~~~[L REPORT 82-14 US Army Corps of Engineers

Cold Regions Research & Engineering Laboratory

Comparative analysis of the USSR Construction Codes and the US Army Technical Manual for design of foundations on permafrost

CRREL Report 82-14 May 1982

Comparative analysis of the USSR Construction Codes and the US Army Technical Manual for design of foundations on permafrost

Anatoly M. Fish

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COMPARATIVE ANALYSIS OF THE U.s.S.R. CONSTRUCT ION CODES AND THE U.S. ARMY TECHNICAL MANUAL FOR DESIGN

PEAI'OAMING ORG. REPORT NUMBER OF FOUNDATIONS ON PERMAFROST ,. AUTHO"(. ) CONTRACT OR GI'tANT NUM8E"(.)

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II. Kt:y WOI'tOS (C_II ..... _ .......... 1. "nH ..,. fn4 111' ... "". .., .. h.d: maw) SeMina ~acity Safety factors Design criteria Settlement analysis Foundations (strucrures) USSR Permafrost

20.. "'_"ACT ~ _ .. __ .... It . _ ..,. ..t I~I"'''' bloc.lr __ ,

A comparative 5tudy was made of design criteria and analytical methods for footings and pile foundations on perma. frost employed in U.S5.R. Design Code SNiP 111876 (T977) and U.S. Army Cold Regions Re5e:Mch and Engineering Laboratory Special Report 8Q.34 developed in the early 1970's by the U.S. Army Corps of Enaineers and pubUshed in 1980. The absence of adequate constitutive equations for frozen soils and of rigorous solutions of the boundary pro/). ems has made it necessary to incorporate (explicitJy or implicitJy) various safety factors in the foundation analy~s. From the review it is concluded that the principal difference between these practices is in the assessment and iPplication f iPpropriate values of safety factors, which leads to a substantial discrepancy in the dimensions and cost of footings nd pile foundations in permafrost.

DO ,i:-." M73 ~DtnOM 0 " , NOV . 5 IS OIl$OLE T t:. U' .,-- ---

PREFACE

This report was prepared by Anatoly M. Fish, Research Associate, Massachusetts Institute of Technology. Funding was provided by contract no. DAAG 29-77-0016 between the Civil Engi-neering Department of the Massachusetts Institute of Technology and the U.S. Army Research Office.

This report was technically reviewed by T.C. Johnson, F .H. Sayles, W.F. Quinn and E.F. lobacl, all from the U.S. Army Cold Regions Research and Engineering Laboratory. Special appre

CONTENTS

Abstract ............................................................................................................................. . Preface ................................................................................................................................ ii Introduction ....................................................................................................................... . U.S.S.R. system of 5I.andards .... ............... .... ............................................ ........ ...... ............. . U.S.S.R. Design Code SNiP 111876 (1977) ~b50ils and founda tions on permafrost ........... 2

General regulations......................................................................................................... 2 ClassifiCiition of soils ................................................................ .. .................................... 2 Basic regu lations for foundation design .......................................................................... 3 Analysis of subsoils and foundations .............................................................................. 3 Design of foundations f()( special soil condit ions, and appendices .................................. 10

SR 80-34 (1980) design and construction of foundations in areas of deep seasonal frost and permafrost .................................................................................................................. 10

Genetill information .................... .. ................................................................................. 10 Foundiltion design ........... ........ ...................................................................................... 11

Conclusions ..................... ..... .... ..... ..... .. ... .............. ........ .... ........................ ......................... 19 Literature ciled .............. .. ..... ......... ..... ... .. ........................................................................... 19

ILLUSTRATIONS

Fi~ure 1. 2. 3. 4. s. 6. 7. 8.

9.

10.

TABLE

Table

Diagram for analysis of foundations ..................................................................... . Creep curves of frOlen soil at constant stresses .................................................... . Possible errors in determining foundation sell lemenls ......................................... .. Diagram fOf determination of foundation settlements ........................................ .. Creep curves in logarithmic coordinates ............................................................... . Time dependent failure of frozen soil ................................................................... .

Detetm in~ion of pile beating capacity .................. .............................................. . Determination of the pile bearing capiu:ity accOl"ding to recommended Sov iet practice .............................. .................................................................................. . Diagram for detcrmining pile bearing c

CONVERSION FACTORS, US. CUSTOMARY TO METRIC (51) UNITS OF MEASUREMENT

These conversion factors include all the significant d igi ts gillen in the conversion lables in the ASTM Metric Practice Guide (E 380), which has been approved for use by the Department of Defense. Converted values should be rounded to have lhe same precision as the original (see E 380).

Multiply By To obloln

inch 0.0254- metre inch 2 0.00064516- metre2 root 0.3048- meue pound 0.4535924 ki logram pound force 4.448222 newton ton 0.02916667 kilogram degrees Fahrenheit t. c ; (~c-32)/l.8 degrees Celsius -Exact

COMPARATIVE ANALYSIS OF THE USSR CONSTRUCTION CODES AND THE US TECHNICAL MANUAL FOR DESIGN OF FOUNDATIONS ON PERMAFROST

Anatoly M. Fish

INTRODUCTION

This paper is princi/>illy a discussion, from the viewpoint of frozen soil mechilOics, of foundation analytiQI and design methods employed in tlle U.S.S.R. Design Code SNiP 11-18-76 3 (1977) and U.S. Army Cold Regions Research and Engineering Laboratory Special Report (SR) 80-3422 (1980)t. ThermophysiCilI problems of frozen soils as well as the design of foundations on thawing soils are nOI considered in this review. In the present work, the author does not pretend 10 undertake a detailed and comprehensive critical review of the theoretiul bases of analyse~ used in the U.S. and U.S.S.R. design practices. It is obvious that any accepted theory or analytical method, no k:u than ilny s~ndard test procedure for determining soil properties, has both positive ilnd nega.live features, and can be the subject of 5e/>irate discussion . The author pilrticipated in the prcp.1ration of the former edition of the SNip4, a Design Manual! and other documents. As a con-sequence of this familiarity with the details of the development of standards governing Soviet design practice, Ome of the commenury will extend beyond a mere exposition of the Gontents of the current Yersion of the SNiP. The purpose of the author's leview is to identify both the strong and weak aspects of the latest edition of the Soviet SNiP and of SR 80-34 as a whole, and to discun needed research to milke design of foundations on permafrost more reliable and onomical .

U.s.s.R. SYSTEM OF STANDARDS In the U.S.S.R. all design and construction of

buildings, and strUCtures, and aho the tening of con

tSped.IJ Report 80-14 wu prep~red wIth the fin~J objIClive 01 public"kwl .s ~n offkJ,J.J cnlinee,,", m~"u~l : O~rlmenl of the Army Trehnkoll M~nuolll 1M 5-152-4 .lind Oepvlment of ttle AI' ForGe M~ujI88t9 . OIjpltf", Arctie

U.s.s.R. DESIGN CODE SNiP 111876 (1977) SUB-SO ilS AND FOUNDATIONS ON PERMAFROST

The main su.ndatd document on design of found3,-lions on permafrost is SNiP 11 -18-763 whic;;h is pre-pared by NllOSP (Scientific Research Instiwte of FoundatiOtls and Underground Structures), Moscow, with the ~rticipation of design and research insti-tutes such as lENZNIIEP (Leninyad). FUNDAMENT PROYEKT (Mo5Gow), TSNIIIS (Moscow) and PROM STROYPROYEKT (Krasnoyank). The current Yer sian went into effect on 1 January 1978. The chap-ter was developed mainly on the basis of six refer-cnces4 -9 and ,"overs foundation design for civil and Industrial buildings, It docs not rover design of special structures such as roads, railroads, bridges (except some speCifics of foundation design), lonnels, or dams. The requirements of thi~ chapter a'~o do not apply to subsoil i nd foundation design fO( hydro tet:hnieal structures, airfield pavements, machinc-s with dynamic loads, and buildings and structures in areas of subsidence caused by COil mining, eiC. Dc sign of these structures is covered by the regulations in special chapters of the SNiPl o.

