Presentations

Lateral Pile Capacity

Description
MODEL STUDIES ON IMPROVEMENT OF LATERAL CAPACITY OF PILES IN SAND.
Categories
Published
of 11
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Related Documents
Share
Transcript
  MODEL STUDIES ON IMPROVEMENT OF LATERAL CAPACITY OF PILES IN SAND E.Saibaba Reddy , Professor of Civil Engineering, JNTUH, esreddy1101@gmail.com   Rakesh Reddy.E, UG Student, JNTUH, rakesh15794@gmail.com  ABSTRACT : This paper presents the details of two series of experiments carried out on model piles embedded in sand. The test results are compared with the results obtained from an equivalent plain pile. The additions of attachments have shown considerable increase in the lateral capacity of a pile. For these piles, theoretical estimates are made and compared with the experimental results. The theoretical estimates and the experimental results are found to  be in good agreement. The second part of the paper presents the details of the test series carried out on model vertical piles under oblique pull. Experiments were carried out on three model piles of different lengths. The load and the displacement of the pile head were observed till failure of the pile. The uplift capacity is analyzed as a function of obliquity of load. The theoretical estimates of the pile capacity under oblique pull were made. Key word :  Pull-out, oblique, attachments, pile, capacity.   1.0   INTRODUCTION Lateral resistance of pile increases with depth up to a critical depth. Beyond this depth, the lateral capacity of a pile does not increase significantly with depth. The lateral capacity of a pile, in such a situation, can be improved by increasing its lateral dimensions. Broms has suggested a few attachments to pile [1, 2] at shallow depths, to improve its capacity to lateral loads. So far no attempts appear to have been made, either in laboratory or in field, to examine the effect of these attachments on the lateral capacity of a pile. An experimental investigation was carried out on model piles to study the effect of four attachments, suggested by Broms, in improving the lateral capacity of a pile. A number of investigations on vertical piles under inclined downward forces were reported [3,4,5,6] however, only a few references are available on the behavior of  piles under oblique pull [7,8,9] the second part of this paper presents the details of an experimental investigation carried out on vertical model piles under oblique pull. The tests were carried out under different oblique angles. The ultimate pullout capacity of  pile under oblique load observed during experiments is compared with the theoretical estimates. In the rest of this paper the details of the two series of experiments are  presented. The experimental results are compared with the respective theoretical estimates.   2.0 MODEL STUDIES Model laboratory studies were carried out on a number of model piles with and without attachment to improve the lateral capacity of piles. All tests were conducted on piles embedded in sand. The properties of sand used for the investigation, details of model piles used and the test procedure is explained below. 2.1 Soil Properties:  The sand used in both the test series was a dry angular silica sand having D 10  = 0.3mm and uniformity coefficient C u  = 2.8 was used. Direct shear test indicated a friction angle (Ø) of 35 o  for the initial porosity of n = 41% used in the tests, corresponding to a unit weight (γ) of 16 KN/m 3  and a relative density of D r   = 0.6 (60%).    2.2 Model Studies on Improvement of lateral Capacity of Piles  For this investigation a total of 15 model piles were fabricated with four types (Type-1, 2, 3 and 4) of attachments. Four piles were fabricated with attachment placed at different depths, along the pile (Table 1). Besides these piles, three plain piles (without attachments) were fabricated with different (360, 480 and 600mm) lengths. All piles were fabricated with steel rod of 12mm diameter. The details of each model pile are presented below. Table 1. Details of model tests Pile Model   Test Conditions   Remarks   Plain pile   D = 360, 480 and 600mm   --   Type  –   1   a = 100, 200 and 300mm   D = 600mm   Type  –   2   a = 100, 200 and 300mm   D = 600mm   Type  –   3   a = 100, 200 and 300mm   D = 600mm   Type  –   4   D = 360, 480 and 600mm   a = 50mm   Model pile type  –   1  In this, three 12mm diameter and 600mm long piles were fabricated; each was welded with a pair of two steel rods as shown in Fig. 1. The attachment was positioned at three elevations (a = 100, 200 and 300 mm) as shown in Fig. 1. Model pile type  –   2  In this, three 12 mm diameter and 600 mm long piles were used. Each of these piles was welded with a cross beam, of 12 mm diameter and 180mm long, at different elevations as shown in Fig. 2.    Hook for loading             2             d           a                   1             d            1         0         0      D  =   6   0   0   a= (d 1 +d 2 )/2 a=100, 200 and 300 Figure not to scale, All dimensions are in mm (a) Front view   12 mm dia. steel rods   Weldin   3.5   (b) Top view Fig.1 . Model Pile Type-1     a   180      D  =   6   0   0   a=100, 200 and 300 Figure not to scale All dimensions are in mm (a) Front view   12 mm   180   Fig.2. Model Pile Type-2      D  =   6   0   0   a=100, 200 and 300 Figure not to scale  All dimensions are in mm   (a) Front view   Vanes   (b) Top view   Fig.3. Model Pile Type-3    Model pile type  –   3  The third model was developed by welding four vanes as shown in Fig. 3. The vane dimensions and their locations are presented in Fig. 3. Model pile type  –   4  The fourth model pile was fabricated by welding a large (40 mm) diameter rod of 100mm long over the 12 mm diameter pile as shown in Fig. 4. In this model, unlike other three models, different trials were made by changing the length of the pile as shown in Fig. 4. This was achieved by testing initially with a total length of 600mm then for the next trials the pile length was cut from the bottom, to obtain a total length of 480mm and 360mm as shown in Fig. 4. Method of sand filling and pile installation  The sand was placed in a circular tank of internal diameter 1120 mm and 1200 mm high (Fig.5). The tank was filled with sand in layers of 100 mm thick. Each layer was compacted, with a rammer under a constant height of fall, to ensure a constant unit weight of 16 kN/m 3 . The density of sand was measured by placing a number of containers along the depth of the tank (Reddy, 1986).The pile was installed by jacking gradually into the sand up to the required embedded depth. Dial Gauge   Hook for loading      1   2   0   0   Pile   sand   1120   Pulley   Test   Load   Brick   Masonry      D  =   6   0   0            1         0         0   40   D=360, 480 and 600 Figure not to scale  All dimensions are in mm   (a) Front view 40 mm Dia   Figure not to scale All dimensions are in mm Fig.5. Details of test tank (b) Top view Fig.4 .Model Pile Type-4 Pile Loading After installation of the pile, a dial gauge (least count 0.002 mm) was positioned to measure the horizontal deflection of the pile head. The horizontal load was applied at the pile head  by means of a wire rope passing over a pulley mounted on to the side of the tank as shown in Fig. 5. The load on the pile head was increased in steps of about 10 N. The horizontal

Fact Sheet 3Q14

Jul 23, 2017
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks