Determining the Tensile Strength of Soil-Cement

Deep soil mixing was proposed as a means to improve the poor subsurface conditions at the site of a proposed new electrical substation situated in Burnaby, British Columbia, Canada. Tender documents specified minimum compressive and tensile strengths, as well as a minimum compression modulus, with no acknowledgement of the inter-related nature of these attributes, and no bench scale testing to inform prospective bidders. This paper discusses the contractual risks introduced by use of the set of inconsistent criteria adopted in the project specification, and provides details and results of the trial program utilized by the contractor to establish a mix design criteria that would achieve the specification. Further, the paper discusses two testing options employed for the determination of the tensile capacity of soil-cement, the variation in results obtained for each method, the variation in the relationship of each method to the unconfined compressive strength (UCS), and compares these to previously published relationships.