Correlation Between Soaked & Unsoaked Cbr Values Of Different Soil Samples

2019 JETIR June 2019, Volume 6, Issue 6 www.jetir.org (ISSN-2349-5162) CORRELATION BETWEEN SOAKED & UNSOAKED CBR VALUES OF DIFFERENT SOIL SAMPLES Chandravali Pandey1, Dr. Shubha Agarwal2 1 Research Scholar, Master of Construction Technology & Management, LNCT, Bhopal 2 Professor & Head “Department of Civil Engineering” LNCT, Bhopal Abstract:- Pavements are a assortment of materials. These materials, their associated properties, and their interactions determine the properties of the resultant pavement. Thus, a good understanding of these materials, how they are characterized, and how they perform is fundamental to understanding pavement. The materials which are used in the construction of highway are requires not only a meticulous understanding of the soil and aggregate properties but also the binding materials. soil and aggregate properties affect pavement stability and durability and binding materials may be added to improve these pavement features. Soil is considered as a complex material or deposition of earth material, which includes widely different materials like boulders, sands, gravels, clays and silts. These earth material derived naturally by the mechanical and chemical disintegration of rocks or decay of vegetation, that can be excavated by manual or mechanical means depending on the availability. The supporting soil underneath pavement and constructed road is called sub grade. Undisturbed soil underneath the pavement is called natural subgrade. Compacted sub grade is the soil compacted by controlled movement of heavy compactors. The performance of pavements depends to a large extent on the strength and stiffness of the sub grade. CBR test is important method of evaluating the sub grade strength, among the various methods but quick estimation of CBR is most important for highway engineer so this study is focus on comparison of soaked and unsoaked CBR value. This Study is an attempt to understand the influence of soaking on CBR value subjected to different days of soaking and the corresponding variation in moisture content Key words:- Unsoaked & Soaked California bearing ratio, Maximum Dry Density & Optimum Moisture Content, Liquid Limit, Plastic Limit, Plasticity Index. I. INTRODUCTION Damages of roads by floods are common phenomena and a huge Expenditure is required almost after each flood for convalescence of the roads. Therefore, research aiming at finding the modes of damages to roads under flood has become necessary. Several factors may appear to be responsible for such damages, which need to be confirmed by experiments. This study aimed at determining the effects of depth of submergence and duration of submergence on the sub grade strength of soil samples collected from the nearby borrow areas, where plenty amount of material is available for the construction purpose. The material which is collected for testing is different in quality and property, so that the material was separately tested in the laboratory.CBR tests were performed with different heights of submergence after normal soaking period and also after prolonged submergence. Index and identification tests were performed for classification and for determination of the suitability of the studied soils as sub grade material. Design of the various pavement layers is very much dependent on the strength of the subgrade soil over which they are going to be laid. Sub grade strength is mostly expressed in terms of CBR (California Bearing Ratio). Weaker subgrade essentially requires thicker layers whereas stronger subgrade goes well with thinner pavement layers. The pavement and the subgrade mutually must sustain the traffic volume. The Indian Road Congress (IRC) encodes the exact design strategies of the pavement layers based upon the subgrade strength which is primarily dependant on CBR value for a laboratory or field sample soaked for four days. The subgrade is always subjected to change in its moisture content due to rainfall, capillary action, overflow or rise of water table. For an engineer, it's important to understand the change of subgrade strength due to variation of moisture content. This project is an attempt to understand the influence of soaking on CBR value subjected to different days of soaking and the corresponding variation in moisture content. It is observed that the CBR decreases and the moisture content increases for high degree of soaking. II. OBJECTIVE It is common that the subgrade strength for highway pavement design is determined by CBR test measurement. This can be from the laboratory CBR test or directly from field CBR test. The correlation between the result of CBR unsoaked value and CBR soaked value is hardly found. This Thesis objective is to obtain a local correlation between the results of CBR laboratory test without soaked and CBR soaked value. The correlation is based on the comparison CBR unsoaked test results and CBR soaked value which has the same fraction of gravel, sand and clay in soil. III. SCOPE The present scope of work for this thesis is to ascertain the CBR value under different soaking time conditions and to study the influence, in the samples under varying soaking. 1. 2. 3. 4. To collect a particular soil sample and determine its basic physical property such as LL,PL,PI and grain size distribution To study the soil under modified proctor compaction and determine the MDD and OMC for the soil sample To carry out CBR Test for sample soaked in different times To study the influence of soaking on sub grade strength JETIR1906C54 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 326

