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INTRODUCTION

A pressuremeter test is one of field methods of geotechnical survey forthe determination of deformation behaviour and strength properties ofground. The tests are carried out by means of applying loads on the wallsof small-profile boreholes (most often within uncased sections), up toa depth of about 100m. They are applicable in virtually any type of soil andin rocks classified as class R 6 through R 3, i.e. those with extremely lowto medium strength; they usually must be replaced by dilatometer tests inthe cases of the R 2 to R 1 class hard and very hard strength rocks (with theexception of those found in tectonically disturbed zones). They are appliedin the course of surveys for all types of difficult constructions and they areespecially suitable for underground construction projects. In the case oftunnels, they are used for the verification of properties of the soil and rockin the overburden and along their sides.

The pressuremeter principle was patented by Louis Mnard, a Frenchengineer, in 1955 (at that time being still a student at the cole Nationaledes Ponts et Chausses in Paris). In the following years he continued toextensively develop the production (many types of the apparatus) and theuse, till his premature death in 1978. The method rapidly spread all over theworld and has become one of the most frequently used specialist geotech-nical tests. The respective types of the apparatus are manufactured by seve-ral companies (apart from 2 French firms, which are successors of the ori-ginal Mnards firm, there are others, for instance, English and Japan).PUDIS a.s. has had this field testing method in its portfolio since 1979 (ifwe neglect the measurements carried out by a Czechoslovak prototype forthe Prague metro in 1968 1969); at that time the company used its firstapparatus for the determination of geotechnical properties for the Strahovtunnel construction (today it owns 4 pieces of the Mnard-type apparatus).

PRESSUREMETER TESTING METHODOLOGY

Pressuremeter tests are used to determine the relationship between thedeformation of borehole walls and the radial pressure acting on them.

VOD

Presiometrick zkouky jsou jednou z ternnch metod geotechnic-kho przkumu pro stanoven petvrnch a pevnostnch charakteris-tik hornin. Provdj se zatovnm stn maloprofilovch vrt (nej-astji na nepaench secch), a to a do hloubky cca 100 m.Pouiteln jsou prakticky ve vech druzch zemin a ve skalnch horni-nch td R 6 a R 3, tj. s extrmn nzkou a stedn pevnost, u hornins vysokou a velmi vysokou pevnost R 2 a R 1 u zpravidla mus btnahrazeny dilatometrickmi zkoukami (s vjimkou zn tektonickyporuench). Aplikuj se pi przkumech pro vechny typy nronchstaveb a zejmna jsou vhodn pro stavby podzemn. Pro tunely ovu-j vlastnosti zemin a hornin pedevm v jeho nadlo a bocch.

Princip presiometrickho pstroje patentoval francouzsk inenrLouis Mnard v roce 1955 (tehdy jet student pask cole Nationaledes Ponts et Chausses) a v nsledujcch letech iroce rozvjel jehovrobu (ada typ) a pouvn a do sv pedasn smrti v roce 1978.Metoda se rychle rozila po celm svt, stala se jednou z nejastjipouvanch specilnch geotechnickch zkouek. Pslun aparaturynyn vyrb nkolik firem (mimo 2 francouzsk, kter navazuj napvodn Mnardovu, napklad anglick a japonsk). PUDIS, a. s., dis-ponuje touto metodou ternnho testovn horninovho prosted ji odroku 1979 (pomineme-li men eskoslovenskm prototypem prometro v letech 1968 1969), kdy svm prvnm pstrojem napklad zji-oval geotechnick charakteristiky pro projekt Strahovskho tunelu (v souasn dob vlastn 4 aparatury typu Mnard).

METODIKA PRESIOMETRICKCH ZKOUEK

Presiometrickou zkoukou se zjiuje zvislost deformace stn vrtuna psobcm radilnm tlaku. Tento se stupovit zvyuje a po kapa-citu pstroje nebo k dosaen meznho tlaku, pi kterm nastane poru-en horninovho prosted (vyvj se smykov plocha nad a pod presi-ometrickou sondou).

Schma presiometru typu Mnard zachycuje obr. 1. Presiometrickvlcov sonda se skld ze 3 bunk: stedn mic a dvou krajnchochrannch. Do mic buky se pivd kapalina, zpravidla voda, jejobjemov zmny se sleduj volumetrem, ochrann buky se pln ply-nem (nejlpe duskem). Ochrann buky zabezpeuj rovnomrn pe-tvoen stny vrtu po cel dlce mic buky zajiuj splnn okra-jovch podmnek zkouky. Na povrchu ternu zstv druh st pre-siometrick aparatury ovldac a odetac jednotka (tlaky se sledujprostednictvm pslunch manometr, objemov zmny volumet-rem). Tyto dv sti jsou propojeny hadicemi pro veden zatovachoplynu a kapaliny. Nkter novj pstroje jsou ji vybaveny pota-em a tiskrnou, take jsou ihned k disposici vsledky zkoukys petvrnmi diagramy.

Pro pstroje typu Mnard se vyrb presiometrick sondy prmru 74,58 a 44 mm. Pro zkouky se pipravuj jdrov vrty prmru 76 mm(NX), 60 mm (BX) a 46 mm (AX). Zatovac kapacita pstroj typuGA (resp. rozsah radilnho tlaku vyvozovanho na horninov prosted)je 8 MPa.

Zatovac postup a vyhodnocen presiometrickch zkouek bylnejprve normalizovn ve Francii, kde pslun nvrhy (viz lit. 1 3)zpracoval osobn Louis Mnard. Po svtovm rozen byla zkoukastandardizovna napklad v USA (lit. 5). Relativn velmi brzo bylypslun smrnice a normy (lit. 4 a 6) zpracovny i v eskoslovensku(co byla zsluha pedevm bratislavskch specialist zejmnaProf. O. avody, DrSc. a Prof. Ing. M. Matyse, Ph.D.). Rovn souasn nvrhy evropskch norem se tak zabvaj presiometrickouproblematikou (lit. 7 a 8).

