mechanical behaviour of granitic residual soil involving...

IAEG2006 Engineering geology for tomorrow's cities

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IAEG2006

Engineering geology for tomorrow's cities

Abstracts of the 10th IAEG International Congress

Nottingham, United Kingdom 6 - 10 September 2006

Editors: Martin Culshaw, Helen Reeves, Tim Spink, Ian Jefferson

Contents

Author index............................................................................................................................................. 3

Theme 1 - Geology of megacities and urban areas ................................................................................ 29

Theme 2 - Legacy of the past and future climate change....................................................................... 38

Theme 3 - Urban landslides ................................................................................................................... 46

Theme 4 - Planning and geohazards ...................................................................................................... 63

Theme 5 - Urban site investigation ........................................................................................................ 76

Theme 6 - Dereliction, pollution and contaminated land....................................................................... 89

Theme 7 - Environmental urban geotechnics......................................................................................... 95

Theme 8 - Substructures and underground space................................................................................. 102

Theme 9 - Geodata for the urban environment .................................................................................... 112

Theme 10 - Infrastructure for the city and its region ........................................................................... 120

Theme 11 - Resources for the city ....................................................................................................... 127

Theme 12 - The future of engineering geology.................................................................................... 137

Reviewers ............................................................................................................................................. 139

Notes..................................................................................................................................................... 140


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IAEG2006 IAEG2006 has been organised by the UK branch of the IAEG, the Engineering Group of the Geological Society of London and the Conference Office of the Geological Society of London. IAEG2006 has been financially supported by the Geological Society of London. IAEG2006 Organising Committee Executive sub-committee Prof Mike Rosenbaum (Honorary President) Prof Jim Griffiths (Chair) - University of Plymouth Dr Andrew Pitchford (Secretary) - CIRIA Dr Graham Garrard (Treasurer) - Halcrow Group Prof Martin Culshaw (IAEG Representative) - British Geological Survey Dr John Perry (Engineering Group of the Geological Society Representative) - Mott MacDonald Geoscientific programme sub-committee Prof Martin Culshaw (Chair) - British Geological Survey Dr Helen Reeves (Editorial Officer) - British Geological Survey Dr M de Freitas (Field Trip Liaison Officer - Europe) - Imperial College Mr Dave Giles (Field Trip Liaison Officer - UK) - University of Portsmouth Dr Laurance Donnelly (Field Trip Liaison Officer - UK) - Halcrow Group Dr Ian Jefferson (Poster Programme Officer) - Birmingham University Publishing, external relations and accompanying persons sub-committee Ms Helen Edmonds (Chair) - Geotechnical Consulting Group Dr Helen Reeves (Publications Officer) - British Geological Survey Mr Tim Spink (Webmaster and Pre-Congress Publications Officer) - Mott MacDonald Mr Richard Nicholson (Corporate Sponsorship Officer) - CAN Geotechnical Ltd Mr Rodney Chartres (Accompanying Persons Programme Officer) Ms Georgina Worrall (Congress Administrator) - Geological Society Conference Office Finance sub-committee Dr Graham Garrard (Chair) - Halcrow Group Dr Jim Griffiths (IAEG2006 Chair) - University of Plymouth Ms Georgina Worrall (Congress Administrator) - Geological Society Conference Office Prof Martin Culshaw (Geoscientific Programme Chair) - British Geological Survey Ms Helen Edmonds (Publishing, External Relations and Accompanying Persons Chair) - Geotechnical Consulting Group Mr Duncan Murchison (Geological Society Treasurer) - Geological Society External liaison Dr Niek Rengers (IAEG) - ITC Prof Barry Clarke (Ground Forum) - Newcastle University Mr Derek Smith (British Geotechnical Association) - EDGE Consultants UK Ltd Mr Mike Packman (QJEGH Editorial Board) - Southern Water © The Geological Society of London 2006 Abstract book prepared by Bedrock utilising The Conference Tool Kit © Bedrock 2006 www.conferencetoolkit.com


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Theme 7 - Paper 372 Effect of confining pressure on the strength behaviour of granular material simulated by the discrete element

method Md. Abdul Alim - Deptartment of Civil & Environmental Engineering,

Saitama University. Kiichi Suzuki - Department of Civil & Environmental Engineering,

Saitama University. Kazuyoshi Iwashita - Department of Civil & Environmental Engineering,

Saitama University.