SNiP 111876 consists of the following sections : 1. General regulations. 2. ctassirlcation of soils. 3. Basic regulations of foundation design. 4. Analysis of subsoils and foundations. S. Specifics of design of foundations on ice-rich

soils and ground icc. 6. Specifics of design of foundations on saline

soils. 7. Specifics of design of foundations on frozen

OI'ganic soils and peat. 8. Specifics of design of foundations in seismic

permafros t regions. 9. Specifics of design of foundations for bridges

and culverts. Appondix 1. Design values of th~rmophyslcar

characteristics of unfrozen and frozen soi Is.

Apptndix 2. Temperature regime of winter-ventilated crawl spaces.

Appendix 3. Depth of thawed ground under buildings and Slfuctures.

Appendix 4. Depth of seasonal freeze-thaw of soil.

Appendix 5. Analysis of stability .nd strength of foundations on frostheaving 5011.

Appendix 6. Design values of strength charac tcristks of frolCn soils.

Appendix 7. Analysis of foundation settlements on icc-rich soils and ground ice.

2

Since the American reader is not familiar with their cootent, the various iCc-tions will be considered briefly.

General reguLllions In this section the following basic requirements

are formulated: 1. Scope of SNiP 11-18-76. 2. Meeting the State Standards and Codes. 3. Scope of geocryological sur'leys, the amount of

in situ data needed and labO!"atory testing of soils. 4. Monitoring of subsoil conditions during GOO

suuction and use of a structure. On ly general requiremenh for the scope of cngj

neerlng surveys of frozcn soils are Included in this SNiP. Their scope corresponds approximately to Figure 4-1 of SR S0-34 22. More deLliled infOl'mation On this question is contained in State Standards and Special Instructions 1 0,1 t .

The most importan t regUlations of [he section concern the following:

I . Design of structures, taking into account pos-sible changes In the tempcrotture-moiSlure regime of subsoils during the period of their usc.

2. Compilation (before construction begins) of special programs of observations of found;ulon and subsoil conditions during construction and usc of the structure.

3. Development of measures for environmental protection. An Ucft"thll m.tlna lhI! fnl lWO ....

tulllJom involves romendOOiI (:Old rq.ions OfIlinccr ~ ."..:Uco II'Id AlItn no exmordhwy difficulties, Su, -tfna the dtrrd would require .lfeloprnent of I melhod for IHllmltins the 1COffOmk: OMteqUOnCfl bf chanpJ in the temperatut'e rwtimI of the frozen

~ St>ocIaI _kal salu'lano. _wlnl i

to their granulomeuic com~hlon adopted in the SNiP does not differ substantially from that of un-frolen soils9 . However, frozen soil( are fu rther clauified acco.-ding to :

I. Oyogenic structure. 2. Degree of ice-Gemcnling and rheological

properties. 3. Ice content. 4. Organic content. S. S.h content. Fraun soils are subdivided according to cryo

genic strucllue. lntO tWO categories: " msivc" (fused) structure and reticuLite-layered (laminar cellulilr) structure.

According to the degree of ice-Gemcnting and rheological properties, (rolen soils are divided into three groups:

1. Solidly frOZt'l1-soils cemented by ice with a compmsibility COfffidenl of Q < 0.001 cm21 kgfand various temperatures (depending on granulometric oomposition) lower than -l.~C.

2. PlastIC frozent-sandy and clay ~ils cemented by Ice with (J > 0.001 cm2JI(gf, degree of sal-uration G > 0.8 and with temperature (de-pending on gr1Inulomeuic compo5ition) from o to -1.SoC.

3. Loosely froLen--nt}e-gtained soils and sands not cemen ted by ice, with Wil ler conttnt w .. 0.03.

SpeGial de~ign provi~ons apply If lhe (rozen )Oil belongs to one of the follow'"g cWS('S :

1. /cHiCh solis - when the fraction of ice inclu-siom 'I > 0.4.

2. hOly frolen soilS- When the orpnic content g> 3% of the mineral parts for sandy soils and 5% for clayey soils.

3. Sofine frozen SOils-when the salt content (depending upon granulometric composition) is greattr than 109i of the dry soil weighL

Pe;aty and s,aline frozen 5Oil~ can also be clani-ned as solidly frOlCO or plutic frozen soils, depend ing upon their temperature and organic. and ~h conlCnt. The Importance of such a cLissificatJon will be shown later; here we merely note that the classifiea.tion is the basis (or selection of I) the scope o( field and laboratory tests of $OU, 2) the effective types of foundations, 3) the methods of roundation analysis.

Relationships12 among the simplest physical characteristics of frozen solis and some or their properties are also giV1m in this section.

tPIUII( Is a con\lentlon~1 Wm used In Ihe SNiP LO refer to "o~en sons that underio subst~nllal ddorm~tlon unGeI modehte toad,.

3

Bui

is scattered in various SNiPs, However, since the construction cost depends substantially upon the safety fa(.tQrs that are chosen, this problem Is v.'Orthy of discussion in the framework of the present anal ysis.

One of the most Important requirements of SNiP 11 .18-763, compared with the previous edition., is the increased reliability (more conservative desigll) of stru(.lUres ()(\ frozen ground that is achieved by incorporating the following safety factors:

1. Overload safety coefflclents. 2. Soil safety factors , 3. Reliability coefficients. averlaod safety coefficients are used in analyzing

the bearing capacity, stability, and settlements of foundations. Their absolute valUes, which are tabu lated in a special chapter of the SNiPl), depend on the statistiC

hue.., ........ laIecl12 In many ta5II .... CIJftSieo _'''_Il00--.. __ 10-tN, thI COle of l'ICOnIUucdon far tJlCIIlIded win-lda/_"" ...... "_lhotdwlNl~ roundlaian NtdernDnClIhoukf lib mID ICCOUnI Ihe economic GIIftIOCIUIIICI at UCWIfye tealelDents, ___ ... _Ior ........ in"' ..... ......... __ .... 11",11""'"",_ 1111 til b,._ III __ Ie 5I/oIy _,n dw

ysif of WUkmenu. l'II .. oq 4 would bIooInI S' Sc-...

whIR 1' ~ 1 III ecvnomk tlfl" fKtor.

(S)

SUd! a .. ruy _ could_"oIa n_oI ~'II "'.c , 2)1 _ . ...An), IICh . dw.....-ordw ....... _ .. dIoncool _dw_"' ... _ ..... 01 _on_In>IL Thoycould ...... latod _dl ........ Iypeof_ ............. , ond dlnad, ___ .. "" _II of """"",ed",, mateNIt. ..... 1QnIp1:IId-.tlC. As~ -_ ............ ""-.._ ... mlild .'.:SSRry.

