MATEC Web of Conferences 162, 01004 (2018) https://doi.org/10.1051/matecconf/201816201004 BCEE3-2017

Simulation of of bored piles

Ahmed Majeed1,*, Olla Haider1

1 Building and Construction Engineering Department, University of Technology, Baghdad-Iraq

Abstract. This study focuses on how one can possibly predict the ultimate load for the piles that did not reach failure. This challenge was acquired through Chin- Konder method by which, the estimated settlement that correspond to failure load is defined. Hence, this research aims to make a comparative study between the results of pile load tests carried out in Al-Basrah sewage treatment plant project, and those results induced from the numerical analysis in term of ultimate pile capacity. Consequently, it may give a clear idea on the ability of numerical simulation in getting close to the actual behavior of piles. In the current study, a numerical study using Plaxis 3D program has been performed on bored piles by the assistance of site investigations of . Mohr- Coulomb and linear elastic models were adopted in the simulation for soil and pile respectively. Ten bored piles were used in this analysis under different values of loading. The diameter and length of pile are 0.6m and 24m respectively. The test results indicate that, an excellent agreement has been found as a response of pile capacity between the field and numerical studies. Also, ideal load- settlement curves were created using Chin- Konder method to predict the failure load of bored piles. Also, the results have demonstrated that, the pile capacity obtained from the simulation process is larger about 51% than that design load estimated before the design of piles. This may present a priority to use the finite element method to be accounted as an effective approach in the primary analysis.

1 Introduction Herein, the pile load test is normally carried out to verify and to check the response of foundations in term of bearing The noticeable disparity in pile design techniques and the uncertainties associated to the traditional theories due to the huge numbers of parameters involved in analysis, capacity and settlement. The major challenge in this necessitates that to alternative analytical ways is essential concern is not how to get the design load of pile, but to account for the whole behavior of piles. In this study, a estimation of the behavior of pile that did not reach to numerical modeling using Plaxis 3D Foundation failure is still dialectical. Thus, restoring to alternative was performed on bored piles placed into layered soil to approaches to expect the actual work load would be greatly validate the field test results which has been implemented required. There are several studies related with this scope, under same conditions. [7] demonstrated that, for 1.2m diameter bored cast in-situ Thereupon, the traditional methods for calculating the piles executed in residual , a reasonable agreement has problems of pile bearing capacity are still insufficient to be been gained between the ultimate pile capacity obtained accounted in design. As presented, the simplified analysis from the finite element analyses in 2D Plaxis and full scale for the conventional theories ignore some of the facets tests. The values of pile settlement in both analysis were involved making the solutions inaccurate and deficient to 2.6 and 4.9mm under the maximum load equal to 825 tons. be relied unless verified by certain reliable methods. [8] analyzed the results of four static pile load tests and a Thus, the main role for using the finite element method, is these results have been validated using Plaxis 3D to thoroughly understand and realize some of the practical Foundation program. The model used in the analysis is aspects of bored piles which are hard to obtain using the Mohr coulomb. The pile length and diameter are 9m and conventional design methods. These traditional methods 0.62m respectively. Plaxis and in-situ measured load- have emerged over years to afford conservative solutions displacement curves showed a good correlation. seeking the cost and safety, therefore it is important to [4] carried out a comparative study in order to assess the revise and adjust the bearing capacity with those results behavior of driven piles which have a diameter of 0.35m obtained from the field load tests especially for strategic and embedded length of 10- 12m supported 8 stories- projects. building. The case study compared the field results with

* Corresponding author: [email protected]

© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).

MATEC Web of Conferences 162, 01004 (2018) https://doi.org/10.1051/matecconf/201816201004 BCEE3-2017

numerical simulation using Plaxis 2D. The result of finite N values N values N values element analysis shows that the ultimate axial capacity is 0 10 20 30 40 50 0 10 20 30 40 50 in good convergence with the axial capacities obtained 0 10 20 30 40 50 0 0 using empirical method and field results. 0 5

5 [6] Found out that, the simulation of cast in situ piles with

5 10 a diameter of 620mm and penetration length equal to 15m 10 10 is an effective method in design. The piles were installed 15 15 15 in , and the numerical analysis has been done (m) Depth

Depth (m)Depth 20 Depth (m)Depth 20 20 using Plaxis 3D software. The test results displayed a 25 B.H1 pronounced agreement between the two studies in term of 25 B.H5 25 B.H9 30 load- settlement curves. 30 30

[10] Performed a numerical analysis on a bored pile with dimensions of 0.6m diameter and 26m in length, and N values subjected to axial load using 2D Plaxis software. 0 10 20 30 40 50 N values N values 0 10 20 30 40 50 According to the details, the pile is penetrated in 0 0 10 20 30 40 50 a clayey silt and decomposed of organic matter. The 0 0

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simulation results in 2D Plaxis showed a good agreement 5 5 10 between the field and the finite element results. 10 10 In summary, this research displays a numerical 15

