Geotech Practice Problems

[owillis28]

A soil sample has a water content of 20%, a degree of saturation of 80%, and a specific gravity of

2.68. The dry unit weight is most nearly _____

A moist soil sample in a tare can is put on a balance and the mass of the soil plus can is found to be

48.30 g. After oven drying, the mass of the soil plus can is found to be 41.22 g. The mass of the

empty tare can is 7.41 grams. The water content of the soil is most nearly _____

A clay deposit has a unit weight of 100 lbf/ft3 and an unconfined compressive strength of 2000 lbf/ft2.

What is most nearly the depth at which the horizontal soil pressure is zero?

A dry sand has a minimum unit weight of 105 lb/ft and a maximum unit weight of 125 lb/ft . The unit

weight in place is measured at 121 lb/ft . What is the relative density?

Five pounds of moist soil has a water content of 20%. How many pounds of water must be added to

increase the water content to 30%?

A fine-grained, inorganic soil sample has liquid limit of 45 and a plastic limit of 30. Classify the soil

according to the Unified Soil Classification System.

 

[EL Nica PE]

A soil sample has a water content of 20%, a degree of saturation of 80%, and a specific gravity of2.68. The dry unit weight is most nearly _____

A moist soil sample in a tare can is put on a balance and the mass of the soil plus can is found to be

48.30 g. After oven drying, the mass of the soil plus can is found to be 41.22 g. The mass of the

empty tare can is 7.41 grams. The water content of the soil is most nearly _____

A clay deposit has a unit weight of 100 lbf/ft3 and an unconfined compressive strength of 2000 lbf/ft2.

What is most nearly the depth at which the horizontal soil pressure is zero?

A dry sand has a minimum unit weight of 105 lb/ft and a maximum unit weight of 125 lb/ft . The unit

weight in place is measured at 121 lb/ft . What is the relative density?

Five pounds of moist soil has a water content of 20%. How many pounds of water must be added to

increase the water content to 30%?

A fine-grained, inorganic soil sample has liquid limit of 45 and a plastic limit of 30. Classify the soil

according to the Unified Soil Classification System.

Atthached are the relationship that will solve most of these problems.

 

[djgint]

Atthached are the relationship that will solve most of these problems.

Answers

Dry Density = 100 pcf

Water Content = 20.7 %

Height = 40 Ft

Relative Density = 82.6 %

Weight of water to be added = 2.5 lb

USCS = ML

 

[djgint]

AnswersDry Density = 100 pcf

Water Content = 20.7 %

Height = 40 Ft

Relative Density = 82.6 %

Weight of water to be added = 2.5 lb

USCS = ML

Let me change my answer for the nearest depth from 40 ft to 20 feet, I forgot to divide Unconfined compression strength by 2.

 

[owillis28]

Let me change my answer for the nearest depth from 40 ft to 20 feet, I forgot to divide Unconfined compression strength by 2.

For the correct answers, see forum topic below

study schedule, anyone in?

 

[EL Nica PE]

AnswersDry Density = 100 pcf

Water Content = 20.7 %

Height = 40 Ft

Relative Density = 82.6 %

Weight of water to be added = 2.5 lb

USCS = ML

it's right! I have 100; looked at the wrong answer. sorry

shortcut;

Gammawater(Gs/(1+Gs(w/Sr))

=62.4*(2.68/(1+2.68*(20/80)))=100.14

 

[owillis28]

For the dry density I got 120psf. The parameter are more typical for this range (120). Looking at the Gs and Saturation

Here are the equations that I used to arrive at the answer

Know specific gravity, water content and saturation

Find e (void ration)?

e = ((2.68)(0.20))/0.80

e=0.67

Unit Weight (gamma??) = ((SG)(pw))/(1+e)

= ((2.68)(62.4))/(1.67)

= 100.14 lb/ft

El Nica - How did you arrive at your answer?

owillis

 

[djm120]

AnswersDry Density = 100 pcf

Water Content = 20.7 %

Height = 40 Ft

Relative Density = 82.6 %

Weight of water to be added = 2.5 lb

USCS = ML

how do you get 40' for a height on problem 3? a little background would help. thanks.

 

[owillis28]

how do you get 40' for a height on problem 3? a little background would help. thanks.

Answers!

A soil sample has a water content of 20%, a degree of saturation of 80%, and a specific gravity of

2.68. The dry unit weight is most nearly 100 lbm/ft3

A moist soil sample in a tare can is put on a balance and the mass of the soil plus can is found to be

48.30 g. After oven drying, the mass of the soil plus can is found to be 41.22 g. The mass of the

empty tare can is 7.41 grams. The water content of the soil is most nearly 21%

A clay deposit has a unit weight of 100 lbf/ft3 and an unconfined compressive strength of 2000 lbf/ft2.