ZKUENOSTI PUDIS, A. S., S PRESIOMETRICKMI ZKOUKAMI PRO TUNELY

THE EXPERIENCE OF PUDIS a. s. IN PRESSUREMETER TESTING FOR TUNNELS

JI HUDEK

Obr. 1 Schma Mnardova presiometru:1 ovldac jednotka, 1a regulanventil diferencilnho a michotlaku, 1b mie tlaku a objemu, 1c jednotka snmn, ukldna tisku dat, 2a hadice pvodu vodydo sondy, 2b hadice pvodu plynudo sondy, 3 hloubkomr, 4 tye, 5 presiometrick sonda, 5a hornochrann buka, 5b stedn micbuka, 5c doln ochrann buka, 6 zemina, 7 presiometrick vrt, 8 dut tlo sondy, 9 pipojovacpruba sondyFig. 1 Diagram of a Mnard pressuremeter1 - control unit, 1a - pressurization, differential pressurization and injectiondevices, 1b -pressure and volume measuring devices, 1c - acquisition, storage and printing out of the data, 2a - line for liquid injection, 2b - linefor gas injection, 3 - depth measurementsystem, 4 - rods, 5 - pressuremeterprobe, 5a - upper guard cell, 5b - centralmeasuring cell, 5c - lower guard cell, 6 - ground, 7 - pressuremeter borehole,8 - probe body, hollow, 9 - probe rodcoupling

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Dle standardnho normovho postupu se pi zkoukch odetajobjemov deformace po 15, 30 a 60 sekundch. Pi vyhodnocen jenutn respektovat korekce tlakovch a objemovch ztrt dle pslu-nch kalibranch kivek. Zde je zejmna dleit normov kritrium(lit. 8) omezujc rozsah objemovch korekc (parazitn deformace napklad membrn a povlak presiometrick sondy a propojovachadice) hodnotou 25 %. Z tto toti vyplv hranice, do jak tuhostihorninovho prosted (vyjden presiometrickm modulem petvr-nosti) lze jet pout konkrtn aparaturu. Tato hodnota se vtinoupohybuje (pedevm v zvislosti na typu povlaku presiometricksondy) v intervalu EoM 2000 a 5000 MPa. Pi vyhodnocen je dlerespektovn inek hydrostatickho tlaku (resp. vrtnho vplachu).

Z petvrnch diagram (pklad na obr. 2) se stanovuj ze zvislos-ti objemov deformace na vyvozenm radilnm tlakovm napt (resp.pedevm z funkce teen mezi 30 a 60 sekundami) nsledujc hrani-n body mezi temi fzemi (prunou, pseudoelastickou a plastickou):

po zatek pseudoelastick fze, tj. radiln napt, pi ktermdochz k optnmu uzavrn pr i dlcch ploch rozeve-nch po uvolnn v dsledku odvrtn. Toto napt se nkdy(nesprvn) oznauje jako tlak v klidu;

pf hranice mezi pseudoelastickou a plastickou fz petvoen(resp. konec linernho stadia petvrnho diagramu) oznaova-n jako mez teen i dotvarovac napt;

pLM mezn radiln tlak, pi kterm se poruuje materil na stnchvrtu (vytven kluznch ploch v dsledku pekroen smyko-v pevnosti). Je zpravidla extrapolovan (pi jeho vlastnmdosaen by se v dsledku vvoje smykovch ploch vrt zava-lil), konstruovan napklad jako asymptota (ve smru osyseek) k petvrnmu diagramu.

Nejdleitjm vsledkem zkouky je Mnardv presiometrickmodul petvrnosti EoM, kter je stanoven vdy z linern pseudoelas-tick fze petvrnho diagramu (a je tedy maximln hodnotou modu-l petvrnosti v zvislosti na napjatostnch oborech). Tento je zpravi-dla potn ze vztahu:

EoM = 2 (1 + ) (vo + vm) . p /vkde zna: vo zkladn objem stednho lnku sondy (nulov ten)

vm objem vody natlaen do mic buky stednm tlakempm

p/v smrnice petvrnho diagramu v linern pseu-doelastick fzi

Poissonovo sloVe popsan postup plat pro tzv. standardn Mnardovu zkou-

ku. V ppadech nutnosti zjistit nejen modul petvrnosti, ale i modulpru nosti se v linern pseudoelastick fzi zaazuje smykas postupnm odlehenm a optnm zatovnm (tzv. modifikovanMnardova zkouka) a ze stejnho vztahu se analogicky (ale na pod-klad prunch petvoen) stanov Mnardv presiometrick modulprunosti EM.

Presiometrick zkouky se umsuj do zjmovch interval hor-ninovho prosted, obecn L. Mnard doporuoval jejich provdnv metrovch vzdlenostech. Jejich vsledky se asto zobrazujv hloubkovm diagramu.

PRESIOMETRICK ZKOUKY PUDIS, A. S., PRO GEOTECHNICK PRZKUMY

Zkuenosti PUDIS, a. s., s presiometrickmi zkoukami pro geo-technick przkumy sahaj a do konce 60. let minulho stolet(prototyp eskoslovensk vroby zapjen VUT Brno pro menna I. provoznm seku trasy C praskho metra), pravideln pou-vn po zskn presiometru typu Mnard GB od roku 1979.V letonm roce byl pekroen poet 10 000 presiometrickchzkouek realizovanch tmto pracovitm. st jich byla pro nro-n pozemn a mostn stavby s plonmi i pilotovmi zklady, prokter ji i nvrhy evropskch norem (EUROCODE 7 lit. 8) obsa-huj algoritmy pro nosnost a sedn se vstupnmi geotechnickmicharakteristikami pmo stanovovanmi z vsledk presiometric-kch zkouek.

Z geotechnickch przkum pro tunelov stavby realizovalPUDIS, a. s., jednu ze svch prvch sri presiometrickch men(brzy po zskn presiometru typu Mnard GB v roce 1979) na traseStrahovskho tunelu, kter je soust Mstskho okruhu v Praze(zde paraleln provdl i dilatometrick zkouky). Velk mnostv(nkolik set) presiometrickch zkouek probhlo pro dosud nejn-ronj tunel v esk republice Mrzovka budovan rovn na

The pressure is stepwise increased until the capacity of the apparatus isexhausted or the limit state is reached under which the ground environ-ment fails (a shear plane develops above and below the pressuremeterprobe).

