 Soil grains come from weathering of bedrock ◦ Physical weathering – granular soils ◦ Chemical weather – creates clay  Soil is either residual or transport ◦ Residual is result of weathering of existing bedrock ◦ Depth is greatest in hot humid climates ◦ Transported have been moved from original location ◦ Amounts increase at farther distances from tropics ◦ Canada and northern us mostly transported soils

 Moved by ◦ Gravity – landslides – same grains but usually less dense ◦ Wind – fine sand and silts – deposits in mounds or dunes ◦ Water – carries soil grains – stream velocity will determine where soil types are deposit ◦ Glaciers – deposited all types of soil as they advance and resides

 Purpose of Soil investigation is to determine ◦ Allowable bearing capacity for foundations ◦ Water resources ◦ Estimate infiltration and seepage rates  Information required in soilds investigation ◦ Depth thickness and properties of each soil layer ◦ Location of groundwater table ◦ Depth to bedrock  Before field investigation preliminary information can be found ◦ Geological and agricultural soils maps ◦ Aerial photographs ◦ Area reconnaissance

 Geophysical methods seismic or electrical ◦ Useful indicators of depth to the water table and bedrock  Probing or jetting with a stream of water  Test pits or trenches ◦ Suitable for shallow depths only  Hand augers ◦ Suitable for shallow depths only  Boring test holes ◦ Typical way to investigate soils

 One story building ◦ 30 to 60 m apart to a depth of 6 -10m with one deeper hole to check the deeper soils  Four story buildings ◦ m apart to a depth of 10-15m with some holes to a depth one and one half times the width of the building and at least one deep hole to bedrock  Highways ◦ Test holes every 300m apart to a depth of 3m

 Sampler 60cm long with a 50mm outside diameter is driven by a hammer with a mass of 63.5kg and falling 75cm – the sampler is first driven 15cm to be sure that it is below the bottom of the test hole – then the number of blows required to drive it another 30cm is recorded as the N value  Most common strength test done in field  Values obtained are affected by the depth of overburden – espically in sandy soils  To correct this value N=N’ x (1x100/po)1/2 is used  Example page 83  Chart page 83

 Vane ◦ Vane is shoved into soil and torguq is applied until it twists – gives shear strength or cohesion ofo cohesive soils  Cone ◦ Simple cone is driven through soils – with the number of blows required for each foot or meter being recorded – indicates the depth of fill or the dept to layer changes

 New test to replace standard penetration test Page 86 and 87

 Sample number, depth and type  Field test depth and results  Depth to layer changes  Field soil description ◦ Type of soil grains ◦ Moisture conditions ◦ Consistency or density ◦ Seams and stratification ◦ Other distinguishing features

 Page 90 table 2-4  Approximate soil strength from field test is can be determined using table 2-5 on page 91