Ita ... kncNn drat ........ mGt _~ iCil &ypI of .......... I COIIlIIItl1lld PfQbIMI, NqUlrlni a ......... of nrIouI founcktion Iype& ond dotaIloII .............. n .... _ atan .......... ....,--1ImpIIIY .........

~ ........ 1IrIy In ""

The bearing capacity of piles in permafrost in the case of partial thawing of frozen ground is determined by taking into account the negative friction of the soils caused by settlement of the thawing layer (pro-vided drainage takes place). The magnitudes of friction forces are taken to be equal to those of un-frozen soils9

One conc;liiIii ltat tfiilOtIOWihj an: 1:iiit( prem-he$ of 1ho SNIP In -" to _III _'ty ... Iy>~.

1. Frozen soUls. COMIdnd as An Ideally cohesive medium (e.,. oJnd, 0).

2. Froan _ ... _ to _iona ",m ......... _ ..... clffenl ..... Wocondy from _ 24-111.,,-,,"

In merer'lClt 10 point 1, It ilnotdear why, for the arne soil, the fticdon ...... need not be abn Into account when Ihe toi I jl frozen, ewen thou., KCDI'& Inl to the sNIP',...,.. of the lhlwed or Ihawint; lOll boar"'I-'IV"'" lib Into ICCOUftt bodl coheiIon and Medon of the soli, no matter how .... " dIey .... 11Ie __ ..... dI. frozen

IOII~ 24-Iw -.... _

Po := -rh, overburden pressure wI := stress distribution coefficient in the flh

~yer of the subsoil depending upon the depth of the ~yer and the foundation shape, eU:.

hi := height of the fit! lIyer tJ:= 0.8, a dimensionless coefficieflt

E\ '" deformation modulus of flh liyer m := number of layers.

Either the deformation modulus E\, determined in silU, or the ~boratory determined compressibility coefficient a\ for eilch layer is used in the analysis, taking into account neither the time factor nOf the annual temper.tture change of frozen soiL The SNiP also a1l0ws the settlements to be calculated on the bisis of the solution of the nonlinear problem.

SoIcII .. __ .. "''''-1Yi& 0/ __ , .... ".,.. ......... 1'oI1ow1ni ~

1. F_ ............ oflloonoodliinlo:ooflOlidI, 1IWIIooo_ .... _1OIdIy _ .... pIoodo:_ ........... _If .... ...... cu ............. n..tolft,ka. nac_ iiIIi\' pIoodo: "-... 11"'-......... _~ .... IoI .... ~ _ ...... -...... -_ ...... ...... " .... OWIty .... _

2. "II .. b ..... " dlrRadt .,1IIIIn1aIn ......... _ ...... "'. __ MII_ .. o'C, ........," ..... __ "'_I0Il. 1 ... ..-... ,-_ ....... .......... 10 .... aIiI ... ar to hlOlldly r __ Fartolldly_ ..... no .... .... tlllOlylls ............ Far ..... tIor-... ~ tile 5NII' _l1li- ... , ...... Il00.1 ._ ....,. ... _ ... tin __ .... SN" ......... _ ................ _l/IpuIalld In ... 10 .... foI' .. _ far "'lPICII1ooof _ ... L

'- hll".U .... _ .... " ........ toI1dofar __ ,,.,_t1o,.._ ...... __ ...... _ ... '11 ................ _ ...... t_~_

"_""'_,.22"'''_'' ............ ' c:ansIdInWe IIMcatI:III.

The SNIP recommends determining pile foundi-lion settlement by USing data from field tests of piles under s~tic loads. HowevCf, the SNiP does not rev ommend a specific method of calculation.

SettlemVlt anolysls of foun(/otl(){ls on ground k~ and kNkh solis

This section is the most important auomplishment of the SNiP. For the first time in construction pr.tc lice an official regulation allows the construction of

7

large buildings and structures on subsoils containing iu-rich solis and ground icc.

Settlements of foundations on ground ice and ice-rich soils are estimated by the formula

Yt'hcre

(10)

51 := immediate settlement doe to the soil (ice) consolidation as a result of chanFS in its air porosity

53'" settlement due to the viSGoos flow of ice.

11 is asstlmed that settlement S 1 occurs rapidly after application of the load. Its absolute value is insiJ1ifica.ntj however, the formula for estimation of 51 is given in SNiP. ThcsettlementS3 iseslimared on the basis of an approximate solution of the boundary problem of a nonlinear visro-elastic ~If spau with a variable temper.tture regime6, 16 i.e.,

I ; (",,+"'l+l)(WI+l- W,) (11) /=1

P :: total avenge design unit load under the foundation

Po:: overburden pressure n'" strain twdening puameter b :: foundation width t >:: dUr.J.tion of use of structure (suucturc's

lifetime) K := parameter of defofmability, the re-

ciprocal of the "viscosity" coefficient of Ice determined by the linear segment of lhe rheologiuJ curve

k,t"+1 :: temperature distribution coeffiCients in the /Ih layer of the subsoil, depending upon the subsoil temperature and the depth of the layer

(,,)1' WI+ 1 =: stress distribution coefficient in the fltIlayer of the subsoil, depending upon the foundation ma.pe, the layer depth and the value of parameter n

m := numbH of layers. Graphs of the values of "". ",1+" Wj and "'1+,

are given in two works6,t6. For the c.ase when the patilmeter n := 1, these values are also given in tables in the SNIP] . Equation 11 is recommended by SNiP 11 18-76 only fOf'" settlement analysis of foundations on ground ice, but it can also be applied to settJement ,tnalyscs for foundations on ice-tiro soils6.

The method of seulement analysis for founda-tions on icc-fich soils employed in the current issue of the SNiP is based on the same assumptions as those stated above (Of ground ice, but in somewhat Simplified form. The SNiP gives the formulas (or determining the design allowable load q* on iu-riGh soils and ground ice, depending on the foundatiOfl shape, the ratio of the foundation's sides, and the temperature.

...... l1li !hi compu .... by iIii pro-_al .... SNIP wfU be-.wly _ma .... ;

rtIIOftI fot dill wi. be aamlned fwdter. It is """ __ Ion. for .... ~_a ..... .............. _ aI _ ...... 1IId _""''''', -"" "' .... _ wltII dopdI,. well ..... temperature c:hInII with dIM. and repment eq 11 In .... simple form ":

S,(" - Ho) b t I!WI' (12) Equot/onIlll11d 12 .. b It ___ .. ISII .....

........ ., .... _"'_ ... any-cbflll 11M of 1M ........ tlowver, the lOIudoI ~ __ -= _1n ....... ,nI .. i"'" ... ,." ...... Ity , /C. All _In ill .... .... Inod ... nay....,.rv _ dIo ....... "' .... 1IltIIi.l6I'Il .......... .

Eq:aIIo::II11114112 _ -.... ....... bas.

~ ___ "''''nc:nII:_ .. tIc; ,.._.-dIo leo flow law In .... __ 1I.1i

tntl,. C' .. p a,

a,

I,Tim.

