Authors: Swarnaprava Sahoo , SK Jaish Quadri, Bishwajit Kar, Chandan Mallik, Surajit Pattnaik
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Soil stabilization is a mechanical or chemical alteration of one or more soil properties to create an improved soil material possessing the desired engineering properties. \'e aim of this article was to review bio enzyme-based soil stabilization techniques with an emphasis onBio-enzymes production, mechanism of soil stabilization and future challenges, and opportunities of the sector. Soils are stabilized to increase strength and durability or to prevent erosion and dust generation. Cost-effective soil stabilization technology has been a fundamental part of any construction and is very important for economic growth in any country. In some cases, construction has been challenged due to the high cost of soil stabilization processes. Besides, methods of stabilizations using common stabilizing agents are getting costly. Currently, there is a growing interest to identify new and green technology to improve construction techniques and to expand the road network. Ere fore, the search for new materials and improved techniques to process the local materials has received an increased focus. For developing countries, bio enzymes are now creating an opportunity to improve soil stability with tremendous effectiveness in the overall process of soil stabilization. In the world, bioenzymes have been used in different projects for several years and are generally proprietary products, often of patented formulation that needs intensive field tests. Currently, the use and production of bio enzymes is becoming the most promising key for the advancement of a country by saving time, energy, and finance. It also reduces environmental pollution due to carbon emission by the conventional stabilizers. \'us, a better understanding of this emerging technology is of utmost importance to exploit any improvement it can offer to soil stability. With little research and practice, it is possible to produce soil stabilizing bio enzymes using local raw materials. Due to this, production of low cost, easily and widely applicable, and environmentally friendly enzymatic formulations from locally available raw materials should be the interest of research and academic institutes of any country. system is applied to several major cities across the globe to demonstrate its use and usefulness.
Soil stabilization is the permanent physical and chemical alteration of soils to enhance their physical properties. In its broadest senses, it includes compaction, pre consolidation, drainage, and many such processes. However, the term stabilization is generally restricted to the process Which alters the soil material itself for improvement of its properties. It is the collective term for any physical, chemical, or biological method, or combination of such methods employed to improve certain properties of natural soil to make it serve for intended engineering purposes. Improvements include increasing the dry unit weight, bearing capabilities, volume changes, the performance of insitu subsoil, sands, and other waste materials in order to strengthen road surfaces, and other geotechnical applications. It is required when the soil available for construction is not suitable for the intended purpose and mainly aimed at increasing resistance to softening by water through bonding the soil particles together, water proofing the particles, or combination of the two.
Concept of stabilization is 5,000 years old and has been considered as old as construction has existed. Ancient Chinese, Romans, and Ices buildings and road ways which existed till today utilized different techniques of soil stabilization. Stabilized Earth roads were used in ancient Egypt and Mesopotamia and the Greeks and Romans used lime as a stabilizer. 'Us, building material dates back 5,000years when lime and clay were mixed and compacted to form bricks used in the construction of the pyramids and about2,000 years ago when the Romans used lime to improve thequality of their roads .
Modern stabilization techniques are aimed at assuring adequate subgrade stability, especially for weaker soils. Soil stabilization is generally costly and requires huge investments. In some cases, construction has been hindered due to the high cost of soil stabilization techniques and depletion of stabilizing materials. Development of cost-effective materials and processes has been a crucial part of any construction for years. Hence, cost-effective road construction techniques are vital for economic growth in any country.
As a result, there is an urgent need to identify new and cost-effective materials to improve construction techniques and expand road networks.
Recently, the search for new materials and improved techniques for processing the local materials has received an increased interest. In the past decades, a number of organic and inorganic chemical additives and different standard soil stabilizers like hydrated lime, Portland cement, and bitumen have been developed worldwide. However, more attention has recently been given to the use of bio enzymes as soil stabilizers
II. MATERIALS & METHOD OF EXPERMENTS
Locally available silty clay soil which was used for this project. This soil was collected from Mayurbhanj District.
The soil contains 83% particles finer than 75 micron. Fig 1 depicts the particle size distribution of this soil. The basic properties of soil or soil parameters obtained on conducting appropriate tests are as per IS: 2720 have been formulated in various parts. This part covers method of preparation of samples for the various laboratory tests covered in the standard.
