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Fatigue behavior of lateritic Soil stabilized with enzyme and effectiveness of flexible pavement with stabilized soil as sub base Dr. I.R.Mithanthaya Dr. A.U.Ravishankar Professor Professor & Head Dept. of Civil Engineering Dept. of Civil Engineering NMAMAIT, Nitte . NITK-Surathkal. Dr. N.Bhavani Shankar Rao Professor Dept. of Civil Engineering NMAMAIT, Nitte .
Contents • Introduction • Objectives of the study • Literature survey • Experimental Investigations • Fatigue Analysis • Design of flexible pavement • Economical Analysis • Conclusions • References • Paper Publications
Concept of soil Stabilization • Soil Improvement or Modification-A very old concept • Importance of soil stabilization in highway construction started after II World War • Mainly two major concerns: 1. Shortage of conventional Aggregates 2. Energy Crisis
Why the Soil Stabilization • When unsuitable site conditions exists : • Find a new Construction site • Redesign the structure to suit the poor soil • Replace the poor soil with good soil • Improve the engineering properties of the soil • To improve the soil properties such as - Volume Stability -Strength & Durability - shear Strength - To prevent erosion &Dust generation
STABILIZATION MECHANISMS. • Mechanical stabilization, whereby the stability of the soil is increased by blending the available soil with imported soil or aggregate, so as to obtain a desired particle-size distribution, • Mixing or injecting additives such as lime, Cement, sodium silicate, calcium chloride, bituminous materials and resinous materials with or in the soil can increase stability of the soil. Chemicals stabilization is the general term implying the use of chemicals for bringing about stabilization.
CHEMICAL STABILZATION • Mixing or injecting additives: • Two types Standard stabilizers : lime, Cement, sodium silicate, calcium chloride, bituminous materials and resinous materials. Non standard stabilizers: Sulfonated Oils, Ammonium Chloride, Enzymes, Mineral Pitches and Acrylic Polymers.
Selection of stabilizer • Selecting the stabilizer type depends on number of factors including: • 1. gradation, • 2. plasticity index (PI), • 3. Availability and cost of the stabilizer and appropriate construction equipment • 4. Its long term effect on strength etc.
Concept of Enzyme Soil Stabilization • Demonstrated by the termites and white Ants – Build the shelter by Ant Saliva- which are rock hard and stand firm despite of heavy rainy seasons. • Enzyme –Natural , Non toxic , non flammable, Non Corrosive liquid enzyme formulation fermented from vegetable extracts that improves the engineering properties of the soil.
Clay Particle –Water Relation • Behavior influenced by ability to absorb exchangeable cat ions and the amount of water. • Negative charge on the surface of clay particles attracts positive (Hydrogen) end of water molecule. • Water molecules are arranged in a definite pattern-Adsorbed layer
Removal of absorbed water by enzyme • Absorbed water in the structure of soil • Elimination of absorbed water in he soil
Mechanism of Enzyme Stabilization • Enzyme catalyze the reaction between the clay and the organic cations and accelerate the cat ion exchange process to reduce the adsorbed layer thickness. Enzyme replaces adsorbed water with organic cations, thus neutralizing the negative charge on a clay particle.
Mechanism of Enzyme Stabilization The organic cations also reduce the thickness of the electrical double layer. This allows enzyme treated soils to be compacted more tightly together. Enzyme promotes the development of cementatious compounds using the following, general reaction: H2o + clay Enzyme Calcium Silicate Hydrates
Net Effect of Enzyme • Film of adsorbed water is greatly reduced. • The soil particles acquire a tendency to agglomerate • As a result of relative movement , the soil get condensed which in turn reduces the swelling capacity
Need for present Investigation • Recently developed technique. • Produced by number of private agencies • More attention is given in foreign countries • Rigorous technical investigation is very essential • Unclear how these product will work and under what condition. • To better understand their potential value for road construction
Objectives of the Investigation • To study the change of geotechnical properties of the lateritic soil by stabilizing with enzyme. • Study of quantitative changes in geotechnical properties this soil with different dosage of enzyme. • Study of fatigue behavior of enzyme stabilized lateritic soil.
