The increasing importance of monitoring the field performance of foundations to validate numerical analysis

Large civil engineering projects are designed using predictions based on numerical analysis, developed by software engineers often using simplified models to describe the real world with global parameters to define its material properties. Without feedback on actual performance there can be no calibration of a design method and hence confidence in its predictions of interaction between structures.

As ‘Green Field’ sites become increasingly rare and some of the existing infrastructure may be fragile and surrounded by modified materials, design methods are being stretched to their credible limits. For the design of a new development to be considered safe, the resulting stress levels and movements that occur both in the new and existing structures must be tolerated for their serviceable lives. Without effective monitoring there is no feedback data and hence no way of determining if a new development has been safely integrated into the existing infrastructure.

While working at the Building Research Establishment (Garston) the authors developed a number of field instrumentation systems to address the imbalance between the increasing power of theoretical predictions and the available feedback information on performance. This paper examines how data from these systems has been used to understand pile foundation performance in different soils. It describes how the data can be interpreted to determine engineering performance of piles and the changes that occur in pile soil stiffness parameters with increasing load and emphasises that the information can only be obtained from monitored performance in the field. Developing numerical design models that can incorporate the changes that occur in the real world is essential if accurate predictions are to be made on performance. The values determined from the instrumented field tests discussed in this paper are compared to values normally obtained from laboratory tests and those used in design.

• INTRODUCTION

• PILES IN EXPANSIVE SOILS

• VERTICAL AND SHALLOW ANGLED RAKED CAST-IN-PLACE PILES

• LARGE DIAMETER PILES SUBJECTED TO LATERAL LOADS

• CONCLUDING REMARKS

• Acknowledgements

• REFERENCES