The parameters of the soil obtained on conducting appropriate tests are given in the Table 3.1
B. Terrazyme-Bio Stabilizer
C. Properties Of Terrazyme
D. Dossages Of Terra-Zyme
A dosage for expansive clayey soil was 200ml for bulk density of 1.98gm/cc. So, Bulk density of soil= 1.98 gm/cc
For Dosages 1: 200ml for 5.0m3 of soil = 1.98 × 5 ×1000 = 9900kg of soil.
For 3kg of soil = 3×0.022ml = 0.06ml enzyme.
Clean potable water as obtained from laboratory of Civil Engineering Department of GIFT Autonomous College was used for mixing and curing of soil specimen.
Same as water
Solubility in water
Brown colour liquid
III. EXPERIMENT PROGRAMME
A. Preparation Of Soil Smple
Different mix of Soil + Terrazyme solution with geocell & original soil sample obtained to conduct specific gravity test, coarse and fine grained analysis of soil, Liquid and Plastic limit of soil , Modified Proctor test of soil ,UCS test on standard mould of sample size 38mm diameter and 76mm height , Tri-axial test of soil sample of size 75 mm(diameter) & 150mm (height). The curing period for the UCS soil sample are 7, 14, 21 &28 days respectably.
B. Mixing Procedure
Proper quantity mixing of Terrazyme solution with soil should be ensured to get correct test results of the soil specimen strength. For original soil sample initially the oven dried soil is weighed for required quantity and poured into another mixing tray or mould which is completely dry. For mixing with Terrazyme, the above-explained procedure is followed. Terrazyme which is mixed with water and according to OMC add the solution to the soil. Different terrazyme dosages 200 ml of (4m3, 3.5m3, 3m3 2.5m3, 2m3, 1.5m3, & 1.0m3) is mixed and tested.
C. Curing Procedure
After preparing the soil sample, sample was kept air tight container for 7, 14, 21 and 8 days. Maintain the moisture content properly.
D. Specific Gravity Of Soil
Specific gravity of soil particle (G) is the ratio of a unit volume of soil solids to the mass of the same volume of gas-free distilled water at a stated temperature (270C).
IV. PARTICLE SIZE DISTRIBUTION
A. Sieve Analysis Of Coarse Grained Soil
The soil contains 83% particles finer than 75 micron. Rest 184 gram of oven dried soil are taken for Sieve analysis by the help of sieve shaker machine. The different sieve size are 4.75mm, 2.36mm, 1.18mm,0.600mm, 0.450mm, 0.212mm, 0.150mm, .075mm.
IS: 2720 (Part 4): 1985. Scope: To determine grain size of soil fraction passing through 4.75 mm IS sieve and retained on 75 micron IS Sieve.
B. Grain Size Distribution Of Fine Grained Soil By Hydrometer Analysis
Hydrometer method is used to determine the particle size distribution of fine-grained soils passing 75 µ sieves. The hydrometer measures the specific gravity of the soil suspension at the centre of its bulb. The specific gravity depends upon the mass of solids present, which in turn depends upon the particle size. Hydrometer analysis is an indirect method of assessing the size of soil particle bashed on stokes law which relates the velocity with which a spherical particle settles in a still liquid to the diameter of the particle. Hence the size of particle determined in this method is known as equivalent diameter. Hydrometer at any instant measures the relative density of soil suspension.The amount of soil taken 50 gms of oven dried which is passing through 0.075mm.
IS: 2720 (Part 4): 1985. IS: 2720 (Part 4): 1985. Scope: To determine grain size of soils.
V. LIQUID LIMIT TEST
The liquid limit is the moisture content at which a soil ceases to be plastic. After receiving the soil sample it is dried in air or in oven. The soil passing 425 micron sieve is used in this test. It becomes semi-fluid and tends to flow like a liquid under an applied pressure. This limit is used for classification of soils for engineering purpose. The apparatus used for determining the liquid limit is liquid limit device i.e. Casagrande apparatus.
IS: 2720(Part 5)-1985-Methods of test for soils of determination of liquid and plastic limit.
Consistency of fine-grained soils may be defined as the relative ease with which a soil can be remolded. Consistency limits may be categorized into three limits called Atterberg limits. They are 1) Liquid limit 2) Plastic limit.
VI. PLASTIC LIMIT TEST
The plastic limit is the lowest moisture content at which a soil can be deformed without cracking. It is the upper limit of moisture content for tillage operation for most crops, except rice. Tillage operations in soil at moisture content above the plastic limit result in smearing and puddling of the soil.
IS: 2720(Part 5)-1985 - Methods of test for soils of determination of liquid and plastic limit.
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