Numerical simulation tests using the Discrete Element Method (DEM) were carried out to investigate the stress-strain-dilatancy response of granular materials, giving special emphasis to the confining pressure. Three randomly generated samples were selected using a computer code and were placed in circular discs in a square loading frame. The assembly was isotropically consolidated, and then strain-controlled biaxial compression tests were carried out. These were undertaken to investigate the effect of confining pressure on the mechanical behaviour of granular materials. The stress-strain and volumetric curves show good agreement with the behaviour of granular materials like sands. With an increase in confining pressure, failure stress increases, while dilatancy is reduced. The maximum dilatancy index occurs at the peak stress level.

_____________________________________________

Theme 7 - Paper 378 Mechanical behaviour of granitic residual soil involving

the effect of chemical contaminants L.J Andrade-Pais - Department of Civil Engineering, University of Beira

Interior. L.M. Ferreira-Gomes - Department of Civil Engineering, University of

Beira Interior.

The demographic and technological evolution is confronted by geo-environmental problems. When chemicals or contaminants are introduced into the soil, they affect the soil properties such as the grain size curves, the structure, compressibility and stress-strain behaviour. However, classical soil mechanic models and method to incorporate the effects of contaminants have not yet been developed. This study proposes the analysis of the mechanical behaviour of granitic residual soil when it is blended with lime and wasted lubricating oil and also when it is subject to saturation by using BETX components (petrol). These concepts can improve the use of these types of soils in geotechnical engineering works.

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Theme 7 - Paper 380 Examples of the use of environmental urban geotechnics for brownfield redevelopment

Ivan Vanicek - Czech Technical University in Prague. Jan Valenta - Czech Technical University.

Environmental geotechnics has a very important role in brownfield redevelopment. This is demonstrated through the basic phases of the redevelopment process. Practical examples of the evaluation and characterisation of the locality including the preliminary phase of the investigation, based on the study of historical documents, geoenvironmental maps and site visits, are presented. The results of this evaluation form a very useful tool to use in the decision making process. It can help with the preliminary feasibility study and help define the successive stages of investigation from the municipality perspective, to define urban plans. The second group of examples will examine the situation where the subsoil is physically affected and often comprising made ground containing artificial deposits resulting from of open pit mining. In the made ground the main focus is devoted to the reduction of total and differential settlement and therefore the different methods for subsoil settlement prediction and improvement are presented.

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Theme 7 - Paper 388 An environmental investigation scheme used in

Lithuanian urban areas Kastytis Dundulis - Engineering Geology, Vilnius University,

M.K.Ciurlionio 21, Vilnius, Lithuania. Saulius Gadeikis - Engineering Geology, Vilnius University,

M.K.Ciurlionio 21, Vilnius, Lithuania. Sonata Gadeikyte - Engineering Geology, Vilnius University,

M.K.Ciurlionio 21, Vilnius, Lithuania.

Many questions arise when trying to estimate the interaction between the geological environment and the infrastructure of urban areas. This interaction is very complicated in terms of the various interrelations and complexities. On the other hand, other specialists, whose fields of interest are quite distant, need this kind of information. Consequently, the estimation of the engineering geological conditions of urban areas by traditional components of the geological environment: geological structure, relief, hydrogeological conditions, geotechnical parameters of soil as well as geological phenomena and processes, would be incomplete. It is also necessary to present information about an area's historical development, chemical and physical pollution peculiarities, technological load intensity, groundwater protection and stability of soils. Our experience in the research of urban areas in Lithuania has enabled us to build up a complex geological and infrastructure based environmental investigation scheme. The composite parts of the investigations are presented in the scheme. A database was compiled and several special maps reflecting geotechnical system peculiarities were made from the available datasets. Finally, the division of areas (based not only on the geological information but also on the infrastructure load influence) was used to evaluate the urban areas and to forecast a dynamic area development.

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Theme 7 - Paper 403 Surcharging as a method of road embankment

construction on organic soils Wojciech Sas - Department of Geotechnical Engineering, Warsaw

Agricultural University. Edyta Malinowska - Department of Geotechnical Engineering, Warsaw

Agricultural University.