Depth (m) Depth 15 15 20 investigation for the bored piles executed in Al-Basrah (m)Depth Depth (m)Depth 20 20 sewage treatment project and a comparison of pile capacity 25 B.H2 25 B.H6 25 is performed with the field results at failure to understand 30 B.H10 30 how far the numerical approaches get close to field ones. 30

N values 2 Site investigation and soil details N values Fig.1. Variation of standard penetration values (N) with depth for 0 10 20 30 40 50 different 0 10 20 30 40 50 0 0 The project is located at Hamdan region which is a part of

5 (%) 5 Al-Basrah governorate. The field explorations were carried 10 0 5 10 15 20 25 30 35 40 45 50 out on the soil layers to obtain their characterization. Ten 10 boreholes were made at different zones, each one describes 15 0

Depth (m)Depth 15

5

stratification of soil under a certain structure. According to 20 (m)Depth 20 [2], drilling was performed using flight auger. The 25 B.H3 10 undisturbed samples marked (U) were obtained using 25 B.H7 15 30 Shelby tubes. Split spoon samples (SS) were obtained from (m)Depth 30 20 standard split spoon used in a Standard Penetration Test 25 B.H1 (S.P.T), which was performed for each test boring at N values 30 different intervals depending on the stratification of the 0 10 20 30 40 50 N values soil. 0 0 10 20 30 40 50 The N-Values for S.P.T. and the variation of water content 5 0 Water Content (%) with depth are shown in Figures (1) and (2) respectively. 10 5 0 5 10 15 20 25 30 35 40 Then, the N values are corrected by taking a percent of 10 0 15 60% (N60) and the water content values are somehow 15 Depth (m)Depth 5

useful to calculate the unit weight of the soil in different 20 Depth (m)Depth 20 cases (wet or saturated), which are basically required in the 10 25 B.H4 25 B.H8 numerical analysis. 15 The soil investigation along the depth of boreholes exhibits 30 30 Depth (m)Depth 20 that, the type of brown/gray silty or clayey silt with some organic matters or salts at certain depths was shown 25 B.H2 to be prevailed. Further drilling up to 21m presented sillty 30

sand to dense sand and beyond which the soil is very dense sand with N-values up to 50 according to soil report.

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MATEC Web of Conferences 162, 01004 (2018) https://doi.org/10.1051/matecconf/201816201004 BCEE3-2017

N values N values 0 10 20 30 40 50 0 10 20 30 40 50 0 0

5 5

10 10 15 15 Depth (m) Depth

Depth (m)Depth 20 20 25 B.H5 25 B.H9 30 30

N values N values 0 10 20 30 40 50 0 10 20 30 40 50 0 0

5 5

10 10 15 15 Depth (m)Depth Depth (m)Depth 20 20 25 B.H6 25 B.H10 30 30

N values Fig.1. Variation of standard penetration values (N) with depth for 0 10 20 30 40 50 different boreholes 0 5 Water Content (%) 0 5 10 15 20 25 30 35 40 45 50 10 0 15

5 Depth (m)Depth 20 10 25 B.H7 15 30 (m)Depth 20 25 B.H1 30 N values 0 10 20 30 40 50 0 Water Content (%)

5 0 5 10 15 20 25 30 35 40 10 0 15 5

Depth (m)Depth 20 10 25 B.H8 15 30 Depth (m)Depth 20 25 B.H2 30

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MATEC Web of Conferences 162, 01004 (2018) https://doi.org/10.1051/matecconf/201816201004 BCEE3-2017

Water Content (%) Water Content (%) 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 0 0 5 5

10 10 15 15

20 (m)Depth 20 Depth (m)Depth 25 B.H3 25 B.H7 30 30

Water Content (%) Water Content (%) 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 0 0 5 5

10 10 15 15

Depth (m)Depth 20 Depth (m)Depth 20 B.H4 25 25 B.H8 30 30

Water Content (%) Water Content (%) 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 0 0

5 5 10 10 15 15 Depth (m)Depth

20 (m)Depth 20 25 B.H5 25 B.H9 30 30

Water Content (%) Water Content (%) 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 0 0

5 5 10 10 15 15 Depth (m)Depth 20

Depth (m)Depth 20 25 B.H10 25 B.H6 30 30

Fig.2. Variation of water content values with depth for different boreholes. An exhaustive analysis was made to obtain the soil properties for each type. The values of specific gravity, and the unit weights at dry and saturated states for each layer which empanel within the physical soil characterization were calculated based on the visual with the aid of water content logs. The parameters which are basically relied on specimens extracted from undisturbed samples were obtained (undrained shear strength cu) especially for the

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MATEC Web of Conferences 162, 01004 (2018) https://doi.org/10.1051/matecconf/201816201004 BCEE3-2017

Water Content (%) Water Content (%) fine grained soil, nonetheless for some reason there were project. The structures that were supported by these piles depths at which no samples had been taken, the shear and their function are presented in Table 2. The diameter 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 0 strength details were induced based on standard values and length of piles used are 0.8 and 24m respectively. The 0 found by [9] which stipulate that the N-values and soil pile load tests were carried out on working and trial piles 5 5

consistency must be known. by means of Kent ledge dead weights according to [1]

10 10 The stiffness properties