Suction- Swell Relationship of Stabilized Expansive Soil

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Suction- Swell Relationship of Stabilized Expansive Soil

Premalatha K

Professor, Department of Civil Engineering, College of Engineering Guindy, Anna University,

Chennai-25, Tamilnadu, India.

Angammal S

Post Graduate Student, Department of civil Engineering, College of Engineering Guindy, Anna University, Chennai-25, Tamilnadu, India.

Abstract: Soil that has potential for volume change under changing moisture conditions are generally called as expansive soil. The swelling of soil is due to release of suction in the soil. Hence it is necessary to study the relationship between suction and swell characteristics of expansive soil. The suction-swell relationship of stabilized expansive soil will be different from the natural soil. Locally available soil (natural soil) was collected and it was found that it is CH type soil as per IS classification system. The soil water characteristics curve (SWCC) was measured using pressure plate extractor apparatus and the swell pressure was measured using oedometer by expanding loaded method. The soil was stabilized by using hydrated lime (L), sodium chloride (NaCl), and both at different percentage. The optimum percentage of stabilization agents are 4% lime and 3% of NaCl. The SWCC and swell pressure of both stabilized and natural soil were determined at different initial water content and density. The important observations made from the present study are: i) The influence of the stabilization agent in the consistency limits. ii) The influence of the stabilization agent in the swell pressure. iii) The influence of the stabilization agent in the SWCC. iv) The relationship between suction-swell pressure of stabilized and natural soil.

Keywords: Stabilization, Suction-Swell, Expansive clay, Soil water characteristics curve.

  1. INTRODUCTION

    The swelling of soils in India has their origin in subaqueous decomposition of basalt rocks or weathering in- situ. The mineral montmorillonite is formed under alkaline environment. This soil is popularly known as black cotton soil in India. The soil is mostly residual in character and the thickness of deposits is less than 5 m in most cases. However, transported soil deposits of black cotton soils are known to exist and these deposits are much thicker and are around 8.0 m. The marine deposits present in the narrow tidal coastal plains along the east and the west coast India have undergone desiccation over a period and these desiccated clays exhibit characteristics similar to expansive soils. The expansive nature of the soil is most obvious near ground surface where the profile is subject to seasonal, environmental changes. Active clay undergo volume change upon wetting and drying. Expansive soils occur in an active zone which starts at the ground surface down to the saturated part of the zone of capillary rise above the ground water table. Usually lower the shrinkage limit and wider the range of plasticity index, the more likely is the volume change to occur and greater the amount of the suction change .The parent materials that are associated with

    expansive soils can be placed in two groups .The first group comprises of the basic igneous rocks such as the basalts of the deccan plate in India, the dolerite sills and dykes in the central region of south Africa and the gabbros and norities west of Pretoria North, Transvaal etc. In these soils, the feldspar and pyroxene minerals of the parent rocks decompose to form montmorillonite and other secondary minerals. The second group comprises the secondary rocks that contain montmorillonite as a constituent which breaks down physically to form expansive soils. Examples of these types of rocks are bed rock shale found in north America, marls and stones in Isreal and the shale of South Africa. The swelling of soils in India has their origin in subaqueous decomposition of basalt rocks or weathering in situ. The mineral montmorillonite is formed under alkaline environment. This soil is popularly known as black cotton soil in India. The soil is mostly residual in character and the thickness of deposits is less than 5m in most cases. The expansive nature of the soil is most obvious near ground surface where the profile is subject to seasonal, environmental changes. There are many correlations that are useful in identifying potentially expansive soils. It may also be possible to identify them visually.

