Analysis of Pile Group under Lateral Load

Artikel terkait : Analysis of Pile Group under Lateral Load

Abhijit Deka

Assistant Professor, Department of Civil Engineering, Central Institute of Technology Kokrajhar, Assam, India. Email: a.deka@cit.ac.in 

ABSTRACT 

      The pile cluster foundation may be a geotechnical composite construction, consisting of the 3 parts piles, pile cap and therefore the soil, that is applied for the inspiration of tall buildings in associate degree increasing variety. The behavior of the inspiration system is set by complicated interaction effects between the weather associate degreed an understanding of those effects is crucial for a reliable style. This study presents the 3 dimensional finite part analysis of pile cluster foundation below lateral load by exploitation ANSYS software system. The soil is sculptured to be pure clay and is assumed as undiversified and isotropic  within the analysis. Elasto-Plastic behavior of the soil is numerically sculptured to follow Drucker–Prager Yield criterion. The study doesn't take into consideration the event of pore water pressure within the soil since the load applied is instant. A constant quantity study was conducted to review the behavior of pile teams below lateral load with numerous configurations. The impact of pile length, pile diameter and configuration of piles within the cluster were studied. during this study, the spacing of piles and length to diameter (L/D) magnitude relation were altered.

INTRODUCTION

       Many buildings and structures need the employment of deep foundations to utilize the bearing  capability of stronger soil layers. Pile teams square measure one specific variety of deep foundation unremarkably used for big structures [1-3]. additionally to vertical masses that has to be sustained by the piles, vital lateral masses is also gift and should be accounted for in style [4 -8]. These lateral masses will come back from style of sources like wind forces, collisions, wave or ice impact, earthquake shaking, phase transition and slope failure [9-10].

      Investigation of nonlinear response of pile teams is a vital issue within the analysis and style of the many applied science structures like bridges, high rise buildings and towers etc. [2]. In past, several analytical/numerical ways for analysis of pile teams have utilized simplified assumptions like replacement the soil medium by Winkler springs, treating the soil medium as associate degree elastic time [11-12], and neglecting the interaction between numerous elements (namely, the pile-cap, the piles and therefore the soil medium).

      The present study was directed at understanding the response of heaped-up cluster foundation subjected to lateral masses in clay soil. The analyses were performed to review the impact of pile length and pile diameter on the lateral load carrying capability of the pile cluster with increasing spacing between the piles. The impact of pile cluster configuration was additionally studied here. 

MODEL DESCRIPTION, MATERIAL PROPERTIES AND BOUNDARY CONDITIONS

      A three dimensional model of pile and soil was used for this study as shown in Fig. 1. The soil was sculptured to be pure clay and was assumed as undiversified and isotropic  within the analysis. Elasto-Plastic behavior of the soil was accustomed follow Drucker-Prager Yield criterion. The study didn't take into consideration the event of pore water pressure within the soil since the load applied was instant.

      Soil was initial discretized 2-dimensionally by four noded plane eighty two solid parts, that was later extruded with 20-noded brick part (ANSYS manual four.2). Again, pile and pile cap were discretized 2-dimensionally by four noded plane forty two solid parts, that were extruded with 20-noded brick part.

      The boundary conditions were thought of as a correct restrain on the mesh. The nodes happiness to the fringe of the mesh were mounted against displacement in each horizontal directions; nevertheless stay liberated to have displacement vertically. The nodes constituting very cheap of the mesh were mounted against displacement in each horizontal and vertical directions as shown in Fig. 2

      Two varieties of material were thought of within the pile-soil model. The property of concrete was appointed for the pile, whereas soil properties (Clay) were appointed for the soil. the main points of the various properties got in Table 1.

RESULTS AND DISCUSSION

      Though there square measure several factors that have an effect on the response of the pile behavior, solely 3 major factors were thought of during this study. These square measure divided into 3 cases as mentioned below.
Case 1: lateral load capability of 1x2 pile cluster below variable length and glued diameter.
Case 2: Lateral load capability of 1x2 pile cluster below mounted length and ranging diameter.
Case 3: impact of pile cluster configuration on lateral load capability.

      Here, the pile length (L) and diameter (D) square measure chosen in such the way that the L/D magnitude relation remains same for each Case one and Case a pair of. every of the higher than mentioned case has been mentioned severally below.

Case 1: lateral load capability of 1x2 pile cluster below variable length and glued diameter.

      The arrangement of the pile for this case is shown in Fig. a pair of with detail specification as mentioned in Table a pair of. it absolutely was discovered from Fig. three that lateral load carrying capability remains virtually same with increase long of pile within the pile cluster. Again, for all the 3 lengths of the pile (6.0m, 8.0m and 12.0m), the lateral load carrying capability will increase with increase in spacing between the piles. this can be owing to the very fact that because the spacing will increase step by step, the overlap of stress zone of of the individual pile within the cluster decreases, which ends in a rise in load carrying capability of the pile cluster.

