These soils will have large cracks on the surface due to the shrinking of the clay minerals figure 4. Swelling pressure and retaining wall design in expansive soils. The desert area of egypt is an arid area consists of highly problematic soils. For non swelling soils, the object is to find the greatest assured cbr value for some range of densities and moisture contents, whereas the objective of the test program for the expansive soils is to find the moisture content ranges which will preclude. This soil is characterized by its extreme hardness when dry and with high swelling potential during the process of wetting. Mechanical stabilization was applied by means of fiber. Expansion potential of an expansive soil is most commonly expressed in terms of the amount of swelling that occurs during inundation in the consolidationswell test. Shridharan et al 1985 classified the expansive soils using the free swell index as below. Published pdf deposited in coventry universitys repository. The swelling pressure value is very high of the order of 295 kpa. The centrifuge setup is composed of a damon iec cru5000 centrifuge with a model. The map above is based upon swelling clays map of the conterminous united states by w. The differential free swell value of the soil is 140%, indicating that the soil is highly expansive.
Calcium chloride is a hygroscopic material and hence, is preeminently suited for stabilization of expansive soils, because it absorbs water from the atmosphere and prevents shrinkage cracks occurring in expansive soils during summer. It was observed that the swelling potential of the surface expansive soil layer at a depth of 030 mm was released. These areas are underlain by soils with little to no clays with swelling potential. Swelling potential of compacted expansive soils ijert.
Expansive soils occurring above water table undergo volumetric changes with changes in water content katti 1979, nelson and miller 1992. In some cases, these types of clays could present swell pressure values greater than 400 kpa. Expansive soil is typically characterized by its potential for significant volume change with varying water content. Different characterization of expansive soil behavior was observed from site to site. Correlations between the various indices and the potential volume change were obtained and used to determine the potential of each to be included in the establishment of an expansive soil index esi, a summation of the indices. Earth sciences research journal empirical correlations for. Expansive soils when an expansive soil is compacted it will not retain its density as an increase in moisture content will cause it to swell and thus lose density. The interaction between light structures and expansive soils as mainly active clays was studied since the 1950s.
Data insufficient to indicate the clay content or the swelling potential of soils. Swelling potential of some expansive soils from sudan. Swelling soils is one of the major problematic soils at these locations. Swelling potential prediction of expansive soils using. A unified swelling potential index for expansive soils request pdf. Reduction of swelling pressure of expansive soils using eps geofoam 497 as shown in figure 3, for the case of bentonite, swelling is reduced by 37. Samples of different expansive soils were collected from many locations of these desert areas. Soil engineers did not recognize the problem of expansive soils until 1930.
Changes in soil volume present a hazard primarily to structures built on expansive soils. Lime treatment of an expansive soil for swelling potential. Determination of swelling potential is quite important in design of foundations on expansive soils. Less than 50 percent of these areas are underlain by soils with clays of high swelling potential. The primary factors are a change in water content and the. Expansive soils pose a severe threat to civil engineering infrastructure worldwide. Expansive soils as used in this manual also include marls, clayey siltstones, sandstones, and saprolites. Foundations on expansive soils provides the practicing engineer with a summary of the state of theart of expansive soils and practical solutions based on the authors experience. The results also evolved the importance of sand as a stabilizer of expansive soils. The outcome is a set of reliable soil swelling indices for different levels of risk. Expansive soil treatment methods in colorado ahmad ardani colorado department of transportation 4201 east arkansas avenue denver, colorado 80222 final report. In australia, it is generally assumed that the backfill behind a retaining wall is non expansive material. The efficiency of typical chemical and mechanical soil stabilization techniques in mitigating the swelling problem of an expansive soil is investigated through a comprehensive experimental study.