  2. LITERATURE REVIEW

    Gueddouda et al. [7] evaluated the effect of salt, lime, cement, combinations of lime and cement, and combination of lime and salt on the swelling potential of expansive soil. Stabilization of combined lime + cement has given satisfying results. Stabilization using lime + salt, has given better effect than the combined lime and cement stabilization. For a combination of 6% lime +1.5 M NaCl, stabilization 80% reduction in free well and more than 95% reduction in swelling pressure were observed. Thyagaraj et al. [9] examined a lime precipitation technique in stabilizing an expansive soil through laboratory investigation. Precipitation of lime was achieved by sequential mixing of expansive soil with calcium chloride and sodium hydroxide solutions. The swell potential of soil specimen was reduced to 0% of the untreated value of 4.95%.The reason for the reduction of swell potential was the strong lime modification reactions and poorly developed cementation products formed during the early stages of curing in the treated soil. khemissa et al. [8] studied about the stabilization of expansive clay using cement and lime. It has been concluded that the mechanical properties of expansive clay treated with

    mixture of various cement and lime content is improved. The best performance was obtained for the combination of 8%cement and 4% lime. Potential is gradual up to swell percent of 8% and is rapid beyond this value. Puppala et al. [2] studied about the swell prediction model. The swell prediction models were generated based on a limited number of expansive clays and pertain to a specific suction and void ratio. The new parameter, mechanical hydro chemical parameter is used for both matric suction and clay mineralogy information. Yaqoub et al. [11] investigated the volume change behavior of swelling soil. In this paper the author concluded that swelling occur for degree of saturation higher than 80%. If hydraulic diffusivity decreases the equilibrium swelling pressure will increase. It is observed that the coefficient of permeability of expansive soil depends on degree of saturation and void ratio. The swelling rate of expansive soil decreases as the surcharge pressure increases. Christopher et al. [5] studied about the emerging trends in expansive soil stabilization. Properties of expansive clay can be improved by changing soil micro fabric, pore sizes and constituents. Chemical stabilization can be accelerated by injection techniques and deep soil mixing technique. Instead of using one additive as stabilizing agent, it is advisible to use of number of additives to achieve economy. In addition nanotechnology also has been proven to be a suitable method for stabilization of expansive soils.

    The project aim is to study the effects of stabilization in the soil water characteristic curve and study the effect of stabilization in the swell pressure, and also obtain the relationship between soil suction and swell pressure based on drying soil water characteristic curve. The present study are carried out to understand the influence of addition of both Hydrated Lime and Sodium chloride (NaCl) in the soil water characteristic curve (SWCC), and swell characteristics of expansive soil. The lime and NaCl were added to the soil individually and in combinations. Stabilized soil changes the internal force system, which in turn may alter the suction-swell relationship. Hence it is decided to establish the suction- swell relationship for stabilized expansive clays of selected area

  3. METHODS AND MATERIALS

The expansive soil was collected from Shanthi colony, Anna Nagar, Chennai. The soil was air-dried, and the soil classification tests were carried out. The index and compaction characteristics of the soil are presented in Table

  1. To establish the suction-swell relationship, the expansive soil is considered as different initial state. To determine the lime fixation point the pH test was carried out. For that 1% to 8% of lime is mixed with soil to obtain a pH of 12.40 or equivalent to pH of lime. From the observation, for lime content beyond 4%, the pH remained constant as 12, so optimum lime content is fixed as 4%.

    Table- I: Index Properties and Compaction Characteristics of Natural Soil

    S.No.

    Soil description

    Value

    1

    Specific gravity, Gs

    2.70

    2

    Gravel (%)

    0

    Sand (%)

    0

    Silt (%)

    36

    Clay (%)

    64

    3

    Liquid Limit (%)

    74

    4

    Plastic Limt (%)

    32

    5

    Shrinkage Limit (%)

    13

    6

    Plasticity Index (%)

    42

    7

    Free swell index (%)

    70

    8

    Maximum Dry Density (g/cc)

    1.38

    9

    Optimum Moisture Content (%)

    31

    10

    IS Classification of soil

    CH

    1. Preparation of Soil Mix

      The known weight of pulverized dry soil was taken. The dry weight of lime was calculated for different percentage and added to the dry soil. Similarly, the dry weight of NaCl also calculated. As per different combinations, the dry soil mix was prepared and the tests were carried out by adding respective water content.

    2. Pressure plate apparatus (Axis translation technique)

    To determine the suction pressure to the soil, the pressure plate apparatus was used. The apparatus consists of totally six specimen rings of dimension 60 mm internal diameter and 10 mm height, which is made of Poly Vinyl Chloride (PVC) material. The sample was packed in a specimen ring of required density and water content. The prepared specimens were subjected to full degree of saturation by submerging in water, such that the sample was allowed for drainage at both top and bottom .After assuring complete saturation of specimens were tested in the pressure plate apparatus .The saturated specimens were placed on the air-entry ceramic disk with maximum capacity of 15 bar in air pressure chamber. Initially, air pressure of 2 bar was applied for 24 hours on the saturated specimens.

