Back Ground

Several aspects of pile response to axial load are still not fully understood and need to be further investigated.

A number of methods for the prediction of the axial capacity are available in the literature, frequently based on experimental results collected by load tests on full scale instrumented piles. These methods generally supply values for “lumped” coefficient to be used in very simple equations to evaluate unit shaft friction and base resistance as a function of the pile type / soil type combination. More detailed information on the load transfer mechanism from pile to soil have been obtained by accurate research, mainly conducted on model pile inserted in a soil box (1-g lab) or in centrifuge tests. Very rarely these studies have been carried out at full scale level.

The main scope of the present research is the investigation of the complex pile-soil interaction mechanisms which develop at pile shaft and base during static axial loading.

 

Experimental testing site

At the experimental site, 6 testing piles have been executed with different technology (bored, with bentonite or polymer mud, and Continuous Flight Auger, CFA), lengths (15 to 24 m) and diameters (0.7 to 1.0 m). All piles are fully instrumented along the shaft by means of wire stain gauges and steel tubes. The latter will be used both for integrity testing and for the placement of retrievable multiple extensometers.

The testing piles will be static axially loaded: 5 of them by means of the standard procedure, with reaction piles (14 CFA piles, D = 0.8 m and L = 24 m), and 1 by means of the Osterberg Cell.

 

Prediction Event

Recent research in pile foundation carried out in the last 25 years supports theoretical based approaches to be used in geotechnical design. Despite that, scattered predictions are often observed, especially in sands. For this reason, the proposed Prediction Event will check our ability and skills in assessing the load-settlement response of an axially loaded pile. Predictors are invited to attend and disseminate this stimulating initiative!

Only one pile will be tested in this Prediction Event (ET4): it is a bored pile, drilled under polymer suspension, 24 m length and 1 m diameter. Results from the standard slow maintained axial standard load test will be available in the near future.

 

Instructions for the Predictors

Engineers from Industry and University (which are not involved in the organization of the Araquari Experimental Testing Site) are invited to participate in the Prediction Event.

The Participants are challenged to predict the static load bearing behaviour of the bored pile (ET4), including:

  1. the pile axial load (Q) versus head displacement (w) curve, up to a head displacement of w/D ≥ 10%;
  2. the shaft (Qs) and base (Qb) loads at failure (conventionally fixed at w/D = 10%);
  3. the distribution of axial load (N) along the shaft of the pile at failure (N versus depth z, at w/D = 10%);
  4. a brief description of parameters and models used for calculations.

Predictors wishing to participate should reply to at least one question (a, b or c) by filling up the Excel file: Template for the prediction_new.xlsx.
Description of parameters and adopted models should be described in a pdf file: Template for reports.doc.

The predictions (including above mentioned excel and the pdf files) have to be sent by email to araquari.ets@gmail.com before May 8, 2015. Please state this information:

  • Full Name;
  • Affiliation;
  • Email address;
  • Phone number.

The winner of the competition will be awarded during SEFE 2015.

Predictions will be kept anonymous.

By May 20, 2015, each Participant will know his own position in the rank and, at that stage, will grant the permission to have his identity publicized at the eventual publications.

Predictions that do not follow the instructions discussed in this document will be excluded from the competition.

The contents received in the Prediction Event remain as property of the Organizing Committee for future publications.

Instructions for Predictors 2.pdf

 

Pictures