Horizontal Slip-Form Construction—Section Stability

Horizontal slip-form construction with low slump concrete is adaptable to geometrical cross sections with large longitudinal dimensions. Section heights of 5 ft (1.5 m) or more have been readily constructed. A limitation of the method has been the lack of a simple method for evaluating the section stability. To provide the needed information, an experimental slip-form constructed wall section was analyzed by the finite element method using mechanical properties from laboratory tests converted to field mix conditions. Results showed that section stability can be determined by a comparison of the maximum shear stress with the undrained shear strength from unconfined compression tests on fresh concrete. Using results from the finite element method, a simplified analysis uses the relationship between a shape factor and stress ratio to determine the maximum shear stress. Comparison of this stress with the available undrained shear strength gives a measure of the factor of safety for the slip-form constructed section.