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flow pore pressure rel ief wells were used. However, pore pressure data

are available for such cells and are shown in Fig. 20 for Cell 10. At that

cell six, 2-in. (51-mm) diam slotted pipes were used. The data are for

piezometric elevations measured by pneumatic piezometers installed near

the dredge level within the cell fill for the time at which the vibratory

probe had penetrated to the bottom of the fill . Excess pore pressures are

evident , keeping in mind that the piezometric level that would normally

be encountered at mean tide is elevation 6.4 ft (1.9 m). Since interlock

tensions are related to pore pressures within the fill , these data strongly

suggest a pretesting of the interlocks for this condition of compaction

pore pressure

  relief.

In closing, the writers than k Brow n and F orrest for their thoughtful com

ments. Special thanks are also due for their kind support during

construction.

Errata.—The following corrections should be made to the original paper:

Page 1657, line 7: Sho uld rea d, con struc ted in the U nited States, wh ich

instead of, constructed in the Un ited States, an d

Page 1672, Table 1, footnote c should read   t = pL/2)  (sec a) instead of

t = pL/2  (sec a)

U N D I S T U R B E D S A M P L I N G O F S A T U R A T E D

S A N D S B Y F R E E Z I N G

3

Discussion by T. J. Pilecki

4

The em pirical in situ m ea su re m en ts of soil characteristics in con

nection with the evaluation of liquefaction potentials is considered by

the auth ors on the first pa ge of their article. Th e state m en t em piric al

indicates that all of the remaining methods used in Soil Mechanics are

theore tical an d therefore  fool proof.  This is far from the truth. As a

matter of fact , Soil Mechanics is based on the Rupture phenomenon,

described by Coulomb as a shear strength function, and thus it is em

pirical in principle. Soil Mechanics is, therefore, not based on any one

theory, but on an amalgamation of experimental datas, gathered over

the years. This am algam ation of data is set tog ethe r in different form ulas

according to the standa rd, non-scientific proc ess , called a poste rio ri.

The article further indicates that only a special method of sampling

will give undisturbed samples of a sandy or gravelly material. This is

February, 1982, by Sukhmander Singh, H. Bolton Seed and Clarence K. Chan

(Proc. Paper 16874).

Consulting Soil Engr., 1040 Keith Ave., Berkeley, Calif. 94708.

653

   D  o  w  n   l  o  a   d  e   d   f  r  o  m   a

  s  c  e   l   i   b  r  a  r  y .  o  r  g   b  y   U  n   i  v  e  r  s   i   d  a   d   D  e   C  o  n  c  e  p  c   i  o  n  o  n   0   8   /   2   4   /   1   4 .

   C  o  p  y  r   i  g   h   t   A   S   C   E .

   F  o  r  p  e  r  s  o  n  a   l  u  s  e  o  n   l  y  ;  a   l   l  r   i  g   h   t  s  r  e  s  e  r  v  e   d .

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also far from the truth. First of all, soil is remolded due to drilling and

vibration. The insertion of the freezing units also remolds the soil mass

and then, during the f inal sampling, additional remolding occurs. After

that, the soil is still further disturbed by the transport and extraction of

smaller diameter samples from the larger units. During the time of freez

ing and thawing, whether we like i t or not, some disturbances will be

introduced into the soil structure, although it is obviously true that the

magnitude may be quite small , if we are lucky.

Finally, the article introduces additional illusions as to the correct re

sults of testing in a She ar Box or Triaxial Co m pres sion ap pa ratu s.

It is absolutely false to think that these tests give correct results with

respect to Cou lom b's p ara m ete rs, 4> an d c. The fact is that th es e an d

similar laboratory tests do no t give tr u e values of thes e param eter s,

as com pared to the rea l one s of the natu ral soil m ass in situ. These

laboratory tests give results pertaining to the structural characteristics of

the testing ap pa ra tu s i tself an d of the proces s applied in the actual

testing, as well as the properties of the tested samples. As a matter of

fact, there is a colossal difference b etw ee n pa ram eter s obta ined in a lab

ora tory and the rea l param eters .

The article proved that disturbances to soil sampling can be reduced

to a small fraction by the freezing process. However, this applies to a

small portion of the overall process of evaluation of the basic parame

ters. The benefit of freezing is rathe r small wh en com pare d to the overall

engineering aspect of Soil Mechanics, which is the maximum economy

of the testing comb ined w ith the m axim um precision. These tw o entit ies

are, de facto, all that there is, or should be, in all engineering consid

erations. They are the prime engineering principles of consultations.

This writer wants to emphasize that the expenses on sampling should

be kept in proportion to the overall scope of the undertaken project. Of

course, other facets of the testings together with their costs as well as

errors incurred, should be observed and considered.

I t is obvious that high advantages may be drawn from the util ization

of other m eth od s of testings, such as the empirical in situ m eas ure

m en ts of soil characteristics. These em pirical proc edu res are gener

ally much more economical and at the same time, they give much more

precise evaluation of soil pa ram ete rs, simp ly by elimin ating the tes tin g

appa ratus erro rs. Such tests as Stand ard Penetration Tests or Standard

Cone Penetration Tests are most suitable for sandy and gravelly soils,

as long as they are performed by experienced pers on nel. T hese tests are

the only ones that can give in situ results of liquefaction potentials,

whereas any other tests performed in the laboratory, will give the liq

uefaction tests potentials not of the real soils but of the soil samples and

of testing equipment combined.

65

J. Geotech. Engrg. 1983.109:653-654.

   D  o  w  n   l  o  a   d  e   d   f  r  o

  m   a

  s  c  e   l   i   b  r  a  r  y .  o  r  g   b  y   U  n   i  v  e  r  s   i   d  a   d   D  e   C  o  n  c  e  p  c   i  o  n  o  n   0   8   /   2   4   /   1   4 .

   C  o  p  y  r   i  g   h   t   A   S   C   E .

   F  o  r  p  e  r  s  o  n

  a   l  u  s  e  o  n   l  y  ;  a   l   l  r   i  g   h   t  s  r  e  s  e  r  v  e   d .