Road embankments in urban areas are very often located in difficult and problematic soil conditions. The problematic soils consist of soft plasticity clays and organic or calcareous soils. These soils can be characterized as highly deformable with a low initial shear strength and an insufficient bearing capacity. Under the load of the road embankment the problematic soils show a large deformation both vertically and horizontally. The settlements often appear quickly but may also continue for a long time due to creep. The low shear strength often causes stability problems and consequently the load has to be placed in stages, or alternatively, the soil must be improved through a prior treatment. The choice of a construction method has to be based on the soil type, its initial properties and the height of the embankment. In this paper a method of surcharging in the embankment construction on soft soils is presented. Using this method it is possible to eliminate the primary consolidation settlement and to compensate the secondary compression. The application of the precompression technique will be presented on the basis of tests embankments constructed on organic subsoil. The calculations of the settlement will be made using the nonlinear stress-strain characteristics obtained from the laboratory tests. The results of field investigations show that most horizontal movements in subsoil under embankment appear during loading. Therefore, the calculation of settlement course may be done by a one-dimensional consolidation theory using a nonlinear constitute soil model.

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Theme 7 - Paper 458 Influence of the migrating stiff layer on building object foundation in the Loess Massif in Podkarpacie Region,

Poland J. Jaremski - Faculty of Civil and Environmental Engineering, Technical

University of Rzeszow, 35-959 Rzeszow ul. W. Pola 2, Poland.

The presented and considered tests prove formation of a stiff layer in the loess massif, also in terraces of the Wislok River, formed of silty soils. From the tests it appears that formation of that layer is the main reason of generation of the foundation settlement, i.e. additional deformations. It is

IAEG2006 Paper number 378

© The Geological Society of London 2006 1

Mechanical behaviour of granitic residual soil involving the effect ofchemical contaminants

ANDRADE PAIS, L.J1. & FERREIRA GOMES, L.M.2

1 Department of Civil Engineering, University of Beira Interior. ([email protected])2 Department of Civil Engineering, University of Beira Interior. ([email protected])

Abstract: The demographic and technological evolution is confronted by geo-environmental problems. Whenchemicals or contaminants are introduced into the soil, they affect the soil properties such as the grain sizecurves, the structure, compressibility and stress-strain behaviour. However, classical soil mechanic models andmethod to incorporate the effects of contaminants have not yet been developed. This study proposes theanalysis of the mechanical behaviour of granitic residual soil when it is blended with lime and wastedlubricating oil and also when it is subject to saturation by using BETX components (petrol). These concepts canimprove the use of these types of soils in geotechnical engineering works.

Résume: L´évolution démographique et technologique est confrontée par des problèmes géo-ambiental. Quandle sol est contaminé par des agents chimiques, la distribution granulométrique, la structure, la compressibilité etson conduite concernant la tension - extension sont affectées. Cependant, les modèles classiques de lamécanique des sols ne comportent pas encore convenablement ces situations. On propose dans cette étudel’analyse de la conduite du sol résiduel granitique quand on mélange du chaux et du huile de graissage usé etaussi quand le sol est exposé aux conditions de saturation avec composants BETX (essence). Ces conceptspeuvent développer l’usage et connaissance de ce genre de sol quand il est contamine au niveau de la géniegeo-technique.

Keywords: soil mechanics, soil-structure interaction, contaminated land

INTRODUCTIONUrban and industrial development, the use of soils in various engineering works and the increase of contamination

leads to the availability of soils decreasing. The re-use of contaminated soils for building and construction calls forknowledge of their mechanical behaviour and their physical, chemical and mechanical improvement. There is a trendto improve the use of contaminated soil or else to re-use it in embankments or as dressings for embankments or infoundations or sub-foundations for roads.

Aiming at a better knowledge of the affinity between the chemical agent and the granitic residual soil, severalproportions of lime and lubricating oil were blended. This process leads to a stiffness increase by developing potentiallinks between particles. After knowing the inherent behaviour of the granitic residual soil, the artificial soils obtainedwere compared as to its mechanical behaviour. The concentration of components was chosen so that an exothermicreaction occurs to correct pH and neutralize heavy metals contained in the lubricating oil (Meegoda et al. 1996).

