SWrucWural Analysis of HisWorical ConsWrucWions – Jerzy Jasieńko (ed)
© 2012 DPNH ProcławH PolandH ISSN 0860-2395H ISBN 978-83-7125-216-7
oEMAoKS ON TeE rSEFriNESS OF DEEP
FOrNDATIONS FOo TeE SToENdTeENINd
OF FOrNDATIONS IN eISTOoIC AoEAS
eenrók machlaNI cilip machlaO
ABSToACT
qhe state of construction knowledge in the past; the lack of effective tools for measuring the
mechanical parameters of the ground; and later building extensions and additions over the óears have
created a situation where there is insufficient loadJbearing capacitó in foundations laid down centuries
agoK qhe traditional methods of reinforcing foundations – often ineffective and dangerous – have been
sóstematicalló supplanted in recent óears bó new technologies based on the use of deep foundations in
order to increase the loadJbearing capacitó of building foundationsK qhe development of cities is
inherentló accompanied bó rising ground levelsK qhe former ground floors of buildings often end up
below ground levelK lld street surfacesI as well as their infrastructureI are frequentló found at the same
level or lower than the foundations of later structuresK qhereforeI it is essential to select foundationJ
strengthening technologies in order not to destroó precious historic structures which maó be hidden
deep in the ground waiting to be discoveredK qhe article includes analósis of various deepJfoundation
technologiesI taking as the main criterion their usefulness in preserving potential relics of the past
buried in the groundI as well as their conformitó with the principles of construction theoróK qhis
analósis is supplemented bó original research carried out on injection pilesK
heówordsW
NK
aeep foundationI ptrengthening of foundationsI ConstructionI fnjection piles
INToODrCTION
qhe state of construction knowledge in the past; the lack of effective tools for measuring the
mechanical parameters of the land; and subsequent expansion and additions through the ages have
created a situation where there is insufficient loadJbearing capacitó in foundations laid down centuries
aF
bF
FigK N rnearthed cellar in the oemuh pónagogue Eauthor’s photoF
agoK qraditional underpinning methodsI often ineffective and dangerousI have in recent óears been
sóstematicalló replaced bó new technologiesI based on the use of deep foundation to increase the loadJ
N
O
mhdI holw – eenrók machlaI biuro]krozKpl
mhdI holw – cilip machlaI fKpachla]krozKpl
URV
bearing capacitó of the structure’s foundationK Among theseI the greatest use has been made of
technologies based on the formation of deep foundation using cement groutingK
qhe development of cities has alwaós been accompanied bó rising ground levelsK qhe old ground
floors of houses are frequentló below ground levelK lld street surfaces and infrastructure are now often
in at the level of or below the foundations of later buildingsK qhe original entrances to townhousesI
with preserved decorative stone portalsI are hidden beneath the surfaceK cigsK N and O show some
examples of historic structures found below ground level during excavation workK
aF
bF
FigK O mlac pzczepański aF wooden path and wells bF NPthJcentK wells and septic tanks
Emhoto bó bK ChromaJaubisF
fn the historic urban buildingsI manó valuable premises built in ancient times as underground
structures remain in the groundK An example is shown in the photographs EcigK PF – a partialló filled
block sewerK
aF
bF
FigK P Block sewer Eauthor’s photoF
qhe photo below EcigK 4F shows the floor of a foundation with emptó space below itI and the remains
of an unsuccessful previous underpinningI located at the same level a few meters EOJPmF next to itK
qhe introduction of pressure grouting under the foundation would cause cementation of the channel
and a significant surrounding areaK
fn moland’s current "Act on the mrotection of Cultural Assets" xNzI in article PI point O of the first
chapterI it states that "the protection of cultural assets depends on protecting them from destructionI
damageI devastationI”K ConsequentlóI in accordance with the prime rule for reconstructionW "Do not
destroy"I historic buildings cannot be saved at the expense of others which at that time have not óet
been identifiedK
qhe choice of technologó to strengthen the foundations thus becomes important in order not to destroó
valuable historic structures embedded in the ground and waiting to be discoveredK As a result of rapid
development in the methods used to create deep foundations on the market there are manó technologies
availableK qhe differences between them and their impact on the environment are often difficult to grasp
for the conservation services responsible for the protection of historic assetsK qhis article analóses
different deep foundation technologies for strengthening the foundations of historic buildingsK
USM
FigK 4 soid under the foundation with the remnants of an incorrectló underpinning Eauthor’s photoF
OK
COMPAoISON OF SEiECTED TECeNOiOdIES
qhe studó has adopted three criteria bó which the suitabilitó of each technologó can be classified
according to the "do not destroy" principleK
qhe first criterion adopted is the amount and direction of pressure applied to the cement grouting into
the groundK ConsequentlóI there is the possibilitó of cementation of underground structuresK
aepending on the amount and direction of grout supplied under pressureI different areas under the
surface of the site can be irreversibló damagedK get grouting maó be distinguished bó the grout feed
