Geotech Problems

[EL Nica PE]

 

[GTScott]

Great! I will add these to the To-Do list for tonight.

The consolidation problem is a good one as there is a trick to it. I have seen a similar problem on another sample somewhere.

-GT

 

[3gorgesdam]

t = Tv (Hd)^2/Cv

11 Min = Tv (25mm/2)^2/Cv (1)

t = Tv (4m*1000mm/m)^2/Cv (2)

Solve for t = 1126400 min = 782 day

Note: No need to know Tv nor Cv. They cancle out.

Answer (d)

 

[EL Nica PE]

For #10 here are the choices

A)4144 yd^3

B)5260 yd^3

C)3550 yd^3

D)4890 yd^3

 

[GTScott]

I hate these borrow problems...here is what I did rather quickly, someone correct me if I wander from what I should have done...

In place needs to be 108 at 14.5% UWd=108pcf

Borrow material, properties given...UWd=(Gs*UWwater)/(1+e)=79.63pcf

Ratio = 108/79.63 = 1.362 (need about 36.2% more)

Volume Required = 82,500 ft3 for 100 LF of embankment

Borrow Volume = Vreqd * ratio = 82,500 * 1.362 = 112,365 ft3 /27 = 4,162 yd3

(A)

I did this one wrong the first time and adjusted the unit weight of the embankment by the MC which does not need to be done since they give you UWd.

-GT

 

[Road Guy]

I used the similar format, but I get the required volume = 107,500 CF ?

but that give me a required excavation of 5400 CY

???

I hate these too, but NCEES

them

 

[3gorgesdam]

cross-section area Across = 825 ft^2

Volumn in ft^3 = 82500 ft^3

Volumn in yd^3 = 3055.555556 yd^3

r drye = 108 lb/ft^3

e of borrow soil = 1.1

SG of solid = 2.68

r drybr =SG*rw/(1+e) = 79.63428571 lb/ft^3

Massb = MassE

r drybr*vbr = r drye*1ft^3

vbr =r drye*1ft^3/r drybr 1.35619977 ft^3

Total vbrt =1.35619977*3055.555556 yd^3

Total vbrt = 4144 yd^3

I did it in excel while watching cartoons with my son.

'.02'

 

[Road Guy]

yeah, I am dumb I did the middle area at 25' X 25' instead of 25 X 15