THE STRENGTH OF FROZEN SOILS UNDER BUILDING FOUNDATIONS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82-00039R000100100071-2
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 11
• Document Creation Date: January 4, 2017
• Sequence Number: 71
• Publication Date: February 12, 1951
• Content Type: REPORT

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Titles TFI~ S'!'R~taT~ n~ ~'ROZ~ii SOILS UNDER 9UZLUINQ F'OU~D~1T~OlV~
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Declassified in Part -Sanitized Copy Approved for Release 2012J05/25 :CIA-RDP82-000398000100100071-2

 Declassified in Part -Sanitized Copy Approved for Release 2012/05/25 :CIA-RDP82-000398000100100071-2
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TM~ STRF~IOiTN QF ~'~0~~ ~ ~~~DIIVO i
FOUNDATION6
9~ 8oresantsev
the resistance of various soils to external loads show that
Studies of
to three basic groups acoordin~ to internal resia-
soda can be divided in
eformation: 1) soda in which resistance is provided by internal
Lance and d
2 sails in which resistance ie created mainly by cohesion; and
friction; )
soils in which resistance ie provided by bath internal friction
lastly 3 )
and ooheDion~
We shall not enter ie~~a detailed e~,aasifiQation of these three
a caf soils becaus� this complex problem should be the eub~ect of a
group

4
al stud w� will merely show the place occupied by frozen soils in
specs Y3
this clasaification~
hall consider some research data on the behavior of frozen soils
We s
ad Fi ure l shows typical compression (stress-strain) diagrams
under to ~ ~
N. A. Ts tovichf Corresponding 1~ember, Aaede sciences USSRi
obtained by Y
e of frozen clay at -10~1~�C (Figure 1~ right) and frozen sandy lQBm
-t for cube
E.
- at �3.l�C (Figure l~ left)
ro ortional limit ar?d the section showing recti-
In the diagrams the p p
ar�nt
linear dependence between stress and strain are both clearly app
a lied load (beyond the proportional limit)
With a further increase in pp
different. At low temperatures (-10 ~ strain
the diagrams become quite
the a lied load is increased almost until the latter
increases only as pp
_ t , ~
z ~ ~ e i. e. there is no definite yield point This
reaches the rupture vale ~
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r Declassified in Part -Sanitized Copy Approved for Release 2012J05/25 :CIA-RDP82-000398000100100071-2

 Declassified in Part -Sanitized Copy Approved for Release 2012/05/25 :CIA-RDP82-000398000100100071-2
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that observed in the oleava6e of oubeo o!
typo of rupturo io similar to
brittl� folida~
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r a relatively pith temperaturo (-3~~' , tho
In the �eaond oases fo
a certain period o~ inareaeint strain with
point is olearly aeon after
etratn continuer to incre8ae markedly with no
inoreaeint etx�ae, iiei ~
the deformation speed r@maine almost oon-
increae4 in the applied load and
i
{ etant~ a Institute
~ hie field effect (experiments in 1946 by th
We also observed t y
e o f Soienoee USSR~~ in the Leningrad Conetruo-
rmaf root 8tudi�e, Aoad ~Y`
of Pe
reesin a 3 x 20 om die into frozen olay at
tion ~gineerint Institute) in p g
2 the yield point appeared a a
. ~ sit 289 and cohesion 2.28 kB/cm ~
3 , hums y
~ 22k em.
unit stress of 1 ~ g/
f deformation of frozen soils ~de~' load
~ Cone equently ~ the type a
e behave similar to brittle solids ~ 3
indicates that soils at low temperature
eratures they acquire properties eimi~.ax' '~o
while at relatively high temp ,
those of plastic �olide~
e is created by cohesion. Thum experimental
a In both cease, reeistano
e etren th of frozen soils with the excap-
il data forces the conclusion that th g
-called ~~dry frost"7 is provided mainly by ,
Lion of dry sandy soils (the eo
leads to the same conolueion. In order to
i
cohesion. A theoretical study
baoic rinciples underlying theoretical
chow thin we briefly consider the p
determinations of the rupture loads
a uniformly-distributed bar load (the two-
For the simplest case of
entl recommended that soil ~ e bearing . ` '
dimene tonal problem) ~ it is f raga y
determined by laeticity theo Prandtl ~ a
capacity limit be theoretically
a Friable Mediums 'Szd � AN SSSR~ 1942) �
Sokolovskiy! V� V�, The Statics of
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~r A' e' z , f Declassified in Part -Sanitized Copy Approved for Release 2012J05/25 :CIA-RDP82-000398000100100071-2

