Soil Stab-Use of-New.ppt DR MSA Edusat.ppt rev 1.ppt

Soil Stab-Use of-New.ppt DR MSA Edusat.ppt rev 1.ppt - Use...

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Unformatted text preview: Use of Locally Available Materials and Stabilisation Technique Dr. M.S. AMARNATH Bangalore University Bangalore Soil Stabilization The soil stabilization means the improvement of stability or bearing power of the soil by the use of controlled compaction, proportioning and/or the addition of suitable admixture or stabilizers. Basic Principles of Soil Stabilization…. • Evaluating the properties of given soil • Deciding the lacking property of soil and choose effective and economical method of soil stabilization • Designing the Stabilized soil mix for intended stability and durability values Need for Soil Stabilization Limited Financial Resources to Provide a complete network Road System to build in conventional method Effective utilization of locally available soils and other suitable stabilizing agents. Encouraging the use of Industrial Wastages in building low cost construction of roads. Methods of Soil Stabilization • • • • • • Mechanical Stabilization Soil Cement Stabilization Soil Lime Stabilization Soil Bitumen Stabilization Lime Fly ash Stabilization Lime Fly ash Bound Macadam. Mechanical Stabilization • This method is suitable for low volume roads i.e. Village roads in low rainfall areas. • This method involves the correctly proportioning of aggregates and soil, adequately compacted to get mechanically stable layer • The Basic Principles of Mechanical Stabilization are Correct Proportioning and Effective Compaction Desirable Properties of SoilAggregate Mix • • • • • • Adequate Strength Incompressibility Less Changes in Volume Stability with Variation in water content Good drainage, less frost Susceptibility Ease of Compaction. Factors Affecting Mechanical Stabilization Mechanical Strength of aggregates Gradation Properties of the Soil Presence of Salts Compaction Mechanical Strength • When the soil is used in small proportion to fill up the voids the crushing strength of aggregates is important Gradation • A well graded aggregate soil mix results in a mix with high dry density and stability values Properties of soil • A mix with Plasticity Index, results poor stability under soaking conditions. Hence it is desirable to limit the plasticity index of the soil Presence of Chemicals • Presence of Salts like Sulphates and mica are undesirable • Presence of Calcium Chloride is Beneficial Compaction • Effective Compaction is desirable to produce high density and stability mix Soil Cement Stabilization • Soil Cement is an intimate mix of soil, cement and water, compacted to form a strong base course • Cement treated or cement modified soil refers to the compacted mix when cement is used in small proportions to impart some strength • Soil Cement can be used as a sub-base or base course for all types of Pavements Factors affecting soil cement stabilization • • • • • • Soil Cement Pulverisation and Mixing Compaction Curing Additives Soil THE PHYSICAL PROPERTIES • Particle Size Distribution • Clay content • Specific Surface • Liquid limit and Plasticity Index Cement A increase in cement content generally causes increase in strength and durability Pulverisation and Mixing • Better the Pulverisation and degree of mixing, higher is the strength • Presence of un pulverised dry lumps reduces the strength Compaction • By increasing the amount of compaction dry density of the mix, strength and durability also increases Curing Adequate Moisture content is to be retained in order to accelerate the strength Additives There are some additives to improve properties • Lime • Sodium hydroxide • Sodium Carbonate • Calcium Chloride Design of Soil –Cement Mix • Soil – Cement specimens are prepared with various cement contents in constant volumes moulds • The compressive strength of these specimens tested after 7 days of curing • A graph is plotted Cement content Vs compressive strength • The Cement Content Corresponding to a strength of 17.5 kg/cm2 is taken as design cement content Soil Lime Stabilization • Soil- Lime has been widely used as a modifier or a binder • Soil-Lime is used as modifier in high plasticity soils • Soil Lime also imparts some binding action even in granular soils Soil-Lime is effectively used in Expansive soils with high plasticity index. Factors affecting Properties of SoilLime Lime Content • Generally increase in lime content causes slight change in liquid limit and considerable increase in Plasticity index • The rate of increase is first rapid and then decreases beyond a certain limit • The point is often termed