CA2063573A1 - Pile moulding process and tooling assembly for implementing the same - Google Patents

Abstract

FILE MOULDING PROCESS AND TOOLING ASSEMBLY
FOR IMPLEMENTING THE SAME

Abstract A pile moulding process comprises feeding a setting ma-terial (6) into a pioneer hole (1) or into the soil, With high-voltage discharges of electricity induced in the mate-rial (6) fed in, and displacing the material-supply and discharge-induction zone (7) along the height of the pile being moulded. The total energy of discharges at a given depth is such that the respective section of the hole (1) or of the soil is widened to match the pile diameter specified for the given depth. The effect of discharges is to create around the pile being moulded a fixed-soil zone (3) of higher strength and a compacted-soil zone (9) featuring improved construction properties.
The tooling assembly for pile moulding comprises a pipe (3) to supply material and an electric discharger complete with electrodes (10 and 11) arranged coaxially, spaced apart, and mounted over an insulation rod (15) passed through the first electrode (10). The first electrode (10) is connected with that end of the pipe (3) which contains its discharge opening (17) so that its axis is parallel with that of the pipe (3) and the distance between the second electrode (11) and the discharge opening (17) of the pipe (3) is not less than the interelectrode space (16).
FIG. 1

Description

PILE .-~ULDI`~G P~OCE'a~ A~TD 'rOOLI rG ~S~ /'i3LY
~OR Ii~lPL~.~EL~'r Ii~G r~lE :i~]E
~'ield ~f the Invention The present invention relates to the I'ield ~f ~lilling an~ construction or, more specific~lly, to pile ~ouldin~
processes and tooling asse~blies and can'be ~sed to ~ e pile f'oundations in the process of co~strlctin~ or reconst-r~ctinO blildinOs ~nl en~ineeri~ str~ct~res.
~'rior ~rt There is '~no~qn a process of pile fabrication (DE,C, 2651023), usad to reir.force existi~C~ fol~ndcltions and co~pris-ing the step~ of ~rilling a hole ~ the lse of a chlrn-and-rotary d~illing rig and casing pipes as a means of ?rotecti-on, inserting the rei~forci~g bars, an~ trolucing into the hole a pipe to be ~lsel to pi~p in ceme~t-a~d-san~ ~ortar.
After ~eliverin~ the necessary ~nortar and bef'ore its setting, an i~jection pipe is p~ssed t~lerethrolOh, ~hich pipe is used to pu~ in ce~nt mortar at hioh ~ress~re to ac.hieve a sprecld at the footing of t~.e yile formed in the process.
This process is 1isadvclnt,igeols i~ tnat tne pile ~as a lo,v bearing cap~city aro~n~ its side slrfqces, inas~cn as the hole for the pile is formed by soil excavation, ,~nd a layer of less dense soil is f'orlmed ~rol~l its walls, ~hich fails to contrib~te to the flnctio~ing of t~e pile. It is for this reason that the pile has to be made of ~reater length so tnat its loNer en~ ~olld r~st against lense soil (rock or ~o-raine).
hnother disa~vantaOe of tnis process is 13w efficiency -d~e to havin~ to c-rr~ olt tne ~per~tions comprised in the ~rocess in slccession, i.e. sin~ing a ilole, then installin~
c~sin~ Qipes, e~tr~ctir.O the drillir.g tool, i~.serting iqto ~0 the hole a ~i~e to _llo~ of pl~pirg in ce~ent-and-sand mortar, ~illing the hole with this mortar, re~oving the casing ~ipes and th pipe lsed to olmp in ce~e.nt-and-sand mortar, install-i~q~ i.q the hole an injection pipe, anl feeding in ce~aent ~or-tar, with an interval to be maintained in betlNeen the latter 2063~73 "

two of -t`ne listed oper~tlons, this being associs-lted with the setting of the pile ~ateri~l ~vhich acts ~3 ~cker ~lrin~
tne p~mpin~-in ~t hi~h press~lre of ce~ent ~ort~r.
There is ~nown a pile fabricatior asse~bly (J~
4~0994) compri3in~ a 2iPe desi~ne~ to feel in settiq~ mate-rial ~nd connected to a .~ortar p~mp. ~he ~ipe i5 sunk intO a hole, and setting ~aterial ls fe~ into it to for~ the body of a pile, the pipe bein~ e~tracted as the ~aterial fills the hole.
rhe assembl~ in q~lestion i9 lisa~v~nta~eois in tnat the ~ile it is capable of prod~c ng has a low bearing cap~city becalse the asse~bly c~n only provide for feeding ~ateriil into the hole, qot for c3~pactin~ the slrro~ndin~ soil. T~e 10N bearing cu!~city of the ?ile is flrther dle to the sett-ing .lateril oein~ mixed -~ith /vater or soil ~hile it is fed into the hole. 3esiles, t;~ere ~ occlr discontiqlities in the ~ile ~ateris~l along the pile ;qei~Lt owing to grolnd wa-ter or claJ mortar brea~ G thro~h inside tne pipe.
~nother dis~dv~nta~e of t~LiS ~sse~oly is tn~t the pile