Objectives of the Investigation (Continued) • To evaluate the influence of various parameters such as dosage of enzyme, curing period, on stress level and frequency of stabilized soil subjected to repeated loading • To establish a relationship between fatigue life, enzyme dosage and curing period of stabilized soil.
Objectives of the Research (Continued) • Analysis of flexible pavements for low and high volume roads with stabilized soil as sub base material. • Economical Analysis: Initial Cost savings in the design of low and high volume roads using stabilized soil. • Field experimental investigation to study the performance of road constructed using stabilized soil. • To develop new design charts for low and high volume roads at par with IRC Codes.
Materials Used • Lateritic soil • And one commercially available enzyme
Variation of CBR with time for soil with very high Plasticity . • Variation of CBR with time for soil with medium Plasticity . • Increase in CBR values is of the range from 130 to 1800 times of the original value • (Isaac et al. 2003). • I
Sharma (Scientist-IRRI New Delhi) has conducted laboratory studies on use of bio-enzyme stabilization of three types of soils • 260% Increase in CBR value.-(After 4 weeks curing) • 100% increase in UCS • Silt with medium plasticity soil showed 300% increase in CBR value
Effect of Bio-Enzyme use on soil stabilization was conducted at Soil Mechanics Laboratory, Thailand (1996) to determine the effects on CBR • Increase in CBR is more than 100% as compared to 28% -Untreated • Investigators also reported reduction in gravel loss, road roughness, dust levels on the Enzyme treated road sections.
Bio-Enzymatic soil stabilization in Road Construction (Everyman’ Science VOL XLI No.6 March 06 Page No.60-69- Dr. C.Venkatasubramnyam School of Civil Engineering SASTRA Tanjavur.) • In this study 5 types of soil (From low to high clay content) are considered. • Based on strength variation study has been done on cost saving by the use of enzyme stabilized sub base. • The overall saving in the total cost of construction is 30-40%
Field study : Prof. Hitam & Yusof-Palm oil research Institute Malaysia (1998) • 27 Kms of road was constructed with enzyme treated soil. • The section of the road was monitored for four monsoons. • No surface damage was observed
Experiments on enzyme treated soil • Enzyme is used for stabilization. (Nature Plus-USA). • Physical/Chemical Characteristics of Enzyme • Boiling Point: 212° F • Specific Gravity (H2O = 1): 1.000 - 1.090 • Vapor Pressure (mmHg): As Water • Melting Point: Liquid • Vapor Density (Air = 1): 1 • Evaporation Rate : As Water • Solubility in Water: Infinite pH: 3.10 - 5.00 • Appearance and Odor: Brown clear liquid
Enzyme Dosage • Enzyme is to be added to water before mixing maintaining the OMC • It is in terms of ml per kg of soil • Four dosages are selected • The enzyme is to be mixed with • 200 ml/3m3 to 200 ml/1m3
FATIGUE ANALYSIS • CBR Test conducted for optimum dosage of enzyme shows the improvement in CBR with curing period. • Since the increase in CBR value compared to untreated value is more than 500% , the pavement acts as semi rigid. • Hence enzyme treated soil is tested for repeated load condition
Fatigue Behavior of materials • Term FATIGUE refers to premature failure under the action of repeated loading. • Push-Pull type (Repeated) of loading system is adopted in Lab. • Depends on : • Nature of loading • Magnitude of max. load • No. of cycles to failure • Surface finish of test specimen • Temperature
Fatigue Analysis • Fatigue behavior of stabilized soil under repeated loading. • Test has been performed using fatigue testing machine. • A cylindrical specimen of length to diameter ratio of 2 is used. • The Fatigue test equipment that is capable of applying the repeated loads at a frequency 0 to 12 Hz is used in the present investigation.
Effect of Enzyme content on Fatigue life of Enzyme treated soil specimens at different stress level Lateritic Soil
Effect of load repetitions on Ultimate UCS strength(Lateritic soil)
Regression analysis • Main Objective: To develop a statistical model that helps in predicting effect of ED,CP and SL on Unconfined compressive strength and fatigue life and to test the model adequacy. SPSS software is used for the analysis. Multiple linear regression analysis is adopted in this study The fitness of model with the actual data is verified by Q-Q plot.