), corresponding to (5 %) of pile diameter.Moreover, the increasing the undrained shear strength of clay from (20 to 60 kPa) has no significant effect on the load transfer mechanism of piles in the two cases .It can be concluded that the load capacity of the free standing pile group is about equal to the piles in piled raft case, indicating that the interaction effect is not significant, therefore, it is suggested to apply an efficiency factor (αG) of (1) in designing the piled - raft foundation in clayey soil when calculating for pile load share.

Development Bearing Capacity of Piles Embedded in Clayey Soil

Awf Al-Kaisi; Falah H. Rahil; Mohanned Q. Waheed

Volume 36, 3A , March 2018, , Page 315-321

https://doi.org/10.30684/etj.36.3A.10

Abstract

The load carrying capacity of piles resulting from base resistance and shaft resistance, the load transfer mechanism of piles is complicated since the mode of failure of these components ... Read More ... The load carrying capacity of piles resulting from base resistance and shaft resistance, the load transfer mechanism of piles is complicated since the mode of failure of these components is different in addition to the effect of pile installation on the soil surrounding of piles .The intended task of this paper is studying the behavior of pile group model driven in clayey soil subjected to vertical axial loading, and the assessment of the development of resistance of each of the two components, tip resistance and skin friction of the piles of during loading. Twelve piles group tests are conducted at three grades of undrained shear strength (cu) of clayey soil which are (20 or 40 or 60 kPa) where the configuration of the pile groups used in all tests is (2 x 2). Two different pile lengths (L) are selected (300 and 450 mm), these lengths represent the slenderness ratio (L/D) of (10) and (15) respectively, so that the center to center spacing between the piles (Sp) used are (3D) and (5D). It was observed that the most of the load capacity of piles is mobilized at settlement of around (1 – 2 mm), corresponding to (5 %) of pile diameter (D) , however, the development of full shaft resistance of piles appears at a low displacement range and is only of about (1 to 2 %) of the pile diameter while the pile end bearing will mobilize at a higher displacement range in the range of (5 to 10%).The changing of undrained shear strength of clay from (20 to 60 kPa) has no significant effect on the load transfer mechanism and the mobilization of shaft resistance and end bearing with increasing the settlement. It was concluded that a low ratio load sharing of piles tip, especially with increasing slenderness ratio (L/D) , which supports the fact that the piles in the weak clayey soils behave as a floating pile which leads to neglecting end bearing capacity in calculating the total pile load capacity as indicated by some references.

Treatment of Soft Soil by Sand Columns

Namir K.S. Al-Saoudi; Mohammad M. M. Al-Kaissi; Nawres A. A. Rajab

Volume 32, Issue 9 , September 2014, , Page 2106-2118

https://doi.org/10.30684/etj.32.9A1

Abstract

Stone or sand columns are most widely used to improve the engineering properties of soft saturated soils. In principles, sand columns technique is very close to the well-known stone ... Read More ...

Mathematical Estimation for the Bearing Capacity of Sand Column Inserted in Soft Clay Soil

Awf Abdul Rahman Al-Kaisi; Hiba Hussein Ali

Volume 31, 5 A , May 2013, , Page 816-827

https://doi.org/10.30684/etj.31.5A2

Abstract

Sand column is one of the soft ground improvement methods. It is made up of well compacted sand pile, it is used for enhance the load capacity of soft clay soils, reduce the settlement ... Read More ...

Keywords = end bearing

Comparison of the Behavior for Free Standing Pile Group and Piles of Piled Raft

Abstract

Development Bearing Capacity of Piles Embedded in Clayey Soil

Abstract

Treatment of Soft Soil by Sand Columns

Abstract

Mathematical Estimation for the Bearing Capacity of Sand Column Inserted in Soft Clay Soil

Abstract