2~ labri^ation ti~e it is c~able of` providinG is ~lite lon~, since ~ art fro~ the nole sin~ing anl the fillin~ of the ho-le with setting ~ateri~l there are the vperations th~t have to be carriel o~t to preve~t -the ;~sills of the hole f~o~ c~v-ing in, i.e. inst~lling cssin~ pipes inside the ~lole or fill-ing it witn cl~y ~ort~r.
Discloslre of the Inve~ltion ~ he invention is based lpon the objective of Qrovidi~gs ~rocess ~nd a toolin~ ~ssenblJ for pile ~oulling such th-t woul~ ~fforl of fcr~ing aroln~ the pile a higher density soil zone contrib;lting to the pile function and thereby increasing t.he bearing ca)acit~ ~f tne pile, ~s well as lecreasing the pile ~oul~inG ti~e on accolnt of reduced n~.~ber of o~erations.
rhe ob~ective as stated above is achieved br proviling that in a process of ?ile ~oulding by way of feelin~ into the pile for~tion zone of setting ~aterial taere are high-volt~-ge ~ischar~es of electricity ~eing inducel in the ~aterial 20~3573 fed into pile formation zone, with the material-~upply and discharge-induction zone being displased ~o-Nn the pile for-m3tion zone, consistent with the formation of the pile shaft, ~d with the total ~ner6y of discharges :~t a given depth of the pile form~tion zone being 3uch that the ~ia~e-ter of the respective section of said zone is increased to sult the pile diameter specified for this depth.
The increase in the be~rin~ capacity of the pile afford-ed by the proposed methol of fabrication is lle to the fact tnat in the process of high-voltage di3charges being induced in the setting materi~l fed into the pile for~ation zone there occur periodically discontinuols increases in pressure, le~di~g to this zone being widened, the soil around it being compacted, free and pore-contained ~ater being squee2ed off, an~ setting material infiltrating the free~soil pores. As a res~lt, there is for~ed around the pile a zone of fixed soil, and a zone of packed soil around the previous zone. 3esides, the proposed process per~its of al1justing the cross-sectio-nal area of the pile with height by adjusting the total ener~y of discnarges with the depth of the pile formation zone, t'nereby controlling the bearing capacity of the pile in the process of ~o~l~ing as a function of the soil type.
In the proposed process there are no operations to pro-tect the hole walls from caving in by any of tne existing ~nown ~ethods (casing pipes, clay .mortar), and the time require~e~t for pile fabrication is also reduce~ by integrat-i~g in the material supply, pile shaft formation, and soil com~ction operltions.
Setting material may be fed into a pioneer hole used -s pile for~ation zone.

2063~73 Setting 3aterial may likewise be fed directly into the soil which in this clse serves as plle for~ation zone.
This enables further reduction of the ~ile moulding time -by avoiding the hole sinking operation.

,Yhen moulding a pile lavin~ its radius chan~ing wit~
hei~ht, the nu~ber of discharges ~ay be conveniently varied d~ring the displacement of the -~terial-s~pply and disc;~l~rge--induction zone in a manner such that at a ~iven depth of the pile for~ation zone this nu~oer is directly related to the 10 pile ra~ius specified for this depth.
~nen mouldi~g a pile '.l~Vi~g its radius changinO ~:vitn height, tne discharge frequency nay be v~riel during the dis-place~ent of the material-sl?ply and discharge-induction zone in a manner such that at a given depth of the Pile formation zone its value is ~irectly related to the pile radiu3 speci-fied for this ~ep-th.
i~hile mo~lding a pile in a pioneer hole, it is advisable that the number of discnarges, n, at a given depth of the pile formation zone be equal to:
r - ~ ~
n = exp 3 , (1) K(~t\ ~ - rO) where: r is the pile radius specified for the given depth,m, rO is the radius of the ~ioneer hole, ~, ~ is the energy of one discharge at the given depth,J, K is a coefficient accountin~ for the intensity of accumulation of irreversible defor~ations in the soil, and i9 a coefficient accounting for the soil properties.
In one of the embodi~ents providin~ for pile fabrication directly in the soil, the ~aterial-supply and discrlarge-induc-30 tion zone is displaced ~eeper down into the soil, ~Nith the num-ber of discharges, n, at a given depth being equal to n ~ exp r - X ~ ~ (2) K ~ ~ ~
where: r is the pile radi~s speclfied for the glven depth,m ~ is the energy of one discharge at the given depth,J
X is a coefficient f~cco~unting for the intensity Or accu~lation of irreversible 1eformations in the soil, and a ooefficient ~ccounting for the soil properties.
According to anotner embo~i~ent proviling for pile fab-~0 rication directly i~ the soil, the ~aterial-supply and dis-charge-induotion zone is displaced down into the soil depth, ana, on rea¢hinB the ~apth oorresponding to the s~ecified pi-le height, the m~teri~l-supply and dischar~e-ind~otion zone is displaced ~pwards, with the energy of the disoharge, ~1~
incident to the downward displacement of the ~aterial-slpply and discharge-induction zone, being determined from the re-lation d3 = ' (J) (3) 1 13.12 :: ~here: d ls the ~aximum cross-sectional size of tne tooling assembly, providing for the s~pply of ~aterial and induction of ~ischarges, mm, and f is the soil strength coefficient aocording to Pro-todya'~onov's scale, while the n~mber of discnarges, n, ~t the given ~lepth during the ~pward displaceme~t is determined from the relation r - X ~ (4) : K (~ ~ _ 0 5 d) 2063~73 ~here: W ls the energy of one discharge at the glven depth durlng the ~pward displace~ent of the material--supply and di~charge-induction zone, J, r i8 the pile radlus specified ~or the given depth, m, K is a coefficient accounting for the intensity of accu~-~lation of irreversible deformation~ in the soil, ~ is a coefficie~t accounting for the soil proper-ties, and d is the maximum cross-sectional size of the tooling asse~bly, providing for the supply of ~aterial and inductlon of discharges, m.
~hile moulding ~ tapere~ pile, it is advisable that ma-teri~ pply and discharge-induction zone be displaced ~ith step increment ~ h derived from the relations.