A diagram of the Mnard-type pressuremeter is shown in Fig. 1.The pressuremeter cylindrical probe consists of 3 cells: a measuringcell in the middle and two guard cells on its ends. A liquid, usuallywater, is supplied to the measuring cell; the volumetric changes of theliquid are monitored using a volumeter. The guard cells are filled witha gas (preferably nitrogen). The guard cells ensure uniform deforma-tion of the borehole wall throughout the length of the measuring cell,thus they ensure that the boundary conditions are met. The secondpart of the pressuremeter apparatus, i.e. the control and read-out part(the pressures and volumetric changes are monitored through pressu-re gauges and a volumeter), remains on the terrain surface. The twoparts are interconnected by the loading gas and the liquid feedinghoses. Some newer types of the apparatus are equipped witha computer and printer. They provide immediate test results andstress-strain curves.

The diameter of pressuremeter probes which are manufactured forMnard-type apparatus is 74, 58 and 44mm. The diameter of theboreholes which are prepared for the testing is 76 mm (NX), 60 mm(BX) and 46 mm (AX). The loading capacity of GA-type apparatus(or the range of the radial pressure applied to the rock mass) is 8 MPa.

The loading procedure and evaluation of the pressuremeter testswere first standardised in France, where the respective specificati-ons (see Ref. 1 3) were developed personally by Louis Mnard.Once the test had spread all over the world, it was standardised, forinstance, in the USA (see Ref. 5). Relatively very soon, the relevantdirectives and standards (Ref. 4 and 6) were prepared even inCzechoslovakia (primarily owing to specialists in Bratislava, main-ly Prof. O. avody, DrSc, and Prof. Ing. M. Matyse, PhD.). The cur-rent drafts of European standards also deal with the pressuremeterissues (Ref. 7 and 8).

According to the standard procedure, the volumetric strain is readevery 15, 30 and 60 seconds during the tests. The pressure lossesand volumetric losses determined according to the respective cali-bration curves must be respected when the evaluation is being car-ried out. The standard criterion (Ref. 8) which sets a limit to theextent of the volumetric corrections (parasite strain, e.g. that ofmembranes and coatings on the pressuremeter probe and the inter-connecting hose) at a value of 25% is particularly important here.This is because this value is a basis from which a limit for the stiff-ness of the rock mass is derived (expressed by means of the pressu-remeter modulus of deformation) to which a particular type of theapparatus is applicable. This value varies (above all depending onthe type of the coating of the pressuremeter probe) mostly within theinterval EoM 2000 to 5000 MPa. The effect of the hydrostatic

Obr. 2 Pklad charakteristickho petvrnho diagramu presiometrick zkoukyFig. 2 An example of the characteristic stress-strain curve obtained by a pres-suremeter test

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pressure (or the pressure of the drilling fluid) is another factor whichis respected during the assessment.

The stress-strain curves (see, for example, Fig. 2) are used for thedetermination of the dependence of volumetric strain on the inducedradial compression stress (or, above all, the dependence on the func-tion of creep in the time interval between 30 and 60 seconds), whichallows the determination of the following boundary points betweenthree phases (elastic, pseudoplastic and plastic):

- po is the beginning of the pseudoplastic phase, i.e. the radialstress under which the pores or joints which opened after therelaxation caused by the drilling again close. This stress is insome cases called (incorrectly) a pressure at rest.

- pf is the border between the pseudoplastic and plastic phases ofdeformation (or the end of the linear stage of the stress-straincurve), which is referred to as the creep limit or creep stress.

- pLM is the limit radial pressure under which the material of theborehole walls fails (slipping planes develop as a result ofthe shear strength being exceeded). It is usually extrapolated(the borehole walls would collapse if the limit were rea-ched); it is constructed, for example, as an asymptotic line tothe stress-strain curve (in the direction of the coordinate axis y).

The most important result of the test is Mnards modulus ofdeformation EoM, which is always determined from the linear pseu-doplastic phase of the stress-strain curve (therefore, it is the maxi-mum value of moduli of deformation relative to the stress ranges).It is usually calculated from the relationship:

EoM = 2 (1 + ) (vo + vm) . p /vwhere: vo is the basic volume of the central part of the probe

(a zero reading)

Mstskm okruhu v Praze (velk rozmry tpruhovho tunelua rozpletu s malm nadlom tvoenm velmi mlo pevnmia zvtrnm a tektonikou poruenmi horninami a souasns podchodem pod starou a ptipodlan zstavbou). Zkouky zdebyly provdny jak v etap podrobnho przkumu ve vertiklnchvrtech z povrchu ternu, tak i pi etap doplujc z przkumn toly.Podmnky tchto zkouek v podzem ilustruje fotografie na obr. 3.Jako pklad vsledk jsou na obr. 4 uvedeny hodnoty presiometric-kch modul petvrnosti zjitn ve vji (skladajcho se z 5 rznorientovanch vrt) ve stanien 14,512 km vchodnho tunelu podulic na Doubkov. Pslun vrty a presiometrick zkouky bylyv tomto ppad realizovny v rmci doplujcho geotechnickhoprzkumu z pedstihov vyraen kaloty pravho bonho tunelu.Horninov prosted tvoily zdrav jlovit bidlice libeskho sou-vrstv (ordovik). V nadlo tunelu byl zjitn prmrn presiometric-k modul petvrnosti EoM v hodnot cca 170 MPa, v bocch 620a v podlo 1000 MPa. Pi interpretaci do statickch vpot je tytomoduly nutn redukovat s ohledem na vystien objemovhoa asovho mtka zkouek. Tato redukce zde inila piblin 50 %.

Z dalch geotechnickch przkum pro tunelovan sti naMstskm okruhu v Praze je dleit pedevm sek pejchar Pelc-Tyrolka (vetn podchodu Vltavy a Stromovky), kde bylo cel-kem nkolik set presiometrickch zkouek (pedevm menz przkumn toly).

Pi geotechnickch przkumech pro tunely na silninm okruhukolem Prahy byly presiometrick zkouky jak ve vrtech z povrchuternu, tak i z przkumn toly pro stavby 514 (tunel Lochkov) a 513(tunel Komoany).

V rmci mimopraskch geotechnickch przkum realizovalafirma PUDIS, a. s., presiometrick zkouky napklad pro silnintunel Hebe a dle pedevm na dlnici D8 tunely Radejna Prackovice (opt z povrchu ternu i z przkumn toly).

