Soils taken from the upper two feet of the monterey shale exhibited pis that averaged about 18 medium expansion potential. Expansive soils as used in this manual also include marls, clayey siltstones, sandstones, and saprolites. Investigative modelling of behaviour of expansive soils improved. Possible explanations for extent for expansive soils simple correlations between soil plasticity and expansion potential soil expansion potential astm d4829 this test was developed in orange county, california in the mid1960s and introduced in the 1973 uniform building code as ubc test standard 292. Expansive soils can be found in humid environments where expansive problems occur with soils of high plasticity index i p or in aridsemi arid soils where soils of even moderate expansiveness.
This characteristic of swelling and the swelling pressures of expansive soils is attributed to the presence of montmorillonite or combination of montmorillonite and illite clay minerals in such soils. Pdf volume change and strength behavior of expansive clay stabilized. Expansive soils are widely distributed in the world and found in more than 60 countries and regions. The liquid limit, plastic limit, and plasticity index of soils are also used extensively, either individually or together. The form of the equation in terms of plasticity index is, where, s k m p2. Stabilization with additives such as lime and cement has been practiced for many years and has proved effective in improving the behavior of expansive soils.
At the same liquid limit, the higher the plasticity index, the more cohesive the clay. Simple correlations between soil plasticity and expansion potential. Influence of lime on plasticity behaviour of soils hussain, m. Holtz and gibbs 16 demonstrated in 1956 that plasticity index and liquid limit are useful indices for determining the swelling characteristics of most clays. Soil plasticity dry density the greater the density, the greater the. The property of a material to be deformed repeatedly without rupture by the action of a force, and remain deformed after the removal of force. However increasing the lime content beyond 5% had a marginal effect in further reducing the plasticity index. Expansive soils, which are considered as problematic soils, have worldwide distribution and hence, their proper identification and characterisation becomes an absolute necessity in the perspective of the present day geotechnical engineering practice. Content, ii plasticity index, iii shrinkage limit can be qualitative indicators of expansive characteristics. The atterberg limits were determined for some samples see table 3. Foundation engineering for expansive soils fills a significant gap in the current literature by presenting coverage of the design and construction of foundations for expansive soils. The components of expansive soil were analyzed with edax, and it is shown that the main contents of expansive soil in the northern hubei have some significant effects on engineering properties of expansive soil. The plasticity index is the size of the range of water contents where the soil exhibits plastic properties.
A 1972 survey of the highway departments in the 50 states, district of columbia, and puerto rico indicated that. An expansive soil is suspected to occur if following of the factors are satisfied. Expansive soils is a nationally recognized problem which has plagued individuals concerned with the design, maintenance, and operation of highway systems. Calculation shall be in accordance with aashto method t91 figure vi19. Figure 5 swelling potential of soil by use of the atterberg limits of plasticity index and plasticity ratio 4. Hence, in the unified soil classification system, the liquid limit is used to distinguish between clays of high compressibility and those of low compressibility. According to astm, the expansion index has been determined to have a greater range. The offset with the horizontal axis gives the critical clay content for cohesive behaviour. Soil properties and the unified soil classification system. Your guide to the design and construction of foundations on expansive soils. Numerically, it is the difference between the liquid limit and the plastic limit. Expansive soils can be found both in humid environments where expansive problems occur with soils of high plasticity index, and in aridsemiarid soils where soils of even moderate expansiveness can cause significant damage.
It is the difference between the liquid limit and plastic limit of finegrained soils. 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. Standard test methods for liquid limit, plastic limit, and. Pdf classification procedures for expansive soils researchgate. The expansive soils due to their large water holding capacity are.
The purpose of this study was to investigate in the laboratory three different techniques that can be used lo re 1 w 2 w 3 bulky soils. Higher the plasticity index, more plastic the soil is. This paper intends to discuss relative merits of various methods available to a field geotechnical engineer to achieve this important goal. Differences in plasticity of clays are reflected by the plasticity index. Stabilizer design based on plasticity index pi and soil gradation is also a widely accepted method. Soils developed in the upper two feet near the tuffaceous facies of the monterey shale exhibited plasticity indexes pis averaging 25 highly expansive. Expansion of soils can also be measured in the lab directly, by immersing a remolded soil. Adsorbed water in the clay particles allow the particles to slip over. Characteristic expansive or swelling materials are highly plastic clays and clay shales that often contain colloidal clay minerals such as the montmorillonites. China is one of the countries with a large distribution of expansive soils, which have successively been found in more than 20 provinces and regions, occupying nearly 600,000 km 2. The completion of the above is followed by visualmanual descriptive of the soil. It could be observed that, in general, soils have shown an immediate decrease in plasticity index upon addition of lime. Geotechnical aspects of buildings on expansive soils in. Engineering properties of expansive soil springerlink.
Variation of plasticity index the plasticity index variations for different soils are depicted in figs. Then the plasticity properties of soils including liquid and plasticity limits as well as plasticity index, already measured, were compared with those of the experimental specimens mixed with eggshell powder in different proportions. However, some subsoils treated by this methodology have exhibited premature failures. The plasticity index of the soil is the numerical difference between the liquid and plastic limits. Part i deals with theory and practice, and summarizes some of the theoretical physical properties of expansive soils. In expansive soils second revision page 1, clause 4.
B we believe that the reason is that expansive potential is not. The plasticity index is one of the most important of the properties of soil. Simple correlations between soil plasticity and expansion. The plasticity index refers to the range of plastic properties a soil exhibits at varying levels of water content. Expansive soils can be found in humid environments where expansive problems occur with soils of high plasticity index i p or in aridsemi arid. Impact of climatic variation on design parameters for slab. Various aspects of expansive soils relevent to geoengineering practice simple correlations between soil plasticity and expansion potential soil expansion potential astm d4829 this test was developed in orange county, california in the mid1960s and introduced in the 1973 uniform building code as ubc test standard 292. Test methods for liquid limit, plastic limit, and plasticity. For classification, clay is a finegrained soil, or the finegrained portion of a soil, with a plasticity index greater than 4 and the plot of plasticity index versus liquid limit falls on.
Expansive soils prevail over a large area of sudan and have caused significant damages to irrigation systems, water lines, sewer lines, buildings, roads and other structures located on these soils. Influence of mineralogy and plasticity index on the. The adsorbed water in clayey soils is leads to the plasticity of soil. Soils with a high pi tend to be clay, those with a lower pi tend to be silt, and those with. The plasticity index is essentially the difference between liquid limit and plastic limit values. Impact of climatic variation on design parameters for slab on ground foundations in expansive soils ronald f. It indicates the range of moisture content over which the soil can exhibit plastic properties. Laboratory investigation of the effect of eggshell powder. 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. Snethan 1984 based on field and laboratory studies on expansive soils of united states of america used liquid limit and plasticity index as criteria for identifying expansive soils. Addition of calcium chloride to expansive soils reduced plasticity index pi, free swell index fsi%, swell potential and. Empirical correlations for the swelling pressure of expansive clays. Important physical properties of expansive soils involve index properties, dry.
628 1266 1294 446 1332 689 260 293 367 1503 1243 701 1363 23 809 799 217 440 119 1123 716 192 1470 219 85 23 1435 8 70 1030 647 416 732 1205 798 237 1253 810 379 1196 1187