    After application of this air pressure, the weight of the specimen was noted. Then, the air pressure was increased to 4 bar and the same procedure was repeated up to the air

    pressure of 14 bar. After completion of 14 bar the specimens were taken and kept for oven drying for 24 hours and it were weighed for moisture content determination. Finally, the soil- characteristics curve was obtained from the graph drawn for suction pressure and gravimetric water content. The soil water characteristics curve determined for different initial conditions as listed in Table II.

    Table-II: Soil with different initial condition for suction test.

    Water

    State of

    Bulk

    Soil with different

    content

    soil

    Density

    Stabilizers

    (%)

    (g/cc)

    Natural soil

    74

    Liquid

    1.103

    State

    32

    Plastic

    1.728

    State

    13

    Solid

    1.728

    State

    Natural

    Soil

    67

    Liquid

    1.103

    +2%lime

    State

    45

    Plastic

    1.728

    State

    15

    Solid

    1.728

    State

    Natural

    Soil

    55

    Liquid

    1.106

    +4%lime

    State

    43

    Plastic

    1.728

    State

    28

    Solid

    1.728

    State

    Natural

    Soil

    66

    Liquid

    1.056

    +2%lime+

    2%

    State

    NaCl

    37

    Plastic

    1.728

    State

    13

    Solid

    1.728

    State

    Natural

    Soil

    57

    Liquid

    1.116

    +4%lime+

    State

    3% NaCl

    37

    Plastic

    1.728

    State

    23

    Solid

    1.728

    State

    IV RESULTS AND DISCUSSION

    1. Effect on Atterberg Limits

      The liquid limit, plastic limit, and shrinkage limit tests are determined in the laboratory. The above values of soil mix with lime and NaCl are presented in the Table III and Table IV.

      Table-III: Atterberg Limits Test Results for the Addition of Lime and NaCl Mix with Soil in individual

      Natural Soil

      Atterberg Limits

      With

      Stabilizers

      Liquid

      Plastic

      Plasticity

      Shrinkage

      Combination

      limit

      limit

      index

      limit

      Natural Soil

      74

      32

      42

      13

      Natural

      67

      45

      22

      15

      Soil+2%L

      Natural

      55

      43

      12

      28

      Soil+4%L

      Natural

      56

      42

      14

      16

      Soil+6%L

      Natural

      62

      36

      26

      11

      Soil+2%NaCl

      L = Lime, NaCl = Sodium Chloride

      Table-IV: Atterberg Limits Test Results for the Soil Stabilized with Different combinations of Lime and NaCl

      Natural Soil

      Atterberg Limits

      With

      Liquid

      Plastic

      Plasticity

      Shrinkage

      Stabilizers

      limit

      limit

      index

      limit

      Combination

      Soil+2%L

      +

      66

      37

      29

      14

      2%NaCl

      Soil+2%L

      +

      64

      35

      29

      12

      3%NaCl

      Soil+4%L

      +

      58

      40

      18

      23

      2%NaCl

      Soil+4%L

      +

      57

      37

      20

      23

      3%NaCl

      Soil+6%L

      +

      58

      45

      13

      17

      2%NaCl

      Soil+6%L

      +

      58

      40

      18

      26

      3%NaCl

      L = Lime, NaCl = Sodium Chloride

      The natural soil has the liquid limit value of 74%. When the soil mixed with 2%, 4% and 6% of lime, the liquid limit decreased to 67%, 55% and 56% respectively. When 2% of NaCl is added to the natural soil the liquid limit decreased to 62%. The liquid limit of the soil specimen decreased up to 7% on addition lime. This is because the electrolyte

      concentration on addition of ca2+ ions reduces the double layer thickness leading to reduction in liquid limit. But beyond 4% lime content the liquid limit remained constant because the influence of stabilization on double layer reduction is insignificant. The variation of liquid limit with lime content is shown in Fig 1.