 Declassified in Part -Sanitized Copy Approved for Release 2012/05/25 :CIA-RDP82-000398000100100071-2
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~o~over~ at studies have ehownj Prandtl~e eyeten~ of oliding 'urfaooo
must be ohanged slightly in order to bang the theoretio+~ pioture of Boil
rupture into agreement with the e~leoto aotua~ly observed in nature This
oh~lge relates to the soil region situated under a 3'oundation, in whioh no
eliding eurfaoei aotually odour (oontrsdioting F~randtl~s ideas
~ the
A bearing bulb Forme beneath foundations, whioh together with
~ foundation det`orme the surrounding ground With aacur~,cy auffioient for
a e that t1~ie b�arin bulb has the form of a
praotioal purposes, we oan as um g
Then the ~
reotangular prism (i.e. ha'~t a right triangle dross aeotion)~
formation of sliding surfsoes will be as in Figure 2. This system has ~
already brought us oonsiderably oloser to the pioture observed in nature.
The limit of soil~e bearing oapaoity is expressed by Prandtl~s formula, "
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whioh we have changed slightly:
P o+kq! (l)
rup ~ 2
here o ie cohesion; q is the intensity of a uniformly distributed load on
the soil ~ s surface, whose action ie equivalent to the action of the soil ~ a
t`#
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~f ~
r ~ cot ~ ~ ~
~
. ~ ~ s ~ e ~ C ~r ~ t~~
I 1 ~
r ~ + ~w ~ ~ ~
t ~
C
Where ~ is th� soil~a angl� of internal friction.
Ae seo~, from the form of (l), its first term gives the resistance due
to cohesion while the second term gives the resistance due to the loading
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action of the grounds own weight and to the internal friction caused by
a this action.
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' ' ' ~ ~ Declassified in Part -Sanitized Copy Approved for Release 2012J05/25 :CIA-RDP82-000398000100100071-2 ,

 Declassified in Part -Sanitized Copy Approved for Release 2012/05/25 :CIA-RDP82-000398000100100071-2
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w inveoti ate for different ~glea of internal friotion the ;
Wo no g
a
~ for foundations of ordinary oiae~ frequently
rel anon between ~tbes a txo terms
tioe~ ~'i re 3 shows a grap~de8oribing the variation
enoQUn'~ered ir, prat ~
l ae a funotion of interns friotion an6'le for
of eaoh term in formula ( )
n .0 meters aide Dunk 2.d meters de,p into the ground
the oae0 of a foundatio 3 ~
n a denei of 1 ~ 8 tone aubio meter and oohee ion of 2 ~ 0 kg om
and havi g
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ahowe thnt the 11apeoi~io weight~~ o� th� aeoond term in form + ;
The graph ~
uee of ~ Tnus at f 30' ~hn term k2q ie l8~
val
e ~na1l for low ~ ~
(1) i
� 20' it ie 13~d; and at ~ ~ l~' it ie only
of tine total resistance; at
ns wider than 3 meters, the value of the seoond term of
{ 11~~ For foundetio
s Thus analysis of the formula for the bearing ~ap-
(1) will be still lee
Navin cohesion 2.0 kg/om2 and up the reeie-
achy limit ahowe that in soils g ,
can in most cases be disregarded ae of negligible
tents of internal f riotion
~ nder load can be considered as provided
influence and that soils �trength u
s 24� and lower Most frozen
solely by oohesion for internal-f riotion angle
' la have ve low internal friction and considerable oohesion~
eoi ry
,
n of internal friction in frozen soils? in comparison
The sharp reduotio
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n tQm eratL~res above 0�C is explained by the considerable
~ with soils havi g p
4
f soil articles due to water freezing in the pores In the
dissooiation o p 1
der load internal �riotion decreases b�cause of the
deformation of soils un
f ra namic processes, even though the particles come closer
presence o hyd dy
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t0 each Other
into considerations we should think that in both
Taking those effects
ils the an le of internal friction is usually less
clayey and sandy fr�zen so g
than 20�~
stic of the amount of cohesion, we employed N. A.
For the oharacteri .
frozen soils' average temporary resistanoe to
Tsytovich~8 data on natural
a of a Dube } when completely saturated with
compression (temporary resistant
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 Declassified in Part -Sanitized Copy Approved for Release 2012/05/25 :CIA-RDP82-000398000100100071-2
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l~ ~e assume that the cubes could be normally deformed and that tho
ooheoion was numerically equal to the ~~anger~tial breaking point under exper-
imAr~tal oon~it~.or~e~ then soaQrding to the ebo~e d8te tt~e ccheeion Q~ frQeen
eailo varies ,from ~.5 to is kg/cm~
The temporary resiatanoo to oomprooaion i� g~vari by the ~ollowir~
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igurea ~
Temperature: Up to -8~5� From -a!5' to -I~5� ~`roia -1.5� to w2~~�
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Sande 22 ~7 3~ i
Sandy Loam l1 22
Clayey Soils ~0 ~6
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Qla~?e 6 17
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Dusty Silt Soils 5 15 ~3
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Consequently, theoretical studies of resistance forces aoeounting for
strength under load fully confirm the conclusion that for most frozen er,ile
these resistance i'orces are creatod mainly by cohesion alone Starting
from this bneic principle, we consider it correct to adapt the Saint-Venant ~
theory of strength the so-called maximum strain theory,' to determine
frozen sails ~ resistance to load.
We first consider the case, very important in engineering] of the effect
of a uniformlydietributed bar load the two-di?~eneional problem) We must
first clarify how valid is the assumption of
uniform transmission of pres-
aurae to the soil by rigid Foundations (with which we must de~1. most fre-
t
quently) for loads near critical values.
Rigid foundations trithin elasticity limits transmit pressure to the
soil quite nonuniforrnlyj moreov�r if the soil has considerable oohesion~ the ~
,k., pressure distribution diagram along the foundations bottom has saddle-
like form (see Figure l~)
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