Degradation has its potential origin also in the underground storage tanks of petrol (gasoline), which are verycommon in developed countries as well as in developing countries. These storage tanks are located at petrol stations,fuels storage areas, industrial or service areas. Some of them being very degraded due to their old age. The loss offuels takes place at the very refuelling terminals, where possibly infiltration occurs near to the foundations of the localstructures, blended with rain-water and clean up water. In Portugal, more than 1250 contaminated places may existamong the existing 5000 storage tanks (Celeste Jorge 2000). These kinds of substances, which permeate into the soilor into discontinuities filled with weathered rock may affect the environment and also the mechanical behaviour ofthese various materials.

To know the mechanical behaviour of the granitic residual soil when subject to petrol (gasoline) and dryingsaturation circumstances, this soil was remoulded at maximum dry density and optimum water content. Aftermeasuring its intrinsic behaviour, the soil samples were saturated with petrol for 6 months. Afterwards, tests ofcompressibility and resistance were made.

NATURAL AND CONTAMINATED SOIL CLASSIFICATIONThe soil, which in the present research serves as matrix to the mixture of wasted lubricating oil and lime and petrol

saturation, is a granitic saprolitic soil, which basically results from the alteration of feldspar through kaolinization. Thegranite belongs to a calc-alkaline group and from the mineralogical point of view it contains two types of mica wherebiotite is predominant. The rock texture is porphyritic with mega crystals of potassium-sodic feldspar (Andrade Pais2002).

Four groups of samples were obtained: i) Granitic natural residual soil – NS; ii) Granitic natural residual soil withvarious proportions of mixture, artificial soil – M5 to M20; iii) Granitic natural residual soil with 5% of waste


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lubricating oil – OS5 (the 5% content of oil was chosen to be added to the soil because its lubricating effect goes tohigh values); and iv) Granitic residual soil with petrol – NSG. Grain size characteristics are presented at Table 1 andFigure 1.

Table 1. Grain size characteristics of tested soilsEffective Liquid Plasticity Clay

Sample size-D10 limit-wL index - IP activity - At Classification

(mm) (%) (%)

NS 0,006-0,13 40,4-42,5 1,7-5,6 very low SW-SM with G

M5 0,20 43,0 4,6 - SW-SP with G

M10 0,19 44,0 11,6 - SW-SP with GM15 0,20 44,0 10,8 - SW-SP with G

M20 0,20 46,5 12,7 - SW-SP with GOS5 0,10 30,50 11,50 - SW with G

NSG 0,007 46 10 - SW-SM with G

0

10

20

30

40

50

60

70

80

90

100

0,001 0,010 0,100 1,000 10,000 100,000 1000,000Size (mm)

Perc

enta

ge fi

ner t

hen

a gi

ven

size

NSGNSM 5M 10M 15M 20OS5

Figure 1. Grain size curves of tested soils

The classified granite residual soil belongs to group SW-SM with gravel. Clay activity is normal to low, revealingthe presence of kaolinite, a low expansion clay. Liquid limit and low plasticity index, reflect the presence of micaminerals, retaining water in internal cleavage. The classified granitic soil mixture belongs to group SW-SP with graveland the soil with gasoline is SW-SM with gravel, (ASTM D2487 1985).

The comparative granulometric curves of natural soil and M5-20 soils show that the addition of the mixturechanges the particles original dimension a great deal. The thin particles of soil agglutinate themselves due to the limeand the oil effect, making flakes of bigger dimensions with lime hydrate nuclei. Results of chemical analysis of thesoil did not indicate the presence of any metals or organic chemicals with concentrations exceeding the minimumallowable concentration levels for hazardous waste classification (Fabrin & Wagner 2002). As far as NSG soil isconcerned, with petrol the granulometric curve is similar to the one for NS soils, with the fines percentage slightlyincreasing.

INTRINSIC BEHAVIOUR OF GRANITIC RESIDUAL SOILThe granitic residual soil was disaggregated with the fingers and remoulded with a water content close to the liquid

limit in a soft state and tested in the oedometer in an axis-symmetric condition with null radial deformation.Therefore, it was possible to define the intrinsic compression line, in a K0 condition, with a compression index of Cc =0,14. The intrinsic compression may be defined through the following equation: [e = 0,7187 - 0,0458*ln σ`v]. Thecritical state line in e-logσ´v space was determined by estimating the final voids ratio after great deformations of thetests made in the direct shear test. The critical state lines in (e - log σ`v) space and in (q-p’) space are illustrated inFigures 1a and 1b, respectively.


