The Bearing Capacity of Foundations in Weak Rock

This project is an extension of the research previously undertaken by Williams (1980a) and Chiu (1981) at Monash University. The aims of the research project are to obtain a better understanding of the mechanics of base resistance and to develop techniques for predicting the performance of end-bearing foundations in weak rock.

The laboratory investigations include the development of a model rock which is homogeneous and isotropic. This is achieved by the compaction and consolidation of a mixture of mudstone powder, cement, water and calcium chloride, and allowing the mixture to become fully cured. The strength and deformation properties of the model rock, including its consolidation, drained uniaxial and triaxial compressive stress, and tensile stress characteristics are determined. Model rock of different water contents are manufactured by varying the compaction pressure. The properties of the model rock are found to be highly reproducible and very similar to those of Melbourne mudstone. This enables the conduction of model end-bearing pile tests on the model rock without the unknown and random influences of discontinuities and other defects as observed by Williams (1980a) for his in-situ tests. The effects of different pile diameters, rates of loading, embedment ratios and boundary conditions, and the strength and deformation characteristics of the foundation rock on pile behaviour, are studied through the model pile tests. The failure mechanisms are studied either by sectioning the specimens after the model ile tests or by using a stereo-photogrammetric technique. The load-settlement behaviour is re-examined in relation to the observed mechanisms […]