Vznamn jsou i presiometrick men PUDIS, a. s., pro elez-nin tunely (nov trasy i rekonstrukce). V roce 1988 to bylo pro roz-plet III. Vinohradskho elezninho tunelu, zde se dokonce jednaloji o presiometrickou st kontroly spnosti zpevovac injektev tunelovm nadlo pod Anglickou ulic. Na optimalizaci elezni-n trat Zbeh Kraskov to bylo pro tunely Mal Huba, Hnv-kov I a Hnvkov II a trat Kraskov esk Tebov pak tunelyTebovick a Kraskov. Na elezninm koridoru byly presiometric-k zkouky pro dva tunely u Nelahozevsi. Z novch tras byly sriezkouek pro tunel Bezno (zde byla aplikovna i dilatometrickmen) a v Praze na stavb Novho spojen pro tunely Vtkov.

Pro prask metro se presiometrickmi zkoukami podlelPUDIS, a. s., pouze menm pro IV. provozn sek trasy C NdraHoleovice Ldv, a to dvma sriemi zkouek pro traov tunelpobl stanice Kobylisy.

Obr. 3 Presiometrick zkouky z przkumn toly Mrzovka (pstroj Mnard typ GA)Fig. 3 Pressuremeter tests carried out from within the Mrzovka exploratorygallery (the GA type of Mnard pressuremeter)

No. 4/1249

Eop [MPa]

Scale for pressuremetermoduli of deformation

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Obr. 4 Tunel Mrzovka presiometrick vj pod ulic Na Doubkov s vsledkymodul petvrnosti Eop v 5 ovovacch vrtech v libeskch bidlicch1 navky, 2 deluviln sedimenty, libesk bidlice: 3 rozloen, 4 zvtral, 5 navtral, 6 zdrav, 7 hladina podzemn vody (po snenrabou toly) Fig. 4 Mrzovka tunnel a fan of pressuremeter boreholes under NaDoubkov Street; with the results of measurements of moduli of deformationEop in five verification boreholes through the Libe Shale 1 man-made ground, 2 diluvial sediments, Libe Shale: 3 decomposed,4 weathered, 5 slightly weathered, 6 fresh, 7 water table (drawn downby the gallery excavation)

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V nronch secch se pouv presiometrie i u tunel menchprofil. Pkladem v tomto smru je kolektor Hlvkm most pi pod-chodu pod eitm Vltavy, vrtn i mic prce zde byly provdnyz pontonu na ece (viz. foto . 7), dle kolektor Centrum (smchov-sk st) nebo napklad raen kolektor esk Krumlov Latrn(r. 1989).

Z ve uvedenho pehledu je zejm, e v souvislosti s rozvojemtunelovho stavitelstv v esk republice v poslednch asi dvacetiletech se pi geotechnickch przkumech iroce uplatuj jakomodern metoda presiometrick zkouky a jejich dodavatelem je zdenejastji PUDIS, a. s. Je to i v ppadech, kdy zpracovatelem cel-ho geotechnickho przkumu pro pslunou stavbu je jin pr-zkumn organizace a PUDIS, a. s., zde dodv pouze presiometric-k zkouky a jejich zhodnocen (nebo napklad jet i laboratornzkouky mechaniky hornin).

Dlouhodob zkuenosti PUDIS, a. s., s presiometrickmi zkou-kami byly zroeny i pi geotechnickch przkumech pro tunelova podzemn stavby v zahrani. U naich nejblich soused veSlovensk republice to bylo v roce 1994 pi przkumu pro podzem-n sklad jadernho paliva v jadern elektrrn Mochovce a v roce2005 pro dlnin tunely na D1 v seku Hubov Ivachnov. Jidve (v letech 1985 1987) to bylo v Alrsk arabsk republice,kde se sice jednalo o adu przkum pro pehrady (asi 10 pev-n na ekch v podh Atlasu), ale jako doplujc konstrukce zdebyly i podzemn stavby (napklad obtokov tunely). Z dlninchtunel to byla presiometrick (a dilatometrick) men v letech1991 1992 v Rakousku v oblasti Semmeringu (zde to byly zkou-ky a do hloubky 100 m).

PRESIOMETRIE PI GEOTECHNICKM MONITORINGU KONTROLA INJEKNHO ZPEVNN

Presiometrick zkouky lze aplikovat krom geotechnickch pr-zkum tak pro rzn kontroly pi realizaci staveb. Pklademv tomto smru bylo oven injeknho zpevnn hornin v nadloautomobilovho tunelu Mrzovka v Praze (esk republika). Tentotpruhov tunel (schma na obr. 5) byl velmi nronou podzemnstavbou se kou vrubu 16,6 m, vkou 12,5 m a prezovou plo-chou 165 m2 (v rozpletu a 335 m2). V sti trasy je tunel vedenvelmi mlko pod povrchem ternu, napklad v oblasti pilehlk ulici Ostrovskho mocnost tunelovho nadlo kles a na 16 m.Z tohoto na navtralou a zdravou skaln horninu (ordovick libesksouvrstv mkk jlovit bidlice s nzkou pevnost R 4 zde pr-mrn pevnost lomk 12 MPa a masiv s vysokm stupnm tekto-nickho poruen) pipad pouze 5 m. Tunel zde prochz pod 100let starou zstavbou (a ptipodlan), jej zklady jsou pouze12,5 m nad jeho vrcholem. Bezpen raen Novou rakouskou tune-lovac metodou vyadovalo mimo vertikln lenn vrubu jetdoplujc soubor sananch opaten. Jednm z nich byla zpevova-cch injekt. Jejich kolem bylo vyplnit rozdlovac plochy injek-n sms a doshnout:

snen pravdpodobnosti provoznch havri (typu nadmrnchvlom nebo ztrty stability ela vrubu) z dvod vskytu mimo-dn nekvalitnch skalnch hornin;

snen extrm prbhu poklesov kotliny; omezen sedn nadlo tunelu s ovlivnnm povrchov z -

stavby; zamezen nhlm ptokm podzemn vody do tunelovho dla.Injekt byla provdna z dve vyraen przkumn toly. Byla

pouvna injekn sms cementov, stabilizovan bentonitem.Systm uspodn injeknch vrt (a 21 kus v jednom vji)v pnm ezu zachycuje obr. 5. Vzjemn vzdlenost injeknchvj byla 3,5 m a mocnost oblky proinjektovan horniny od 3 mdo 5 m. Injekn tlaky byly voleny do 6 MPa (trhac do 17 MPa).