as lime fixation point This is considered as design lime content Type of Lime After long curing periods all types of limes produce same effects. However quick lime has been found more effective than hydrated lime Calcium Carbonate must be heated at higher temperature to form Quick lime calcium oxide( CaO) Calcium oxide must be slaked ( by the addition of water) to form Hydrated lime Compaction Compaction is done at OMC and maximum dry density. Curing • The strength of soil-lime increases with curing period upto several years. The rate of increase is rapid during initial period • The humidity of the surroundings also affects the strength Additives • Sodium metasilicate, Sodium hydroxide and Sodium Sulphate are also found useful additives Soil- Bituminous Stabilization • The Basic Principles of this stabilization are Water Proofing and Binding • By Water Proofing inherent strength and other properties could be retained • Most Commonly used materials are Cutback and Emulsion • Bitumen Stabilized layer may be used as Sub-base or base course for all the roads Factors affecting properties of soilbitumen Soil • The particle size, shape and gradation of the soil influence the properties of the soil-bitumen mix. Types of Bitumen • Cutbacks of higher grade should be preferred • Emulsions generally gives slightly inferior results than Cutback. Amount of Mixing • Increasing proportion of bitumen causes a decrease in dry density but increases the stability after a certain bitumen content • The optimum bitumen content for maximum stability generally ranges from 4 to 6% Mixing • Improved type of mixing with low mixing period may be preferred Compaction • Effective Compaction results higher stability and resistance to absorb water Additives • Anti stripping and reactive chemical additives have been tried to improve the properties of the mixes • Portland cement can also be used along with the soil bitumen Use of Locally Available Materials in Road Construction Necessity Scarcity of good quality aggregates / soil for road construction Production and accumulation of different waste materials Disposal and environmental problem Economical and gainful utilisation Limitations of Using Waste Materials Quality of waste is not controlled by their manufacturers Characteristics of by-products vary in a wide range Road construction practice is accustomed to traditional materials of steady quality Specifications of layers compaction of traditional materials are not suitable for waste materials General Criteria for Use of Waste Materials Amount of yearly produced waste material should reach a certain lower limit The hauling distance should be acceptable The material should not have a poissonous effect The material should be insoluble in water The utilisation should not have a pollutional effect to the environment Special Requirement for Using Waste Materials Free from organic matter Should not swell or decay as influenced by water Should not be soluble in water Particles should be moderately porous Industrial wastes Thermal Power Stations * * * Fly ash Bottom ash Pond ash Steel Plants * * * Blast furnace slag Granulated blast furnace slag Steel slag Utilisation of fly ash Thermal power - Major role in power Indian scenario - Use of coal with high generation ash content - Negligible utilisation of ash produced Bulk utilisation Civil engineering applications like construction of roads & embankments Utilisation of fly ash Can be used for construction of Embankments and backfills Stabilisation of subgrade and sub-base Rigid and semi-rigid pavements Fly ash properties vary widely, to be characterised before use Major constituents - oxides of silica, aluminum, iron, calcium & magnesium Environmentally safe material for road construction Possesses many favourable properties for embankment & road construction Favourable properties of fly ash Light weight, lesser pressure on sub-soil High shear strength Coarser ashes have high CBR value Pozzolanic nature, additional strength due to selfhardening Amenable to stabilisation Ease of compaction High permeability Non plastic Faster rate of consolidation and low compressibility Can be compacted using vibratory or static roller Engineering properties of fly ash Parameter Range Specific Gravity 1.90 – 2.55 Plasticity Non plastic Maximum dry density (gm/cc) 0.9 – 1.6 Optimum moisture content (%) 38.0 – 18.0 Cohesion (kN/m2) Negligible Angle of internal friction (j) 300 – 400 Coefficient of consolidation Cv (cm2/sec) 1.75 x 10-5 – 2.01 x 10-3 Compression index Cc 0.05 – 0.4 Permeability (cm/sec) 8 x 10-6 – 7 x 10-4 Particle size distribution (% of materials) Clay size fraction Silt size fraction Sand size fraction