~ h = r' (1-b) sin i2 arc tan ~ b) tan 2~ ~} a.t r'~r~
and . (5) ah = r'(1-b) tg {2 arctg [(1-b) tg -~-]} at r~ r~, , where: b is the ~llowable relative deviation fron the speci-fied pile ra~i~s, i9 the specified angle of pile taper, and r' and r" are the specified pile ra~ii for the preceding and subsequent lncrement, respectively.
The objective as stated above is also achieved by pro-viding that the tooling assembly aesigned for pile fabrica-tion an~ comprising a pipe to supply setting material, con-tains additionally an electrlc disoharger complete with electrodes arranged coaxially and spaced apart, of which one has ~n annular for~ and is ~ounted over an insulation rod .. . . .. . . .
. - - ~ :
. ' - ' ~

2063~73 pasqed therethrough while the other is secured to the end of thiS rod and connected to a current-carrying rod arrang-ed lnside the insllation rod and connected to the central core of a coaxlal cable whose screen braiding i~ connected to the rirst elactrode, .qit`q the di.q~eter of the se¢o~d electro~le exoeedlng t~lat of the ins~lation rod, the first : electrode being rigidly connected with that end of the plpe : : which contains its lischaree opening so that the axis of t~he first electrode i~ r~r311el with that of the plpe, and : 10 :the distance bet.~een the discharge opening of the pipe and the~secon~ el~ct.rode is ~ot less t~an the electrode- to--electro~e ~ap.
-~ Ning to the ~resence of the electric discharger atta-ched: to tne setting naterial supply pipe near its ~iscnarge ~15 oyening, the pro~ose1 tooling asse~bly .~ay be used to i ple-~nent the prooess as lescribed a~ove, per~itti~g of ~eeding : : ~ the s-tting ~aterLal whiIe si~n~ltaneolsly inducing high-vol-: tage di~charges therein. Also, the tooling assmebly i3 sui-table ~or having a pile mo~I~ed in a borehole as well as 2~ .~directl~ in t'ne soil.
In the follo~Ning~ the invention is ~ade ~ore fllly ~ apparent through a ~etaile~ de~cription of tne best ~odes of :~ ~ : carrylng it into effeat, ~ith due references made to the aoco=panying drawi~s.
S~m~ary of the Drawings FIG.1 ill~strates a pile ~oulding process ~ccording to one Or the e~bo~i~ents of the invention, FIG.2 illlstrates a pile ~o~ldi~ process accordin~ to another e~bodi~ent of the invention, FIG.3 illlstrates the first stage of the pile ~o~l~ling process according to the thir~ enbodi~ent of the invention.

2063~73 ~, FIG.4 lllustrates the secondstage of the pile mouldin~
process according to the thlrd e~bodi~ent of the invention, FIG.5 ill-~strates a tooling assembly to use for pile fabrication, according to the invention, and FIG.6 ill~strates the change in the characteristics of the soil around the pile fabricated in accor-dance with..the invention.

3est r~dodes to Carry out the Invention ~e proposed process is carried out into e~fect as fol-lows. Any known method, th-us rotary drilllng, is used to sink a pioneer hole 1 (FIG.1~ of a ~iamet~r less than that oi the pile to be fabricated (in the case of a cylindrical pile~
or equal to the mini~lm dia~eter oi the pile to be fabricat-ed (in the case of a pile with the diameter changinO with height). Reinforcin~ `~ars are positioned in the hole 1, if so specified, and a tooling assembly 2 is lowered into the bottom 2art of the hole 1, said tooling asse~bly oomprising a pipe 3 to s;upply a setting material and an electric dis-charger 4. The plpe 3 is conne^ted to a mortar pu~p (not ~hown), .qna the electrio lischarger 4~to a current pulse ge-nerator 5. A setting ~naterial 6 based on cement or synthetic : binders i3 fed 1nder pressure, contin~ously or in portions, throA~h She pipe 3 ~hile current pllses are supplied from the generator 5 to the electrodes of the electric discharger 4 to produoe hi~h-voltage discnarges of electricity within the .~aterial 6. Thus, the zone 7 to be found lnler~eath the botto~ end of the toolin~ assembly 2 is a zone ~hsre material i3 supplied, and discharges are induced. ~ach discharge pro-dl¢ed within the hole 1 filled partially or completely withthe ~aterial 6, causes a discontin~lous increase in Qressure.
The res~lta~t inp~ct effects have the result o~ co~pacting :.
, - - ~ .
-2063~73 g the ~n~terial 6 ~rlthin the zone 7, ~idening the hole 1 ln ltslower part, squeezin~ free and ~ore-contained water away fro~ the adjacent soll, and havin~ the ~aterial o infiltrat-lng soil pores freed from water to for~ a fixed-soil zone 8 oi high stren~th, as also q compacted-soil zone 9 sit~ated aro~nd the zone 8 an~ havlng i~proved building q~alities (higher bearin~ c~picity of the soil due to ~ lo~.~er volds ra-tio an~ a higher ~odulls of defor~ation). The free s~ace formed as a rés~lt of a~terial 6 ~eing compacted, is gradual-1~ ly~filled by new portions of ~.aterial so tnat eac.1 slbseqlentdischarge occurs in a ~ew volume o~ ~naterial.
The tot~l ener~y of discharges - tneir number in this cdse - is selectel so ~s to ~ss~re the lower p~rt of the hole 1 being Ni~ened to ~atcL1 tne pile diameter specified for the lower part,of the pile. It is in this ~ay that the pile foot-ing is for3e~.
As established eYperi~entally by the inventars, the ener-gy of each dischar~e ~ust be at least 5 kJ Nhile the pressi-re of the hydrallic strea~ within the hole 1 ~ay rise fro~ 50 2~ to 2?0 ~Pa. h`ith 1ischarge energies below 5 ~J, the pile for-.~ation time is longer than the ~aterial setSing time, res lt-in iQ a lower pile ~aterial strengtn. Induction~of dischar-Oes witn ener~ies above 2~ kJ is not reco~mended because in-creasing loads on the hole walls ~a~ lead to exoee~ing the per~issible soil oscillation velocity and to a seis~ically har~ful effect ~lpon the neighbouring ~ilildings and structures.
~esii1es, the weight and size c~racter~stics of the asse~bly designed to i~plement the proposed process ~ill increase ~Nith increaslng dlscnarge e~1ergy.
~0 Further, the tooling asse~bl~ 2 and, hence, the Qaterial -supply a:~d discharge-in~uction zone 7 therelnder are di3plac-ed ilpwards, as sho-~n by arrow in ~ it~ a step incre~ent h, and the process as described above i3 repeated, thls for~-ing the silb~eq~ent pile ~haft sections. In theeVent ~hen a pi-le is febricate~ witA a radius cAanging with hei~ht, the nu~-ber of discharOes at each su`osequent step is increased as against that at the ~receling step in case the Qile rali1s is :: :