Nareeman3 there are many factors that govern the expansion behavior of soil. The problem of expansive soils is well known to engineers and expansive soils identifying the problem builders. As more water is absorbed, the plates are forced further apart, leading to an increase in soil pore pressure handy, 1995. Request pdf a unified swelling potential index for expansive soils soil swelling is a term generally applied to the ability of a soil to undergo. The most extensive damage occurs to highways and streets fema, 1997. Depth of footings below the natural and finish grades shall not be less than 24 inches for. Swellshrink behavior of expansive soils, damage and control. Snyder, 2015, there are no studies about the effect of moisture condition on the swelling potential of limetreated soils. Expansive soils are often referred to as swelling clays because clay materials are most susceptible to swelling and shrinking. It affects construction sites throughout the us and canada and other areas of the globe, and particularly those in the desert, rocky mountain and the midcontinent regions. Swelling behavior of clays is of great importance for numerous engineering applications due to the prevalence of expansive clays around the world. These swelling soils typically contain clay minerals that attract and absorb water. An additive for stabilization of swelling clay soils by bahia louafi and ramdane bahar. Swelling clays can control the behavior of virtually any type of soil if the percentage of clay is more than about 5 percent by weight.
Since swell potential and swell pressure are key properties of expansive soils, the. The pile should be embedded deep in the soil so that the uplift forces due to expansive. Evaluation of the swelling pressure for expansive soils. The swelling potential of the expansive soil mainly depends upon the properties of soil and environmental factors and stress conditions. The soils that exhibit significant swelling potential i n colorado can be divided into three general groups. This paper is a comprehensive study on expansive soils, its nature, shrinkageswell. From laboratory investigations, factors in fiuencing. Severe and widespread damage in residential buildings, sidewalks and pavements in various parts of the middle region of saudi arabia is caused by the development of heave and swelling pressure in the expansive shales in the region. Definition of expansion potential for expansive soil john d. Expansive soils the potential for expansive soils is linked to the type of soil as illustrated in figure 3. When water is introduced to expansive soils, the water molecules are pulled into gaps between the soil plates. Request pdf a unified swelling potential index for expansive soils soil swelling is a term generally applied to the ability of a soil to undergo large changes in volume due to increased. Soils developed in the upper two feet near the tuffaceous facies of the monterey shale exhibited plasticity indexes pis averaging 25 highly expansive.
Expansive soil, swelling, shrinkage, causes of expansive soil, treatments of expansive soil. The primary factors are a change in water content and the amount and type of clay size particles in the soil. Therefore lateral swelling pressures induced by expansive soils are ignored in routine design. Reduction of swelling pressure of expansive soils using.
Soils with smectite clay minerals, such as montmorillonite, exhibit the most profound swelling properties. Pdf swelling potential of compacted expansive soils magdi. Swelling behaviour of expansive shales from the middle. Chemical stabilization was generated by traditional agents consisting of lime and cement, and by a commercially branded polymer cbr plus. Experimental study on the swelling behavior of expansive soil at. Pdf determination of swelling potential is quite important in design of foundations on expansive soils. Department of civil engineering, institut teknologi medan, indonesia. Swelling potential behavior of expansive soils treated. In this paper an attempt has been made to develop a correlation for swelling potential, sq accounting both soil state and soil type representative. Expansive soil, centrifuge, lime treatment, swelling.
A briefly description of the equipment and the procedure test are summarized as follows. Another additive that as been found to be quite promising in reducingh the swelling characteristics and improving the engineering behavior of expansive soils is fly ash. Expansive clays are present in mexico city, united states, australia, africa and south america, among others. Percent swell versus time plot for bentonite the compression of sample for black cotton soil and. Addition of calcium chloride to expansive soils reduced plasticity index pi, free swell index fsi%, swell potential and. The effect of lime content on the bearing capacity and. Paper open access evaluation of the swelling pressure for. Soil properties are poor and less profitable when used as the basis of a building or construction. A guide to swelling soil for colorado homeowner associations. Pdf swelling potential of compacted expansive soils. The colorado geological survey recently published and released a guide to swelling soil for colorado homebuyers and homeowners, second edition. Increase in moisture content in expansive soils causes the following effects.