...:/(>-:"'== - 0: (I ..... (13)

""'"' i cnep linin rail In uniuIII ClDIIIII'I81an " . ..,.... .............. n snln hIRtIairC .......... at empIrtcaI ....... , a:GIPIId. btGnItY , -_In"C_dIolIF

,,' _,-Uo+"121 /C I( dIformIIIIUtv ' ....... mm.,

The_Manual" _ ... ......,..,. .... dof_n..,_/CIIId .... _ ... ..... PII'ameIII''' tram short ..... unIuIII CD .... .. cnop ...... It" _1I1Il dIo .,.,II1II'{ ... .. ..... "dIo'_of_ 0.005 m:n/IIr I". 2). In ...-.II1II. bo _____ 1bIf .. L Oodlo ____ ".",_ y_1t dIo_ ....... ___ ........ ... Ieo _ .... _IIn1,-_""Ih&!ii'i . _ ... -.-.. ~ .. IIOiIC_ dill prl ., ....... tAlGI ........... _ .... ......,.wy ..... .

....... -"_Ieoflow .... ....., ...... ...y ... -~., ... "' .. "'

,

i It) )I('".~ (14) (1 ... .,.

0' ~ COIIII.

m I -p;j;Gr;-Ie,.., , ,

Figure 2. Creep curves of frozen roll at constant streSSts (m-Inflectlon {fallureJ points, tm -time to faIlure).

8

\iwttore SS1 Utd S'2 ~ the tetUemenb due to viKOUS /""" of ice .. tinaled ......... dolann.bUlIy _ .ents ~ mel K'2 In eq 1311 timeJ" and'2 rapec-lively

For eumptt. Ie, us i55Umt chlllM deformatHlfty toeffJclent Ki hid been determined at time '1 co 24 r MId dlt sec:ondary creep itl. 'IIrts It tlme'2 20 days att. initiation of the at. If she settlement

.. dmoled ..... "' .......... "',. , .. _lu .. ...... _ ... _d_ (accordl", lOeq 15 .... '" 6 0.31 by. _ N. 4. """""'"" wi'" .... lenlcment..umaWd .... "1 K'2 dtt.mlned for the , .... , ,. Fl_ 3 ".., ................ demon. "".

don trrorN VInUI 1M rado of'2 ind'1 II dlf ercnt VII .. of 5. If it "_1'Md dull the sec:oncwy

_'.,.~t'2 365 clip or ani year,lhe error flmov ..... up 10 20. ~lnl""" .... va'ue of

The MiI1ull17 requirlei tM. the derormlbilit~ (vlKOlilyl coofflcJ ... of Ice ... do..-m'ned by"'. .. 11_ ...... lofche~curw. Howeer. ~1 is well known dial strain rate .. 1ft IPP'OXlmately

~ f'uIIctian 111 ... only tot smalllDWtIeL This ~ procedure is tNIOfIrIbIy 'MIld only If

load on the surfKe don not excerdo. 1

'0r---~--~--~--~--'

.. .!oJ. (!.

Eqn.1lOa 1. _I0Il_ oIIIiIIIIOoP' II\' ... --'" DIlon of SIooJo-" .... 1Ion Ito!,. _ I< s-Iblt 10 CIlIa fIda ~11

I. CNnto"' ... - .... durIfta ... ~ "'""-2. a..,.. 01 ......... 11_ with dop1/! ondwllll ......

1. _lYoftlle'-n .. "'-p. Ifl.lo_II1I .... __ ...... _ _~ ... 17""""'_

S2(.,,-(P-P.Ib I+~i ~. (18) 1IIo ... 1yoh of lIo&yOkov\ """'"""V data2" _ lI1I.rho .... _' ..... Of_ ........ on ..... , IJ'OUAd ice.,.. In ..... r I ~t willi ... 1hIoretkaI "' .... _ .... byoql .. tho ............ ....... ... 0I1ot0ll __ 1o ItIu _ 11\' ...... .,. _ .... ...,.In .............. ,..,.wlA be _ below, _ ... CQIIIIdorJIIon of 5R 110-304

,

~ 18con .... 110 .... lIodto ... ..-_ offoullda-..... 111_" on aIltvIIOS of.fnIUn.JOll., __ _

Oesign of foundations f spec~1 soil conditions, md ippendioes

The final sectlon~ of the SNiP ate devoted to recommended design methods for founduions on salioe and peaty frozen soils, for foundations in seismic: regions, and for foundations on thawing soils. The SNiP gives numerous data on the design resistance of frozen saline and peaty soils to normal pressun:: and' shear along adfreezing surfaces, depending on the soil type, the temperature, and the mineral, salt, and peilt content.. Analysis of subsoils is performed by the method discussed above.

The coefficients of the decrease in bearing capacity for footings and pile foundations in seismic regions. depending on th e type and temperature of the frozen soil and on the region's seismic aClivity, are of great intereSL However. the basic requirements for founda tion de-.ign in ~ismic regions are not inclUded in SNiP 1118-76, but in other SNiPs.

Foundation stability and strength under the action of frost heave forces are also anal yzed by known methods 12. The design values of frost heave forces given in the SNiP depend upon the type of soil, the degree of water S

Special Report so.34 pro~jdes guicb.nce to tnt engineer, bot since it does not prescribe.a spt(;i(j, course of action, it lea~es the engineer rcsponsible for any design decisions. For Instance, the report abounds with references to other publications; how

c~tr, It is well known that authors sometlmcs el uci date the same questions differently. Such references expose.an engineer to the constantly chilnging state of the construction an. and the latest achievements of 5clence, but increase the likelihood of his ,haasing

. something other than the optimum solution to a particular problem. AppMently, its purpose! is to throw light 00 the most important problems con nected with the design and conwuctlon of buildings and structures, especially fo undations on permafrost, and to set examples fOf their solutions.

In contrast, SN iP 11 18-76 is an official state docu ment, kavlng the force of law for all institutions and organlutions throughout the U.S.S.R. The SNiP docs not permit variance from its basic regulations. and II exempts itn engineer from responsibility fO( his de,kions. In the SNiP references are permiued on ly 10 Other SNiPs, the number of which is limited. It probably makes design more conservative, and in some QSes It makes II. dimeull 10 adopt nonstandard solutions. It is written in language that does not allow variouslnterPl'eQlion~ Many questions are omitted under the assumption th~t the answers are known, One of the purposes of the SNiP 11 -1876 is to prollJde the comprehensillC information nec.euary to simplify dnign procedures for foondations on permafrost.

FourKbtion delign Sped.ll Report 80-34 and the Soviet SNiP arc sub-

stantially different from each other, whic:h makcs comp~rl50n dlfficult. However, their main ~ctioosboth dealing with the design of foundations- arc com panblc. The~ c:onsiSt of three parts: foundation bearing capacity, settlement analyst'S, and determin ation of pile bearing capacity,

Antilysis of foundtltion bttlrlng capoclty In SR 80-34 one method for analyzing the ultimate

bearinl upacity is ba~d on the hypothesis that fro zen soil 15 pure ly II cohesive m,lIerial, a conservative assumption becallse internal friction and adfreeze fO(us arc negltedt _ It is a.s~umed that the long term strength limit is lero (0_ ::: 0) and that the de crease In soil strength with time is described by Vyalov's equation

tin 'Om' cues Intun~ (rlctlon un ~Ito be t;attn IntoiICcount; I'Iowhtrj the c"curn~Wlm undu ... hld! li'Ie Incorpor~tiotl Of In lunill frluion 1\ pos,jjblc 1ft nOt uprcued durly in SR 81).34.

