GEOTECH HELP PLEASE

[boo]

can you please somebody tell me how can find the UNIT WEIGHT OF SOIL WITH HAVING THE

WEIGHT OF SOIL= 3.2 AND SG=2.66 water content =12.8%

THANKS

 

[PEin2010]

unit weight of soil = specific gravity * density of water = 2.66 * 62.4 = 165.98 lb/ ft^3

 

[civilized_naah]

unit weight of soil = specific gravity * density of water = 2.66 * 62.4 = 165.98 lb/ ft^3

No, that's the unit weight of a solid block of soil - with no voids

The data (WEIGHT OF SOIL= 3.2 AND SG=2.66 water content =12.8%) is not sufficient. You need volume info also.

 

[PEin2010]

agree ---that is the unit weight of solids in the soil composition.

@ civilized_naah, can't you calculate it this way?

so if you draw the mass-volume diagram

you can assume for 1 cu.ft of soil.

mass of soilds = 165.98 lb

given the water content of 12.8%, mass of water = mass of soilds * water content = 21.25 lb

mass of voids = 0

and so total mass = 165.98 + 21.25 = 187.23 lbs for 1 cu.ft. or in other words, wet unit weight of soil = 187.23 lb/ cft?

Thanks

 

[Badger]

I agrree with civilized_nah. You need more information either S,e, or V.

Something is missing from your question, you have weight of soil = 3.2; what is the size of the sample?

 

[phillyphan]

I agrree with civilized_nah. You need more information either S,e, or V.
Something is missing from your question, you have weight of soil = 3.2; what is the size of the sample?

Is this for a Proctor Test?

If so, the volume is 1/30 cu. ft.

 

[PEin2010]

:mail-296:

can somebody please comment on my answer below? Did I do it right?

Thank you!

agree ---that is the unit weight of solids in the soil composition.
@ civilized_naah, can't you calculate it this way?

so if you draw the mass-volume diagram

you can assume for 1 cu.ft of soil.

mass of soilds = 165.98 lb

given the water content of 12.8%, mass of water = mass of soilds * water content = 21.25 lb

mass of voids = 0

and so total mass = 165.98 + 21.25 = 187.23 lbs for 1 cu.ft. or in other words, wet unit weight of soil = 187.23 lb/ cft?

Thanks

 

[RJs]

Time to relax and get ready for tomorrows exam. One of my senior studied SO hard a day before the exam and he had headache on the exam day and had to go to exam room taking tylenol.

 

[Badger]

:mail-296:

can somebody please comment on my answer below? Did I do it right?

Thank you!

agree ---that is the unit weight of solids in the soil composition.
@ civilized_naah, can't you calculate it this way?

so if you draw the mass-volume diagram

you can assume for 1 cu.ft of soil.

mass of soilds = 165.98 lb

given the water content of 12.8%, mass of water = mass of soilds * water content = 21.25 lb

mass of voids = 0

and so total mass = 165.98 + 21.25 = 187.23 lbs for 1 cu.ft. or in other words, wet unit weight of soil = 187.23 lb/ cft?

Thanks

Well if you are making the assuption Vv=Vw, or totally saturated, where S=1, you can use e=w(SG)/S = .128(2.66)/1 so e=0.3405

Now you can get the dry unit wgt Yd = (SG)Yw/(1+e) Yd = (2.66)62.4/(1.3405) Yd = 123.82 pcf

Ysat = (1=w)Yd =139.7pcf

You might note the dry unit weight of sand is 100pcf, wet ~125 pcf, gravel dry 95, wet 125, wet clay 125 pcf. And solid basalt is about 188 pcf and solid granite ~168 pcf.

So when you consider that and get wet weight of 187 pcf and a dry weight of 167 pcf, you might have missed something.

I had to work a lot of these problems, because I did the same thing you did.

I hope this helps.

 

[littlewheels4]

:mail-296:

can somebody please comment on my answer below? Did I do it right?

Thank you!

agree ---that is the unit weight of solids in the soil composition.
@ civilized_naah, can't you calculate it this way?

so if you draw the mass-volume diagram

you can assume for 1 cu.ft of soil.

mass of soilds = 165.98 lb

given the water content of 12.8%, mass of water = mass of soilds * water content = 21.25 lb

mass of voids = 0

and so total mass = 165.98 + 21.25 = 187.23 lbs for 1 cu.ft. or in other words, wet unit weight of soil = 187.23 lb/ cft?

Thanks

Well if you are making the assuption Vv=Vw, or totally saturated, where S=1, you can use e=w(SG)/S = .128(2.66)/1 so e=0.3405

Now you can get the dry unit wgt Yd = (SG)Yw/(1+e) Yd = (2.66)62.4/(1.3405) Yd = 123.82 pcf

Ysat = (1=w)Yd =139.7pcf

You might note the dry unit weight of sand is 100pcf, wet ~125 pcf, gravel dry 95, wet 125, wet clay 125 pcf. And solid basalt is about 188 pcf and solid granite ~168 pcf.

So when you consider that and get wet weight of 187 pcf and a dry weight of 167 pcf, you might have missed something.

I had to work a lot of these problems, because I did the same thing you did.

I hope this helps.

I believe this is correct, but the original post is a little vague. I am not sure if he is asking for wet or dry unit weight. I am guessing that he is looking for dry unit weight based on given water content.