Presiometrick zkouky kontrolujc spnost injekte bylysoust geotechnickho monitoringu vstavby tunelu. Jejich ko-lem bylo poskytnout podklady pro posouzen innosti zpevujcch(sananch) injekt, a to jak po strnce zven tuhosti, taki pevnosti horninovho prosted.

Kontroln presiometrick zkouky byly situovny do jdrovchvrt prmru 60 mm, kter byly umstny do vj uprosted meziinjeknmi vji (obr. 5). Pro srovnvac men zachycujc stavped injekt slouily dovrchn vrty situovan v ose przkumntoly. Posouzen bylo zaloeno na statistickm zpracovn vsledkz obou etap. Ke zkoukm byl pouit presiometr francouzsk firmy

vm is the volume of water pumped to the measuring cell using themedium pressure pm

p/v is the slope of the stress-strain curve in the pseudoplasticphase

Poissons ratioThe above described procedure is applicable to the so-called

standard Mnards test. In the cases where it is necessary to deter-mine not only the modulus of deformation but also the modulus ofelasticity, a loop is added in the linear pseudoplastic phase, with gra-dual decompression and repeated loading (the so-called modifiedMdards test), and the Mdards pressuremeter modulus of elastici-ty EM is derived from the same relationship analogically (but on thebasis of elastic deformation).

Pressuremeter tests are located at specific intervals of interest inthe ground environment; in general, L. Mnard recommended thatthey be carried out at 1m intervals. Their results are often displayedin the form of a vertical diagram.

PRESSUREMETER TESTS CONDUCTED BY PUDIS A.S.FOR THE PURPOSE OF GEOTECHNICAL SURVEYS

PUDIS a.s. experience in pressuremeter tests for geotechnicalsurveys goes back to the end of the 1960s (a Czechoslovakia-madeprototype, which was borrowed from the Technical University inBrno for the purpose of measurements on the 1st operating sectionof Prague metro Line C); the regular use started in 1979 after thepurchase of a Mnard GB pressuremeter. This year, the number ofpressuremeter tests carried out by this workplace has exceeded10,000. Part of the tests was conducted for complex buildings andbridges founded on spread footings or piles, i.e. the structures forwhich the algorithms for the loading capacity and settlement havebeen contained even in the drafts of European standards (EURO-CODE 7 ref. 8) the input geotechnical characteristics were deter-mined directly from the pressuremeter test results.

One of the first series of pressuremeter measurements, whichwere carried out for tunnelling projects by PUDIS a.s. within theframework of geotechnical surveys (soon after the Mnard GB-typepressuremeter had been obtained) were the measurements along theroute of the Strahov tunnel, which is part of the City Circle Road inPrague (dilatometer tests were carried out there in parallel).

A large number (several hundreds) of pressuremeter tests wereconducted for the till now the most difficult tunnelling project in theCzech republic, the Mrzovka tunnel, which was also built on theCity Circle Road in Prague (large dimensions of the three-lane tun-nel and a trouser leg section, which was built under a shallow coverconsisting of very weak rock disturbed due to weathering and faul-ting, passing under old, up to five-storey buildings). The tests werecarried out in the phase of both the detailed survey (in vertical holesbored from the surface) and an additional survey (from within anexploration gallery). The conditions under which the undergroundtests were carried out are illustrated in Fig. 3. An example of theresults is presented in Fig. 4 showing the values of the pressureme-ter moduli of elasticity determined in the eastern tunnel tube, ina fan consisting of 5 boreholes drilled at chainage km 14.512, underNa Doubkov Street. In this particular case, the respective boreho-les and pressuremeter tests were carried out within the framework ofan additional geotechnical survey, from within the top heading exca-vated in advance as a part of the right side-wall drift. The rock envi-ronment consisted of sound Libe strata of clayey shale (theOrdovician period). The average pressuremeter modulus of defor-mation EoM values of about 170MPa, 620MPa and 1000MPa weredetermined in the overburden, on the sides and in the sub-grade res-pectively. When these moduli are being incorporated into structuralcalculations, they must be reduced with respect to the need to allowfor the volume and time scale of the tests. This reduction made uproughly 50% in this particular case.

Another significant geotechnical survey of those carried out fortunnels on the City Circle Road in Prague is, above all, the surveyalong the route section between pejchar and Pelc Tyrolka (inclusi-ve of the passage under the Vltava River and Stromovka Park),where several hundreds of pressuremeter tests were carried out(mostly measurements from within an exploration gallery).

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The geotechnical surveys for the tunnels on the Prague City RingRoad comprised pressuremeter tests carried out in boreholes drilledboth from the ground surface and from within the exploration galle-ry for construction lots 514 (the Lochkov tunnel) and 513 (theKomoany tunnel).

PUDIS a.s. carried out pressuremeter tests also in the frameworkof geotechnical surveys outside Prague, for example for the Heberoad tunnel or, above all, the Radejn and Prackovice tunnels on theD8 motorway (again from the ground surface and from within anexploratory gallery.

The pressuremeter measurements carried out by PUDISs. r. o. for railway tunnels (new lines and reconstructions), are alsoimportant. The work for the bifurcation chamber of the VinohradyIII railway tunnel in 1988 represented the pressuremeter part of theprocess of checking on the effectiveness of the stabilisation groutinginto the tunnel overburden under Anglick Street. Regarding thework on the optimisation of railway lines, the tests were conductedfor the Zbeh Kraskov line (the Mal Huba, Hnvkov I andHnvkov II tunnels) and the Kraskov - esk Tebov line (theTebovice and Kraskov tunnels). The pressuremeter tests were car-ried out on a railway corridor, namely for two tunnels nearNelahozeves. Of the new railway lines, series of tests were conduc-ted on the Bezno tunnel (dilatometer measurements were also app-lied to this tunnel construction) and on the Vtkov tunnels in Prague(the New Connection project).

'The Prague metro required PUDIS a.s. to carry out pressuremetertests only for the 4th operating section of Line C (between NdraHoleovice and Ldv stations); two series of the tests were perfor-med there, namely for a running tunnel near Kobylisy station.

