COHESIVEANDNON-COHESIVESOILSandUNBOUNDGRANULARMATERIALSforBASESandSUB-BASESinROADSProf.Dr.Ir.AndreA.A.MolenaarNootdorp,January2015a.a.a.molenaar@tudelft.nl
COHESIVE AND NON-COHESIVE SOILS and UNBOUND GRANULAR MATERIALS for BASES and SUB-BASES in ROADS Prof. Dr. Ir. André A.A. Molenaar Nootdorp, January 2015 a.a.a.molenaar@tudelft.nl
ForewordSoils such as clay and sand, and unbound granular materials such as gravel and crushedrock,are the backbone of road and railway structures.Without proper attention to thesubgrade, subbase and base, road and railway structures will fail within a short period oftime.Soils and unbound granular materials are complex materials because they have formed fromrocks through weathering and transportation of the weathered material by air,water or ice.Water and vegetation play also a large role in the characteristics of the soils that are actuallyformed.Therefore it will be obvious that any engineer who is working in the road or railwayengineering industry should haveabasic understanding of the behaviourof thesematerials.Thelecturenotes togetherwiththeclasses that will begiven onthis subject will give you thatbasic understanding.The reader will observe that the lecture notes in front of him/her cover a substantial amountof subjects. The reason for this is that the SANRAL Chair in Road Engineering at theUniversity of Stellenbosch and the Chair of Road Engineering at the Delft University ofTechnologyhavedecided todevelopa set of lecturenotes onpavement related topics thatare of interest not only to South-African and Dutch students but also to students of otherparts of the world.Thelecturenotes havebeenpreparedusing lots of information andnot all theinformation isdeveloped by the author himself. Especially on the topic of soil forming and clay mineralogyinformation isdrawn from existing textbooksand sometimes entire sections from thosetextbooksarereproduced.Wherethisisthecase,thisisexplicitlymentioned.Othermainsources on these two topics were the lecture notes taken on these topics by prof.Jenkinswhen hewas still a student at the University of Natal and byprof.Molenaar when hewasstudying at the University of Texas at Austin. Since these hand written notes and thehandoutsaccompanyingthemarenotofficial literature,itisverydifficulttorefertothemTherefore theauthor likes tomention herethat these notes werea sourceof informationandhe likestothank prof.Everitt andprof.Schreinerof theUniversityof Nataland prof.KennedyoftheUniversityofTexasforpreparingthem.Amajorsourceof information wastheresearchdoneonvarioustypesof soil and granularmaterials inSouthAfricaandtheworkdoneattheDelft Universityof Technologyonsometropical soils as well as sands and granular materials. The literature used is mentioned in theliteratureoverview.The author likes to thank especially prof. Jenkins of the University of Stellenbosch in South-Africa for the proof reading,his valuable comments and actual writing of some sections. Alsoir.Houbenof theDelftUniversityisthankedforproofreadingandthecommentsmade.In spiteall the efforts made,some errors might always occur.The reader is therefore invitedto send his comments by email to theauthor so that corrections and improvements can bemade.I wish you much pleasure with reading and studying the material and wish you alreadysuccess when youareplanning to doan exam on this topic.January 2015A.A.A. Molenaara.a.a.molenaar@citg.tudelft.nl
Foreword Soils such as clay and sand, and unbound granular materials such as gravel and crushed rock, are the backbone of road and railway structures. Without proper attention to the subgrade, subbase and base, road and railway structures will fail within a short period of time. Soils and unbound granular materials are complex materials because they have formed from rocks through weathering and transportation of the weathered material by air, water or ice. Water and vegetation play also a large role in the characteristics of the soils that are actually formed. Therefore it will be obvious that any engineer who is working in the road or railway engineering industry should have a basic understanding of the behaviour of these materials. The lecture notes together with the classes that will be given on this subject will give you that basic understanding. The reader will observe that the lecture notes in front of him/her cover a substantial amount of subjects. The reason for this is that the SANRAL Chair in Road Engineering at the University of Stellenbosch and the Chair of Road Engineering at the Delft University of Technology have decided to develop a set of lecture notes on pavement related topics that are of interest not only to South-African and Dutch students but also to students of other parts of the world. The lecture notes have been prepared using lots of information and not all the information is developed by the author himself. Especially on the topic of soil forming and clay mineralogy information is drawn from existing textbooks and sometimes entire sections from those textbooks are reproduced. Where this is the case, this is explicitly mentioned. Other main sources on these two topics were the lecture notes taken on these topics by prof. Jenkins when he was still a student at the University of Natal and by prof. Molenaar when he was studying at the University of Texas at Austin. Since these hand written notes and the handouts accompanying them are not official literature, it is very difficult to refer to them. Therefore the author likes to mention here that these notes were a source of information and he