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  HYDRAULIC LATERALLY EXTRUDED PILE: A METHOD TO ENHANCE THE BEARING CAPACITY OF PILE 1 Dinesh Bishnoi, 2 Venkateswarlu.P, 3 Swapnali S. Pawar, 4 Upendra M, 5 Jignesh B. Patel 1,2,3,4 Post Graduate student, 5 Assistant Professor, Applied mechanics department, SVNIT, Surat, Gujarat, India, Phone Number: 1 +91 8780093039, 2 +91 9904849487, 3 +91 7666469660, 4 +91 8178518767, 5 +91 9725757937. E-mail: 1 dineshbishnoi664@gmail.com, 2  pvenkateswarlu95@gmail.com, 3 swapnali9660@rediffmail.com, 4 upendarjntuk@gmail.com, 5  jig8107@gmail.com . ABSTRACT Constructions of foundation for heavy structure within confined spaces or on the areas which consist of  problematic soil is a challenge. Pile foundation is one of the solutions for the mentioned problem but for heavy structures plain pile may be uneconomical. In the present study a new pile (Hydraulically Extrude Pile (HEP)) is proposed, which acts as a plain pile while driving operation and after reaching the desired depth, extrusions along its shaft are embedded in to the soil. These extrusions provide additional bearing resistance to the pile. Plain pile and HEP were tested at three different relative densities (30%, 45% and 60%). The ultimate loads corresponding to 6mm (5 % failure criterion) settlement were determined for  both the piles at the above relative densities. The test results show that the HEP provided an increase in capacity of about 37% when compared with plain pile. As the relative density increases, the bearing capacity ratio of HEP and plain pile also increases. Keywords: Hydraulically Extruded Pile, Bearing capacity, Extrusions INTRODUCTION India is one of the fastest developing countries; the construction of heavy infrastructures and high rise  buildings is increasing continuously. Construction of foundation to support these heavy structures within confined spaces or on the problematic soil is a challenge. Pile foundation is one of the solutions for the above mentioned problem but for heavy structures, plain pile becomes uneconomical due to wider and longer piles. Thus there is need to enhance the capacity of pile by making some modifications in plain  pile. Considerable research has been conducted on the behavior of helical piles and anchors in various soil conditions using numerical modelling, laboratory and in situ tests (Abdelghany and EI Naggar, 2011; Ghaly et al., 1991; Iskander and Hassan, 1998; Juran and Komornik, 2006; Kurian and Shah, 2009; Livneh and EI Naggar, 2008; Tsuha et al., 2007, 2012; Wang et al., 2013). Koutsoftas (2002) studied several case histories on high capacity piles in very dense sand. One of the case had tubex piles of 406mm OD, 7.9mm thickness driven to depth of 14m. The results of load test data showed that tubex piles can develop very high capacities and can achieve significant penetrations into dense soils. The greater penetrations allow much higher capacities and compensate for the higher unit costs.Gorasia et. al. (2012) conducted series of tests on ribbed piles having variable rib spacing in kaolin clay. He reported that an increased ultimate bearing capacity can be achieved by modifying the profile of the shaft. There was an increase in capacity of about 3% to 57% for different rib spacing compared with the plain pile. The ribbed piles capacity was shown to be reduced with a large rib spacing (40mm) but consistently increase as the rib spacing was reduced. Furthermore, the difference between the improvement in the 10mm and 20mm spaced ribs was only 1%. This suggests an optimum spacing has  been found since the additional work required to install closer spaced ribs only increased the piles © 2018 Deep Foundations Institute 319  improvement by a small amount. A wider range of geometries will need to be tested to verify this. Qian et. al. (2017) studied the behavior of ribbed piles under pull-out tests. Both physical and numerical modelling were done to study the effect of S/D ratio in ribbed piles and to know the failure mechanism of ribs. Shear wedges were formed ahead of the ribs and these wedges connect to each other to form larger shear zones around the pile to increase the pile resistance. Under reamed piles are also efficient in increasing the capacity of the pile. Cai et. al. (2006) performed a series of static load tests to analyze the bearing capacity of bored piles with straight shaft and another with reamed enlargements. He found that compared to a reamed enlargement installed in clay soil, the reamed enlargement installed in sandy soil greatly loosened the soil around pile and resulted in lower value for  bearing capacity. The main objective of the study is to investigate the effect of extrusions on bearing capacity of pile and understand the settlement behavior of hydraulically extruded pile. To compare the results of both the piles (plain and HEP pile) in terms of bearing capacity and check the effectiveness of proposed pile.  