II

(19)

where an (t m) is the time-dependent frolen soil strength in uniaxial compression; 1m Is time to failure. Spec.ial Rcport 80-34 recommends that the par.meters (J and Bin eq 19 be determined by the f'C)ul ls of at lust two laboratory t~LS on undlsturb1 q. co SF (1.3 x 5.7 'n + 'Ynh ) (20)

where iI si. safety factor SF::: 2 j) 4dded. Notice thai the recommended safe ly factor deptnds upon neither the number of lesl'l nor variations in the soil char .ilCler isties.

SNlPll'..,. ..... = .... = tNt frozen tolls un be ~Mdend II ideally oahMive media, but adfreetfnl DftllS arr .. ken InlO ~nl (loC'C eq 6,_ The minimum

r.umber of reQund 1:eJtS It "he. The soil,,'ety faelOf' het eq I) don dtpmd on Iht num_ of telb or on ~.6atJon.ln 1M ddrmlnod pltlmflClt wish teSC*l to 1.ts lver. viJue. For the CIM of idultatt dill., when bft .. no Ydtions In dt.nrurisdct. the toU

ftty baar wi" ~ e~ to UllJry. In other words, meorttic:ally .... burlna capacity of foundatJont. on rroun solls ."thN.ted by tha SNiP ~Id t.. (tHina into ilCCOU,1l !he awrKtion c:oefflclenu) up 10 so. bo.. .... Ify, OIdm ... d by SR 81).34. Howewr.ln 1o __ .dI_ ...... .-wd_

e ~ iI. C*'tIIn tatter in II.xperlm.nut duJ.. ~ikl5R 1(1.34, .... SNIP _1010 _, .... iIe_., -.. "",,,,-c.1PKi1Y on-...

fOlea The Wluence of the litter on the founcbdon t.....1,. -'IY .... lie slpln..n' ...., .... dHqree-,....t btl.,,,, sa 10-)4 .nd SNIP in the .nluation 01 f001lnl bNr1f1ll3P&ity Is thereby m.aanifled Tile rwa.1ed idfreui,. (or", and &h~ inlom.ti friction 01 the .011 eM lhut be. Inllll'p,UId ~.In oIddhJon&I ufrty fac:1OI fmpJkitJy iMOrpORlCd in SR 80-3 ...

AI was rrtentloned Ibcwt .In Important future 01 me SHIP that ft nollnduded in SR JO..14 ;, iI: JOup of l:J.blft show"" lite rctkWtc:e of frozen soH of QllQUf types ro normal presue Ind shelf ... Ione adftalina ~f~. For prwlimlNf'y dNl", Md ewer.

for flAi:1 .... of _lmpotWn IotrlKWl't'I, dieM nib_ offer an opportunity to dec:teae the 'Oil of JOII tadn .. whidl ts c.onsiderJbae,.and to sirnpllf'l the desil" proc:edure.

The c:onwenteme and ilmplldty of the SNIP method of c:akulitina bear"- c:apity can be demon stuted by lPPlylnl It "" an ex.ample: in SR 8().34 (p.I66-170). lntheSReumpte.thedimensions a.lwla1ed for .a foo"nl on frozen inorpnlc: wwly sill with" temperature of 3CtF (. -1.1OC) are 4.5

~ U It 20.21 It' (18.813 om'). The deW.,. 100d f'Jd = ISO tom. Foundidon depth is 7 ft. Th. appuenl yfet} fxl'Ot SF ... 2.25. The lifetime or the struc:&ure iI 2S ycm.

A,c:a,rdina to the SNIP table of ~Iowable burin, c:aPKitin, for thk type of soilf And this ,,",pet wr., the nomiRiI reslttance, wilhout .. larp 'rror, un be uken as R .. 9.4 .,/",,2, Tht nomln.1 burin, ~c:ity of the foundation, by eq 6, wUl be "",,110

Q & ltucRF z 1.1 ~ 9.4 ~ 18,813 .. 194,526

kif or 194.S tom.

Auotdin. to eq 2 ... deIII" Ioid on the suMolI, even wUhout IIki", Into I(;C.OUnt ~zJns form,

""" Q. ;: J1 = l!!J 162 tons,. 1 SO 10M.

It, 1.2

Thk comparison demoMtn.leI the uwanYp of ......... Iolled ... 1_ for pnIImlrwy .... sl .. proc:eduRl when the moil lICGIIomlal constrUC-tion ... _ (principlo) '" _ of f_don I. belnllliKled.

The values of Iho froan wli dwxwl,tlcl ub-ullllld in the SNIP .. called Ion& term .. i&t&nce5 !hoy __ ~ by "I 19 ... kl ...... 1IUdIn:'t 1ft-time til be SQ.l00 yars. For pre-imln.ary ClkuladoN It is not IftIP(II1Int .dw the

lllion irt for 25 yus 01100 yun. since: 1. _ ., .............. don!ram tIqIOrimenlll

dati an un~1n for periods of dint I --. 2. y.,.10_ of die tInaJ dl ........... of die

_ ... poooIble cUina die ~,..,. cedIn.

AclulIIy ... ...,...._., .... oxporimenlll do" for toni periods of lin .,. nol, J5 ~ rule, .... sw. """Ib. The nominal dwacttristk values. with 1"OIpect. to time can wary u mud! OIl 1 CIOt6 Of tThis b I very IOU." approxlmalion since Ills impcmib~ to nUbll$h litf~t correSPOndence between Amer~n and Soviet soli dusifiatlons without hiving I comp]ue de wiptu,n of me soil

12

...... -.. ..... 1ho lOll _ ond I"~ the number or tall, the _I proGadunI. _Ie. ~ of desi.,. ....... Iood 10 _ of 1110_' ronal eII_. ""Ich ... be _,I. __ _ Ihose "dma1lOd by ""I burtna ~ty. Ia 1110 __ side"'d ............ __ .. dwi ..... 12.llIi lit .. _ '''Iul/od by SR 80034 for PlY f;a,tor of 2. It a not dlffkull til show IhIt In ... example the Ions term .tren ..... of the froan toll. Cillc:ullted by c.kinllnto KCOUnl chI,tructure'l lifetime of 100 years, dlflws from that caIcuIIIecI '0' , 250year IInICIIn llfelfme by only _.1!1, I ........ eII_ is_lO .... -..cyof .... rneuuremenll.

Fin.alIV, if an adequase cornlilion betwIn Iht soil d.,wfk;alJom of the SNIP and SR.80-34 WD'II developed. the walues of fro,.. "'" ... _ R "'" R.d _lolled in die SNIPo,iI/!' be_ In wntern desl.,. pracdce.

Creep thformotion Analysis of deformation (settlement) is the most

important part of foundation design. Most reported foundation failures have been caused by nonuniform settlement rather (him inadequate bearing c:apacity.

