Lateral load-deflection behaviour of single piles - An analysis of the small pile deflections

Size: px

Start display at page:

Download "Lateral load-deflection behaviour of single piles - An analysis of the small pile deflections"

Anabel Blake
6 years ago
Views:

1 Lateral load-deflection behaviour of single piles - An analysis of the small pile deflections Abderrazak Tharrafi 1, and Ali Bouafia 1,* 1 University Saâd Dahleb at Blida, Faculty of Technology, Dept. Civil. Engineering, P.O.Box: 270 R.P Blida 09000, Blida, Algeria Abstract. The paper aims at presenting a simple method for estimating the pile head deflections on the basis of the interpretation of a full-scale vertical pile loading test. On the basis of theoretical considerations and the analysis of many full-scale pile loading tests, it has been shown that a similarity exists between the loading curve of a vertical loading and that of a lateral loading which leads to derive a ratio of initial lateral stiffness to initial vertical stiffness from these curves as a function of the pile slenderness ratio and the pile/soil stiffness ratio. From the results of a vertical loading test on an identical pile, it is therefore possible to estimate the pile head deflections on the basis of such a ratio. * Corresponding author: ali.bouafia@univ-blida.dz

2 Source parameters and fault plan solutions of July 18 and 22, 2014 Gulf of Suez earthquakes, Egypt Abd el-aziz Khairy Abd el-aal and Gad-Elkareem A. Mohamed National research institute of astronomy and geophysics, Helwan, Cairo, Egypt Abstract - In the current work, we computed recent seismicity and present kinematic regime in the northern and middle parts of Gulf of Suez as inferred from moment tensor solutions and focal mechanism of local earthquakes that occurred in this region. On 18 and 22 of July, 2014 two moderate size earthquakes of local magnitudes 4.2 and 4.1 struck the northern part of Gulf of Suez near Suez City. These events are instrumentally recorded by Egyptian National Seismic Network (ENSN). The events have been felt at Suez city and greater Cairo metropolitan area while no casualties were reported. The source mechanism and source parameters of the studied earthquakes were estimated using the near-source waveform data recorded by very broadband stations and validated by the P-wave polarity data of short period stations. The new inversion method and software used in this study treat the effect of the source time function, which has been neglected in most of the program sets of the moment tensor inversion analysis with near source seismograms. The obtained results from inversion technique indicate that the estimated seismic moments of both earthquakes are E+15 Nm and E+15 Nm corresponding to a moment magnitude Mw 3.8 and 3.7 respectively. The fault plan solutions obtained from both inversion technique and polarity of first-arrival indicate the dominance of normal faulting. Key words: focal mechanism; source parameters; inversion method; Gulf of Suez; Egyptian National Seismic Network (ENSN)

3 Laterally loaded single piles in sand - centrifuge modelling Hocine Haouari 1, Ali Bouafia 1, 1 University Saâd Dahleb at Blida, Faculty of Technology, Dept. Civil. Engineering. P.O.Box: 270 R.P Blida 09000, Blida, Algeria Abstract. The analysis of lateral load-deflection behaviour of single piles is a key parameter of serviceability limit states design as well as ultimate limit states design of pile foundations, and an important field of research on pile-soil-structure interaction. However, the response of a laterally loaded pile is a rather complex problem of soil/pile interaction due to the three-dimensional character of the lateral soil reaction, the diversity of key mechanical and geometrical parameters and the inherent nonlinearity in soil behaviour. The aim of this paper is to present the main experimental results obtained by centrifuge modelling of small-scale models of single piles embedded in sandy soil undertaken in the IFSTTAR centrifuge (Nantes, France).The centrifuge tests were undertaken to highlight the separate effects of the density of the sand, the pile installation method and the roughness of the pile/soil interface on the P-Y curves. These latter were derived by first fitting the experimental bending moments profile along the pile model and then double differentiating and double integrating such a profile to determine respectively the soil reaction P and the pile lateral deflection Y. The P-Y curves were then interpreted and the experimental profiles of the subgrade reaction modulus and the soil lateral resistance were determined. Corresponding author: ali.bouafia@univ-blida.dz

4 Comparative study of four consolidation settlement estimation methods of a railway embankment. Ahcène Benamghar 1,, and Mohamed Boudjellal 2 1 LTPiTE Laboratory, ENSTP, 1 Rue Garidi Kouba, Algiers, Algeria 2 ENSTP, 1 Rue Garidi Kouba, Algiers, Algeria Abstract. Embankment is one of the oldest and most common constructions of public works due to its low cost, simplicity and good performance. This is why it is often required for economic reasons even if underlying soil is of poor quality. Meanwhile, this is not without risk, since we notice sometimes significant damages such as intolerable settlements, landslides and erosion. These risks are particularly dangerous in the case of railways where tolerances are mainly severe. In this work we propose a comparative study of four theoretical methods for estimating the consolidation settlement of a railway embankment. These methods are Terzaghi (1925), Asaoka (1978), Tan (1995) and Chunlin (2014). We applied each method to estimate the final settlement of the 15m high embankment at PK of the railway under construction Boughezoul- M sila (Algeria). Corresponding author: a.benamghar@enstp.edu.dz