-- ~o lncreased~ m d vice versa. The step lncrement ~ h i3 deter-mi~ed ln rel~tio~ to the principle speoified ~or the pile radius changing with height and to the desired pile fabrica-tion acclracy. Thus, for the fabricati~n of a cylindrical pile, the qtep increment ~ h remains con~tant, its v-lue be-lng equal to ~ h = r-sl~ ¦arc cos (1-b)l , (o) where: r is the specifled pile radius, and -b is the allowable relative deviation fro~ the specified pile radi-1s.
For the fabrication Or a tapered yile, the step increment h is determined fro~ the relation ~ h = r'(1-b) Sin {2 ~rotg [(1-b)t ~ ]~ at r'~ r'' or (7) Q h = r'(1-b) tg l2 arctg [(1-b) tg ~ } at r'c r'', where r' and r" are the specified pile radii at the prece;l-i~g and subsequent steps, respectively, and ~ is the speci-fied an~le of the pile taper.
With this step;i~cresent the nu~ber of discharges, ~ , ~er each ~tep ~ay be ~elected such that the radius of the pi-le section being ~oulded at each step be less than the specl-fied radius r by the value o~ br. ~hi~ is related to the fact that at each step there is a plle section ~oulded in the for~ of a spherical seg~ent with a surface area exceedin~
that Or Sl si~ilar pile section of the specified radius. Thus, the proposed prooess afford~ a plle of a somewhat smaller volume Nlth no detriment to the bearing capacity, per~itting material savings on thi~ account.
The procedlre as described above is c~ntinued until a plle shaft of height h is fully for~sd. This done, the tool-ing assembly 2 is extrac~ed. ~hile feeding in the material 6, its flo~ rate i9 SO oontrolled that its level in the hole 1 should be at the elevation of the hole ~uth.
It h~ been established e~perimentsully that the effect - ~ ' . ' ,' . .

.,, ., . -.
~, ~

2~3~73 of the first discharge is to increase the radius r~ of the pioneer hole 1 to the value of r1 eqlal to r1 = X ~ , m , (8) where: X is a coefficient accounting for the soil proper-ties, and '`~ i9 the ener~y of one discharge, J.
~fter n discharges the incre~se of ~ rn = r-rO in the radi-us of the hole 1 can be ~eter~ined from The empirical rela.
tion ~ rn = ~ rl (K ln n + 1) (9) ~ where: A r1 = rl-rO is the hole radi~s increnent due to the effect of the first discharge, and K is a coefficient acco~nting for the intensity of acc~ilation of irreversible defor~tions in the soil.
It follows from the equations (8) and (9) th-1t the n~ber of discharges, n, reqlired to for~ a pile section of radi~s, r, ie eq1al to r - X ~
n = egp = (10) K (~ ~ ~
The coefficient K and X are determined e~pirically. The coef-ficient ~ depends on the state of the soil, -~nd its v3lles lie 'Ni thin the range of 0.2 to 0.7. The coefficient ~ depends on the soil type and increases with i~creasing soil density.
Eor sand, the coefficient ~ is eqlal to 0.0~163 while for loam it is 0.0021.
I~ t~e case 1nder consi~eration, wherein the pile is fabri^ated ~ith the ra~ils cnarlgin~ with hei~ht, the total ener~y of discharges is varied -~ith tne advance of the tooling asse~bly 2 by ~Nay of varying tne n1~ber of lischar~es propor-tionate to the req~ired change in the pile radi1s, as follo~s irom eq~ation (1~). The tjoling assembly in this case is ad-vanced liscretely, with a step incre~ent of ~ h, ~hile the discharge freq~ency in this case is constant, being selected 2063~73 on the basls of the specl~ied pile m~uliin~ time, with due consi~eration oi the propertles of the setting material ~SQ, but not less than 0.05 Hz. The total energy o~ discnarges ~ay also be adjlsted in relati~n to the height of the pile bein~ for~ed by way of rarying the discharge frequency in accordance with the variation o~ the pile ra~ius. ~bvio~sly, the greater the required pile radils at t'ne given depth, the higher the discharge frequency ~ust be at this depth, and vice versa. In this case the tooling asse~bly 2 is advanced continuously at a constant speed.
Selecting discharge freq~ency values ~ust ta~e into ac- -co mt the ~act that the pile formation process includes wi-dening the hole 1 and compacting the soil around it. This process can ta~e different co~rses depending on the relation betNeen the discharge freq~ency and the pres ure fall veloci-ty in the ~aterial-fiiled hole. If the discharge frequency i~ no greater than 0.1 ~z, then every ne~t discharge will occur after the pressure drops co~pletely, and the soil con-solidatlon is co~plete, the soil increasing in density as dlscharges are i~d~ced. l.ith the frequency increasing above 0.1 Hz, the soil structure degradation processes and the soil co~paction processes coincide in ti~e, and this leads to fas-ter pile shaft formation. On the one h~nd, in this case, inc-reasing discharge freqllency will ~llow of decreasing the ener-gy of each dischar~e while providing for their total energyto be s~fficient for de~rading the structure of the soil and for compacting it. 0~ the other hand, with a high freqlency of discharge~, each subsequent discharge occurs lnder the con-ditlons of an incomplete soil consolidation process dependent upon the flltration properties of the soil, which properties determine the water yield velocity. Owing to this fact, the effectlvenes3 of eaoh discharge is reduced, while the energy spent i~ pile for~ation ls increased. Thus, with the initial soil voids ratio value oi 0.~90, increasing the frequency of ~5 discharges fro~ 0.09 Hz to 6 Hz will reduce the effect of compaction due to one discharge by a factor of g. ~arying the dischar~e frequency will allow of ad~usting the pile for~ati--- .- -2063~73 on speed within very wide limits. Decreasing the dischar~e frequency below O . 05 Hz is not recom~ende~ becalse the ~ile body formation time i~ this c~se becomes co~menslrable with the ~aterial setti~g ti~e. In this case, ~ischarges prod~ce ~n unfavourable effect upon the form~tion of material struc-tlre in the setting process, leading to lower bearing capa-city of the ~ile. The upper dischar~e frequency li~it is set by the capability oi the current pulse generator.
In the embodiment ~nder discussion, the pioneer hole 1 is the pile for~ation 30ne. In another pile fabrication e~-bodiment the pile formation zone is the soil, i.e. the pile is mo~lded directly in the soil, without having to sink a nole. In this oase, tne tooling assembly 2 (FIG.2) is intro-d~ced into the soil to a depth of 0.3-0.5 m by any Xnown ~e-thod, thus by rot&ry drilling or by pressin~-in, and the setting ~aterial 6 i5 fed in, just as previously described, to wet the respective s3il zone and have high-voltage d1s-charges of electricity ind~ced within this zone in à number such th~t the for~ation of the top pile section of the speci-fied dia~eter .~ould be assured. Following this, the toolingassembly 2 is ~dva~ced deeper into the soil by a step incre-ment ~ h defined by equation (o) or equation (7~ depending on the for~ of the pile being made. Since the ~aterial 6 is fed into the soil, the nu~ber of discharges, n, at this depth is greater than that used when the material is supplied into ~ pioneer hole, being determine~ from the relation r - X ~
n = exp , (11) K ~ ~
where r is the pile rali~s specified for the given depth.
On re~ching the depth h equal to the pile height, the tooling a~sembly is extracted, and relnforcing bars are ~ount-ed in the pile if 50 required. In the process of pile fabri-c~tion, the flow r~te of tne ~terial 6 is so cantrolled ~s to ~ave its level ~t the elevation of the top sectio~ of the plle.

