(SANITIZED)SOVIET PAPER ENTITLED, "PILE FOUNDATIONS FROM THERMALLY REINFORCED WEAK SOILS"(SANITIZED)

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A025500480001-6
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 13
• Document Creation Date: December 27, 2016
• Document Release Date: April 15, 2014
• Sequence Number: 1
• Publication Date: February 26, 1964
• Content Type: REPORT

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PILE FOUNDATIONS FROM THE THERMALLY
REINFORCED WEAK SOILS ?
LITVINOV x)
US SR
Collapsible loess soils are very abundant in many
countries and especially in the Soviet Union where they
cover vast areas. Numerous cases of excessive differential
settlement occur on these soils, often followed by
collapse of various buildings and other structures owing
to the high compressibility of such soils when wetted
,
,,,,ozf under anplied load.
?
This has already brou,-Tht about-great damage and
41 will do so in the future, for an immense number of large
bildinos and structures have already been erected on
.? settling soils and the rate of important construction on
t ?
,irsuch soils is steadily increasing.
Different methods of less soil stabilization have
odj .
, been suggested by a number of investigators. These methods,
c.
however, do not ensure the degree of consolidation required,
Or otherwise involve too much cost and labour.
The-Sourthern Research Institute for Industrial
Construction (Academy of Construction and Architecture,
Ukrainian SSR) has developed different methods for the
thermal consolidation of loess soils.
Thermal treatment of loess and other soils can be
accomplished by two methods. -
The first method, attributed to N.A.Ostachev, consists
in blowing hot air under .pressure into the soil through
heat proof pipes and bore holes, the air having been heated
to a temperature of 600-800?C in special stationary or
.? movable furnaces. This method has not found to have been
used in construction work.
The second Method, as offered by the author, has found
',? wide application on building sites. It 'involves burning
various fuels An the. soil .being treated, the process of com-
..bustlon taking place in sealed bore holes with:control of
the temperature and chemical composition of the combustion
products (Fig.li.
: . Heating of the soil to a temperature high enough to
. . cause the necessary changes in the soil characteristics is
achieved mainly by infiltration of ,the compressed heated air
or of the incandescent products of combustion through the
k ? .t. i ?
pores in the soil.
X) Academician-secretary of the Academy of Construction and
Architecture of the Ukrainian SSR.
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This method, which has been. successfully applied in
practical construction work, involves less complicated
equipment and less laboa. while being more effective and
economical than the first method, which facilitates and
"?rl2-extends the range of its application. -
This paper describes the basic requirements for
:.(1-1'`: -designing and manufacturing ,of piles from thermally
'reinforced soils using the second method of thermal
'stabilization applicable to collapsible loess and other
soils of similar porous structures.
i..f!
??? 'the t he rine 1 hot hod of consolidation the set-
, i''tling..properties. of loe.ss soils can b.e entirely eliminated
.tzto u=to -depth of 10 t6.,1.5..metars belowl.the footing 'base,
while the load bearing, -Capacity,is -grently inCreased.
,
. ? ? ?
From the engineerincyand.economical standpOint the
.thern4ily rainfor.ced sbils'anould? be
,1/4? _ ?
recommended ? for: the 'following purpose:- -;
frr
(a) To consolidate loess soils in the foundations
..f.i;.?/, of important residential and industrial
. buildings,. as well as other speCial types of
chi '1/4( ?itrud-tures-;? which.. do not 'allow differential
settlement.
(b) To eliminate the possibility of failures of
various existing buildings and structures due
to excessive differential settlement.
(c) To 'prevent landslides and similar other causes
of failurep.
? Due -to simple ;temperature control during ? soil., firing
(by blowing in .different amounts. of air".per kg. of 'liquid
or solid fuel or per cubic metre of gaseous fuel') in a
wide range of temperatures (up to 2000?C), the second method
can be adopted not-.only.for manufacturing of:the piles and
'Eruniferm .Consolidation' ..of larga.voluthes -of -1,oess 'soil,
at temperatures ?between 300P and, 1.,00.0?C, but for other
'structural purposes ? as well., when, .higher; temperatures' are
:* required causing. fusion of the soil. :."
:
To"facilitate penetration.of incandescent .dir into
? the soil, the'pressure of the hot gases should be maintained
above that of the atmosphere by .pumping cold air, into the
?bore hOles. Raising the excess pressure greatly increases
the effectiveness ,of thermal treatment and is*.ec.ononiical.
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". The temperature of the products of combustion must not
t exceed fusion temperature of the soil to be consolidated.
?re This is easily ensured by regulating the supply of cold
"air. The amount of fuel required per unit of time (kg per
c hour for 'solid. and liquid fuel or m3 per hour for gaseous fuel)
determined in'accordance with the permeability of the -
soil.