      Fig. 1. Soil with different Lime content

      The plastic limit of the natural soil is 32%. When soil is mixed with 2%, 4% and 6% of the lime, the plastic limit increased to 45%, 43% and 42% respectively. For 2%NaCl the plastic limit increased to 36%. Beyond 4% lime very slight decrease in the plastic limit is noticed. The lime induced flocculation enhanced the inter particle resistance against movement, thus the plastic limit decreased. A decrease in the plasticity index was observed with the addition of lime and NaCl with soil. It is to be noted that with the above treatment, the plasticity index of the expansive soil decreased from 42% to 26%.

      Fig.2. and Fig.3. shows the variation of the liquid limit, plastic limit, shrinkage limit and plasticity index for different percentages of lime with 2% NaCl. When 2%, 4% and 6% of lime added along with 2% NaCl, the liquid limit decreased from 74% to 66%, 58% and 58% respectively. For the same combinations, when NaCl is increased to 3%, the liquid limit decreased to 64%, 57%, and 58% respectively. The plastic

      limit increased from 32% to 37%, 40% and 45% respectively for lime and 2% NaCl. For lime and 3% NaCl, the plastic limit increased to 35%, 37% and 40%. The test result values are tabulated in Table IV.

      The plasticity index decreased with increase in lime content. For the combination of soil with 6% lime and 2% NaCl, the plasticity index decreased by 69%, and for the combination of soil with 6% lime and 3% NaCl plasticity index decreased by 57%. The significant improvement in the consistency of the soil is contributed by an appreciable decrease in liquid limit and plasticity index.

      Fig.2. Soil with 2%NaCl with different Lime content

      Fig.3. Soil with 3%NaCl with different Lime content

    2. Influence of Stabilization on Soil Water Charateristics Curve (SWCC)

      The suction tests were carried out by adding lime and NaCl for various proportions. From the soil water characteristic curve (SWCC) the following data were calculated for the interpretation of the suction – swell relation. For the suction test the samples were prepared at different initial water content corresponding to the mix proportion. From the SWCC air entry value (i), residual water content (w r), residual suction (r), and slope of the curve (cw) for natural soil were obtained. The above mentioned parameters are obtained from the graph, and they are shown in Fig.4. Similarly the SWCC for the mix proportions 2%Lime+natural soil, 4%Lime+ natural soil, 2%Lime+2%NaCl+ natural soil, 4%Lime+3%NaCl+ natural soil are obtained.

      The SWCC parameters determined made from the graph are presented below in the form of tables. The SWCC parameters for stabilized soils are determined and it shown in Table-V to Table-IX.

      From the Table 4.3 it is found that the air entry value and the slope of SWCC of natural soil decreased with decrease in initial water content. Since the residual suction of the natural soils at different initial conditions is greater than 1400 kN/m2, it is not possible to report the residual suction value.

      Fig.4. Suction versus Gravimetric Water Content for Natural soil

      Table-V: Natural Soil with Different Initial Condition

      Sl.No.

      State of Soil

      Bulk Density(g/cc)

      Initial water Content Wi(%)

      Residual Water Content Wr (%)

      Air Entry Value i (kN/m2)

      Residual suction r (kN/m2)

      Slope of SWCC

      1

      Liquid State

      1.103

      60

      150

      >1400

      0.08

      2

      Plastic State

      1.728

      45

      130

      >1400

      0.06

      3

      Solid State

      1.728

      37

      90

      >1400

      0.04

      Table-VI: Soil and 2% of Lime with Different Initial Condition

      S.No.

      State of Soil

      Bulk Density(g/cc)

      Initial water Content Wi(%)

      Residual Water Content Wr (%)

      Air Entry Value i (kN/m2)

      Residual suction r (kN/m2)

      Slope of SWCC

      1

      Liquid State

      1.103

      74

      47

      120

      800

      0.33

      2

      Plastic State

      1.728

      67

      43

      80

      700

      0.26

      3

      Solid State

      1.728

      55

      34

      35

      450

      0.19

      From the above Table-VI, it is found that 2% addition of lime, the air entry value and slope of SWCC decreased with decrease in initial water content. But the air entry value was lesser than that of the natural soil and the slope of SWCC was greater than that of natural soil. Since the slope of SWCC was greater than natural soil, the soil+ 2% lime reached the residual stte and the residual suctions were lesser than 1400 kN/m2. In addition, increase in the initial water content increased the residual suction.

