Chalk as fill.

This thesis contains a review of literature relevant to the use of chalk as common embankment fill, and the results of a considerable amount of testing to find the variability of the density and plasticity of the Chalk, its strength properties and compressibility. Various available empirical suitability tests are reviewed, and the final section concludes with six case records which illustrate practical experience and demonstrate the relevance of the research. In assessing the variability of the Chalk over 600 determinations of intact dry density and 200 plasticity tests have been carried out on samples collected from almost all parts of the outcrop in England. These tests indicate the extreme variability of the material, which during excavation may behave in extremes as a rock or a slurry. Strength tests have been carried out on remoulded Chalk using the triaxial and C. B. R equipment. It is shown that the undrained triaxial shear strength is strongly dependent on the remoulded liquid limit of crushed chalk and that the liquid limit approximately corresponds to the saturation moisture content and to the point at which the triaxial strength becomes negligible. Effective strength tests show that while the effective angle of friction varies only slightly for most remoulded chalks, it may increase with time as a result of recrystallization of aragonite within a fill. Compression tests on blocky chalk and on chalk fines above and below their liquid limit are reported, and indicate that few field problems are likely to arise from this type of compression. The collapse of chalk fill upon wetting has been modelled in the laboratory and is shown to provide a much greater threat to the satisfactory performance of embankments. The investigations into suitability have indicated that no completely satisfactory test exists to predict the performance of chalk in earthworks. The use of a simple hand dynamic penetrometer is proposed, and its results are correlated to those of the vibratory crushing test