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e CSL= -0,0531Ln(σ´v) + 0,682R2 = 0,896

e AL = -0,0458Ln(σ´v) + 0,7187R2 = 0,9905

0,250

0,300

0,350

0,400

0,450

0,500

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1 10 100 1000 10000Vertical stress, σ´v (kPa)

Voi

d ra

tio, e

NS - Crit ical State Line

NS-Anisotropic Line

qucs = 1,5762p´

R2 = 0,9854

φ ´=38,6ºc´=0 kPa

0

200

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600

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0 200 400 600 800 1000Eff. Cambridge, p'´(kPa)

Dev

iato

r st

ress

, q (

kPa)

NSq(ucs)-CIU-NSLinear (q(ucs)-CIU-NS)

a) b)

Figure 2. Line of the anisotropic behaviour and the critical state line of the granitic residual soil from Covilhã: a) in (e - log σ`v)

space; b) in (q – p’) space.

MECHANICAL BEHAVIOUR OF THE CONTAMINATED SOIL

Compressibility behaviourOedometric trials of axis-symmetric compression were made under a K0 condition with null radial strain and

saturated elements, by using samples of 63 mm diameter and 20 mm height for the M5-20 and NS soils and also of100 mm diameter and 40 mm height for the NS and NSG soil.

In the soils artificially “cemented” (M5-20), the initial vertical effective stress will have to consider the yieldingtension of the interparticle “cement” developed, which normally is low. The initial increment of 1.2 kPa and themaximum vertical effective stress of 3067 kPa were used in this work. The following increment was double theprevious one during 24 hours.

The samples of NS, M5 to 20, OS5 and NSG soils were obtained from the compaction curves with maximum drydensity and optimum water content. Their physical features are summarized on Table 2. From the one-dimensionalconsolidation testing an increase of virtual preconsolidation stress (σ´p*) for the soils influenced by the contaminativeagents used, is noticeable. As for the M5 to 20 soils, the increase of virtual preconsolidation stress has no relation withthe proportion of the mixture used, Figure 2, and Table 2.

Table 2. Characteristics of samples and one-dimensional consolidation test results of soilInicial void Dry unit Virtual

Sample ratio -e0 weight - γd preconsolidacion(kN/m3) stress -σ p* (kPa)

NS 0,471 17,9 110-140

OS5 0,434 18,2 120

M 5 0,567 16,3 190M 10 0,468 17,2 200

M 15 0,521 16,2 210

M 20 0,530 15,9 200

NSG 0,425 18,4 170


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Figure 3. One-dimensional consolidation test results of natural (NS), artificial soil (M5-20) and soil with petrol (NSG)

The artificial soils show higher values of compression index (Cc) and for stresses below σ´p* than the NS soil,which means an improvement in stiffness. The OS5 soil shows an increase of compressibility and a decrease of σ´p*due to the pure oil lubricating action.

In Figure 3, we can even see the space void ratio-effective vertical stress log (e-log σ’ v) to have a tendency tobecome linear for high stresses (higher than the 3.1 MPa achieved), supported by the Cc variation to σ’v. In sampleswith lower initial void index, the Cc value is only converging for high stresses due to the breaking of particles and alsodue to the great number of interpeculiar contacts (Coop, Atkinson & Taylor 1995). It is therefore convenient to definetwo different spaces on the index field of effective stress-voids: the space defined by the line which determines apossible loose state of casing for a remoulded soil and the space beyond that line where the soil can only exist due toits original or raised structure. Behaviour of the soil artificially structured is placed on the right side of the intrinsicbehaviour curve, which emphasizes the meta-stable behaviour. For remoulded natural soils and the same verticaleffective stress, the structured material can coexist with void indices as high as possible beyond the border of thestable space (Vaughan & Kwan 1984).

Shear strain behaviourSome trials using the direct shear box were made, which were drained and consolidated according to the following

increments to each sample with the vertical effective stresses of: σ`v = 26; 44; 82 and 157 kPa. The shear box used hascircular sections with 100 mm diameter and a sample height of 40 mm. The samples tested at resistance were obtainedfrom the maximum dry unit weight and optimum water content of M10-M20 soils with no restoration time.

On the M10 to 20 soils, initially there is an increase of strength due to the ionic exchange and consequentflocculation of particles, where even the clays may take on the typical behaviour of a granular soil. The value ofeffective cohesion (c´) decreases and the peak friction angle (φ´p) increases in accordance with the increase of mixtureproportion on the soil (Figure 4).

