DA Bruce, BSc, PhD, CEng, MICE, MIWES, MASCE, MHKIE, FGS. This paper was first published in GE’s May 1986 edition.
Querulous eyebrows were raised in the 1975 Offshore Technology Conference in Dallas, Texas, when Gouvenot and Gabaix presented the conclusions of their test programme on the effects of postgrouting on large diameter pile performance:
- an increase in ultimate load of up to three times in sands and clays,
- similar increases in creep load,
- highly repeatable performance under cyclic loading with almost no permanent set, and
- direct relationship between ultimate load and volume of cement grout injected.
Since then, grouting techniques have been employed confidently throughout the world, as a routine construction process. By exploiting the higher values of skin friction and end-bearing resulting, engineers have been able to reduce pile dimensions safely. There are thus relative savings in plant and labour costs, as well as reductions in material requirements – a key logistical factor especially in developing countries.
Equally, where the satisfactory performance of conventional piling has been threatened, either due to faulty or inappropriate installation techniques (e.g. Logic, 1984), or due to interference by later construction activities (e.g. Karol, 1983), grouting as a remedial process has gained widespread application.
This review is a synthesis of data published primarily in the last decade on pile grouting. Case histories are presented in three basic categories:
(i) Enhancement by devices placed within the pile (i.e. attached to the reinforcement prior to installation).
(ii) Enhancement by toe/ground grouting (i.e. after concreting), and
(iii) Enhancement by ground consolidation (either before or after construction).
Throughout, the term “grouted pile” refers to a pile which has been treated in one of these categories. It is not used in distinction to the term “concrete pile” for example.