likes to thank prof. Everitt and prof. Schreiner of the University of Natal and prof. Kennedy of the University of Texas for preparing them. A major source of information was the research done on various types of soil and granular materials in South Africa and the work done at the Delft University of Technology on some tropical soils as well as sands and granular materials. The literature used is mentioned in the literature overview. The author likes to thank especially prof. Jenkins of the University of Stellenbosch in SouthAfrica for the proof reading, his valuable comments and actual writing of some sections. Also ir. Houben of the Delft University is thanked for proof reading and the comments made. In spite all the efforts made, some errors might always occur. The reader is therefore invited to send his comments by email to the author so that corrections and improvements can be made. I wish you much pleasure with reading and studying the material and wish you already success when you are planning to do an exam on this topic. January 2015 A.A.A. Molenaar a.a.a.molenaar@citg.tudelft.nl
Contents11.Introduction12. Grains, water and air43. Particle size distribution and interaction with moisture of soils and granular materials134.Soil formingandpedological identificationsystems154.2 Soil formation andpedological identification system185.Mineralogyand soil structure185.1Mineralogy205.2Claymineralogy245.3 The electrical charge on a soil particle and the interaction with water285.4Flocculation and dispersion6.Effectsof compactiononthestructureofasoiland itsengineeringproperties296.1 Shrinkage30306.2 Swelling316.3 Stress - deformation characteristics326.4Influenceofcompactionmethod337.Compactionofcohesivesoils378. Swelling clays378.1 Gradation and plasticity characteristics408.2 Moisture-density relationships, CBRand resilient modulus428.3 Stabilisation with lime, effects on plasticity8.4 Stabilisation with lime and effects on moisture -density,CBR and resilient modulus (M.)438.5Closure46479.Laterites479.1 Formation of laterite489.2 Weathering process499.3Profiledevelopment519.4Theprocessofconcretionarydevelopment529.5Someengineeringcharacteristics629.6Failure, resilientand permanent deformation characteristics679.7 Closure6810.UnboundGranularMaterials7810.2Inventoryof baseand sub-basematerials in theNetherlands8110.3Backgroundontheuseofsand10.4 Principles of the mechanical behaviour of unbound granular (sub)base materials and91sands10.5Factors influencingthemechanicalcharacteristicsof unbound basematerialsand sands9910310.6Parameter estimation procedures11510.7Specifications11. Examples of some problematic unbound granular materials and treatments to upgrade them.11611611.1 Introduction11611.2 Upgrading an Ethiopian natural gravel12111.3ModifyingCinderfromEthiopia13011.4VolcanicmaterialfromYemen13612Compactionof granularsoils13612.1Introduction14212.2Principlesofcompactinggranularmaterials14312.3Compactionequipment12.4 Specifications and field control forsoils15015212.5Rollerapplications
Contents 1. Introduction 1 2. Grains, water and air 1 3. Particle size distribution and interaction with moisture of soils and granular materials 4 4. Soil forming and pedological identification systems 13 4.2 Soil formation and pedological identification system 15 5. Mineralogy and soil structure 18 5.1 Mineralogy 18 5.2 Clay mineralogy 20 5.3 The electrical charge on a soil particle and the interaction with water 24 5.4 Flocculation and dispersion 28 6. Effects of compaction on the structure of a soil and its engineering properties 29 6.1 Shrinkage 30 6.2 Swelling 30 6.3 Stress – deformation characteristics 31 6.4 Influence of compaction method 32 7. Compaction of cohesive soils 33 8. Swelling clays 37 8.1 Gradation and plasticity characteristics 37 8.2 Moisture – density relationships, CBR and resilient modulus 40 8.3 Stabilisation with lime, effects on plasticity 42 8.4 Stabilisation with lime and effects on moisture – density, CBR and resilient modulus (Mr) 43 8.5 Closure 46 9. Laterites 47 9.1 Formation of laterite 47 9.2 Weathering process 48 9.3 Profile development 49 9.4 The process of concretionary development 51 9.5 Some engineering characteristics 52 9.6 Failure, resilient and permanent deformation characteristics 62 9.7 Closure 67 10. Unbound Granular Materials 68 10.2 Inventory of base and sub-base materials in the Netherlands 78 10.3 Background on the use of sand 81 10.4 Principles of the mechanical behaviour of unbound granular (sub)base materials and sands 91 10.5 Factors influencing the mechanical characteristics of unbound base materials and sands 99 10.6 Parameter estimation procedures 103 10.7 Specifications 115 11. Examples of some problematic unbound granular materials and treatments to upgrade them. 116 11.1 Introduction 116 11.2 Upgrading an Ethiopian natural gravel 116 11.3 Modifying Cinder from Ethiopia 121 11.4 Volcanic material from Yemen 130 12 Compaction of granular soils 136 12.1 Introduction 136 12.2 Principles of compacting granular materials 142 12.3 Compaction equipment 143 12.4 Specifications and field control for soils 150 12.5 Roller applications 152
15313Moisture in subgrades and (sub-) base layers15313.1Introduction15413.2 Estimating water content in highway subgrades15513.3Estimationofsoil-waterpotentialcurvesforsubgradesoils(pFcurves)15713.4Estimationofwaterpotentialcurvesforunboundmaterials(pF)curves15813.5Methodtoestimateequilibriummoisturecontent15813.6Practicalconsiderations159References162AppendixA:Laboratorytests,sieveanalysisandplasticity178Appendix B: Laboratory tests, compaction and bearing capacity200AppendixC:TestsusedbySemmelink204Appendix D: Dutch and South African specifications for unbound materials and sands2
