CMP 305
Questions and Answers
Site Investigation: Necessities for planning construction techniques Site Access, Type of
construction equipment, ground water, surface water development
Documents for Evaluating the site Soil Maps, topographic maps, aerial photographs,
USGS topographic quadrangle maps
Info obtained from soil profile uniform soil conditions, number of borings and bore
spacing, type - size - weight of structure
Bore spacing for road work, one story building, multi story Road - 500-1000'
one story - 100-200'
multi story - 50-100'
How far down does boring depth have to be? until suitable soil bearing capacity is found
and depth of ground water(if needed)
Direct Exploration Uses Test pit method, pit or trench, visual inspection, limited depth 15-
20', equipment: backhoe or excavator.
Advantages of Direct exploration view soil profile(type and color)
obtain undisturbed sample
Disadvantages of Direct exploration limited depth, ground water may limit depth,
safety(soil caving in)
Devices for in-place soil testing Pocket penetrometer(TSF), torvane, thumb penetration
Semi-direct exploration Auger Drilling
Auger Types Solid Auger: dry regions, auger removed for sampling(hole will collapse),
Hollow Auger: sampling thru the auger, faster taking samples, (split barrel, shelby tube).
Rotary Drill auger with clay slurry, slurry moves soil up, slurry stabilizes the sides of the
drill hole
Cone Penetrometer Holland, US & Canada, pushed into the ground, records readings in
different sections. Adv: provides a continuous record of test results used for engineering
properties for the entire profile
, Geophysical Testing Road work, fast, quick results, less expensive. Seismic refraction and
electrical resistance.
Seismic refraction velocity of seismic wave transmitted through soil. greater density -
faster waves.
Drilled Samples Disturbed samples
why do we sample use for grain size analysis, liquid limits, plastic limits and plastic index
Testing with Undisturbed samples Split barrel, shelby tube or test pit
Split barrel or standard penetration test(SPT) tube used to collect soil sample at the bottom
of the test hole. pass through the hollow tube auger, measurement - resistance to penetration
Split barrel Specs.
OD, Length, Sample OD, Hammer wt., Drop height OD=2", Length=30", Sample OD 1
5/8", hammer wt.= 140#, Drop height=30"
how does Standard Penetration Test work sampler is driven for 3 consecutive 6"
increments. Count number of blows per 6" increments, Blow count summation(take last two sets
of numbers)
Shelby Tube dimensions Dia. 2-5", Length 4"
How does Shelby Tube work Tube is pushed in, used with the hollow core auger,
Sampling interval 5'
Why is it important to know location of ground water table effects the soil load bearing
capacity, type and size of foundation required, dewatering system, plan for drainage,
Permeability of Soil Property of soil to transmit water and air
Compaction Process of increasing soil density by mechanically forcing particles together.
Removes air from void space. accomplished in matter of hours.
What does compaction improvement do? increases bearing strength, reduced
compressibility, improved volume-change characteristics, reduced permeability
Degree of compaction depends on what? soil's physical and chemical properties, soil's
moisture content, compaction method, amount of compaction effort, thickness of the lift
Well graded aggregates compact more easily than poorly graded aggregates? T or F True
