This is Geotechnical engineering question. Question4 A ten story steel-frame bui

Question

This is Geotechnical engineering question. Question4 A ten story steel-frame building with a 300 ft x300 ft footprint is to be built on a site underlain by alluvial sand and silt with good engineering properties. The depth of the foundation is estimated to be 5 ft below the ground surface and the groundwater table is about 30ft below the ground surface. (a) What is the minimum number of required exploratory borings? (b) What is the minimum required depth of the borings? (c) Name the equipment you propose for drilling and sampling of the soil strata. What is the major problem the field crew might encounter?

Explanation / Answer

(a) For a multi-storey building, borehole spacing should be 10 - 30 m (32.81 - 98.43 ft) in each direction.

Boring number is minimum when the spacing between them is maximum.

Consider spacing of borings be 98.43 ft in each direction.

Minimum number of exploratory borings required = (300*300)/(98.43*98.43) = 9.289 = 10

Minimum number of exploratory borings required is 10.

(b) Minimum depth of borings = 6S0.7 for heavy steel or multi storey building

Where, S is the number of storeys

Here, S = 10

Minimum depth of boring = 6*100.7 = 30.07 m = 98.66 ft

(c) Auger boring with standard split spoon sampler. The main problem the field crew might encounter is the soil will behave like liquid when the ground water table encountered.

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