Case 2: Lateral load capability of 1x2 pile cluster - Length mounted and diameter variable

      Fig. 4 shows the arrangement of the piles within the cluster for the second case. The specifications square measure listed in Table three below and therefore the results obtained square measure shown in Fig. 5. during this case, the lateral load carrying capability of the pile cluster will increase significantly with the rise in diameter of the piles. because the diameter will increase, the expanse of the piles will increase which supplies additional resistance to the lateral load.

      Based on the results of Case one & Case a pair of, it are often finished that increasing L/D magnitude relation merely didn't increase the the load carrying capability. It depends on the diameter of the piles that is that the main think about increasing the lateral load carrying capability.

Case 3: impact of pile cluster configuration on lateral load capability

      The impact of pile cluster configuration was studied by considering 1x2, 2x2 and 1x3 pile teams as shown in Fig. 1, half-dozen and seven severally. The specifications square measure listed in Table 4.

      Horizontal masses square measure applied at the highest as shown within the figure and therefore the results were premeditated in Fig. 8. it absolutely was found that in an exceedingly pile cluster the direct action depends on the orientation of the piles within the cluster. during this case, each 1x3 and 2x2 pile cluster has identical numbers of pile i.e. 4, however the resistance of the 1x3 pile cluster became over the 2x2 pile cluster. this can be owing to the rise within the volume of soil between the piles in 1x3 than in 2x2 pile cluster that will increase the direct action of the group.
 

CONCLUSIONS

      Based on the results of this study, the subsequent conclusions are often created associated with the influence of horizontal load on lateral response of a pile cluster.

• The increase in L/D magnitude relation of pile didn't offer any increase in lateral load capability of pile cluster if the diameter is unbroken constant and length changes.
• The lateral load carrying capability of a pile cluster will increase with the rise in diameter of the piles.
• The lateral load carrying capability of a pile cluster will increase with the rise in spacing between the piles.
• The direct action offered by a pile cluster depends on the orientation of the piles within the cluster. once the quantity of soil between the piles will increase, the resistance of the pile cluster againstthe lateral load additionally will increase.

REFERENCES

 

1. Phanikanth V S, Choudhury D, Reddy C R. “Response of Single Pile under Lateral Loads in Cohesionless Soils” [J]. Electronic Journal of Geotechnical Engineering, 2010(15): 813-830.
2. Zhao M H, Liu D P, Zhang L, Jiang C. “3D Finite Element Analysis on Pile-Soil Interaction of Passive Pile Group” [J]. Cent. South Univ. Technol., 2008(1): 75−80.
3. Poulos H G, Davis E H. “Pile Foundation Analysis and Design”. John Wiley & Sons, New York, 1980.
4. Feng C, Sanshan C, Guoping, J. “Response Characteristics of Pile Foundation under Coupled Loads” [J]. Electronic Journal of Geotechnical Engineering, 2014(19): 10419-10428
5. Zadeh N G, Kalantari B. “Performance of Single Pile under Vertical and Lateral Load in Sand, Clay and Layered Soil” [J]. Electronic Journal of Geotechnical Engineering, 2011(16): 1131-1146.
6. Karthigeyan S, Ramakrishna V V G S T, Rajagopal K. “Influence of Vertical Load on the Lateral Response of Piles in Sand” [J]. Computers and Geotechnics, 2006(33): 121–131.
7. Wu D, Brooms B B, Choa V. “Design of Laterally Loaded Piles in Cohesive Soils Using p-y Curves” [J]. Soils and Foundations, 1998, 38(2): 17-26.
8. Brown D A, Shie C F. “Three Dimensional Finite Element Model of Laterally Loaded Pile” [J]. Computers and Geotechnics, 1990(10): 59–79.
9. Mostafa Y E. “Design Considerations for Pile Groups Supporting Marine Structures with Respect to Scour” [J]. Scientific research, 2012(4): 833-842.
10. Basack S, Bhattacharya A K. “Influence of Lateral Cyclic Load on Pile Foundation with Emphasis on Disturbance at Ground Surface” [J]. Electronic Journal of Geotechnical Engineering, 2009(14): 1-11
11. Bouzid D A, Bhattacharya S, Dash S R. “Winkler Springs (p-y curves) for Pile Design from Stress-Strain of Soils: FE Assessment of Scaling Coefficients using the Mobilized Strength Design Concept” [J]. Geomechanics and Engineering, 2013(5): 379-399.
12. Abbas J M, Chik Z, Taha M R. “Influence of Group Configuration on the Lateral Pile Group Response Subjected to Lateral Load” [J]. Electronic Journal of Geotechnical Engineering, 2010(15): 761-772.