Vol.:(0123456789) 1 3 International Journal of Civil Engineering https://doi.org/10.1007/s40999-018-0388-7 RESEARCH PAPER Load–Displacement Behavior of Driven Piles in Sand Using CPT-Based Stress and Strain Fields Fatemeh Valikhah 1  · Abolfazl Eslami 1  · Mehdi Veiskarami 2 Received: 24 September 2018 / Revised: 24 November 2018 / Accepted: 10 December 2018 © The Author(s) 2018 Abstract The bearing capacity of piles is often estimated by a variety of methods such as the limit equilibrium or the limit analysis. In contrast, the load–displacement behavior, which should not be disregarded in common practices, cannot be obtained as simply as the bearing capacity. The reason is its dependency on the stress and the strain (or the displacement) felds around the pile. In the current work, attempt has been made to predict the load–displacement behavior of driven piles in sand by direct and indirect implementation of the cone penetration test (CPT) data into the displacement feld. CPT often serves as a very successful in situ test which provides a close link between the soil resistance and the bearing capacity, although it brings no direct information. A rather simple procedure is presented to indirectly use the CPT data to fnd the stress and strain felds. While the pattern of the failure mechanism has been obtained by the method of stress characteristics, the dis- placement (and strain) feld has been found by the kinematics of the failure mechanism. The proposed procedure has been calibrated and verifed by 98 case histories including pile load test results in conjunction with CPT data. Comparisons made by this new method show that the CPT-based method of stress characteristics can be successfully used in load–displacement prediction of driven piles. Keywords Pile · CPT · Load–displacement · Stress characteristics method · Displacement feld 1 Introduction Estimation of the bearing capacity of piles has been always a challenging issue for geotechnical engineers due to inher- ently complex behavior of soil, relatively long length extend- ing into a variety of soil layers, deep embedment depth and soil–pile interaction. There are several diferent methods to estimate the bearing capacity of piles: (a) static analysis methods, (b) direct and indirect use of in situ test results, (c) static load test and (d) dynamic methods [1, 2]. Studies show that the bearing capacity may be far difer- ent from the reality if the deformations are neglected [3]. In addition, unless under ideal conditions, such as a rigid-per- fectly plastic materials, there is no precise and unique defni- tion of limit load for footings and piles. As a consequence, the bearing capacity and load–displacement analysis should be accomplished simultaneously, or, in other words, the frst should be determined from the second. The load–displace- ment behavior of piles is often obtained by conducting a pile load test which is very costly and time consuming; or by complicated fnite element modeling, which in turn requires a great deal of efort to properly defne the soil properties to be considered in the analysis. There are also some simplifed methods primarily based on statistical observations ( t -  and q -  curves) which are only rough estimates to obtain satisfactory results. In this study, a semi-analytical method with a theoretical basis based on a universally accepted and commonly used feld test (cone penetration test, CPT) has been proposed. For this purpose, the CPT data, as a very useful tool due to its repeatability, accuracy and continuity of the records [4, 5] has been employed. The procedure comprises three diferent * Abolfazl Eslami afeslami@aut.ac.ir Fatemeh Valikhah fvalikhah@aut.ac.ir Mehdi Veiskarami mveiskarami@gmail.com; mveiskarami@shirazu.ac.ir 1 School of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Islamic Republic of Iran 2 Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Islamic Republic of Iran