2 13 Moisture in subgrades and (sub-) base layers 153 13.1 Introduction 153 13.2 Estimating water content in highway subgrades 154 13.3 Estimation of soil-water potential curves for subgrade soils (pF curves) 155 13.4 Estimation of water potential curves for unbound materials (pF) curves 157 13.5 Method to estimate equilibrium moisture content 158 13.6 Practical considerations 158 References 159 Appendix A: Laboratory tests, sieve analysis and plasticity 162 Appendix B: Laboratory tests, compaction and bearing capacity 178 Appendix C: Tests used by Semmelink 200 Appendix D: Dutch and South African specifications for unbound materials and sands 204
1.IntroductionSoils and granular materials are very important building materials in road and railwayengineering. They are used as subgrade, as subbase and as base for pavements for roads,airfields etc as well as for railway structures.Knowledge on thecharacteristicsand behaviourof soils and granular materials is therefore essential for any road and railway engineer. Thisknowledge deals with the response of the materials when subjected to three dimensionalstatesofstress,theirbehaviourinrelationtowaterandfrost,etcBy nature, soils and granular materials are rather difficult materials to deal with. Particularlynatural soils and gravels show diversebehaviourasa consequenceof geological historythathad an influence on the mineralogical composition, the particle shape and particle sizedistribution. Moreover the actual degree of compaction and moisture content are of greatimportance.Oneshould beremindedthough that in many countries,of which the Netherlands is agoodexample,unboundbasematerialsarenotnatural materialsanymorebutprocessedmaterialsbeing the result of recycling of old concrete and masonry that result from e.g. demolishingbuildings. Also slags from steel factories and blast furnaces are commonly used for roadbasesandsubbases.All thismeansthatthere isawidevarietyof materialsavailableonthemarketnowadaysthatallowgoodqualityroadbasesand subbasestobebuilt.In this set of lecture notes we will deal with those characteristics of soils and granularmaterials that are important for engineering purposes.Much emphasis will therefore beplaced on the mechanical characteristics of those materialsas a function of factors like thegradation, the characteristics of thefines, the degree of compaction etc..2.Grains,waterandairSoils can be regarded as compositions of solid particles, water and air (figure 1)Figure 1 Soil: a composition of solid particles, water and air.The grains form the rigid part of this system, whereas the water and air fill the voids betweenthe grains. The size and shape of the grains, the particle size distribution and the ratiobetween solid material, water and air determine the characteristics of the soil. Severalparameters for this soil system are defined.Figure 2 shows an idealization of the soil systeminwhichthethreecomponentsareseparatedandrepresentedbythreevolumes.1
1 1. Introduction Soils and granular materials are very important building materials in road and railway engineering. They are used as subgrade, as subbase and as base for pavements for roads, airfields etc as well as for railway structures. Knowledge on the characteristics and behaviour of soils and granular materials is therefore essential for any road and railway engineer. This knowledge deals with the response of the materials when subjected to three dimensional states of stress, their behaviour in relation to water and frost, etc. By nature, soils and granular materials are rather difficult materials to deal with. Particularly natural soils and gravels show diverse behaviour as a consequence of geological history that had an influence on the mineralogical composition, the particle shape and particle size distribution. Moreover the actual degree of compaction and moisture content are of great importance. One should be reminded though that in many countries, of which the Netherlands is a good example, unbound base materials are not natural materials anymore but processed materials being the result of recycling of old concrete and masonry that result from e.g. demolishing buildings. Also slags from steel factories and blast furnaces are commonly used for road bases and subbases. All this means that there is a wide variety of materials available on the market nowadays that allow good quality road bases and subbases to be built. In this set of lecture notes we will deal with those characteristics of soils and granular materials that are important for engineering purposes. Much emphasis will therefore be placed on the mechanical characteristics of those materials as a function of factors like the gradation, the characteristics of the fines, the degree of compaction etc. 2. Grains, water and air Soils can be regarded as compositions of solid particles, water and air (figure 1). Figure 1 Soil: a composition of solid particles, water and air. The grains form the rigid part of this system, whereas the water and air fill the voids between the grains. The size and shape of the grains, the particle size distribution and the ratio between solid material, water and air determine the characteristics of the soil. Several parameters for this soil system are defined. Figure 2 shows an idealization of the soil system in which the three components are separated and represented by three volumes