The pressuremeter testing is used even for smaller profile tunne-ls, in difficult sections. As examples, we can mention the section ofthe utility tunnel Hlvkv Bridge passing under the Vltava Riverbed (the drilling and measurement operations were carried out froma pontoon - see Fig. 7), the utility tunnel Centrum (the part in theSmchov district) or the mined utility tunnel under Latrn Street inesk Krumlov.

It is obvious from the above overview that pressuremeter testinghas broadly asserted itself as a modern method in the field of geo-technical survey roughly during the course of the recent twentyyears, in the context of the development of tunnel engineering in theCzech Republic. The testing contractor has most frequently beenPUDIS a.s. It is so even in the cases where the contractor for theoverall geotechnical survey for the particular project is another sur-vey organisation and PUDIS a.s. is a sub-contractor providing thepressuremeter tests and assessment of their results (or, for example,also rock mechanics laboratory testing).

PUDIS a.s. used its long experience in the pressuremeter testingalso at geotechnical surveys for tunnelling projects and otherunderground constructions abroad. It worked for our closest neigh-bours in Slovakia when it carried out a survey for the undergroundstorage for nuclear fuel at the nuclear power plant in Mochovce in1994 and for tunnels on the motorway D1 section Hubov Ivachnov in 2005. Even earlier, in 1985 1987, it operated in theAlgerian Republic Arabic. The main objective of the surveys weredams (about 10 dams mostly on rivers in the foothills of the Atlas)but they also comprised underground structures (e.g. diversion tun-nels). Regarding motorway tunnels, pressuremeter (and dilatometer)measurements were performed in the Semmering region, Austria, in1991 1992 (the testing boreholes reaching a depth up to 100m).

PRESSUREMETER TESTING FOR MONITORING PURPOSES CHECKING ON STRENGTHENING BY GROUTING

Apart from geotechnical surveys, pressuremeter tests are appli-cable to various checks during the construction phase. As an exam-ple, we can mention the verification of the strengthening of the rockmass in the overburden of the Mrzovka vehicular tunnel in Prague,the Czech Republic. The construction of this three-lane tunnel (seethe chart in Fig. 5) with the excavated cross section width of 16.6m,height of 12.5m and cross sectional area of 165m2 (up to 335m2 inthe trouser leg section) was very difficult. A part of the tunnel routeleads very near to the surface; for example, the thickness of thecover in the area adjacent to Ostrovskho Street decreases to about16m. Only 5m of this thickness is made up of slightly weathered andfresh rock (the Ordovician Libe strata weak clayey shale with

Mnard typ GA, uren pro skaln horniny (rozsah radilnho tlako-vho napt 8 MPa) s namontovanou sondou BX (prmr 58 mm).

Na podklad vsledk dvou injeknch pokus (provedenchv obdobnm prosted v rmci doplujcho inenrsko-geologick-ho przkumu a zahrnujc presiometrick zkouky ped a po injek-ti) byla stanovena nsledujc kritria pro horninov prostedzpevnn injekt vztaen k presiometrickm modulm petvr-nosti Eop :

prmrn hodnota > 200 MPa rozsah hodnot mench ne 100 MPa < 22 % rozsah hodnot mench ne 70 MPa < 15 % rozsah hodnot mench ne 50 MPa < 8 % rozsah hodnot mench ne 30 MPa < 5 % Pklad prbhu presiometrickch modul petvrnosti Eop ve

vybranm kontrolnm profilu 008 (sted vrtu v km 4,851 tj. poddomem Ostrovskho . 19/1193) zachycuje obr. 5. Ped injektbyla prmrn hodnota Eop = 131 MPa a po n Eop = 212 MPa.

Posouzen efektu zpevujc injekte v celm seku pilehlmk ulici Ostrovskho umouje statistick zpracovn vsledk pre-siometrickch modul petvrnosti Eop z kontrolnch profil 005a 009 (umstn podl trasy viz obr. 6). Pedevm se zde zv-ila prmrn hodnota (z men u 5 vj) presiometrickhomodulu petvrnosti ze 101 MPa ped injekt na 216 MPa po n.

Obr. 5 Tunel Mrzovka prbh presiometrickch modul petvrnosti poinjekti v kontrolnm profilu 008 (sted vrt v km 4,851) s vyznanm syst-mem injeknch vrt1 zklady dom, 2 deluviln sedimenty, libesk bidlice: 3 rozloen,4 zvtral, 5 navtral, 6 zdrav, 7 evnick kemence, 8 zpadntunelov trouba Mrzovka, 9 przkumn tola, 10 zna injekte, 11 kontroln presometrick vrty Fig. 5 Mrzovka tunnel - the curve for pressuremeter moduli of deformationat the check profile 008 (the boreholes centre being at km 4.851) after thegrouting, with the system of grouting holes 1 - foundations, 2 - diluvial sediments, LIBE SHALES: 3 - decomposed, 4 - weathered, 5 - slightly weathered, 6 - fresh, 7 - evnice Quartzites, 8 - Mrzovka tunnel - western tube, 9 - exploratory gallery, 10 - groutingzone, 11 - checking pressuremeter boreholes

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a low strength R 4 in this particular case the average strength offragments is 12 MPa and the rock mass is disturbed by faulting). Inthis area, the tunnel passes under 100-year old buildings (up to fivestoreys) having their foundations only 12.5m above its top. It wasnecessary for the reasons of the NATM excavation safety to applya set of measures enhancing the positive effect of the decision to usea vertical excavation sequence (side drifts and a central pillar).Stabilisation grouting was one of the measures. Its objective was tofill discontinuities with grout, thus achieving:

- reduction in the probability of operating accidents (such asoverbreaks or a loss of stability of the face) caused by an occurren-ce of exceptionally poor quality rock ;

- reduction in the extremes in the settlement trough curve; - reduction in the settlement of the tunnel overburden affecting

the existing buildings;- prevention of abrupt ground water inflows to the tunnel.The grouting was carried out from within an exploration gallery,

which had been driven in advance. Cementitious grout stabilisedwith bentonite was injected. The cross-sectional arrangement of thegrouting holes (up to 21 in one fan) is presented in Fig. 5. The fanswere installed at 3.5m spacing; the thickness of the envelope impro-ved by the grouting varied from 3.0 to 5.0m. The grouting pressureswere designed not to exceed 6 MPa (split grouting pressures up to17 MPa).