In this 'method, the use of gaseous fuel is. especially
.1-1;effective since starting the firing of the bore holes is
greatly simplified. The walls of the bore hole, and thus
the soil layers are more evenly heated, temperature control
in the bore hole is improved, partial fusion of-the walls
of the bore hole is prevented and the total Cost of
treatment is considerably reduced. The cost of gaseous fuel '
( as shown by information from the site) is but a small part
(about)3 per cent) of the total cost of thermal'treatment of
soil, about 70 per cent of the total cost involving air and
boring expenses.
The burning df the fuel, gaseous, liquid or solid, is
done in the bora hole or directly in the soil mass itself.
The mouth of the 'bore holes are tightly closed by special
shutters and. 0.25 to 0.50 atmosphere excess pressure of the
hot gases, is permanently nv.i.irltlalhoZ1 . There being no outlet,
the incandescent': gaseous products of combustion infiltrate
through the pores in the ground and heat soil mass to the
temperature required.
If sufficient' power is available ensuring an excess
"-cpressUre of 0.25 to 0.50 atm, the thermal treatment of.
large volumes of ground can be carried out simultaneously.
? ' The heat transfer from the hot gases in the bore hole
to, the, soil ,mass is achieved mainly by filtratipn of the? .
_air and incandescent gaseous products of combustion through
cthe ::;..porem of the soil and also by direct transmiasion'
.of heat due to temperature difference between the heat source
_ end_ the- soil .surface.
'
Loess soils, when subjected to thermal treatment,
greatly. change their following physico-mechanical properties:
'
_ , !
(a)_Susceptipility to settle and to be wetted are
entirely eliminated.
(b) Cohesion, compressive and shear strengths are
' greatly increased (Fig.2)
(c) Settlement under an applied load, when the ground
is wet, immediately ceases.
(d) Color changes from natural pale yellow to various .
shades of red.
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The temperature of the hot ga'ses which are formed in
the bore hole due to the. combustion of the fuel can be
controlled by changing the amount of air blown int o the
bore ?hole. By.. increasing or decreasing this amount of air
the. temperature Of the combustion gases is raised or lowered,
. The excess .air blown into the bore hole does not participate
in the chemical . reaction of combustion but merely mixes with
.the products of combustion. and -lowers the temperature of the ?
mixture, serving ...as an additional heat carrier, transferring
the heat through the pores of the ground.
The, temperature of the gases in. the, bore hole (losses
not taken, into :aCcount ) can be determined from the . following
equations:
in_which
?
,
Qr
( 1 0293, VB
the calorific value of the fuel;
VB the amount of air blown int o, the bore
?
hole per kg. of fuel (m3);
? C the average heat
p?
. of Combustion at
-;cal. per kg
equal to 0,235
Table
between the
of fuel and
? liquid fuel
capacity of the products
constant pressure p
per (3,0g) which is t aken
0.000019.tr'.
i is given the approximate theoretical relationship
amount of air blown into the bore hole per kg
the. t emperaturo of the gases in, the bore hole for
(Diesel)
Table 1
.? :
kg
VB m3/kg
degrees
1.1, 2
1
1,5
16.8
?6 -__r_______
F-2-1 2.5 i 3 1 3.,5
0
I
1
1
22,4 128,0
[ ? - 1 ? 1
28000 [ 1670? f1300910500
36.6 39.2
8960
785?
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,The amount of air that is blown inside the bore :
. hole (VB) should be 2.5 to three times the minimum quantity
. which is required for complete fuel combustion.
The amount of air filtering through the walls of the
bore hole into the ground is dependent on the gas permeability
? of the soil and on the pressure in the bore hole and should
? be determined experimentally by a. blowing test. With loess
? soils of 8 to 20, per cent moisture content the quantity
of air that is filtering into the ground is usually 10
' to 40 m3/hr per mptrie bore hole depth.
The air quantity (V,,,,) that is necessary to provide
for an optimum thermal ti4eatment under conditions of
complete fuel combustion and cooling of the combustion
products ( in m3 per kg of liquid fuel or m3 of gaseous.
)fuel) is dependent on the temperature of the hot gases in
the bore hole as determined from the formula above or
from Table 1.'
The quantity of fuel burned during one hour per metre,!
run of the hole is determined from the caloric value of the
fuel, gas permeability, fusion temperature,. moisture content
and volume weight of the soil to be consolidated.
'Increasing the.quantity of fuel burned per hour will
raise the temperature of the hot gases above the calculated
value and fusion of the walls of .the hole may take place. '
Such a hole should be rejected and a new one drilled nearby
(Fig. 4).