-5,0

-4,0

-3,0

-2,0

-1,0

0,0

1,0

2,0

3,0

0 5 10 15

δ h (%)

v (%

)

NSM 10M 15M 20

a) b)

Figure 4. Results of direct shear tests of soil NS and soil contaminated with oil and lime: a) behaviour of normalized shear strengthcurves (τ/σ´

v) versus horizontal displacement (δ

h); b) vertical displacement curves (δ

v) versus horizontal displacement (δ

h).

0,0

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/v

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σ´v<26 kPa

σ´v>82 kPa

σ´v=44 kPa

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Vertical stress, σ´v (kPa)

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izat

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oid

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, e/e

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OS 5

NSM 5-20

NSG


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The mixture of lime and lubricating oil used leads to a stiffness increase due to the potential connectionsdevelopment between particles. The addition of lime into the soil produces ionic exchange mechanisms where the Ca++

cation replaces the lower valency cations, giving rise to flocculation of fine particles, thus gaining some resistance andconsequently improving the properties of the resulting soil (Cristelo & Jalali 2004).

The possible effective cohesion (c´) coming from the interpeculiar connections becomes hidden due to the dilatingphenomenon, which basically controls behaviour, presupposing the rate between dilatancy angle (ψ) increase and c’decrease, Table 3.

Table 3. Physical and mechanical parameters obtained through direct shear test

A conventional triaxial test was used for the study of stress-strain behaviour of NS and GNS soils for samples of100 mm diameter and 200 mm height obtained from the maximum dry unit weight and optimum water content of allsoils. Drainage was allowed at the bottom and the top of the samples. The samples were saturated with water througha backpressure system, isotropically consolidated and cut in pressure according to the conventional courses from theconstant main stress ( 3) and under undrained condition (CIU). Effective stresses of isotropic consolidation were usedfor the set of samples of p’c = 50; 100; 200 and 400 kPa.

The stress-strain-resistance behaviour of the soils is described by a set of parameters, which normally are defined atthe very moment of failure or at other moments related to failure. Normally, different criteria are used depending onthe kind of problem to be solved. The criteria used correspond to the maximum shear stress (qmax) and the shear stresscorresponding to the critical/stable state (qcs). The parameters of strength at failure were obtained through theinvolving linearization and are illustrated on Table 4.

Table 4. Physical and mechanical parameters obtained through CIU trials

With overconsolidated soils, or similar ones, great deformations are demanded to mobilize the maximum value ofdeviator stress, and so the corresponding points may not correspond to a sole involving element. After analysingFigure 5, we can see that the lines properly define surfaces at limit state in both cases. We can see that the failureinvolving the soil NSG and p´c < 200 kPa stays clearly above the corresponding one for the NS sample. Probably thisfact is connected to its state of structure (bonding) developed in the fines of the soil in question due to the action ofpetrol.

Dry unitSample Inicial void weight - γd

ratio -e0 (kN/m3) φ´ c´ (kPa)NS 0,444-0,459 17,57-18,35 41 23

M10 0,503-0513 16,92-17,14 38 26M15 0,660-0,694 15,19-16,39 44 2M20 0,604-0,609 15,16-15,56 47 10

τ max

Failure criterion

Inicial void Dry unitSample ratio -e0 weight - γd

(kN/m3) φ´ c´ (kPa) φ´ c´ (kPa)NS 0,386-0,402 18,5-19,0 39,0 0 38,6 0

NSG 0,376-0,395 18,8-19,1 38,4 17,3 35,7 0

Failure criterionqmax qcs


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Figure 5. Undrained paths in q:p´ space for the NS and NSG soil.

Figure 6. Change rate of Young´s modulus of elasticity extended to NS and NSG soils

The presence of petrol correlates with the maximum dilating tendency shown by the GNS sample during the cut.Regarding the samples subject to a higher confining pressure there is a reduced dilating tendency, even if they show astrong tendency to dilating after failure. The effect of both components, interparticle connections and densest state ofpacking take on important rôles in the mechanical behaviour during the cut, and so discussion on the maximumresistance concerning the point of higher dilatancy rate must take into consideration this reality and, if possible, byseparating the effects.

