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Article
Determination of the Adequate Thickness of Granular Subbase Beneath Foundations

Authors: Mohammed Y. Fattah --- Falah H. Rahil --- Mohammed A. Turki
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2011 Volume: 29 Issue: 9 Pages: 1845-1869
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

Where the native soils have poor structural qualities or are expansive, the soilinvestigation report may recommend importation of soils better suited to providing asubbase for structures. This requires considering two soil layers in bearing capacitycalculations.Calculation of the ultimate bearing capacity of shallow footing on a two layered systemof soil depends on the pattern of the failure surface that develops below the footing. For aweak clay layer overlaid by a top dense sand layer, previous studies assumed that thefailure surface is a punching shear failure through the upper sand layer and Prandtl'sfailure mode in the bottom weak clay layer.In this paper, the bearing capacity of subbase layer underneath by a soft clay layer isinvestigated. The properties of the subbase material are measured in the laboratory.Design charts were obtained which can be used to select the suitable thickness of thesubbase layer for a design allowable bearing capacity.


Article
Bearing Capacity of Closed and Open Ended Pipe Piles in Clayey Soil

Authors: Ban S. Hussein --- Falah H. Rahil --- Mohammed A. Mahmoud
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 8 Part (A) Engineering Pages: 1615-1623
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

This paper investigates the impact of close and open ended condition on the capacity of pipe piles installed in medium clayey soil using pressed or jacked and hammered techniques and tested under the effect of vertical static compression load. 36 experimental model steel pipe piles (18 models for each open and closed ended) introduced and analyzed to clarify the influence of soil plug formation on the behavior of pipe piles.Different parameters are studied such as pile diameters (2.5, 3.5 and 4.1) cm, piles lengths (30, 40 and 50) cm and type of installation methods (pressed and hammered(. Results of the test program indicated that the ultimate load capacity of open-ended pipe piles tended to increase as the pile diameter and length increase for both pressed and hammered. The plugging of open piles does not contribute significantly on the capacity of pile in clay. For all model pile tests the load capacity of the closed ended piles is (5 – 30) % greater than that of the open ended for both type of installation (pressed and hammered) under the same geometric conditions.


Article
Development Bearing Capacity of Piles Embedded in Clayey Soil

Authors: Awf A. Al-Kaisi --- Falah H. Rahil --- Mohanned Q. Waheed
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 3 Part (A) Engineering Pages: 315-321
Publisher: University of Technology الجامعة التكنولوجية

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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 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.


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

Authors: Awf A. Al-Kaisi --- Falah H. Rahil --- Mohanned Q.Waheed
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 4 Part (A) Engineering Pages: 373-380
Publisher: University of Technology الجامعة التكنولوجية

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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 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.


Article
BEARING CAPACITY OF SOFT CLAY IMPROVED BY HEATING THROUGH DIFFERENT SPACING CASED BOREHOLES

Authors: Falah H. Rahil --- Husam H. Baqir --- Hussain N. Alkabee3
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2019 Volume: 10 Issue: 1 Pages: 68-77
Publisher: University of Kufa جامعة الكوفة

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Abstract

This paper presents the effect of heat treatment on ultimate bearing capacity and total settlement of soft clay. The soft clay that was used in this study was prepared by mixing Baghdad’s clay with sufficient water content which gives a shear strength of 7 kPa.Seven model tests were carried out on soft clay inside a cubic steel box of 750 mm side length after heat treatment, two of which were used as a reference without treatment for comparison. A special heating system was designed and manufactured for this purpose by using the gas as a source of heating through boreholes. Four square patterns casing boreholes having 3.5 cm in diameter and 30cm in length with spacing 3d, 4d, 5d, 6d and 7d (were d is the diameter of the borehole) and the time of heating was six hours for each model. A monotonic load was applied on an aluminum square model footing of 150 mm length and 20 mm thick placed on the center of surface area of the soft clay until the settlement exceeds 10% of the width footing. The results showed that the bearing capacity increases and the settlement decreases with spacing increasing until some limiting value (5d) then the bearing capacity decreases and the settlement increases. The 5d spacing is the best one where the bearing capacity increases nine times and the settlement decreases to one tenth compared with that without heating.


Article
Improvement of Ballast Embankment Resting on Soft Clay by Reed and Asphalt Layers

Authors: Namir.K.S. AL-Saoudi --- Falah.H.Rahil --- Kawther.Y.H.AL-Soudany
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2011 Volume: 29 Issue: 15 Pages: 3224-3241
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

The present paper investigates the possibility of using reed and /or asphalt as stabilizing materials for ballast model embankment overlaying a bed of soft soil. Four model tests were performed consisting of a model embankment 500mm base width 300mm crest width and 75mm high. The embankment was constructed on a bed of saturated soft clay 500mm thick with undrained shear strength 16 kPa. The ballastembankment was gradually loaded up to failure by a model footing 200mm wide and 400mm long placed on the crest with continuous monitoring of the generated settlement. The use reed and/or asphalt along the interface surface between the ballast embankment and the soft soil demonstrated significant improvements in both load carrying capacity and reduction in settlement.


Article
Effect of Relative Density on Behavior of Single Pile and Piles Groups Embedded with Different Lengths in Sand

Authors: Falah. H. Rahil --- Mohammed. A. Al-Neami --- Kather Abdullah Naji Al-Zaho
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 6 Part (A) Engineering Pages: 1206-1220
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

The present research investigates the effect of axial relative density on the ultimate load of model piles with different lengths driven in dry sandy soil having small scale model piles.The materials used in this study are divided into three parts they are; sandy soil, steel piles and aluminum pile caps.A total number of 27 model tests are carried out using three relative densities (33%, 60%, and 80%) corresponding to loose, medium and dense sand, respectively. A square section steel solid model piles are used with 18 mm width and (320, 420, 520) mm embedded length (Ld). A 6B distance between the piles center to center is selected to eliminate the effect of group interaction.Two pile groups' configuration (1×2) and (2 × 2) are considered in this study connected by aluminum caps with smooth surface having a thickness of 25 mm.The load applied on the models is measured by a pressure transducer connected to the main line of the hydraulic pressure system and applying up to failure. During all the experimental tests, the loading rate is kept at 3 mm/min. It was founded that relative density has more impact on (2×2) pile group than on (1×2) pile group and single pile. The average rate of increase in the ultimate load from loose to medium is about 15% greater than the average rate of increase from medium to dense. Also, the ultimate load of pile increased about 96% with changing the sand density from loose to medium sand for single and piles group while the average increment is about 81% from medium to dense. The increase in embedded length of pile caused increasing the ultimate load capacity and decreasing the settlement ratio. The average rate of increase in the ultimate load when the embeddedlength changes from 32 cm to 42 cm is about 4% less than the average rate of increase when the embedded length changes from 42 cm to 52 cm. Also, use of (1×2) piles group instead of a single pile, the average rate of increase is about 6% less than the average rate of increase when change from (1×2) group to (2×2) pile group.Finally, when the number of piles changes from single pile to (1×2) piles group, and to (2×2) piles group, the average of increase of ultimate load is about 102.5% and 108.5% respectively.

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