      From the below Table VII, it is found that on 4% addition of lime, the air entry value and slope of SWCC decreased with decrease in initial water content. Since the residual suction of the soil at different initial conditions is greater than 1400 kN/m2, it is not possible to report the residual suction value. The air entry value was greater than that of the natural soil and the slope of SWCC was

      greater than that of natural soil. In addition, the air entry value was greater than that of the natural soil+ 2% lime and the slope of SWCC was lesser than that of natural soil+ 2% lime.

      From the Table VIII, it is found that addition of 2% Lime+ 2%NaCl, the air entry value and slope of SWCC decreased and then increased with decrease in initial water content. The residual suction of soil + 2% Lime+ 2%NaCl at different initial conditions are lesser than 1400, and the residual suction value increased with decrease in initial water content. The air entry value was greater than that of the natural soil and the slope of SWCC was greater than that of natural soil. The air entry value and residual water content were greater than that of the natural soil+ 2% lime. The air entry value was greater than that of the natural soil+ 4% lime and residual suction was lesser than natural soil+ 4% lime.

      Table-VII: Natural Soil and 4%Lime with Different Initial Condition

      SL.NO.

      State of Soil

      Bulk Density(g/cc)

      Initial water Content Wi(%)

      Residual Water Content Wr (%)

      Air Entry Value i

      (kN/m2)

      Residual suction r

      (kN/m2)

      Slope of SWCC

      1

      Liquid State

      1.106

      57

      400

      >1400

      0.1

      2

      Plastic State

      1.728

      49

      170

      >1400

      0.08

      3

      Solid State

      1.728

      34

      120

      >1400

      0.05

      Table-VIII: Natural Soil + 2% Lime+ 2%NaCl with different initial condition

      S.No.

      State of Soil

      Bulk Density(g/cc)

      Initial water Content Wi(%)

      Residual Water Content Wr (%)

      Air Entry Value i (kN/m2)

      Residual suction r (kN/m2)

      Slope of SWCC

      1

      Liquid State

      1.056

      80

      65

      210

      600

      0.34

      2

      Plastic State

      1.728

      60

      54

      170

      600

      0.11

      3

      Solid State

      1.728

      50

      50

      250

      800

      0.15

      From the Table IX, it is found that addition of 4% Lime+ 3%NaCl; the air entry value remains the same for all states irrespective of the initial water content. The slope of SWCC decreased and then increased with decrease in initial water content. Similar pattern is observed for 2% Lime+ 2%NaCl. The air entry value and residual water content were greater

      than that of the natural soil+ 2% lime. But the slope of SWCC is lesser than the natural soil+ 2% lime. The residual suction of the soil at different initial conditions is greater than 1400, for natural soil+ 4% lime+3% NaCl and natural soil+ 4% lime. The residual suction is greater than natural soil + 2% Lime+ 2%NaCl

      Table- IX: Natural Soil + 4% Lime+ 3%NaCl with different initial condition

      S.No.

      State of Soil

      Bulk Density(g/cc)

      Initial water Content Wi(%)

      Residual Water Content Wr (%)

      Air Entry Value i

      (kN/m2)

      Residual suction r (kN/m2)

      Slope of SWCC

      1

      Liquid State

      1.116

      77

      200

      >1400

      0.15

      2

      Plastic State

      1.728

      56

      200

      >1400

      0.05

      3

      Solid State

      1.728

      50

      200

      >1400

      0.10

    3. The Influence of Stabilization on the Percent

      Swell and Swell Pressure

      The treated samples immediately showed a reduction in swell pressure and percent swell. However, a significant decrease in the percent of swell and pressure values were obtained for an increase in lime up to 4%. Moreover, with the addition of 4% lime, the percent swell dropped to zero.