As for the NSG soils, stiffness for the different samples is greater when p´c <200 kPa but smaller for higherconsolidation pressures by expected failure of the connections established, prevailing the lubricating rôle of petrolbetween the grains from there (Figure 6).

At the last state NSG loses mechanical properties through φ’cs reduction and cohesion vanishing, which may causeproblems for foundations in the long term or for the stability of embankments in these conditions.

CONCLUSIONS1. The granitic residual soil used belongs to group SW-SM with G. The classified granitic soil mixture belongs to

group SW-SP with gravel. The comparative granulometric curves of natural soil and M5-20 soils show that theaddition of the mixture changes the particles original dimension a great deal. The thin particles of soil agglutinatethemselves due to the effect of the presence of lime and oil. The same soil mixed with petrol does not undergo anexpressive evolution regarding its granulometric distribution.

2. From the one dimensional consolidation testing an increase of virtual preconsolidation stress (σ´p*) is noticeable asthe percentage of mixture is increased or when the remoulded granitic residual soil is saturated with petrol. Thecomparative compression index (Cc) exhibits increased difficulty on stabilization for artificial soils. The soilscontaminated for stresses below σ´p* show higher Cc values than the NS and OS5 soils, which means a slightimprovement on stiffness.

3. As far as M5-20 soils are concerned, the dilatancy angle (ψ) group is greater than for the natural soil used, whichmeans that the mechanical behaviour of these soils is led by the dilatancy angle, what explains the peak frictionangle (φp). The possible effective cohesion coming from the interpeculiar connections becomes hidden due to thedilating phenomenon which especially makes the control of behaviour, presupposing the relationship between theψ increase and the c´ decrease, for the stress levels studied.

4. Finally, we have to point out that the use of lime and lubricating oil causes a slight improvement in the mechanicalbehaviour, making them more resistant and less compressible for stress levels below σ´p*, even improving withtime of cure. Regarding the NSG soil, there is an improvement on resistance and stiffness for consolidation


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tensions p´c<200 kPa due to the resulting interparticle connections, developing in the field of fines and reflected inthe cohesion developed. However it must be emphasized that there is a loss of mechanical qualities for largedeformations.

Acknowledgements: The authors are grateful to CECUBI and Mrs Teresa M. da Silva for the translation support.

Corresponding author: L. J. Andrade Pais, Department of Civil Engineering, University of Beira Interior, Ed. II - Engenharias,Calçada Fonte do Lameiro, 6200-358 Covilhã, Portugal. Tel: +351 275329976. Email: [email protected]

REFERENCESANDRADE PAIS, L.J. 2002. Idealized zones on space of tensions of mechanical behaviour for the granitic residual soil from

Covilhã. In: Proceedings of the 9th Congress of the International Association for Engineering Geology and the Environment,“Engineering Geology for developing Countries”, Durban, (CD-ROM).

ASTM D24 87-85 1985. Standard classification of soils for engineering purpose. (Unified Soil Classification System), AmericanSociety for Testing and Materials, International.

COOP, M.R., ATKINSON, J.H. & TAYLOR, R.N. 1995. Strength and stiffness of structured and unstructured soils. In DGF -Bulletin 11, Proceedings of the 11th International Conference on Soil Mechanics and Foundation Engineering (ICSMFE),Copenhagen, 3, 1.55-1.61.

CRISTELO, N.& JALALI, S. 2004. Chemical stabilization of residual granitic soils. Geotecnia, 101, July, PortugueseGeothecnical Society, 25-40 (in Portuguese).

FABRIN, T. & WAGNER 2002. The use of lubrificant oil recycle product in the improvement soil properties. In 8th NationalCongress of Geothecnics, Portuguese Geothecnical Society, Lisbon. 3, 1819-1826 (in Portuguese).

MEEGODA, J.N., BIN CHEN, GUNASEKERA, S.D. & PEDERSON, P. 1996. Compaction characteristics ofcontaminated soils-reuse as a road base material. In: Recycled materials in geotechnical applications, 195-209.

VAUGHAN, P.R. & KWAN, C.W. 1984. Weathering, structure and in situ stress in residual soils. Géotechnique, 34, 1, 43-59.CELESTE JORGE 2000. Os diferentes processos de recuperação para os solos contaminados com gasolina. Portuguese

Geothecnical Society, In: 7th National Congress of Geothecnics, OPorto, Portuguese Geothecnical Society, 1143-1166 (inPortuguese).

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