Analysis Study of Lateral Bearing Capacity and Deformation of Square and Circular Concrete Piles as an Alternative Structure for Infrastructure Projects

Piles are one type of foundation that used to transmit the load acting on a structure to the ground below. The required embedment length value depends on the load acting on the superstructure, pile specifications, and soil type. This study was conducted to analyze the lateral bearing capacity and lateral deformation that occurred on square and circular piles with sizes of 30 cm, 35 cm, 40 cm, 45 cm and 50 cm with embedment lengths from 1 meter to 15 meters. The type of soil under review is cohesive soil. The calculation method used is the Broms’ Method and computer software. The results of the analysis show that the lateral bearing capacity of square piles is greater than that of circular piles. The change in L/d ratio does not affect the magnitude of the lateral bearing capacity of rectangular and circular long piles. The resulting lateral deflection value also does not exceed the allowable limit (2.54 cm).


Introduction
The construction of any structure begins with laying a foundation base that bears the weight of all beams, columns, walls, slabs and other household materials [1].Therefore having a strong and solid foundation is a must.Foundations are basically classified into two broad categories.For low-rise houses and bungalows, shallow foundations are used and for high-rise buildings and houses, deep foundations are used [2].A thorough understanding of soil and soil conditions is a must for foundation construction as it plays a major role in understanding the behaviour of the structure, what materials to use and whether the structure will stand firm for a long time or not.So before building any foundation, it is very important to study the type of soil [3].The purpose of the foundation is to distribute the load of the structure over a wide bearing area to carry the load intensity within the safe bearing capacity of the soil beneath it, to load the bearing surface at a uniform rate to prevent uneven settlement, to prevent lateral movement of supporting materials, and to increase the stability of the overall structure.Bearing capacity is the strength of the foundation soil to withstand forces from the superstructure without experiencing shear failure or excessive settlement [4].Foundation soil is that part of the soil that is subjected to additional stress when foundations and superstructures are built on the ground.Foundations transfer forces and moments from the superstructure to the ground below in such a way that stresses in the soil are within permissible limits and provide stability.Soil deformation is a change in the shape or volume of the soil mass accompanied by vertical or lateral movements due to the influence of external loads.The importance of studying deformation in soil is that soil mass deformation affects soil permeability, soil bearing capacity changes with soil deformation due to an increase or decrease in volume, and the safety of buildings and other structures depends on the type and amount of deformation.The bearing capacity and lateral deformation studies with piles discussed in this study can be used as a reference in the construction of retaining wall projects.The size of the retaining wall used is 7 meters wide and 5 meters high, because this size can withstand the lateral forces acting on the retaining wall by adding earthquake loads.The pile shapes used are square and circular piles where the two pile shapes are the most widely used pile shapes in the project.
The purpose of the research in this study was to calculate the lateral bearing capacity and lateral deflection of piles with different shapes, sizes and types of soil, as well as to compare the results of the analysis using computer software with the results of manual calculations obtained.

Methodology
The method used in this study was to identify previous problems, then study the literature and collect the data through SPT and laboratory test (Table 1 and Figure 1).After the data is obtained, an analysis of the lateral bearing capacity is carried out on concrete piles with square and circular shapes with sizes of 30 cm, 35 cm, 40 cm, 45 cm and 50 cm using manual calculations with the Broms Method and using the aid of the computer software.After analyzing the lateral bearing capacity, lateral deflection analysis is carried out on rectangular and circular concrete piles using the broms method and the computer software.After the lateral bearing capacity and lateral deflection values are obtained, the results then will be compared.For the manual calculation method using the Broms method [5], first determine the type of pile stiffness, namely short pile (rigid pile) or long pile (elastic pile) with the formula below.If L < 2.5 then it is classified as a short pile, conversely, if L > 2.5 then it is classified as a long pile.
Then for the calculation of the lateral bearing capacity values can use the graph as shown in Figure 2 and Figure 3.

Result and Discussion
The results of the lateral bearing capacity of circular and square concrete piles can be seen in following figures.

Conclusion
After analyzing the lateral bearing capacity with maximum deflection values for circular and square piles with various diameters and embedment lengths using the Broms method and computer software, it can be concluded that circular piles with diameters of 35 cm, 40 cm, 45 cm, 50 cm and square piles with dimensions of 30 cm, 35 cm, 40 cm, 45 cm and 50 cm with a embedment length of 15 meters can be used in a retaining wall project with a width of 7 meters and a height of 5 meters due to the value of the lateral force acting on the retaining wall is smaller than the lateral bearing capacity of each pile.The lateral deflection value that occurs in the pile foundation does not exceed the allowable lateral deflection limit stated in SNI 8460-2017 [6], which is 2.54 cm.

Figures 4
Figures 4 show a comparison of the lateral bearing capacity of circular piles of various dimensions to the embedment length.

Figure 4
Figure 4 The Lateral Bearing Capacity (Hu) of Circular Piles to the Embedment Length

Figure 5 Figure 6 6 Figure 7
Figure 5 The Lateral Bearing Capacity of Various Diameter of Circular Pile Using Broms Method

Figure 8 Figure 9
Figure 8 The Lateral Bearing Capacity of Various Dimension of Square Pile Using Broms Method

Figures
Figures 10 and 11 show a comparison of the lateral deflection values with respect to embedment length and pile dimensions for circular concrete piles.

Figure 10 Figure 11
Figure 10 Comparison of Lateral Deflection Values with Circular Pile Embedment Length

Figure 12 Figure 13
Figure 12 Comparison of Lateral Deflection Values with Square Pile Embedment Length

Table 1
Summary of Laboratory Test Result