2398328
Description
Flashcards by rhiannonsian, updated more than 1 year ago
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Created by rhiannonsian
over 9 years ago
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| Question | Answer |
| Total overburden pressure (σ or p) | The intensity of total pressure due to the weights of both soil and water, on any horizontal plane at and below foundation level before construction operations are started. p = σ = γD |
| Effective overburden pressure (σ' or p') | the intensity of effective pressure on any horizontal plane at or below foundation level before construction begins, for example for a foundation level at depth H below the water table. p' = σ' = σ - γwH |
| Gross loading intensity (total foundation pressure) (qg) | The intensity of the total pressure on the ground beneath the foundation after the structure has been erected and fully loaded. It is inclusive of the gross load of the foundation substructure, the loading from the superstructure and the gross loading from any backfilled soil or soil water supported by the substructure. |
| Net loading intensity (net foundation pressure) (qn) | the net increase in pressure on the ground beneath the foundation due to the dead load and live load applied by the structure qn=q - σ' (at foundation depth D) |
| Ultimate bearing capacity (qgf) | the value of the gross loading intensity at which the ground fails in shear. Alternatively, it is the maximum loading the ground can resist. |
| Net ultimate bearing capacity (qnf) | for a particular foundation is the value of the net loading intensity at which the ground fails in shear qnf = qf - σ' |
| Presumed bearing value | the net loading intensity considered appropriate to a particular type of ground for preliminary design purposes. The particular value is based on local experience, calculation from strength tests or field loading tests using a factor of safety against shear failure. |
| Allowable gross bearing pressure (qag) | the maximum allowable gross loading intensity of the ground in any given case, taking into consideration the bearing capacity, the estimated amount and rate of settlement that will occur and the ability of the structure to accommodate the settlement. |
| Allowable net bearing pressure (qan) | the maximum allowable net loading intensity of the ground in any given case, taking into consideration the bearing capacity, the estimated amount and rate of settlement that will occur and the ability of the structure to accommodate the settlement. |
| Factor of safety | F= qnf/qan = (qgf- γD)/(qag- γD) The factor of safety should be at least three and may be higher than three if is required to restrict settlement |
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