Gravel size fraction Coefficient of uniformity 1 8 7 – – – 10 85 90 0 – 10 3.1 – 10.7 Differences between Indian & US fly ashes Property compared Indian fly ash US fly ash Loss on ignition (Unburnt carbon) Less than 2 per cent 5 to 8 per cent SO3 content 0.1 to 0.2 per cent 3 to 4 per cent CaO content 1 to 3 per cent 5 to 8 per cent Increase in concentration of heavy metals 3 to 4 times in comparison to source coal 10 times or more in comparison to source coal Rate of leaching Lower Higher Fly ash for road embankment Ideally suited as backfill material for urban/ industrial areas and areas with weak sub soils Higher shear strength leads to greater stability Design is similar to earth embankments Intermediate soil layers for ease of construction and to provide confinement Side slope erosion needs to be controlled by providing soil cover Can be compacted under inclement weather conditions 15 to 20 per cent savings in construction cost depending on lead distance Fly ash for road embankment Typical cross section of fly ash road embankment Approach embankment for second Nizamuddin bridge at Delhi – – – – – Length of embankment - 1.8 km Height varies from 6 to 9 m Ash utilised - 1,50,000 cubic metre Embankment opened to traffic in 1998 Instrumentation installed in the embankment showed very good performance – Approximate savings due to usage of fly ash is about Rs.1.00 Crore Approach embankment for second Nizamuddin bridge at Delhi Spreading of pond ash Second Nizamuddin bridge approach embankment Compaction of pond ash Stone pitching for slope protection Second Nizamuddin bridge approach embankment Traffic plying on the embankment Utilisation of fly ash Four laning work on NH-6 (Dankuni to Kolaghat) Length of stretch – 54 km Height of embankment – 3 to 4m Fly ash utilisation – 2 Million cubic metres Water logged area (soft ground conditions) Compaction of fly ash over layer of geotextile Reinforced fly ash embankment Fly ash - better backfill material for reinforced embankments Polymeric reinforcing materials – Geogrids, friction ties, geotextiles Construction sequence – similar to reinforced earth structures Okhla flyover approach embankment – First geogrid reinforced fly ash approach embankment constructed in the country – Length of embankment – 59 m – Height varied from 5.9 to 7.8 m – Ash utilised – 2,700 cubic metre – Opened to traffic in 1996 – Performance has been very good Okhla flyover approach embankment Filter mediu m Facing panels Geogrids 7.8 to 5.9 m Reinforced foundation mattress of bottom ash Erection of facing panels Okhla flyover approach embankment Rolling of pond ash Support provided to facing panels during construction Okhla flyover approach embankment Laying of geogrids Hanuman Setu flyover approach embankment – Geogrid reinforced fly ash approach embankment – Length of embankment – 138.4 m – Height varied from 3.42 m to 1.0 m – Opened to traffic in 1997 Sarita Vihar flyover approach embankment – – – – Length of embankment – 90 m Maximum height – 5.25 m Embankment opened to traffic in Feb 2001 Polymeric friction ties used for reinforcement Laying of friction ties Sarita Vihar flyover reinforced approach embankment Arrangement of friction ties before laying pond ash Compaction of pond ash using static and vibratory rollers Sarita Vihar flyover reinforced approach embankment Compaction using plate vibrator near the facing panels Fly ash for road construction Stabilised soil subgrade & subbase/base courses – Mixing with soil reduces plasticity characteristics of subgrade – Addition of small percentage of lime or cement greatly improves strength – Leaching of lime is inhibited and durability improves due to addition of fly ash – Pond ash & bottom ash can also be stabilised – Lime-fly ash mixture is better alternative to moorum for construction of WBM / WMM Fly ash for road construction Construction of semi-rigid/ rigid pavements – Lime-fly ash concrete – Dry lean cement fly ash concrete – Roller compacted concrete – Fly ash admixed concrete pavements – Lime-fly ash bound macadam – Precast block paving – High performance concrete Bituminous concrete 40 mm DBM 100 mm BM 75 mm WBM Gr III/WMM 75 mm WBM Gr II/WMM 150 mm GSB 350 mm Typical cross section of flexible pavement – conventional section Bituminous concrete 40 mm DBM 100 mm BM 75 mm WBM Gr III/WMM 75 mm Fly ash + 6% cement stabilised layer 150 mm Pond ash 350 mm Typical cross section of flexible pavement – using fly ash Fly ash admixed PQC 300 mm DLFC 100 mm Pond ash 300 mm Typical cross section of rigid pavement – using fly ash Demonstration road project at Raichur Total length of the road – 1 km Five sections of 200 m each with different