direction perpendicular to the direction of drilling Esee cigK RFK
FigK R qhree tópes of jet grouting xOz
qhis method is highló invasiveK After the drill rod enters the groundI ground petrification occurs with
the cement paste Esingle fluid sóstemFI and gradual extraction of the rod bó rotating itK fn this waóI
a column of soil mixed with cement slurró is createdK aepending on the jet injection sóstemI the grout
can be injected under pressure up to as much as UMM barK qhe columns formed in this waóI depending
on the tópe of soilI can reach a diameter of RmK Buildings from the past that are now underground are
in most discovered in laóers of nonJconstruction banksI with low tensile parameters or voidsK qhis is
the direct consequence of technologies available in the past for creating foundationsK fn such weak
soilsI the petrification range is even greaterK qhis causes the complete destruction of the historic
structure bó the action of both the high pressure and cementationK
jicropile moulding EeKgK qitanF maó also be distinguishedK qhe direction is as in the case of jet
groutingI but the pressure is lowerK fn this methodI a steel rod is drilled into the ground EcigK SFK
qhenI through the injection valvesI the groutI which is pumped under pressureI as a result of which the
outer diameter of the micropile can be increased depending on soil tópe Esee cigK TFI is introduced in
several stagesK then a weak laóer of soil is reachedI there is increased penetration of the soil with
cement slurróK pimilarlóI if a void is reachedI it will be totalló cementedK
USN
rnlike the two previous methodsI traditional micro injection moulding is characterised bó a pressure
of several atmospheres in the same direction as the direction of drillingK qhe grout is introduced into a
previousló made borehole bó injecting tubes Esee cigK UFK
FigK S qfqAk micropile xPz
qhe hódrostatic pressure of the cement slurró column alone acts on the walls of the boreholeK qhere is
no pressure here which would increase the diameter of the micropileK qhe water/cement ratio for this
tópe of micropile is not more than MKRR and in practice it is MKRI and therefore the grout does not
penetrate the soilI and onló seals the edges of the excavationK lnló the occurrence of a void in the soil
might cause an increase the penetration area of the groutK qhis technologó does not use much pressureI
so there is no risk of damage to underground structuresI as is the case with jet groutingK lf these three
technologies for strengthening the subsoilI because of the possibilitó of irreversible damage to historic
structuresI this methodI in accordance with the “do not destroó” principle seems most inappropriateK
aF
bF
FigK T aF Cross section of qfqAk pileI bF micropile diameterI depending on the soil xPz
USO
FigK U qhe micropile moulding process
qhe second criterion adopted was the drilling methodK aepending on the geometró of the screw used
Esee cigK VFI it is possible to drill either with extraction of earth to the surface or without itK Concurrent
verification of the substances extracted to the surface is the onló test for the existence of relics of old
buildingsK fn the case of jet injectionI onló the rod ending with an injecting nozzle is insertedK auring
the moulding of a columnI it is virtualló impossible to verifó the existenceI much less the depthI of
a relicK lnló during the sinking of the rod is the operator ableI seeing increased resistance to drillingI
to indicate the location of the inclusions which might prove valuableK pimilarlóI in the case of jet
grouting earth is not brought to the surfaceK arilling does not use screwsI but onló rods ending in
a crownK qhere isI thereforeI no waó to verifó the existence of monuments under the surface in situI
because the earth is pushed sidewaós and not extractedK
FigK 9 aifferent tópes of drilling rods x4z
diven the technologó traditionalló formed micropilesI where drilling screws are usedI and during the
drilling spoil is extracted to the surfaceI the depth and structure of anó underground obstacles can be
relativeló accurateló determinedK At the same timeI during drilling it is possible to confirm major or
minor resistance at the drill bitI which is a preliminaró verificationK qhis method also seems to be the
most appropriate in the case when the material is able to be verified in situI giving the contractor the
best opportunitó for verificationK
qhe third criterion adopted was the potential effectiveness EpredictabilitóF of deep foundation createdI
and therefore compliance with the principles of the theoró of construction or empirical knowledgeK po
as not to unduló affect the underground structure using inefficient technologó which does not meet the
conditions imposed on it and causes damageK get grouting technologó is based on experience; there are
no methods of calculating the loadJbearing capacitó of such a foundationK qhe tensile parameters of
soil cement are initialló adopted based on nomograms and experience from previous workK qhis
parameter is strongló dependent on the selected injection processI as well as the tópe of land and its
homogeneitóK fn the case of historic areasI where the process of site raising was associated with the
formation of a nonJconstruction embankment laóerI which is characterized bó a strong heterogeneitóI
the process of assessing the soil tensile parameters is highló randomK Collecting of random samplesI
which is required bó the standard for performing jet grouting xRzI maó distort the actual tensile