Pressuremeter tests checking the effectiveness of grouting werepart of the geotechnical monitoring over the tunnel construction.Their task was to provide data for the assessment of the efficiencyof the stabilisation (improving) grouting, expressed in terms of theincrease in the stiffness and strength of the rock mass.

The pressuremeter check tests were carried out in core holes60mm in diameter, which were arranged in fans located in the midd-le between the grouting fans (see Fig. 5). Boreholes which weredrilled in an upwards direction on the centre line of the exploratorygallery were used for the comparison measurements recording thecondition before the grouting. The assessment was based on the sta-tistical processing of the results from both phases. The tests wereconducted using the GA type of pressuremeter manufactured by theFrench company Mnard (the type designed for application in hardrock the range of the radial compression stress of 8MPa) providedwith a BX probe (58mm in diameter).

The results of two grouting tests (which were carried out in simi-lar conditions, within the framework of a supplementary enginee-ring geological survey and comprised pressuremeter tests prior toand after the grouting) provided the basis for the determination ofthe following criteria for the rock environment stabilised by grou-ting, relative to the pressuremeter moduli of deformation Eop:

- average value > 200 MPa- percentage of values lower than 100 MPa < 22% - percentage of values lower than 70 MPa < 15%- percentage of values lower than 50 MPa < 8% - percentage of values lower than 30 MPa < 5% An example of the curve for pressuremeter moduli of deformati-

on at the selected check profile 008 (the centre of the borehole beingat km 4.851, i.e. under the building No. 19/1193 in OstrovskhoStreet) is presented in Fig. 5. The average values prior to the grou-ting and after the grouting were Eop = 131 MPa and Eop = 212 MParespectively.

The assessment of the effect of the stabilisation grouting throug-hout the length of the section adjacent to Ostrovskho Street allowsthe statistical processing of the moduli of deformation Eop determi-ned at the check profiles 005 through 009 (for the locations alongthe route see Fig. 6). The most significant fact is that the averagevalue (of the values measured on 5 fans) of the pressuremeter modu-lus of deformation grew from 101MPa prior to the grouting to216MPa after the grouting. This increase in the values of the modu-li (or decrease in the compressibility) makes up 114%. In addition,the relative characteristics of the variance decreased, which meansthat the homogeneity of the rock mass improved.

It follows from a comprehensive comparison with the above-mentioned contractual criteria that the prior-to-grouting conditionwas worse at all profiles. The after-grouting condition was satisfac-tory at the profiles 005, 008 and 009. Even though the profiles 006a 007 did not meet satisfy the criteria, the degree of strengtheningwas also relatively high: Eop = 84 a 80 MPa prior to the grouting and

Toto zvten modul (resp. zmenen stlaitelnosti) reprezentuje114 %. Tak se snily relativn charakteristiky rozptylu, tj. zvi-la se homogenita horninovho masivu.

Z komplexnho porovnn s ve uvedenmi smluvnmi kritriivyplv, e ped injekt byl stav hor u vech profil. Po injekt-i bylo vyhovujcho stavu dosaeno v profilech 005, 008 a 009.Profily 006 a 007 sice jet nevyhovovaly, ale stupe zpevnn zdebyl relativn tak vysok ped injekt prmrn Eop = 84 a 80MPa, po injekti 135 a 156 MPa. Tyto profily se nenachzelypmo pod nronou povrchovou zstavbou a bezpenost rabytunelu zde byla zajitna souborem dalch opaten. Dleit dlebylo, e po injekti se podstatn zmenil vskyt nejnich zme-nch hodnot, napklad prmrn etnost modul petvrnosti ni-ch ne 100 MPa klesla z 65 % na 27 % a zastoupen modul men-ch ne 50 MPa se snilo z 11 % na 3 %. Zpevujc injekt setedy podailo vrazn zmenit rozsah hornin s nejvy stlaitelnos-t (resp. deformovatelnost). Obdobn prmrn mez teen pf bylaped injekt 2,02 MPa a po n 2,74 MPa, tj. smykov pevnost pi-blin vzrostla o 39 %.

V nadlo tunelu Mrzovka v seku pilehlm k ulici Ostrovskhodolo po injekti k vraznmu zlepen mechanickch charakteris-tik horninovho masivu. Z ve uvedenho je zejm vysok sp-nost zpevujc cementov injekte, kter podstatn zlepila tuhosta pevnost horninovho masivu a umonila bezpen raen nron-ho podzemnho dla pod zstavbou se 100 let starmi bytovmidomy. Kontrola prostednictvm presiometrickch zkouek kvantifi-kovala efekt injekte a spolen s dalmi menmi geotechnick-ho monitoringu pispla k bezpen a technicky optimln realizacinronho automobilovho tunelu.

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Presiometrick zkouky umouj pi geotechnickch przku-mech pro tunely zskat rychle spolehliv informace o petvrnch

Obr. 6 Prbh prmrnch presiometrickch modul petvrnosti ped a poinjekti v seku zpadn trouby tunelu Mrzovka pilehl k uliciOstrovskho (s vyznaenm systmem injeknch vj)1 navky, 2 deluviln sedimenty, libesk bidlice: 3 rozloen, 4 zvtral, 5 navtral, 6 zdrav, 7 evnick kemence, 8 zpadntunelov trouba Mrzovka, 9 przkumn tola, 10 zna injekte 5 m, 11 kontroln profily s presometrickmi vji, 12 ped injekt, 13 zv-en dosaen injekt, 14 poadovan smluvn kritrium: Prmrn presi-ometrick modul petvrnosti Eop = 200 MPa Fig. 6 The curve for pressuremeter moduli of deformation prior to and aftergrouting within the Mrzovka west tunnel section adjacent to OstrovskhoStreet (with the system of fans of grouting boreholes)1 - man-made ground, 2 - diluvial sediments, Libe Shales: 3 - decomposed,4 - weathered, 5 - slightly weathered, 6 - fresh, 7 - evnice Quartzites, 8 - Mrzovka tunnel - western tube, 9 - exploratory gallery, 10 - groutingzone, 11 - check profiles with pressuremeter fans, 12 - prior to grouting, 13 - increase achieved by grouting, 14 - the criterion required by the contract:average pressuremeter modulus of deformation Eop = 200MPa

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LITERATURA / REFERENCES

1. MNARD, L.: Le pressiomtre Louis Mnard. Notice generale. Techniques L. Mnard, Longjumeau, 1960.2. Mode opratoire MS.IS 2. Essai pressiomtrique normal. Dunod, Paris, 1971.3. Techniques Louis Mnard: B.P. n 2 Rgles utilisation des techniques pressiomtriques et exploitation des rsultats obtenus pour le

calcul des fondations. Longjumeau, 1972. 4. AVODA, O. MATYS, M.: Vyuitie presiometrickch skok pri nvrhu zkladovej kontrukcie. [elov publikace VIS . 110].

