huangyhg

foundation engineering
an 8 storey building with raft foundation has to be constructed on the compacted fill which rest directly on the fill for at least -0.40m from zero level. the foundation thickness is only 0.4m with a hunch back on each major columns down the ground for about 0.8m from the ground floor. by the way the raft foundation will be utilize itself as a ground slab. the test used for the soil before constructing the foundation is the so called "plate load test" with a test result of allowable bearing capacity of 320kpa and an average settlement of 6.5mm. the question is: 1.0)can we use the plate load test result aside from soil bearing test result in the basis for a design of foundation? 2.0) after the construction of foundation we conducted a soil boring log test and the result and recommendation is that the foundation has to be constructed below 3m depth from the original natural soil to increase the shear for soil the result as well is only 200kpa. so, what well happen to the foundation if it rest on the compacted fill regardless of the soil bearing report recommendation? 3.0) can you gave us an advice regarding this matters on what to do if there is some problem due to detrimental settlement if the foundation rest on the compacted fill?
i think you should post in the geotechnical forum.
the plate load test will only give some idea of short-term settlement it is not appropriate for designing a foundation.
you should follow the advice of a geotechnical engineer according to borehole logs.
i expect you will suffer unacceptable levels of settlement and quite likely the more serious effect of differential settlement if you continue.
in my view the plate load test dats should be considered as garbage. you have explained a bit about the fill but what is the underlying material on which the fill is sitting. the plate load test would be "okay" for situations where the ground is the same or improves with depth - but if there is any chance that the ground gets weaker (as done in some clay deposits that have an upper desiccate crust) you will get in a lot of trouble. also the plate load test does not consider consolidation settlements - only immediate settlement and shear (if loaded to failure). be careful on it. your raft foundation depth of influece extends deep - do the soil borings and get the geotechnical engineer to give you the recommendations based on your project!
thanks zambo for the adviced we have the same idea, now i could strongly issued a letter to the contractor regarding this matter.
thanks all folk for all the valuable recommendation...

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