parameters both at the top and bottomK fn such soilsI the diameter of the column is also unpredictableK
USP
qhis is similar in the case of streamJmoulded micropilesI where the diameter is formed bó the
pressure of the cement slurró being fedK then forming micropiles in nonJnative land EnonJ
construction embankmentsF the micropile diameter cannot be accurateló predictedK qhe planning
process also involves an initial assumption of the diameter based on research and experience with
different tópes of soilK
fn the case of micro formed traditionallóI when planningI procedures specified bó the standards
relevant to the pile are usedK bstimating the loadJbearing capacitó in this case is fairló accurate with
a considerable marginK pince the injection is performed in a hole made bó drill rodsI the pile geometró
is predictable Esee cigK NMFK
qhe standard for performance injection micropiles allows the use of various technologies of micropile
reinforcement xSzK pteel sections can be used Esuch as pipesI beamsFI and reinforcing basketsK fn addition
to the recommendations contained in the standardI a number of additional standards are referred toI
including the standard for composite structures xTzK fn engineering practiceI steel pipes are often used for
micropile reinforcementK qhe research results presented in papers xUJNNz indicate that in manó casesI the
loadJbearing capacitó of a fusion of steel pipe with cement slurró is not sufficientK fn studies conducted
on a series of N4M samplesI it was found that in certain soils the loadJbearing capacitó of the fixing is less
than the relevant soil bearing capacitóK pimilar fixing defects affect the loadJbearing capacitó of piles
reinforced with fJbarsK cigsK NN and NO show the range of applicabilitó of injection micropiles reinforced
with steel pipes and structural shapers in cohesive and nonJcohesive soilsI respectivelóK
FigK NM jicropile excavated during reinforcement works Ephoto bó authorF
FigK NN pcope of applicabilitó of the injection micropiles with steel structural shapers in cohesive soils xNMz
US4
ft should be noted that each technologó has its limitations and scope of its applicabilitóK jicropile
reinforcement with steel structural shapers without corresponding connectors on the surface leads to
a reduction in micropile loadJbearing capacitóI which gets damaged as a result of loss of fixationI and
not exceeding the loadJbearing capacitó of land along the side surfaceK qhis is confirmed bó studies
conducted on micropiles performed in their natural working conditions under axial force xNNzK qhus
the use of composite piles in manó cases is useless and destroós the structure of the substrateK qhis is
confirmed bó uncovering work carried on foundations strengthened bó micropiles reinforced bó steel
pipesK fn manó case the pipe coating is completeló separated from it Esee cigK NPFK
FigK NO pcope of applicabilitó of the injection micropiles with steel structural shapers in nonJcohesive soils xNMz
FigK NP bxamples of excavated micropiles reinforced with steel tubes
PK
CONCirSIONS
qhe paper presents an analósis of different technologies for creating deep foundationsI noting their
negative effects on underground structure of historic buildingsK qhree of the methods most commonló
used bó designers for strengthening the foundations of buildings in historic areas were analósedK qhe
technologies were analósed in terms of the rule governing the restoration of historic buildings – "do
not destroy"K qhe authors’ analósis of different technologies and own experience make it possible to
USR
conclude that the most appropriate method to use in compact historic buildings is the least invasive
technologóK lf the three methods analósedI the least invasive method is the traditional moulding of
micropilesK qhe paper also presents results of research conducted recentló on the usefulness of steel
shapers as reinforcement for injection micropilesK qhe results of this work indicated the scope of
applicabilitó of this reinforcement in different soilsK
qhe conclusions presented in this article maó serve conservation departments when analósing projects
submitted when obtaining a building permitK
ACKNOtiEDdEMENTS
qhe authors wish to thank jsK blżbieta ChromóJaubis for sharing photos of archaeological sites from
the citó of hrakówK
oEFEoENCES
xNz
xOz
xPz
x4z
xRz
Act of NR cebruaró NVSO on the mrotection of Cultural AssetsK
heller advertising prospectusK
qfqAk advertising prospectusK
dwizdała hK cundamentó paloweK Technologia i obliczeniaI mtkI tarszawa OMNMK
mkJbk NOTNS tókonawstwo specjalnóch robot geotechnicznóchK fniekcja strumieniowaK mhkI
tarszawa OMMOK
xSz mkJbk N4NVV tókonawstwo specjalnóch robót geotechnicznóch – jikropaleK mhkI tarszawa
OMMRK
xTz mkJbk NVV4JNJN burokod 4W mrojektowanie zespolonóch konstrukcji stalowo – betonowóch Część
N-NW oegułó ogólne i regułó dla budónkówI mhkI tarszawaI OMMUK
xUz machla eK male iniekcójne zbrojone rurą stalową jako konstrukcja zespolona – uwagi krótóczneI
kowoczesne Budownictwo fnżónierójneI lipiecJ sierpień OMNN rK
xVz machla eK rwagi do projektowania w zakresie wzmocnienia fundamentów palami iniekcójnómiI
deoinżónieria drogi mostó tuneleI M4/OMNNW PUJ44K
xNMz machla eK male iniekcójne zbrojone kształtownikamiI deoinżónieria drogi mostó tuneleI
MO/OMNOW OUJPNK
xNNz machla eK male iniekcójne w warunkach obciążenia osiowego – werófikacja doświadczalnaI
deoinżónieria drogi mostó tuneleI MN/OMNOW OSJPMK
xNOz mkJUP/BJMO4UO cundamentó budowlaneK kośność pali f fundamentów palowóchK mhkI
tarszawa NVU4K
USS