About hydraulically extruded pile (HEP) Considering the findings of the mentioned authors a new pile named as Hydraulically Extruded pile (HEP) is proposed. HEP utilizes the advantage of tubex pile with additional provision of extrusions inside the annular space of pile. HEP acts as a plain pile while driving operation and after reaching the desired depth, extrusions along the shaft are embedded into the soil. These extrusions will provide multiple number of end bearing resistance to the pile and will also densify sand along the shaft due to displacement of sand by them. These extrusions also enable a large part of soil to bear the load and enhance the capacity of the pile. HEP can lead to economical and efficient solution by reduction in length and section of plain pile. In this paper the behavior and ultimate load capacity of HEP is compared with the plain pile. Effectiveness of HEP at different relative densities is also studied. MATERIALS  Sand Relatively uniform sand was used in the study.The specific gravity of the soil is 2.611. The particle size distribution is shown in Fig.1 and physical properties of the sand is shown in Table.1.The sand is classified is poorly graded sand (SP) according to USCS classification system. All the tests were  performed as per Bureau of Indian Standards (BIS). Fig. 1. Particle sizedistribution curve of the sand 0204060801000.01 0.10 1.00 10.00    %    F   i  n  e  r Particle Size (mm)Gradation Curve 320  Table 1. Physical properties of soil Property of sand Value Specific Gravity (G) 2.611 Effective size of particle (D10), mm 0.21 Mean size of particle (D50), mm 0.7 Coefficient of uniformity (Cu) 4.76 Coefficient of curvature (Cc) 0.76 USCS classification SP Minimum unit weight ( γ min ), kN/m 3  14.87 Maximum unit weight ( γ max ), kN/m 3  17.87 Angle of internal friction at 30% Relative density ( φ ) 28.44 Angle of internal friction at 60% Relative Density ( φ ) 38.29  Model pile The model pile used in the study was made up of Poly Vinyl Chloride (PVC) of hollow section. The outer diameter and height of the pipe are 120 mm and 320 mm, respectively. The thickness of pipe is 3mm for  both the piles. Two types of pile were used in the present study shown in Fig 2(a). The details of Piles are shown in Table 2. (a) (b) Fig. 2. (a)Plain pile and hydraulically extruded pile (HEP) with expanded extrusions. (b) Details of HEP. 321  Pile 1 (Plain Pile) is simple cylindrical in shape with closed end at the end became the simple bearing  pile. Pile 2 (Hydraulically Extruded Pile) consist of an arrangement in the annular space for the provisions of the extrusions. Plastic syringes were used as extrusion material. Total 4 nos. of extrusions were provided in two layers at vertical spacing of 50 mm and 100 mm from the bottom of the pile as shown in Fig. 2(b). The length of extrusions embedded into the sand was 55mm from the face of the pile. Table 2. Details of piles Total Length (mm) Effective Length (mm) Outer Diameter (mm) Thickness (mm) Provision of extrusions Pile 1 320 270 120 3 No Pile 2 320 270 120 3 Yes  Model box A cubical box of size 600mm×600mm×600mm (shown in Fig. 3) was prepared to conduct model compressive test on piles. The dimensions of the box were selected by considering the boundary effects from the pile. Three sides were made up of steel plates (1.02mm thickness) and fourth side was made up of acrylic glass sheet (6mm thickness) to check the relative density distribution throughout the depth. Fig.3 Model box used for the present study  METHODOLOGY The sand was placed in the box by rainfall technique to achieve constant relative density throughout the depth. Several trials were performed on mould of capacity 3000×10 3 mm 3 from heights of 50mm, 250mm, 450mm, and 650mm through a sand pouring jar having 20mm diameter hole. The respective relative densities obtained were 30%, 53%, 65%, and 73%. Back computations were done to determine the height of fall for relative density of 30%, 45% and 60%. The height of fall, relative density, unit weight and angle of internal friction is presented in Table 3. 600 mm 600 mm 600 mm 322
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