The thermal .treatment in one 15 to 20 cm. dia. bore
hole during a period of eight to ten days will result in the
formation of a consolidated zone in shape of pile of 1.5
to 2.5 in diameter and 8 to 10 m. deep.
If the time duration of thermal treatment is increased,
the consolidated zone around each hole will become larger
?(3 in diameter and. 15 in depth or more).'
The setting up of the thermal reinforced piles is
designed in one or several cycles with simultaneous
thermal treatment of a corresponding number of bore holes
in each cycle. '
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To increase the rate of processing the number of cisreles .
should be as low as possible. Thus, in underpinning the
. foundation oof various buildings or eliminating the -conseq-
uences of failures duo to local wetting of the soil) as well
as in many other cases when the total number of piles produced
-varies .from 6 to 30, the work of thermal treatment should
be carried out in one or two -cycles, i.e., du-ring .a period.
- of 10 to 20 days (Fig.5).
? The duration of ???:..?each cycle of burning the calculated
amount of fuel under the conditions assumed is about 10 days
and may increase or decrease depending on the depth of the bore
hole, .the designed diameter of the consolidated zone of the
piles from the thermal reinforced soil and the capacity
of the equipment for pumping air into the bore hole.
In applying the thermal method of consolidation, its
economical ahd engineering advantages in the case under
consideration should be taken into account..The application
of this method is not economically justifiable for under-
pinning the foundations of small and unimportant buildings
,` and structures and when the thickness of the setting soil
is small.
In the course of thermal processing, continueus control
...of the combustion process in the bore hole should be obtained
,bi.'maintaining a temperature between 750 and 10000C at pressures
to 0.50 atm. The burning of the fuel can be observed
' through, a special peep hole in the shutter.
The thermal treatment is considered complete when a
calculated amount of fuel has been burnt inside the pile at
a'pressure not below 0.25 to 0.50 atm: and when a proper amount
'of air has been pumped into the hole.
After firing has been completed and the ground inspected
the bore holes are filled with soil and throughly rammed.
By appltting the ? thermal?method of consolidation 07 large
number .of damaged buildings and other structures have been
saved from collapse and have been erected on weak soils
requiring treatment,' ''?
? .
-
?RGIAN*
?
?
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I.
.rzarnii 1
D of .installation for tharmio stabilisation of oollapsibla looms 'Oils by tam ssoond
East al. 1. Oomprikisor; 2. yipstine for cold air; 3. oontainar for liquid !nal; 4. primp for
supp13r1ng fnal. =dr prossnrs into tb? bore bolo; 5. fug pip* Una; 43. altars; 7. nos:1s; B. cover
with combustion ?bomber; I. bora holo; 10. sons of thermic stabilisation of soli.
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r-
"L,
8.0
7.0
60
50
40
t-
3.0
20
1.0
MM.
c49
/ \
/ . -- -
" :
----
,
1
? 1.0 .. 2.0
P kg/cm2
--- Undisturbed loess ot noturcil moisture content
Loess bvrned in a dry. stote
Undisturbed loess after preliminary wetting
Loess burned after preliminary wetting
30
40
PIG 2
171413
Composite results of shear teats of undisturbed
loess (at natural moisture content and after pre-
limin.ary wetting) and of, thermically stabilised
loesk (dry and after preliminary wetting)4
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Fuel supply
Consolidation pipe
3
FIGURE
RenneticaLly sealed cover with combustion chamber. 1. Combustion chamber; 2, 3 and 4.
oeramic cones lining combustion chamber; 5. metal lid; 6. observation pipe with branch to
manometer; 7. manometer; 8. pipe for supply of excess air to upper part of combustion
chamber; 9. pipe for supply of excess air to lower part of combustion chamber; 10. wedges to
holAnozzle; 11. anchor ties; 12. reinforcing steel of 6-mm rods (total weight 3-4 kg); 13. con-
crete of red brick aggregate; 14. thermo-insulating packing; 16. fixation of metal lid; 16. hollow
ring with lye.
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1
1
1
1
Bottom of excavation pit.
for stabilization work
'Level of foundation base
( 1
I
I
r
2 2-3
/ d=0.1-0.2m
I
I
1
1
Collapsible
loess soil
Non -collapsible
Soil'
? 4?
FIGURE
Thi spread of zones of thermic stabilization (strengthening) of soil around vortical bore holm.
I. Under an pressure of 0.2-0.5 atm. in the bore hole. I/. With no exams pressure in
the bore hole.
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3 a- 2
, 5
PIGIIMIX '
Diairrain of egnipment connections forth. simultainavas burning of 12 bore holes by cols._.
1. Air -collector; Z. movnble compreesors; 3. overflow; 4._ gas -blower; 5. Fes lin 1
es; 6. water .;
7. was colietstOr..
- ? ,
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