According to SR ~34 the imalysis of settlement of footings on all types of frozen soils is based on the following principles:

1. Allowable load on the subsoil surface is de termined by a bearing capacity an;alysis.

2. Analysis of deformation is nec:essary for all types of soils except solid rock formations; allowable limits of settlements are not given.t t

3, Total settlement is estimated by summarizing settlements ofiginating in the separate layers using the formula"

m SIr) '" 2: e ] (t) h] /- ,

where

(21)

EI{t) '" subsoll/1h.layer creep strain at il given temperature

hi'" thickness of the layer m = number of layers.

4. The stresHtr~n relationship is nonlinear and is described by Vy;aloy's eqUation 16. The latter can be represented in ;a form tNt is similar to eq 14

ttln IoOme cases they are limited by loe~1 constf\lctiofl Wltes. "'n floCl three different methods ~re presented In SR 10.34. Of the three. In Ihe luthor's opinion, the method of settle ment analvsb ronsldefcd below Is preferlble.

where

(22)

E,(t) '" average creep main in the (lh layer along the central ax is of Ihc fou ndation.

The magnitude and distri bution of uress under the founda tion is ca lculated by using the elastic theory.

COinparinIIhe SNIP's JPPI'OICh to settlement ..... ysh "'lNt of the SR. .... WI _do INt. )n lllill' of IhI fKl m .. t both memocb are based on thl' IimI IheorItlaI premkes, .. wtain dkacPMCY '" the final ........ iII 0Uf. Speci .. 1 Report 80-34 don hOI,...".1he calaalaUon of Ittll,merus of roundldons on loUdly frozen tolls, but "'11Mb Ihll be cans ..... and, followins die practice Jdop throup,uc: &hi sa.. lAves Ihe dedlion whether to cak:t_ diem or not to .... _ .. "'Met. /u ____ ........ "'IN SNIP IN inaIyds of cWoIftllldonl is neer!!" only for foun-dltlOftI an ..... lIe frozen and .hI"n, soIlio SeU'"

~II of ~ on solidly froun toils Me not _1aIIII ... 11. lItI. ~ ... 01 .... nYln dlffefen ... bet_lito SNIP and SR 81U4 ....,di,. .. _t 1naIysh.. r. From dwflnpofnt Dfuslna 1M lime fEtor In ... onaIYIIo "'_don._II. the SR

DICIt uems &0 be more .Iuac:tlvt. II makes il ~ to IIdmlle the _dement atlnY moment ~ the SItIIc&Urt:'IIffedme. It &alee .... IO.uount the ........ tIir4IninIlffK1Il11d the lem .....

~ 01 JlrJin. II ~kI be mote Q)f'fto

Ete - _In the Imlll 01 lite -'""" -""'" lito .. __ In", canJldoradon IN oubooIl ml*llUN chan .. with 1.Ime It well u the DYef'. &urd.n prIIIWt of the soli. However, the innuence of the II. faaon upon the flnal rMUlli fNV not

...,. ........ daI. A Il'MN'lIUbiClntMt tIscrepIncy in the multi of

coIctda_ from the SNiP and SR 10034 b ....... by IN lactlltol lite deI ..... tion characteristic> Used In Iht~Y58I iI'C ctct.mlnecl by different ..-

In "" SNIP tdemenl of fguncgbOM 00 plutic f ..... "..u .......... ,. 0011 deformadon 1 or compIoHIblfity ~fficienls. (~eq

,. This melhod does not permit dte fidmatlon of accumulation of IlInlanents with time. Nevet-~, from In enJineerlnl viewpoint It could live N--., _h il._ metIIodololY for de""""" lito '""'" SDII'-'U of dolormation Of die c:offtpfMIbIlil'f coeffk6ontl had been dew1-

~ SpecIal ~ 81).34 r_ tNt the do-rormabltl~ parameter I( (see eq 22) be determined

from unconfined CGmprflSion Ielti. The besl corre spondence between the rnults of oslimations and the dati of f;eid obserntiom of structure senlements will be ob~ined if soil defouNlion moduli E, de-termined from fkoId tests with bearin, pYles, art used in the .analysii. If die compressibility coeffic-;eng,. IhI used In the analysis, the expectod )Oulo-mcf1' rni'f' be overestimated by f"tor of 2 to S c:ornp.red with the field observations. It is obvious Nt usinl dlfonnabilily parametcB obtained from unconflMd c:ampression tests Mil take inlO .c:count 1M time fKuw m.ly ,ane sentcment to be overe5b mated 10" even ... _ dearce. Heru, as farlS settlement lnalysis Ii c:oncemod, the fe(;OftImond. [ions of SR 8().34 Im'n 10 be more conservative than Ihe provlsto"s of the SNiP.

Note.t IN btmt d.itl on me tons term (up to 17 yars) IIfIHcalc""""""" to>b of Vv.a.,.2' ihowed that ,hno-dependenl5eUlomenll of beatlnl plo" on ..... tic IT .... ooIh con be _bed by the 'eqladon

S(r) (1 .'1 d{f,)"'" '" (23) .......

d;: diMnew of a pllte ~ Poi~'s filtio

U, n lind ~ .. paramelarS w c:oeffidenl dependl"" upon the

Wpc .1 the looti,. AI:: dtfonnabilily coeflk:ienl of me

frozen soil. ,EqlA.tion 2l was obUlined by ~ modlfk.uion of 'shleic:her's solution ind coincides reasonably well w!lh eq 18. However, tho problem Is how to de termlne !he pararneUlf1 of these eqUitlon) under Qborl;lOty conditions durol willaiw 5ettiemenlS cJoJc to those tNt will be experlenucl under (iekj c.ondl .....

This probWn IS dmely connec:Led with a very ,rnWlml qlM5tion, which should be emphasized In this comparhlon of the lWO dcxumenu: ,",w to rTYIthemllically dna'ibe Ihc (;~p curYCt and cit

mint me paro.neters In eq 13, 14,.md 22. This lion is (undimenu:l, and all the .an.tlysel of

rlnl up.aclty or foundation Hulernenl depend on its lO4utlon. 11 is well known wt the suiln hardeni", IWam

etcr" dependi sfanificanlly on suess. chmain. from rtqtjvelv hlp values (for 10me types of froan soils PI = 8--10) at hip SU'eS5elIO about un.ity for smAil slrmcs. In SR 80-34 it is aumed thai the snin hirdeninlPUMneIer lNy differ from unity, while n the SNIP it is accepted .u unUy in all c:.ueI. The t me hardening parilmelef A also depends upon weu,

i , ~

and both n iIld A Qr'j wary with lime.nd tcmper~ Uft. Hence, &lIthe arYIytiQl methods mentioned abow. which employ constJnt WlIues for these IInns, ta.YC Mt lPf)rOXimllII charKta'. Note that dcforrn.l lion or froun tOil Mtd r.lilure comtitut.e ~ uniftcd physiQl process. Thm:1""' .... "'-.. 01 .... wly,;is of founcktion setdements QMOt be ~ fully solved ..... til ~ unified c:omtitutiYO equation is established which desa'ibes thelonl term f.lihn iIId deformation of the soil. Equations or this twe were .... ted in two worts20, 27 and W8"e verified for vulGus typetof frozen and unfrozen soils ~t~ pie and complex ~trJtn suta

Enlln CIWIp (II consltInl stras A unified ~titudve eqlMtion derived by this author202].24 ,~,l6 on the b;Isi$ of the rate prcxess theory hu the form (for a llyon temperature):

. C ~ar ~m~' 6, e(/)"- - - up-I", 0 I 'm

.......

