68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

EFFECTS OF VARYING MODULUS OF SUBGRADE REACTION ON STRUCTURAL DESIGN OF MAT FOUNDATION

Prapote Boonsinsuk, Amec Foster Wheeler (Canada)
George Chow, Amec Foster Wheeler (Canada)
Siva Nadarajah, Amec Foster Wheeler (Canada)

Geotechnical engineers are normally requested by structural engineers to provide "modulus of subgrade reaction - ks" for the design of mat foundation or slab-on-grade. The geotechnical engineers will provide the values of ks which are deemed applicable to the planned sizes of mat foundation to the structural engineers, who will subsequently use the ks as elastic springs underneath the mat foundation in typical analytical models, e.g., slab on elastic foundation, to determine contact pressure, settlement, bending moment, etc. From the previous paper on the ks by the same authors, the values of ks will not normally lead to the same foundation settlements when comparing the analyses by geotechnical engineers (using elastic modulus) and structural engineers (using ks). Such discrepancy can be resolved by repetitive analyses to be performed between the two engineers to satisfy a common criterion (e.g., similar foundation settlements). This paper presents the effects of varying ks values on the structural design of mat foundation, if used without the benefit of repetitive analyses between geotechnical and structural engineers to match the same foundation settlements.