2063~73 In contrast to the embodiment provi~ing for pile fabrl-cation in a pioneer hole, an ad~itional increlse is ~sslred in the bearing oapacity of the pile in this c~se, beca~se there is no soil excavation incident to the hole sin~ing, and the pile formation is effected by way of openin~ lp the soil Nfrom zero" to the specified pile radius. 3esi1es, an inlubitable advantage of t`ae e~lbodi~ent rroviding for pile fabrication in the soil lies in material and ti~e savings associated with the excl1sion of the hole sinking operation.
Just as in the case where a pile with a radi-ls changing ~Nith height is ~o~lded in ~ ~ioneer hole, the displacement of the toolin~ asse~ly 2 m~y be ~ccompanied by varying the p!llse freqlency in accordance with the principle specified for pile ralils cha;~ing .~ith hei~ht, rather tha~ tne nu~ber of pulses. The considerations set forth previously in connec-tion with the selection of the energy of one discharge and the discharge freqlency hold good ~lso in the case where a ~ile is fabricated directly in the soil.
Fabrication of a pile in the soil in the direction ~from top to bottom" is ~ convenient ~rocedure ~hen reinforcing f'oundations of existing buildings ar.d str~ct~res where there are voids and cavities ~nder the folndation, due to the acti-on of ~ro~nd waters. There is another method of pile fabrica-tion in tne soil that is possible and may be ~rererable ~Nhile putting ~p intermediate s~pports in tne base~ents of buildings z~nd str~ctlres to be reconstr~cted or when layin~
dolNn new foundations for b~ildings and strlctures to be con-str~cted. In~accordance with this e~bodi~ent of the invention, the tooling asse~nbly 2 (FI~.3) is likewise s~nk into the soil, and the electrically cond~ctive setting :a,-~terial 6 is ~ed in, with high-voltage discharges being induced within the soil.
EIowever t'ne ener~y of discharges is selected s~ch that each of them ~Nill give risq to the for:~ation of a f~nnel or cone ~nder t`ne lower end of the tooling assembly 2, with a radi~s approxi.-~ately equal to h~lf the diameter of the tooling as-~embly 2. ~he for~atio~ of a flnnel ~nder the tooling assemb-ly 2 facilit~tes its passage thro~h the soil, the tooling .

~ - ~

assembly 2 sinking into the soil on its own or being pressed into it Nith a slight effort. To provile for the self-sin~-ing of t~e tooling ~ssembly 2 into the soil, the energy of one dischar~e, '~ ust be eqilal to d3f (12) 1 13.12 where; d is the .~axi~u!~ cross-sectional size of the toolinO
assembly, ~, and f is the soil strength coefficient according to Protodyakonov's scale The discharge freq-uency ~ is selected so as to provide for the desired tooling asse~bly sinking speed V:
~ 5.9 ~ ~ , (Hz)~ (13) The speed V in equation (13) i~ lleasured in ~/h.
On re~c~ing the de?th corresponding to the pile ~ase elevatio~ in the soil, pile moulding is e~`fected as describ-ed abo~e b~t i~ the direction fro~ botto~ to topj raising the tooling asse~bly 2 (FIG.4) with a step incre~ent ~ h, the number of discharges, n , at each step being lefined by the relation r - ~
n = exp , (14) ~ (X ~ - 0.5 d) where W is the energy of one discharge at this step, J.
Thus, in this case pile ~ouldi~ is c~rried o~t from sole to top while material supply and disch;~rge indlctions incidcnt to the delivery of the toolir.g ass-~bly to the pile sole for;~ati~n location are effected solely for the purpose of lo-~ering the soil resistance to t~ie doiNnward displace.~ent Or the tooling asse~bly.
The tooling asse~bly desi~ned for ~ile fabrication co~-prises a pipe 3 (FI~.5) to supply the setting material and an electric discil~r~er coinplete Nith electrodes 10 and 11 .. :..
: ~- , . . ..~ -. . ... ~, , . `

:, , .