The swelling tendencies of expansive soils are quantified by the swelling potential andor free swell. Orhan erol january 2004, 109 pages expansive or swelling soils, exist in many part of the world, show excessive volume changes with increasing water content. Mar, 2017 the efficiency of typical chemical and mechanical soil stabilization techniques in mitigating the swelling problem of an expansive soil is investigated through a comprehensive experimental study. The results obtained from the experimental study indicate that the measured free swell, swell potential and swelling pressure are reduced substantially with the increasing percent of chemicals. Part i deals with theory and practice, and summarizes some of the theoretical physical properties of expansive soils. In australia, it is generally assumed that the backfill behind a retaining wall is nonexpansive material. This article and that publication provides an overview of the expansive soil problem in colorado. Investigative modelling of behaviour of expansive soils improved. The outcome is a set of reliable soilswelling indices for different levels of risk. Study and understand the effects of physiochemical properties, moisture content and dry density on their swelling potential. Soils taken from the upper two feet of the monterey shale exhibited pis that averaged about 18 medium expansion potential. A treatment of expansive soil using different additives.
Characteristic expansive or swelling materials are highly plastic clays and clay shales that often contain colloidal clay minerals such as the montmorillonites. A unified swelling potential index for expansive soils. Expansive soils expand and contract due to change in moisture content of the soil. Swelling potential, placement conditions, initial state factor iijjee 1 introduction the swelling potential can be directly determined the swelling tendencies of expansive soils are in the laboratory by performing onedimensional quantified by the swelling potential andor free swellconsolidation test in an oedometer or indirect swell. Potentially expansive soils can be found almost anywhere in the world. Excessive cost of damages to infrastructure mainly due to expansive soils is reported each year. Figure 5 swelling potential of soil by use of the atterberg limits of plasticity index and plasticity ratio 4. The completion of the above is followed by visualmanual descriptive of the. The type and swelling potential of the clay mineral.
The model is based on the concepts of the diffuse double layer, modified by introducing empirical constants to. Potentially expansive soils can typically be recognized in the lab by their plastic properties. Expansive soils present significant geotechnical and structural engineering challenges the world over, with costs associated with expansive behaviour estimated to. Expansive minerals in indiana soils smectitedominated soils tend to hold more water and drain more slowly than soils with less expansive minerals or soils. Lateral versus vertical swell pressures in expansive soils sapaz, burak m. Foundations on expansive soils provides the practicing engineer with a summary of the stateoftheart of expansive soils and practical solutions based on the authors experience. Expansive soils present significant geotechnical and structural engineering challenges the world over, with costs associated with expansive behaviour estimated to run into several billion annually. In this paper an attempt has been made to develop a correlation for swelling potential, sq. Expansive soils as used in this manual also include marls, clayey siltstones, sand, and saprolites. Swelling properties of expansive soils treated with. Expansive soils map over 50 percent of these areas are underlain by soils with abundant clays of high swelling potential.
This depth can be approximated following the guidelines given in the engineer manual em 111011904 1. The increasingly extensive use of concrete slab on ground construction after 1940 has further increased the damage to the structure caused by expansive soils. B we believe that the reason is that expansive potential is not even recognized as a reality in a tropical setting because most published literature about the subject always speak about occurrence of expansive soils only in arid desert settings. To avoid the buildup of these potentially damaging forces, slabs and. Swelling properties of expansive soils treated with chemicals. Consistency limits indicate that the soil is high plasticity. Geotechnical aspects of buildings on expansive soils.
Reduction of swelling pressure of expansive soils using eps. When the soil becomes wet again, the cracks will shrink or disappear. From laboratory investigations, factors in fiuencing the swelling potential of expansive soils have been found. Swelling potential behavior of expansive soils treated with. Overton2 1 colorado state university, usa 2 tetra tech, inc.
A treatment of expansive soil using different additives mohammed y. The effect of lime content on the bearing capacity and swelling potential of expansive soil. The mancos and pierre shales, which are found in large. For nonswelling soils, the object is to find the greatest assured cbr value for some range of densities and moisture contents, whereas the objective of the test program for the expansive soils is to find the moisture content ranges which will preclude. This paper presents the problems and the geotechnical and physicochemical properties of the tested shales. Most ex pansive soils found in addis ababa have free swell and swelling pressure amounting to values of above 100% and 1. The first stage in foundation design on this problematic soil is the evaluation of the swelling potential, based on which one identifies the clays activity and its correlation with the value of the swelling pressure p.
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