Vzkumn stav ininierskych stavieb, Bratislava, 1976.5. ASTM D 4719-87: Standard Test Method for PRESSUREMETER TESTING. 1987.6. SN 72 1004: Presiometrick zkouka. 1990.7. SN 73 1000, SN P ENV 1997-3: Navrhovn geotechnickch konstrukc st 3: Navrhovn na zklad ternnch zkouek. 2000.8. Draft International standard ISO/DIS 22476-4: Geotechnical investigation and testing - Field - testing - Part 4: Mnard pressuremeter test.

International Organization for Standardization, 2005. 9. HUDEK, J. BEZINA, B. aj.: Presiometrick zkouky a jejich zhodnocen (nkolik set zprv). PUDIS, a. s., Praha, 1979 2007.

a pevnostnch vlastnostech horninovho prosted. Ve specilnchppadech se uplatuj i pi monitoringu vstavby. Celkov tak pi-spvaj k optimalizaci technickho een, bezpenosti a ekonomicevstavby nronch staveb v komplikovanm horninovm proste-d. Dal rozvoj presiometrie lze oekvat v souvislosti s aplikacnovch evropskch norem (napklad EUROCODE 7) pro geotech-nick konstrukce.

Firma PUDIS, a. s., provd presiometrick zkouky od roku1979 a v letonm roce jejich celkov poet ji peshl 10 000 (v jednotlivch desetiletch je postupn vzrstajc tendence), co jiv tomto smru ad na prv msto v esk republice. Podstatn sttchto men byla pro geotechnick przkum tunelovch staveb,zejmna pro mstsk okruh v Praze (Strahovsk tunel, Mrzovka,pejchar Pelc-Tyrolka) a silnin okruh kolem Prahy (stavba 514a 513). st jich byla i pro ely monitoringu vstavby tchto tune-l (napklad kontrola injeknho zpevnn). Nkter srie zkouekpro tunely probhly i v zahrani (Slovensko, Alr, Rakousko).Preferujeme ovem men s vhledem na Hradany, jak ilustrujeobr. 7 (przkum pro tunel kolektoru Hlvkm most v seku podeitm Vltavy), a to i kdy mic prce musej bt provdnyz pontonu na ece. Technick pnos presiometrickch zkouekpotvrdila bezpen a ekonomick realizace pslunch staveb.

ING. JI HUDEK, CSc., jiri.hudek@pudis.cz, PUDIS, a. s.

135 to 156MPa after the grouting. These profiles were not founddirectly under the existing buildings; for that reason the safety wassecured by other measures. Another important fact was that theoccurrence of the lowest measured values significantly decreasedafter the grouting; for example, the average frequency of moduli ofdeformation lower than 100MPa decreased from 65% to 27%, andthe percentage of moduli lower than 50% decreased from 11% to3%. The stabilisation grouting was, therefore, very successful inreducing the proportion of rock displaying the highest compressibi-lity (or deformability). Similarly, the average creep limit pf prior tothe grouting and after was 2.02 MPa and 2.74 MPa respectively,which means that the shear strength rose roughly by 39%.

The mechanical properties of the rock mass in the Mrzovka tun-nel overburden, the section adjacent to Ostrovskho Street, signifi-cantly improved after the grouting. It follows from the above datathat the cementitious stabilisation grouting was very successful,substantially improving the stiffness and strength of the rock mass.Owing to the grouting, it was possible to safely carry out the com-plicated excavation under 100-year old residential buildings. Thechecking by means of pressuremeter tests provided the quantificati-on of the effect of the grouting. Together with the other measure-ments which were parts of the geotechnical monitoring, it helped thedemanding excavation of the vehicular tunnel to be safer and tech-nically optimal.

CONCLUSION

Owing to pressuremeter tests, we can quickly obtain reliableinformation on deformational properties of a rock environmentduring geotechnical surveys for tunnels. In special cases, the testscome useful even during the monitoring of the construction process.On the whole, they contribute to the optimisation of the design ofmeans and methods of excavation, safety and economy of imple-mentation of demanding projects in a complicated rock environ-ment. The further development of the pressuremeter testing isexpectable to begin in the context of the application of newEuropean standards (e.g. EUROCODE 7) to geotechnical structures.

PUDIS a. s. has been active in the pressuremeter testing since1979. The number of the tests has exceeded 10,000 this year (thereis a gradually growing trend visible throughout the decades), whichfact ranks the company first in the Czech Republic. A substantialpart of the measurements was performed for tunnelling projects,namely for the City Circle Road in Prague (the Strahov, Mrzovkaand pejchar Pelc Tyrolka tunnels) and the Prague City Ring Road(construction lots 514 and 513 of this outer ring road). Part of thetests was performed for the purpose of the monitoring over the con-struction of the above-mentioned tunnels (e.g. the checking on theeffectiveness of stabilisation grouting). Some series of the tests fortunnels even took place abroad (Slovakia, Algeria, Austria). We,however, prefer the measurements allowing us to view PragueCastle, as shown in Fig. 7 (the survey for the utility tunnel HlvkvBridge in the section passing under the Vltava River), even if themeasurements must be carried out from a pontoon in the river. Thefact that pressuremeter testing is technically beneficial has been pro-ven by the safe and economic implementation of the respective pro-jects.

ING. JI HUDEK, CSc., jiri.hudek@pudis.cz, PUDIS, a. s.

Obr. 7 Presiometrick zkouky pod eitm Vltavy pro kolektor Hlvkvmost (presiometr francouzsk firmy APAGEO) Fig. 7 Pressuremeter tests under the Vltava riverbed for the Hlvkv Bridgeutility tunnel (a pressuremeter of a French company APAGEO)