arran~ed cosxi~lly and ~paced apart along their axis. The pipe 3 conslsts o~ several sections a~ded up as the tooling a~se~bly is sun`~ ~eeper into the hole or soil~ ~IG.5 showin~
the end of the botto.~ section o~ the pipe 3. The electrode 10 - the -~pper one with the tool~ng asse~bly in the working position - has the for~ of a ring screwed over a ~aetal blsh 12, ~hile the lower electrode 11 has the for~ of a cone with a large an~le of taper anl with the vertex f~cing down-wards. This form of the lower electrole 11 will facilitate sin~ing of the toolin~ ~sembly i~to the soil ~ Dlt it is not indispensible, i.e. the lower electrode ~ay be in the form of a flat disc or a ring. Integr~l ~ith the lower electrode 11 is a c~rrent-carrying rod 13 passing along the ~ischarger axis i~side the b~sh 12 and co~nected with the ^entral core of ~ coaxial cable 14 co~ected to one of the leads of the clrrent p~lse generator (not shown). The length of the cab-le 14 sholld be s~fficient to provide for the sinking of the tooling assembly to the specified depth corresponding to the height of the pile to be fabricated. The sp2ce .~ithin the b~sh 12, the current-carrying rod 13 down to the lower electro~e 11, and that sèction of the cable 14 connected to the rod 13, are filled with ins~lating ~aterial, e.g. poly-ethylene, forming an insulation roa 15, N~ose dia~eter is less than that of the electrode tl by~e.g,~ to 10 mm,the space bet-ween the lower end surfa¢e o~ the-electrode 10 and the annular ~ipheralarea of the top surface of the electrode 11, extend-ing beyond the rod 15, for~ing an interelectrode space 16.
The ~pper electrode 10 is welded to the end of the ~ipe

3, the distance fro~ the discharge openin6 17 o~ the pipe 3 to the lower electrode 11 being not less than the interelect-rode space 1~. Other types of connection between the pipe 3 and the electrode 10 are possible, thus the ~i~e 3 ~ay be screwed into this electrode, ln ~hich oase adjust~ent o~ the interelectrode space 16 by shifting the electrode 10 along the b~sh 12 may be effected on disconnecting the pipe 3 fro~
the electrode 10, this facilitating the preparation of the tooling assembly for operation.

. .~ .' 2063~73 The pipe 3 18 eleotrically connecte~ ~ith the ~creen braidin~ of the ooaxial cable 14, which iq i~ tur~ connected to the other le~d of the c?~rrent p~lse generator, connected to its enclos~re. The current-carrying rod 13 ha3 circ~l~r projections 18 ~.~hose purpose iis to preve~t the stresses ac-tive ~etween the eleotroles 10 and 11 d~rin~ dischares from ~: ~ tisturbing the ri~idity of fastenin~ of the clrre~t-carrying : rod 13 .~i:tni~ the ins~lution rod 15.
: In the lo~qer part of the plpe 3, near its discharge ; 10 opening 17, there is installed a non-return valve 19 whose p~rpose is to prevent ingress of soil into the piQe 3. In-istead of a valve 19 tnis function can be served by a ~eflec-tor to oe attached t~ t~e ~ipe 3 ~nder its discharge opening.
The electrodes 10 and 11 ald the :c~rrent-ci-lrrying rod 13 are f-bricate~ Iro~ to~gh (ViSCoils) steel, .vith the s?lr-f~ce layer h~rdened to redlce ~etal erosion from~the ele~tro-de slrface d~ri~g di~clarges.
~he toolln~ asse.~bly is inst.~lled vertically in, e.g., ~ a drilli~g ri~ (not show~ it~ the pipe 3 ~olnbed .vithln : 20 the~swivel ~ead of the rig. lrhe electrode 10 is displ~ced al3rlg the blsh 12 to ~dj-lst tqe intereiectrole space 1~ to the~ ~esired vallle such that vo~ld ass~re ~onversion of dis-char~e ener~y lqto nechanical ~ork at ~xi~u~ efficiency.
~ nere a pile is to be ~oulded ln a ~io~eer hole, t.~e tooling ~ 29 asse~bly ls lowared to tne hole botto.~, and sections are ad-ded u~ to the pipe 3 as it i3 being loweIed. The hole bottoQ
reache~, the ~able 14 is connected to the lnput of the c~rrent p~lse generator, and tne pipe 3 to the ~ortar pu~p (~ot shown). The setting ~ateri.~l is fed via the ~i~e 3 inder 30; pressure to the hole botto?~, and the c~rxent p~lse generator ls p~t on at the sa~e ti.~e to feed o~rrent pulses to the electrodes 10 and 11. .Iigh-voltage discharKes ~rise in the : interelectrode space 16, leading to the lower section of the hole being wilened a~d filled with the settinO ~aterial and ~: 35 to the soil ar3~d this section bein~ fixed and co~pacted. As the pile is being for?aed section by section, the tooling ~s-se?nbly is bein~ ~radually raised up~Nards. The displacement of the tooli~g assembly i9 controlled by, e.g., observing the mark~ traced ~pon t~e si~e s~rface of the pipe or the feed rac'~ of the drilling rig swivel head.
~ here a pile is to be ~oulde~ directly in the soil, the tooling as~e~bly is pressed into the ~oil to a depth of 0.3-0.5 m and i3 1sed to ~ould the pile in a si~ilar l~anner ~hile slnking the tooling -~sse~bly 1eeper and ~eeper lnto the 50il.
FIG.6 presents experl~ental data showing the change in the strength of the 90il around the pile 20 fabricated accord-lng to the invention. Plotted on the horizontal of the graph is the distance ~ from the pile axis in metres, and on the vertical the depth h in metres. As ~ay be seen from FIA~.6, ~ ar?~nl the pile 20 are f~r~ed a ~ixed-soil zone 8 with a compressive stren~th ~ of 0.4 to 1 .~Pa an~ a co~pacted-soil zone con3isti~g of three s~lbzone3 21, 22, and 23 haYing va-l~es of defor~ation molulus E, equal to 480 .~Pa, 330 ~Pa, nd 310 MPa, respectlvely. Left of the graph illustrating the pile 20 with the adjoi~ing soil is a geological sectlon of the sit,e where this pile has been mo-llded. The soil layer 24 is :~ediu~-sized sand wlth a ~roid~ ratio e eq~lal to 0 . 75, - the layer 25 is fine water-satlrated sand (e = ~.72, ~ =
a), the layer 25 i~ d;lsty sand (e = ~.67, ~ = 150 r~Pa, the so$1 angle of inter~al friction ~ , 28, cohesion 5 = 0.04 ~Pa), and the layer 27 is fine w~ter-saturated sand with the same characteristics as those of the layer 25. Un-derlying the l~yer 27 is ~oraine. Co~paring the characteris-tic~ of the initi-ll soil with those of the soil adjoining the pile 20, it can be seen th~t the beari~g c~pacity of the soil aro~n~ the pile and ~nder its sole i9 1 . 5 to 3 ti~es higher.
~he following are specific example3 of e~bodiment of the proposed process.
~xa~ple 1.
Fabrication of a pile section of ~.3 m dianeter ~nd 1 .
height in a w~ter-sat~rated sand soil, ~itn the tooling as-semoly ~lisplaced from top to botto~ as described in connec-, , - --tion ~ith FIG.2.
~etting material: ce~ent nortar Coefficient K acco~ntin~ for the inte~sity of ac~omll~tion of irreversi'ble leformations in the soil; 0.54 Coefficient X accolntin~ for the soil properties: 0.~0163 ~xi~u~ cross-sectlonal size of the t~oling asse.~lbly: 0.09 .
Ce~e~t ~ortar flow rate: 2.3 ~3/h Energy of one discharge: 50 kJ
Dischar~e freqlency: 1 ~z ~l~ber of steps: 14 Ste~ increment val~e: 0.071 ~
er of ~ischarges per step: 16 ~ile section formation ti~se per step: ~.0344 h Forr3ation time for a 1 m lon~ pile section: 0.062 h Example 2 Fabri^ation of a tapere~ pile section with a mi~imum diameter of 0.3 ~, a hei~ht of 1 ~, and ~n angle of taper o~ 14 in a dense loamy soil, with the tooling assembly disp-laced fro~ bottom to top as described in connection ~vith FIGS. 3 ~nd 4.
Setti~g materi~l: cement-sand mortar Coefficient K acco~nting for the intensity of ~cc~ lation of irreversible ~eforrnations in the soil: 3.7 Coef'ficie~t ~ acco~nting for the soil properti~s: 0.003~25 ~axim~ cross-sectional si~e of the toolin~ assembly: 0.09 Yhil~ si~ing the tooling assembly into the soil to a lepth of 1 Energy of one discharge: 33.34 ~J
Disc~h~r~e freq~ency: 3.18 ;~z 3~ ~ffort to be applied to tha toolin~ assembly to ~rovide for itg si~ing: 1 k~
Sin~in~ spee~ of the t~oling ~sse.~nbly: 4~ m/h SinXing ti~e of t~e tooling asse~bly: 0.025 h B. .','hile ~ovi~g t~e toolin~ asse~bly from ~otto~ to top ~nergy of one dischar~e: 50 ~J