'm = '. ~:t;, .. :r O'PVr) .uwJ C, n, '" and 6 Me dimension" pvameten

00 K "lnsunt:aneoUS" $trtnJ1:h of the soil 10 " Frenkel', relaxadon time h = Pl.1nck', constinl It K Boltzmann', consum

(24)

(25)

.... Pt 'IIIO',,_-,,>: Cr p -

G,

t., - -------

" '.

t,IOQ Tlln'

Figure 5. Creep curves In logqrlrhmic coordinates (m-lnfJeclion points, Eo -Initio! strain rote, Em-minImum strain rate).

14

E = i/;tivation erwJY --------, R - lIS consunt T -- ib50Iute cempera ...... k

1m equation (ai_ion) of the IonJ term 1lr'qIh, i.e. Ihe time In ..... from ... initi.ation of the .... untillhe inflection pain. of. cnop cune (F" 2. 5, 6).

SubsUWU .. oq 25 into oq 24, .... 10_ ...... the form:

. . "" . (. ")" ,(/)--,or', "'; 'o'"'C'

\G; (26) \WheN t .. the initial wain r~te at 1h11imI t --,.

1 min,C,-C/'o.",mdnl" n+m ... mI. From a malhernatieal viewpoint, the t1rUd&n of eq 26 corrnponch. to equl.tionl derived In some of this author'!. other workslO,27. HOMMf.OII 24 and 26

YO better dimensions that II" more flexibility In machen'IAI UVlsfomwlons Mtd better correspon. dance to test dal&.

5.,..", .,.." n. strain r. reaches a minimum i' ...........

the ti .... ,. 'm' In dlil CIII", 24 bIc:omIs:

~111"'- - .. -e2 . C '0). ~r.) .... 'm 00 .0

(27)

~ C2 = (AI/to' Takll'lllnlO accounteq 25. eq 27 an be ................. loIiowIn&:

~ I , I b I

I I

J 0

'. t"" Tnn. 10 roillir.

Fl9ur~ 6. Time depentknl (ollun of frozen soli (0 -instontoneous strength, to -relax-ation time).

(28)

An approxim.ue equatibn ror de-r-orm.lfionio ~y be ~ted in Ute following form :

", ~ ,.,/ t t_ (o.So , ... , m (29)

whore to is the In~tantaneou, strain. B:; ell! 0:' ), and ), .. 1-6. EqUiUon 28 eJlprtSM$ the tempeUlure dependendft of the defornutlon proceu at the SKonduy c;recp.nd makn it pcmible 10 aUnlIle (he ICliQhon enerlY of frozen soil 1111 U1n. point. to dHuibc the entirt creep In ac:c;orcbnoe wilh cq 29.utd to del.mine all six plrlmeletS (C, n, m. 6, 10 ;and .,o) three toW ue netded: tWO creep teSIS and ~ I~I fOf 00'

Illhould be noted th.at the. tUolin ra~ on Ute prinwy, ICCOndM.,.and tert"r.,. creop depend upon

~ ritl

A .... rQ.Q. Adfr re 80nd Sir ... in F'tIrmofto.1 (Ibllln!) ~9 ____ ~'~, ____ J'~PC-__ J'f~ ____ 1'~pC-__ l'f,' ____ ~~~oC-__ ~~~'----='?

Lood (!G.) 40 80 120 160 o 20011 10'

~ 0.20 Of FoUl/t. Load

.

-~ ..

c 0.40 -

0.600!--~-!!---'----'!-' --'----:,1:: '.--'---:,I:: .L-,---::.o

Pile type: 8-ln. pipe, 36 fb/ft Pile II!f1gth: 10.9 fr Length below surface: 2a4 ft Embedment In frozen S1)1f: 16.1 ft

Tim. (day.'

5011 profile: 0-1 ft peat, 1-10.4 ft (bottom of pile) silt Backfill around pJle: s1it-'NCI(er slurry Avg temp of frozen sol/: 19.ZOF

Looding Schedule: lQOfXJ Jb increments appl/UJ at 24-hr Intervals. The deflecllon sho....", for an Increment Is that observed j ust prior to application of next Increment.

Note: Plk not ;sobted from soil in thaw zone.

COMPUTATION OF ALLOWABLE OESIGN LOAO

Failure fODd ~ 147,000 Ib SiJrface artO of pile In permafrost - 5230 In. 2 Average adfreeze bond stress at failure: 147,000/5230- 28.1Ibf/ln.1 Adjusting for 10,000 Ib/doy rote of loading (by Interpolation) average adfreeze bond stress at failure ~ 21.5 Assuming failure stress is 4{J1)6 ,eater than overage sustalnoble stress, overo~ sustalnoble adfreeze

strength - 21.5/1.4 z 15.3lbf/in.1 Sustolnoble pile lood capoClty - 15.3 )( 5230" 80,000 Ib Using a factor of safety - 25, al/o'tWble design lood - adjusted failure lood/FS .. 21.5 )( 5230/2.5 = 45,(}()() fb

Figure 7. Determlnotion of pile bearing capacity. (From SR 80-34, Chop. 4, Fig. 4-80.) A and 8 are addltlonol points.

16

''''0

l 'L O'r-__ ~'~ __ ;'~-c6~~8

1" r:,: A

p". '4~.ooo lOt; 8

, ~D':' ____ _

Figure 8. Determination of the pile Moring capacity according (0 rec ommended Soviet practlce7, A and B are additional points.

p. . -- ' SF L. (311

If ills.ueumod tholl' me sb'Ucture In question is a brid,e founcbdon. and Ihe subwiltemperawre equak the test temperature '., "' l), lhr oomfNrison of the allowable toH, wUl be detennined by the rllio:

N" 145,000 x 3.27 . ~ .. 2.93 LII 147,000)( 1.1 Itr kr

and lIIus it will depend upon Ihe number of piles in the founct.tion (Toilble 1),

T ..... I. RodoofaJl_pllololdsf ... ~ __ -.. ..... by the SNIP IN., .... SR 10-)4 (L.,. (The _ .. I. ratio N4IL~ for huIIdtnJ foundltions with """ _ of pO .. 112.44 lot k, 1.2.'

N_bl'ot' .... '" IN foundlttDn > 20 20-11 10-6 '-I

.1110 N,.Jt" 2." I.U 1.71 1.67

Thtse raUos c:onwy the impression tholl' me 'fference btcweon the iPPfOIchct of the SNiP m

me SR WI be up to 100% for bridge (oundollions

17

and 1 SO% (or foundations of buildings. The differ ence mily be less if the different procedures used in obtaining the experimenul curves ilre uke.n into account.

In the SR 80-34 example, the itatic load, applied bV m'LaU Increments of t:J'1 = 10,000 lb .11 24-tlr in-tervals, constilUtes a step loading regime with the rale of loadina C!qtQllo p ." 10,000 Ib/24 ht . It is known !hat the failure load depends subsuntiaUv upon the loading regime. A family of load-deforma-tion curves (similar 10 Fig. 7) Cl therefore be ob-

~ined for the same soil conditions by varying the rale of loading. Strictly speilking, none of the curves produced by this type of experiment WIn be used to determine the pile hearina cilpuitV since the mults of tests under the step loading regime ClnOt be directly lrilnsferred to the creep regime (the real conditions under which piles are used).