      This decrease in swelling characteristics is attributed to the reduced amount of water absorption in calcium saturated clay owing to cation exchange reaction, and also due to the development of acementitious bonding produced by the reaction between the lime and the clay minerals. However, increase in pH due to the addition of lime induced an additional negative charge on the edges of the clay particle leads to edge-to-face attraction which result a flocculated structure. The relatively open structure of the flocculants fabric holds more water, and increased the percent swell and swell pressure, for the soil treated with 2% lime and 3% NaCl. The addition of 4% of lime with 3% NaCl almost eliminates both the swell pressure and percent swell of the treated soil.

      Fig 4.5 Time versus Swell(mm) for Natural Soil at Solid State

    4. Suction Swell Relation

      The suction and swell tests were carried out for different proportions of lime and NaCl. The samples were prepared for soil at initially plastic state condition and the suction values are obtained from SWCC and the samples are initially at saturated condition or state. The suction values

      are limited up to 1400 kN/m2, So that in the graph the curve was extended then the values are obtained (suction values plotted in x-axis see Fig.4.).

      The suction test were carried out by adding lime and NaCl for various proportions. From the soil water characteristic curve the following data were calculated

      Table X: Percent Swell and Swell Pressure Test Results

      Soil Composition

      Swell Percen t (%)

      Swell Pressure (kPa)

      Natural Soil

      12.8

      480

      Natural Soil

      2.6

      82

      Natural Soil + 2% L

      2.75

      252

      NaturalSoil+2%L+2

      %Nacl

      2.3

      102

      NaturalSoil+2% L+3%Nacl

      7.00

      282

      Natural Soil+4%L+2%N

      acl

      1.38

      165

      Natural Soil+4%L+3%N

      acl

      0.30

      38

      L – Lime , NaCl- Sodium Chloride, SL- Solid State, PL-Plastic State

      The decreasing swell characteristics is attributed to the reduced amount of water absorption in calcium saturated clay owing to cation exchange reaction, and also due to the development of a cementitious bonding produced by the reaction between lime and the clay minerals. Samples treated with 4% of lime gives lower selling according to seed et al(1962).However increase in pH due to the addition of lime induced an additional negative charges on the edges of the clay articles leads to edge to face attraction which resulted a flocculated structure. The relatively open structure of the flocculant fabric holds more water, and increase the percent swell and swell, for the soil treated with 2% lime and 3% NaCl. The addition of 4% of lime with 3% NaCl almost eliminates both the swell pressure and percent swell of the treated soil.

      Suction swell relationship with different water content is listed from table XI to table XIII.

      Pressure, for the soul treated with 2% lime and 3% NaCl. The addition of lime with 3% NaCl almost eliminate both the swell pressure and percent swell of the treated soil.

      S.NO

      Water content (%)

      Swell pressure (kN/m2)

      Swell percent (%)

      Suction at different initial condition of soil (kN/m2)

      Liquid State

      Plastic State

      Solid State

      1

      28

      0

      0

      20000

      60000

      4000

      2

      43

      0

      0

      3000

      1200

      0

      3

      55

      0

      0

      300

      0

      0

      Table- XI: Suction Swell characteristics of natural soil + 4% of Lime with Different Initial Condition.

      Table- XII: Suction Swell characteristics of Natural Soil +2% Lime +c2% NaCl with Different Initial Condition.

      S.NO

      Water content (%)

      Swell pressure (kN/m2)

      Swell percent (%)

      Suction at different initial condition of soil (kN/m2)

      1

      13

      102

      2.3

      108

      107

      1200000

      2

      37

      0

      0

      1000000

      105

      17000

      3

      66

      0

      0

      600

      0

      0

      Table- XIII: Suction – Swell characteristics of Natural soil + 4% Lime + 3% NaCl with Different Initial Condition

      SL.NO

      Water content (%)

      Swell pressure (kN/m2)

      Swell percent (%)

      Suction at different initial condition of soil (kN/m2)

      Liquid State

      Plastic State

      Solid State

      1

      23

      38

      0.3

      400000

      109

      20000

      2

      37

      0

      0

      12000

      400000

      2800

      3

      57

      0

      0

      2200

      0

      0

      1. The relationship between swell and suction are different for soil and soil stabilized with different stabilizing agent.

      2. The relationship between swell and suction of both soil and stabilized soil are different for different initial states.

      3. The interaction of stabilizing agent with soil is different at different initial water content.

    4.