: . :
.

, ~

2063~73 - 2~ -l)is¢harge freq~.ency: 1 Hz ber of steps: 6 The renalnin~ dat~ are cited in the T~ble below.

Step Pile di~- Increment Ylmber of ~ile section f3r-No. ~eter at gi- ~er step, liscnarges mation time per ven depth, _ ~ per step step, h 0.30 0.13 3 3.3 x 10~4 1 3.j3 v.14 4 1.1 ~ 10 ~
2 0.36 ~.16 5 1.4 x 10~3 ~ ~.40 0.17 7 1.~4 x 10~3

4 0.44 0.19 11 3.1 x 10 3 ~.49 3.21 18 5.0 x 10~3 6 0.54 31 8.~ x 10~3 Exa~ple 3 Fabrication of a cylindrical pile section of 0.4 m dia-meter and 1.0 m nei~-nt in a pioneer hole of 0.1~ ~ diameter and 1.0 m depth sunk in a claJ soil. Pile fabrlc~ted clS ~esc-ribed in co~nection with FIG.1.
Setting ~æterial; ce~ent - sand .~ortar Coefficient K acco~ntin~ for the intensity of acclm~lation of irreversible defor~ations in the soil: 0.7 Coefficient ~ acco~ntin~ for the soil ~roperties: 3.00302 ~ximu~ cross-sectional size of the toolin= ~sse~bly: 0.09 m Ce.~ent-sand mortar flow rate: 2.02 m3/h Ener~y of one dischar~e: 50 kJ
Discharge freq~e~cy: 1 Hz Nunber of steps: 12 Step incre~ent value: 0.087 m l~Ju~nber of discharges per step: 16 Pile section formation ti:ne per step: 0.0044 h rile section formation ti~e for 1 ~ lenOth; 0.062 h - ~. ..
'. ' ! : ' --" 2063~73 ~ ltho~gh the e~bodiments o~ the inve~tion ~ described above apply to the fab~lcation of cylin~rical and tPpered piles, it wlll be understood th~t the proposed invention can also be used for ot~er for~s of piles,e.s.of graded (stepped) profile (i.e. consistin~ of several cylindrical sections va-ryin~ i~ di~.~eter), ~Nhich c~n be conviniently used in a soil, one or several l~yers of ~Nnich have ~ drastically -eluced stren~th. ~nother possible type i5 cylin1rical-t~pered pile~.
3esides, pile r~dius u~riatio~ with height is obtainable not 13 only by adjusting the number of discharges or the discharge frequency z~s the too'i~g ~ssembly is dis21aced, but also by controlling the energy of individ~ isc~arges. Also, chang-in~ the discharge energy ~a~ be co~bined with vPryi~g the n~lmber of ~isch~rOes or the lischar~e freqlency.
~he pos~ibility of lsing piles of any profile, as appli-cable to t~e specific construction conditions, ~ffords cont-rol of the behri~g capacity of the pile i~ ths process of f~bric~tion in rel~tioII to the physical properties of the soil. ~.ving to the soil arolnd ~he pile bein~ fixed and com-pactel, the bearing c~p~city of the pile proves to be 5 to 6 times ~s great ~s tnat o~ a fillin~ (cast-in-sitl) pile pro-duced b~J a ~nown nethod.
The i~vention also provides for lo~.Yerin~ or - in c~se the pile i9 ~o~ulded ~lirectly in the soil - excluding the costs in-~olve~ in drilling a hole and per~its of dispensing ~with the lse of c~si.~g pipes and clay mortar, i.e. of redlc-ing the nlmoer of o~erations ~nd reducing tne pile fabricati~
on tiLe.
Industrial ~pplicz~`oility 3~ The invention can be ~sed in ~a~ing pile fo~ndqtions in the ~rocess of constructing or reconstructing (rehabilitating) b~ildings ~n~ en~ineering struct~res.

