Investigation of Ground Heave at ICI Mond Division, Castner-Kellner Works, Runcorn

Abstract

AbstractA serious crack was first noticed in the ground bearing floor slab of K-Unit Plant in September 1977, nine years after its construction. By 1981 measurements shoved the floor near the crack to have risen 80 mm above design level. Significant upward movement of structural columns and beams was also recorded. These movements were beginning to disrupt the working of the plant and in 1981 it was decided to investigate the phenomenon.A desk study showed that furnaces once stood on the site, with caustic soda storage tanks nearby. A heavy wall once occupied the approximate line of the present crack. Subsoil contamination by alkali solutions was also suspected.Ground conditions were investigated using light cable percussion boreholes. The nature of the problem, however, called for techniques not covered by BS5930. A magnetic probe extensometer was installed at the point of maximum heave, and in the laboratory soil specimens were subjected to swelling tests using special apparatus and techniques.Chemical tests and X-Ray analyses were also made.Five possible mechanisms of swelling were investigated, and it was shown that the heave resulted from a slow alkali-clay reaction. Predictions of future movements were made and these allowed the remedial work to be planned.