5 P-Y curves for single piles under lateral loads finite elements modelling Hocine Haouari 1, Ali Bouafia 1,, Amina Lachanani 2, and Dalila Tachet 1 1 University Saâd Dahleb at Blida, Faculty of Technology, Dept. Civil. Engineering. P.O.Box: 270 R.P Blida 09000, Blida, Algeria 2 University Yahia Farès at Médéa, Faculty of Technology, Dept. Civil. Engineering , Médéa, Algeria Abstract. Due to the 3D aspect of the pile/soil interaction under lateral loads and the inherent nonlinearity of the soil behaviour, the FEM analysis may be used as a powerful numerical modelling to investigate such an interaction. This latter is governed by many key factors, such as the pile slenderness ratio and the lateral pile/soil stiffness ratio. Moreover, a realistic analysis of such an interaction should take into consideration the non homogeneity of the soil properties. The P-Y curve describes a local relationship at a given depth along the pile between the lateral soil reaction P undertaken by a nonlinear spring at the pile/soil interface and the lateral pile displacement Y at the same depth. The aim of this paper is to contribute to the construction of P-Y curves on the basis of a detailed numerical modelling by finite elements method. Parametric study was carried out to investigate the effects of many factors on the P-Y curves. The Tresca's perfectly elastic plastic model was used to describe the soil non linearity, and pile/soil interface elements have been introduced to take account of the possibility of separation of the pile from the soil. Moreover, a linear elastic finite element model was built to analyse the influence factors usually used to compute the small pile head deflections and derive simple analytical formulae for computation purposes. Finally, backanalysis procedure was undertaken on the basis of an FEM computation in order to estimate the gradient of an assumed linear profile of the elastic modulus of a sandy mass containing a small-scale model pile tested in centrifuge. This gradient was then correlated to the cone resistance measured in sand during centrifugation, which leads to a practical formula for estimation of the soil modulus in Gibson's soil. Corresponding author: ali.bouafia@univ-blida.dz

6 Relationship between the Static and Dynamic Modulus of Elasticity of Rocks Hamed Ahmadi Moghadam 1,, Mehrdad Salehidobakhshari 2 1 Department of Civil Engineering, Lashtenesha-Zibakenar Branch, Islamic Azad University, Lashtenesha, Iran 2 M.Sc., Geotechnical Engineering from Iran University of Science and Technology, Tehran, Iran Abstract. Mechanical properties of rocks are usually determined by static tests which are categorized as destructive tests. Besides, these methods are time consuming and costly. Static modulus of elasticity of rocks (Es) is one of the most important parameter that specifies the relationship between applied stress and strain of specimen. Dynamic parameters of rocks can be determined by dynamic methods. In laboratory one common method is Ultrasonic Pulsing Test, which is known as a none-destructive method, takes only several seconds. Furthermore, uni-axial compression tests cause micro cracks that increase deformation and therefore decrease the modulus of elasticity. These micro cracks are not occurred during dynamic test. In contrast with static test, the specimen is not destructed during dynamic test and it can be used for other tests. In this research it is attempted to find a relationship between static and dynamic modulus of elasticity that can cover a large rang of rocks by collecting and analyzing reliable results from several sources. Keywords: Rock, Static and Dynamic Modulus of Elasticity Corresponding author: hamedahmadi_m@yahoo.com

7 Effect of soil subgrade modulus on raft foundation behavior Omer Mughieda 1, *, Mohamed Sherif Mehana 2, and Kenan Hazirbaba 3 1 Dept. of Civil Engineering, Abu Dhabi University, Abu Dhabi, UAE 2 UNii Engineering Consultancy, 47378, Abu Dhabi, UAE 3 Dept. of Civil Infrastructure and Environ. Eng, Khalifa University, Abu Dhabi, UAE 1, * omer.mughieda@adu.ac.ae, 2 civil_mohamed@hotmail.com, 3 kenan.hazirbaba@kustar.ac.ae Abstract. The present study is carried out to investigate the effect of soil subgrade modulus on bending moment, shear, and deformation characteristics of raft foundation. Subgrade models are an approximate representation for the actual load-displacement behavior of the supporting soil. One of the widely-used methods to model soil subgrade modulus is Winkler method where the interaction between soil and foundations is represented by a number of springs. The main flaw of this model is the lack of coupling between springs and representation of the non-linearity of load settlement behavior of soil. In this work an attempt is made to analyze Winkler method through a commercial software (SAFE V2014) in terms of the effect of soil subgrade modulus on the behavior of raft foundation.

DYNAMIC ANALYSIS OF PILES IN SAND BASED ON SOIL-PILE INTERACTION

October 1-17,, Beijing, China DYNAMIC ANALYSIS OF PILES IN SAND BASED ON SOIL-PILE INTERACTION Mohammad M. Ahmadi 1 and Mahdi Ehsani 1 Assistant Professor, Dept. of Civil Engineering, Geotechnical Group,