On the othc:r hand, accordi", to the Soviet priC-uce 7, me load is applied 10 I tesl pile by the incre-ments ~I 0.2 to O.S Q, but the: durOlition of each increment of loadina is Vl(jed. The nextl~ 41',+ I Is applied if the lenlement (disp~menl) rate of the Pile under the previous step load ~ nOI exceed the conventionalllloWilble value 0 ... 0.2 mm/24 hr. The test is stopped _hen the va-tical displacement ",Ie ilCCetcfates rapidly. 'The vollues of Q art deter-mined approximately by cq 6. ThK test proc:edure 7 Is probably ck>ser to the creep regime and therefore the atKolutt values of nominil beMlng tap.)Cities of piles determined by the SNiP may be less tha.n those determined by the provisions of SR 80-34. However, it ~o,,1d be IlOted that the. SNiP method also annat be repufed as ytlsf.u:toty because it admits Yifia !jon of the loacHteformation curves, d(!JJeoolng on the allowu.le lim/( of the displ.u:emenl rolle of the pile. Nellher method takes Into account lhe Struc-lure's lifetime, even though II is in essential variable In the dermninition of be,uing cap.u:ity of footings under both the SNiP,and SR ~34. Methods for pile seulementanalYlis are not developed in either.

II would be olPPfopriate. inste-ad or perfOfming one pile test, to perform tVlrO short ttnn tHts In st(!JJ loading with different rales of loading

. dP P :. - =- Constant dr

The ~Iues of lo.d increments AP un be the same, while the intervals of 41, _hid! arc constant for NCh lest, musl be different (FiJ. 9 and 10). If it is assumed for the firsl appro)ljlNhon, that the t01a1 piSe: foun-dation W!t1lement would eqtQl the \etlkmetU of the single pile. eq 4 ukcs the form

, b 0'

-------------

------

,

0 I

< 6P ... _r : .0 I u I ~ ..

I 0 ~ I I I

"P, I P, I" 'n

Tim. 10 Foilur "

Figure 9. Diagram for tktermlning pile bearing capacity from two tests with various rates of loading: P ,(0) and P2(b).

." ,; g " .. i 0 z

0:

..

P,

b

,

'" 'n Til" , 10 Foil",., t.

Figure 10. Diagram of long term pile bearing copacltles at variOUS loading regimes: Con-stant !ood-P = Constant (a); Step Ioodlng-P, " P,'-s,(b).

..... S the penniaiIM ullimice value of founlb tkln .,dement dependlns upon the type of struewre land O. is the,.,.. ..... uldmale vwtkaI displace-ment of .... pile.

The pile dilplacanent thit corre5POOck to the inflecllon poIn. of .... _lion I".n -. creep 10 terdlry tnIIIP on the list step of Ioadina un &110 be ICC:eP1ed I llil .... giterion.

I. Is not dllt1cult to -'0 ..... 11. lor ..... pIe. plio Iona ..... boorina -,ty is _bed for con-_.Ioodbyl __

'.-', p-n forP-Constant (l2)

'8

lonlltrm bcann, ujm:ity for step I~ctinl will be siwn by the formula

'.I=(1+n)B1Pi" fOf' P1 .. P1tJl (33) where', is time to fillure KCOfdi .. tocq 32.

The ~meters B I and n gn be usily determined. havin, (rom field lett dati. two nlues of fail ......

and two times 10 failure

where m .. the number of stepl. The value of nomlN.! burin, gpacity of 01 pUo can be estbnated. dependna pm tho ,truet'"" lifetime I is

(11,1 ". p.(t) Tt (34) Comp.ulnc eq 32 mel 33, one can _ that for tho ..... flllu .. times .... bwlnl-'IY of .... plio In """P c:ondItJons wi" be .... by. ,..".. of (1 +n)l/nthanitislnsteplodn ... If ......... thit puame1lBr n,. 1.5 - 2, lite actual rado of allow-ollie _ on piles de_ned by SR 110-34 .... the SNIP ... y In ......... be dose 10 ,.,Ity. '1110 pro-.,.,... method CiII be oppIIed '" piles of_ """"' .... _ .. Il00 01 ................ the dlmenslom do not differ ... ~y""" _ of .... tes. pile- Settlemen. 01 ...... piles ....... be de-.....ined uoI,.lnformllion _ned".,., """ """ All Iht5e questions l/IO ,Iosety c;on ... " wlttI tho

fIO",;Jii,

CONCLUSIONS

I. SR 8034 and the U.S.S.R. SNi P 111876 present methods of foundation dl.osign on permafros t ~sed on reeem knowledge of frozen $oil mechanics d.nd engineering geocryology. AI thc silme time the documents.He nol equivAlent. T hey differ in the

purpo~cs they pursue, Inc )COPC of the prob l cm~ discussed, and thc methods of prcscntatioo of tho m

nruc;ture foundations. CRREL Draft Translation 737. 17. Manual for the dctermination of physical, lhermophysical and mechanical properties of frozen ground. Stroyizdat, Moscow, 1973 (in Russian). 18. Voytkovskiy, K.F. (1960) The mechanical properties of ic;c. Moscow: U.S.S.R. Academy of Sdenc;cs Publishing House (in Russian). 19. Votyakoy, tN. (1975) Frozen and thawing soil physical and mechanical properties of Yakutiya. Izdyo Nauka, Novosibirsk (in Russian). 20. Fish, A.M . (1976) Aroustic and pressuremeter method of inyestigation of the rheological proper ties of ice. Ph.D. thesis, Arctic and Antarc;tic; Scien tifk Researc;h Institute, Leningrad, U.S.S.R. (Trans-lated version being prepared as a CRREL publication.) 21. Vyalov, 5.5. (1980) Settlements of bearing plates on plastic frOlen soils (translated from Russian). Soli Mechanics and Foundotion EngineerIng, vol. 14, no. 6. 22. LineH, K.A. and E.F. Lobacz (Eds.) (1980) De sign and c;onstruc;tion of foundations in areas of deep seasonal frost and permafrost. CRREL Special Re-port 80-34. 23. Fish, A.M. (1979) Mechanical properties of fro

20

zen soils. Research Proposal, contrac;l no. DAAR 2977.Q016. Part B. Cambridge: Massachusetts Institute of Technology. 24. Fish, A.M. (1980) Kinetic nature of the long-term strength of frOlen soils. Proceedings, 2nd Interna-tional Symposium on Ground Freezing, Norwegian Institute of Technology, June 24-26, Trondhelm, p. 95-108. 25. Fish, A.M. OlInd F.H . SOliyles (1981) Acoustic; emissions during crcep of frozen soils. In Acoustic emissions in geotechnical engineering practice (V.P. Drncvich and R.E. Gray, Eds.). A5TM STP 750. American Society for Testing and Materials, p. 194-205. 26. Fish, A.M. (1982) Deformation and failure of frOlcn soils and ice at constant and steadily in-creasing stresses. In Proceedings of the Fourth umodion Permafrost Conference, March 2-6, 1981, Colgory, Canada. National Reseanh Council of Canada. 27. Vyalov, 5.5., Yu.K. Zaretskiy, R.V. MilXimyOlik and N.K. Pek