Invitation to International Prediction Event on the Behaviour of Bored, CFA and Driven Piles in ISC 2 experimental site

Transcription

1 Invitation to International Prediction Event on the Behaviour of Bored, CFA and Driven Piles in ISC 2 experimental site Jaime Santos, Coordinator of the experimental site A. Viana da Fonseca, President of ISC 2 1. INTRODUCTION The Conference ISC 2 (International Site Characterization) will be held in 2004 at the Faculty of Engineering, University of Porto (FEUP), Portugal. The Conference addresses the use and benefits of geotechnical site characterization, in particular field tests for the exploration of the subsurface environment. An experimental site with very extensive site characterization is being undertaken, including a large variety of in-situ tests and also pile load tests (for more details about the conference please visit the web site http// The FEUP and IST (Instituto Superior Técnico) is pleased to organize an International Prediction Event on the Behaviour of Bored, CFA and Driven Piles in ISC 2 experimental site BACKGROUND In the north-western region of Portugal residual soils from granite are dominant. The thickness of these regional saprolitic soils may some times attain more than 20m, with more common values of 5 to 10m. Due to their specific genesis such soils present complex characteristics, which are a consequence, on the one hand, of their overall variability and heterogeneity and, on the other hand, of the spatial arrangement and distribution of the particles and pore spaces. Coarse and resistant quartz grains are bonded by fragile clayey plagioclase bridges, resulting in a fabric with medium to high porosity. The feldspars are subjected to intense weathering processes, typical of high average annual precipitation and well-drained ground profiles. The mechanical and hydraulic behaviour of these soils is often quite distinct from sedimentary soils with similar densities and grain size distributions. The current design practice of bored and driven piles in residual weathered formations is merely semi-empirical and based on bearing capacity analysis (in general, without deformations analysis). Fully instrumented pile load tests are very much informative for the elaboration of specific correlations between load-deformation behaviour and in situ tests results (and also fundamental soil mechanics parameters obtained from precise laboratory tests), for establishing well-based design criteria. The possibility of integrating very wide information in a typical granite residual soil profile will enable an innovative study on this subject. 1/6

2 3. OUTLINE DESCRIPTION OF LOAD TESTS PROGRAM 3.1 Soil Characterization In the experimental site the thickness of the residual saprolitic soils is near 20m. Several in-situ testing techniques (Seismic: CH, DH, SASW, CSWS; Penetration tests: SPT & CPT; Pressuredilatometer tests: PMT, SBPT, DMT; and Load tests: PLT and a full-scale footing testing) have been used in order to have a very sound knowledge of the mechanical characteristics of this soil. High quality undisturbed block samples were recovered and an extensive laboratory testing program was carried out, including isotropic and oedometric consolidation tests, as well as CID and CK 0 D triaxial tests using local strain measuring devices and bender-extender elements. Several papers (see Section 5: References) have presented and discussed the results obtained, giving emphasis to the interpretation of constitutive behaviour differences in stress-strain levels lower and higher than the yield stresses related to saprolitic soils with weak relic structures. This research is on going with the present campaign. Some of the results are presented in Figure 1. Due to soil variations, tests results will be available for each pile location. Figure 1 Some preliminary in situ tests 2/6

3 3.2 Pile Load Tests In the experimental site 3 different kinds of piles are to be loaded axially side by side by static test. The localization of the piles is showed in Figure 2: 10 bored piles (E0 to E9, circular section D=600mm) 2 CFA piles (T1 and T2, circular section D=600mm) 2 driven piles (C1 and C2, square section B=350mm) The bored piles E1 to E8 are reaction piles with 22m of length. All the others are short piles with 6m of length. Piles E9 (bored, L=6m), C1 (driven, L=6m) and T1 (CFA, L=6m) will be loaded by static test up to failure. Piles E9 and E1 are fully instrumented with retrievable extensometers. Similar piles: E0 (bored, L=6m), E2 (bored, L=22m), E6 (bored, L=22m), C2 (driven, L=6m) and T2 (CFA, L=6m) were used for high strain dynamic load tests. These tests offer a unique opportunity to study the installation effects by comparing the behaviour of these piles up to failure. Besides, high strain dynamic load tests in similar piles are available to allow comparisons with the static ones. 4. INVITATION TO THE PILE PREDICTION EVENT The tests will take place very shortly. The bored and CFA piles were already installed in July. The driven piles and high strain dynamic tests were performed in September and the static load tests will take place in November We will make test results available to people who plan to participate in this event soon after. If you know someone who could have interest to participate please send this document and help us to promote this pile prediction event. The auspices of ITC-18 (International Technical Committee on Deep Foundations, chaired by Professor Holeyman) of the ISSMGE are being considered for this activity. One of the terms of reference assigned to ITC-18 consists in addressing the influence of the installation method of piles on their load-bearing behaviour under vertical compression. The activities of ITC-18 can be followed on the following website: The support of Pile Dynamics, Inc to promote this event is also being considered ( In the meantime, please let us know if you are interested to participate in the prediction event by filling in the form attached and , fax or mail to us. 3/6