2019 JETIR June 2019, Volume 6, Issue 6 www.jetir.org (ISSN-2349-5162) IV. DETAILS OF LABORATORY STUDIES California Bearing Ratio The CBR test was originally developed by O.J. Porter for the California Highway Department during the 1920s. It is a load-deformation test performed in the laboratory or the field, whose results are then used with an empirical design chart to determine the thickness of flexible pavement, base, and other layers for a given vehicle loading. Though the test originated in California, the California Department of Transportation and most other highway agencies have Since abandoned the CBR method of pavement design. In the 1940s, the US Army Corps of Engineers (USACE) adopted the CBR method of design for flexible airfield pavements. The thickness of different elements comprising a pavement is determined by CBR values. The CBR test is a small scale penetration test in which a cylindrical plunger of 3 in2 (5 cm in dia) cross-section is penetrated into a soil mass (i.e., sub-grade material) at the rate of 0.05 in. per minute (1.25 mm/minute). Observations are taken between the penetration resistance (called the test load) versus the penetration of plunger. The penetration resistance of the plunger into a standard sample of crushed stone for the corresponding penetration is called standard load. The California bearing ratio, abbreviated as CBR is defined as the ratio of the test load to the standard load, expressed as percentage for a given penetration of the plunger. CBR (Test load/Standard load) 100 The table gives the standard loads adopted for different penetrations for the standard material with a CBR value of 100%. Four Lot of soil samples taken as per classification. Samples are molded at its optimum moisture content to its proctor density was tested for its soaked and unsoaked CBR strength and also carried out IS classification as per IS 2720 and wet sieve analysis also carried out by four soil sample. Thus the process comprises of three parts. 1. On original sample carried out first wet sieve analysis, liquid limit and plastic limit. 2. Estimation of proctor density and optimum moisture content for each soil sample. 3. Molding the soil sample into standard moulds keeping its moisture content and dry density exactly same as its optimum moisture content and proctor density respectively. 4. Determination of CBR strength of the respective soil samples in moulds using the CBR instrument. 5. Each soil sample is tested for its soaked CBR and unsoaked CBR strength after being soaked in water for 4 days. Determination of CBR Value of Soil Subgrade Apparatus: 1. Loading machine-any compression machine can operate at constant rate of 1.25mm per minute can be used. 2. Cylindrical moulds- moulds of 150mm diameter and 175mm height provided with a collar of about 50mm length and detachable perforated base. 3. Compaction rammer, 4. Surcharge weight-annular weights each of 2.5kg and 147mm diameter. 5. IS sieve 19mm, coarse filter paper, balance etc. Fig. No. 1 (CBR Apparatus) The California Bearing Ratio(CBR) test was developed by the California Division of Highways as a method of classifying and evaluating soilsub grade and base course materials for flexible pavements. CBR is a measure of resistance of a material to penetration of standard plunger under controlled density and moisture conditions. CBR test may be conducted in remolded or undisturbed sample. Test consists of causing a cylindrical plunger of 50mm diameter to penetrate a pavement component material at 1.25mm/minute. The loads for 2.5mm and 5mm are recorded. This load is expressed as a percentage of standard load value at a respective deformation level to obtain CBR value. Sieve the sample through 19 mm IS sieve. Take 5kg of the sample of soil specimen. Add water to the soil in the quantity such that optimum moisture content or field moisture content is reached. Then soil and water are mixed thoroughly. Spacer disc is placed over the base plate at the bottom of mould and a coarse filter paper is placed over the spacer disc. The prepared soil water mix is divided into five. The mould is cleaned and oil is applied. Then fill one fifth of the mould with the prepared soil. That layer is compacted by giving 56 evenly distributed blows using a hammer of weight 4.89kg. The top layer of the compacted soil is scratched. Again second layer is filled and process is repeated. After 3rd layer, collar is also attached to the mould and process is continued. After fifth layer collar is removed and excess soil is struck off. Remove base plate and invert the mould. Then it is clamped to base plate. JETIR1906C54 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 327