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Claims (10)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A process of pile moulding by way of feeding into the pile formation zone a setting material (6), c h a r a c t e r i z e d in that high-voltage discharges of electricity are induced in the material (6) fed into the pile formation zone, with the material-supply and discharge--induction zone (7) being displaced down the pile formation zone, consistent with the formation of the pile shaft, and with the total energy of discharges at a given depth of the pile formation zone being such that the diameter of the res-pective section of said zone is increased to suit the pile diameter specified for this depth.

2. A process as defined in Claim 1, c h a r a c t e -r i z e d in that the setting material (6) is fed into a pioneer hole (1) which is used as the pile formation zone.

3. A process as defined in Claim 1, c h a r a c t e -r i z e d in that the setting material (6) is fed directly into the soil used as the pile formation zone.

4. A process as defined in Claim 2 or 3, c h a r a c -t e r i z e d in that in the event of a pile to be moulded with a radius changing with height the number of discharges is varied during the displacement of the material-supply and discharge-induction zone (7) in a manner such that at a given depth of the pile formation zone this number is directly re-lated to the pile radius specified for this depth.

5. A process as defined in Claim 2 or 3, c h a r a c -t e r i z e d in that in the event of a pile to be moulded with a radius changing with height the discharge frequency is varied during the displacement of the material-supply and discharge-induction zone (7) in a manner such that its value at a given depth of the pile formation zone is directly re-lated to the pile radius specified for the given depth.

6. A process as defined in Claim 2, c h a r a c t e -r i z e d in that the number of discharges, n, at a given depth of the pile formation zone is equal to , where: r is the pile radius specified for the given depth, m, ro is the radius of the pioneer hole, m, ? is the energy of one discharge at the given depth, ?, K is a coefficient accounting for the intensity of accumulation of irreversible deformations in the soil, and ? is a coefficient accounting for the soil proper-ties.

7. A process as defined in Claim 3, c h a r a c t e -r i z e d in that the material-supply and discharge-induc-tion zone (7) is displaced down into the soil, with the num-ber of discharges, n, at a given depth being equal to , where: r is the pile radius specified for the given depth, m, ? is the energy of one discharge at the given depth, J, K is a coefficient accounting for the intensity of accumulation of irreversible deformations in the soil, and ? is a coefficient accounting for the soil properties,

8. A process as defined in Claim 3, c h a r a c t e -r i z e d in that the material-supply and discharge-induc-tion zone (7) is displaced down into the soil, and, on rea-ching the depth corresponding to the specified pile height, the material-supply and discharge-induction zone (7) is dis-placed upwards, the energy of one discharge, ?1, during the downward displacement of the material-supply and discharge-induction zone (7) being determined from the relation , where: d is the maximum cross-sectional size of the tooling assembly assuring material supply and discharge induction, mm, and f is the soil strength coefficient according to Protodyakonov's scale, and the number of discharges, n, at a given depth during the upward displacement of said zone (7) being determined from the relation , where: ? is the energy of one discharge at the given depth during the upward displacement of the material-supp-ly and discharge-induction zone, J, r is the pile radius specified for the given depth,m K is a coefficient accounting for the intensity of accumulation of irreversible deformations in the soil, ? is a coefficient accounting for the soil properti-es, and d is the maximum cross-sectional size of the tooling assembly assuring material supply and discharge induction, m

9. A process as defined in Claim 4, c h a r a c t e -r i z e d in that in the event of moulding a tapered pile the material-supply and discharge-induction zone (7) is dis-placed with a step increment of .DELTA. h determined from the re-lations .DELTA.h = r' (1-b) ? sin {2 arc tan [)1-b) ? tan .alpha./2]} at r'>r"
and .DELTA.h = r' (1-b) ? tan {2 arc tan [(1-b) ? tan .alpha./2]} at r'<r"
where: b is the permissible relative deviation from the specified pile radius;
.alpha. is the specified angle of taper of the pile, and r' and r" are the specified pile radii for preced-ing and subsequent steps, respectively.

10. a tooling assembly for pile moulding, comprising a pipe (3) to supply a setting material and c h a r a c -t e r i z e d in that it contains additionally an electric discharger complete with electrodes (10 and 11) arranged coaxially and spaced apart, of which the first electrode (10) has an annular form and is mounted over an insulation rod (15) passed therethrough, while the second electrode (11) is secured to the end of this rod (15) and connected to a current-carrying rod (13) arranged inside the insula-tion rod (15) and connected to the central core of a coaxi-al cable (14) whose screen braiding is connected to the first electrode (10), with the diameter of the second elect-rode (11) exceeding that of the insulation rod (15), and the first electrode (10) being rigidly connected with that end of the pipe (3) which contains its discharge opening (17) so that the axis of the first electrode (10) is parallel with that of the pipe (3), and the distance between the discharge opening (17) of the pipe (3) and the second electrode (11) is not less than the interelectrode space (16).