4 B D DMT4 (22/05/03) DMT5 (22/05/03) PMT1 (10/9/03) CPT4.1 (23/05/03) PMT1.0 S5 (11/09/03) E1 E0 CPT C E5 S4 (11/09/03) E CPT5 C1 E9 PMT2 (10/09/03) A E7 1 2 C2 T LEGEND : PILES E - Bored (D=600mm) T - CFA (D=600mm) C - Driven (300mmx300mm) SITE CHARACTERIZATION S - Borehole with Sampling A - Undisturbed Samples SPT; CPT; DMT; PMT; DPSH; SP DYNAMIC TESTS ON PILES: E0, E2, E6, T2 & C2 (high strain; vertical) STATIC TESTS ON PILES: E9, C1 & T1 (up to failure) 2.00 DITCH FOR SEISMIC PROFILES REFERENCE SLAB 3 T2 E8 E6 E4 E2 CPT2.1 DMT3 CPT3 DMT2 CPT1 S1 - SPT SP2 DPSH DMT1 S0 - SPT S2* S2.1 PMT (09/09/03) S3 - SPT Figure 2 Tests localization 4/6

5 5. REFERENCES Characterising and deriving engineering properties of a saprolitic soil from granite, from Porto. Chapter of the book Characterization and Engineering Properties of Natural Soils. Ed. por Tan, Phoon, Hight & Leroueil, publ. Swets & Zeitlinger, Lisse (ISBN ), Vol.2, pp ). Viana da Fonseca, A., Fernandes, M. & Cardoso, A. S. (1997). Interpretation of a footing load test on a saprolitic soil from granite. GÉOTECHNIQUE, Agosto de 1997, Vol. 47, No.3, pp Thomas Telford, London. (ISSN: ). Viana da Fonseca, A., Fernandes, M. & Cardoso, A. S. (1998). Characterization of a saprolitic soil from Porto granite by in situ testing. First International Conference on Site Characterization ISC 98, Atlanta, USA, April, Vol. 2, pp , Ed. Robertson & Mayne. Pub A.A. Balkema, Rotterdam, Nth (ISBN: ). Viana da Fonseca, A. (2001). Load tests on residual soil. Settlement prediction for shallow foundation design. JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING American Society of Civil Engineers (ASCE), Vol.127, nº 10, pp , Reston, VA USA (ISSN: /01/ ). Viana da Fonseca, A. & Almeida e Sousa, J. (2002). Hyperbolic model parameters for FEM analysis of a footing load test on a residual soil from granite. PARAM 2002: International Symposium on Identification and determination of soil and rock parameters for geotechnical design 2-3 September 2002, Paris. Vol. 1, pp , Proceedings Ed. J-P Magnan, Presses L ENPC (ISBN: ), LCPC (ISBN: ), Paris, FR. Viana da Fonseca, A., Sousa, F. V. e & Ferreira, C. (2003). Deriving stiffness parameters from gross in situ tests and relating them with noble reference values on saprolitic soils from granite, 12th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, MIT, Cambridge, USA.. Vol. 1, pp , Proceedings, Ed. Culligan, Einstein & Whittle. Pub. VGE, Verlag Guckuf GmbH (ISBN: ), Essen, GE. Sponsors: 5/6

6 Expression of Interest to Participate in the International Prediction Event on the Behaviour of Bored, CFA and Driven Piles in ISC 2 experimental site 2003 Please check the item(s) below. You may wish to participate in: (1) Load-bearing behaviour prediction based on in situ and laboratory tests and/or (2) Load-bearing behaviour prediction based on high strain dynamic tests: Yes, I will participate in (Please check Prediction number) (1) (2) No, I will not participate I have not decided at this time but please keep me informed Please type or print: Name: Affiliation: Mailing address: address: Phone: Fax: Please , fax or post the complete form before 10 th of October 2003: Fax: jaime@civil.ist.utl.pt Address: Departamento de Engenharia Civil Instituto Superior Técnico Avenida Rovisco Pais, Lisboa Portugal Attention: Prof. Jaime Santos 6/6