What is most nearly the depth at which the horizontal soil pressure is zero? 20 ft

A dry sand has a minimum unit weight of 105 lb/ft and a maximum unit weight of 125 lb/ft . The unit

weight in place is measured at 121 lb/ft . What is the relative density? 83%

Five pounds of moist soil has a water content of 20%. How many pounds of water must be added to

increase the water content to 30%? 0.42 lbm

A fine-grained, inorganic soil sample has liquid limit of 45 and a plastic limit of 30. Classify the soil

according to the Unified Soil Classification System. ML

Here are the answers? Question 3 should be 20 ft, not 40 feet.

djm120 - Did you get the correct answer? I believe that there is a another forum topic dedicated to this problem. I am pretty sure that I asked how to tackle this problem on a separate post. This should answer all of your questions for this problem.

owillis

 

[owillis28]

Answers!
A soil sample has a water content of 20%, a degree of saturation of 80%, and a specific gravity of

2.68. The dry unit weight is most nearly 100 lbm/ft3

A moist soil sample in a tare can is put on a balance and the mass of the soil plus can is found to be

48.30 g. After oven drying, the mass of the soil plus can is found to be 41.22 g. The mass of the

empty tare can is 7.41 grams. The water content of the soil is most nearly 21%

A clay deposit has a unit weight of 100 lbf/ft3 and an unconfined compressive strength of 2000 lbf/ft2.

What is most nearly the depth at which the horizontal soil pressure is zero? 20 ft

A dry sand has a minimum unit weight of 105 lb/ft and a maximum unit weight of 125 lb/ft . The unit

weight in place is measured at 121 lb/ft . What is the relative density? 83%

Five pounds of moist soil has a water content of 20%. How many pounds of water must be added to

increase the water content to 30%? 0.42 lbm

A fine-grained, inorganic soil sample has liquid limit of 45 and a plastic limit of 30. Classify the soil

according to the Unified Soil Classification System. ML

Here are the answers? Question 3 should be 20 ft, not 40 feet.

djm120 - Did you get the correct answer? I believe that there is a another forum topic dedicated to this problem. I am pretty sure that I asked how to tackle this problem on a separate post. This should answer all of your questions for this problem.

owillis

I went ahead and found the post I was referring too.

Solution and discussion for question no.3

Hope this helps!

owillis

 

[djgint]

how do you get 40' for a height on problem 3? a little background would help. thanks.

I got 40' because I forgot to divide the Unconfined compression strength by 2 which is wrong. I should have divided the unconfined compression strength by 2 thus getting the correct answer of 20'. Cu = 2C. Cohession is 1000 psf. Then use the cohesion in equation (100 pcf x H) - 2C = 0

 

[tymr]

bump

Given: An undisturbed soil sample

e = 0.80

w = 15%

SG = 2.65

Find: Unit weight, Dry unit weight, Degree of Saturation, and Porosity.

Answers to follow.

 

[tymr]

bump

Given: An undisturbed soil sample

e = 0.80

w = 15%

SG = 2.65

Find: Unit weight, Dry unit weight, Degree of Saturation, and Porosity.

Answers to follow.

Using SI Units:

density = 16.61 kN/m^3

dry density = 14.44 kN/m^3

Degree of Saturation = 49.69%

Porosity = 0.44

Using US units:

density = 105.7 lbf/ft^3

dry density = 91.9 lbf/ft^3

degree of saturation & porosity are the same as above.

 

[IlPadrino]

Atthached are the relationship that will solve most of these problems.

Why not create some content at PE Notes - Geotechnical that summarizes this subject in an easy-to-follow manner?

Come on guys... pay forward!

 

[tymr]

Why not create some content at PE Notes - Geotechnical that summarizes this subject in an easy-to-follow manner?
Come on guys... pay forward!

I think El Nica PE wrote that comment before PE Notes was created. I just bumped the thread but didn't seem to get any others to respond. I have contributed content to PE Notes-Geotechnical and would contribute to the construction scheduling but don't have access to Acrobat Adobe Writer. You're not in this alone.....it probably just feels that way.

 

[IlPadrino]

I think El Nica PE wrote that comment before PE Notes was created. I just bumped the thread but didn't seem to get any others to respond. I have contributed content to PE Notes-Geotechnical and would contribute to the construction scheduling but don't have access to Acrobat Adobe Writer. You're not in this alone.....it probably just feels that way.

I'm always talking about CREATING content like the Hydraulics section. So thank you very much for adding the Soil Properties page! I'd suggest you put it on the Geotechnical page (which just contains an outline for now) so that it can be found. It would also be great if someone creates LaTeX equations (it's not hard once you learn and help is available on the Home Page under General Help) so that it can be easily repurposed.

Keep it coming!