pavement sections Pond ash has been used for replacing moorum in sub-base course Stabilised pond ash used for replacing part of WBM layer One rigid pavement section using DLFC and RCCP technology was laid Performance of all the specifications is good Mixing of lime stabilised pond ash Demonstration road project using fly ash at Raichur Compaction of stabilised pond ash using road roller Construction of roller compacted concrete pavement Demonstration road project using fly ash at Raichur View of the demonstration road stretch after three years Demonstration road project using fly ash near Dadri (U.P) A rural road near Dadri in District Gautam Budh Nagar, Uttar Pradesh was selected Total length of road – 1.4 km Bottom ash used as embankment fill Base course constructed using fly ash stabilised with 8% cement RCCP Wearing course – 10 cm thickness RCCP Mix proportion – 1:2:4 30 per cent of cement and 20 per cent of sand replaced with fly ash in RCCP Shoulders – 8% cement stabilised fly ash Demonstration road project using fly ash near Dadri (U.P) – Typical section RCCP wearing course - 0.1 m Stabilised fly ash base - 0.1 m Stabilised fly ash Shoulder Soil cover Bottom ash Demonstration road project using fly ash near Dadri (U.P) Stabilised base course Mixing & laying of RCCP Compaction of RCCP IRC Guidelines / Specifications Guidelines available on pavement construction IRC 60 ‘Tentative guidelines for use of lime fly ash concrete as pavement base or subbase’ IRC 68 ‘Tentative guidelines on cement fly ash concrete for rigid pavement construction’ IRC 74 ‘Tentative guidelines for lean cement concrete and lean cement fly ash concrete as a pavement base or sub-base’ IRC 88 ‘Recommended practice for lime fly ash stabilised soil as base or sub-base in pavement construction’ Guidelines for use of fly ash in road embankments Published recently by Indian Roads Congress (SP- 58:2001) Includes design aspects also Handling and construction – Loose layer thickness of 400 mm can be adopted if vibratory rollers are used – Moisture content - OMC + 2 per cent – Use of vibratory rollers advocated – Minimum dry density to be achieved 95 per cent of modified Proctor density – Ash layer and side soil cover to be constructed simultaneously Utilisation of steel slags Total production of slag from steel industries is about 8.0 million tonnes Types of slags – Blast furnace slag Granulated blast furnace slag (GBFS) Air cooled slag – Steel slag Granulated blast furnace slag Contains reactive silica Suitable for lime / cement stabilisation Air cooled blast furnace slag Non – reactive Suitable for use CRRI work on utilisation of steel slags Characterisation of slags produced at different steel plants Laboratory studies on Lime-GBFS mixes Semi-field studies on Lime-GBFS concrete Test track studies on usage of slags in road works Properties of air cooled slag Property Durgapu r Bhilai Rourkela Delhi Quartzit e Specificatio n requiremen ts Specific gravity 2.78 – 2.82 2.82 – 3.33 2.97 – 2.99 2.67 - Water absorptio n (%) 1.53 – 1.72 0.58 – 1.38 0.74 – 1.29 0.48 2% Max Los Angeles abrasion value (%) 18.80 25.00 14.28 34.00 40% Max Impact value (%) 15.79 14.80 16.90 24.50 30% Max Soundnes s value (%) 1.66 1.17 0.33 0.17 12% Max 43.90 43.10 43.80 - Percentag 46.40 e voids Steel slags Obtained as a waste product during production of steel Particle size varies from 80 mm to 300 microns Compared to blast furnace slag, steel slag contains lower amount of silica, higher amounts of iron oxide and calcium oxide Due to presence of free lime, steel slag should be weathered before using it in construction Road projects executed under CRRI guidance using slags Plant roads at Visakhapatnam Test tracks in collaboration with AP PWD using slags from Visakhapatnam Steel Plant Test tracks in collaboration with Orissa PWD using slags from Rourkella Plant Test tracks at R&D Centre for Iron & Steel, Ranchi using Slags from Bokaro Plant Construction of test track using slag at Orissa Labour based techniques for construction of stabilised layer Lime stabilisatio n of iron slags (Orissa) View of finished surface of road constructed using slags at Processed municipal wastes Processed municipal wastes utilised for construction of test track on village road near Delhi Stabilised municipal waste used for construction of subbase layer Performance of stretch is good Kimberlite tailings Kimberlite tailings are waste produced from diamond mining Can be used in base or sub-base course by adopting mechanical or cement stabilisation High value of water absorption makes them unsuitable for use in bituminous pavement THANK YOU ...
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