    1. Suction swell relationship based on SWCC, initially at liquid state

      The Natural soil exhibits swell properties from low suction values. Addition of 2% lime,4%lime and 2%lime+2%NaCl completely suppressed the swell properties. But addition 3%NaCl with 4% lime stimulated the soil to swell at higher suction value 4000 kN/m2.

    2. Suction swell relationship based on SWCC, initially at plastic state

      For initially plastic state, the natural soil exhibited swell properties from very low suction value. Natural soil +2%lime exhibited swell properties for suction value 13000 kN/m2. For all the combination of stabilizing agent there is no swell and properties of natural soil were suppressed by the stabilizing agent.

    3. Suction swell relationship based on SWCC, initially at solid state

      For SWCC at initially solid state, natural soil exhibited swell properties from lower suction value. The natural soil+2%lime exhibited swell properties at suction value 170 kN/m2. The natural soil+4% lime +3%NaCl exhibited swell properties at suction value 2000 kN/m2. The natural soil

      +2%lime +2%NaCl exhibited the swell properties at higher suction value than 4%lime +3%NaCl.

    4. Suction swell relationship based on SWCC, initially at liquid state

      The Natural soil exhibits swell properties from low suction values. Addition of 2% lime, 4%lime and 2%lime+2%NaCl completely suppressed the swell properties. But addition 3%NaCl with 4% lime stimulated the soil to swell at higher suction value 4000 kN/m2.

    5. Suction swell relationship based on SWCC, initially at plastic state

      For initially plastic state, the natural soil exhibited swell properties from very low suction value. Natural soil +2%lime exhibited swell properties for suction value 13000 kN/m2. For all the combination of stabilizing agent there is no swell and properties of natural soil were suppressed by the stabilizing agent.

    6. Suction swell relationship based on SWCC, initially at solid state

    For SWCC at initially solid state, natural soil exhibited swell properties from lower suction value. The natural soil+2%lime exhibited swell properties at suction value 170 kN/m2. The natural soil+4% lime +3%NaCl exhibited swell properties at suction value 2000 kN/m2. The natural soil

    +2%lime +2%NaCl exhibited the swell properties at higher suction value than 4%lime +3%NaCl.

    V CONCLUSIONS

    1. Effect on Consistency Limits

      The natural soil was found to be CH type soil. Its liquid limit, plastic limit, plasticity index and shrinkage limit values are 74%, 32%, 42% and 13% respectively.

      a) Reduction in Liquid Limit and Plasticity Index Upon addition of 2% lime, 4% lime and 2% NaCl, its liquid limit decreased by 10%, 26% and 12% respectively. And its plasticity index decreased by 47%, 71% and 38% respectively.

      On addition of the combination of 2% lime+2% NaCl, 2% lime+3% NaCl, 4% lime+2% NaCl and 4% lime+3% NaCl the decrease in the liquid limit and plasticity index were in the range of 10% 23% and 30% 69% respectively.

      The electrolyte concentration on addition of ca+ ions reduces the double layer thickness reduces the liquid limit.

    2. Increase in Plastic Limit and Shrinkage Limit

      Upon addition of 2% lime, 4% lime and 2% NaCl, its plastic limit increased by 29%, 26% and 11% respectively. And its shrinkage limit increased by 13%, 54% and 15% respectively.

      On addition of the combination of 2% lime+2% NaCl, 2% lime+3% NaCl, 4% lime+2% NaCl and 4% lime+3% NaCl the increase in the plastic limit and shrinkage limit were in the range of 9% 40% and 8% 77% respectively.

      The lime induced flocculation enhanced the inter particle resistance against movement, thus the plastic limit decreased for beyond soil+4% lime.

      The orders of reduction in plasticity index for different combination of lime and NaCl with the selected CH type soil are

      Natural soil > Natural soil

      +2%lime+2%NaCl = Natural soil +4%lime+3%NaCl

      > Natural soil +2%NaCl > soil+4%lime+2%NaCl > soil+2%NaCl = soil+6%lime+3%NaCl > soil+4%NaCl > soil+6%lime+2%NaCl > soil + 4%lime.

    3. Effect on Swell Properties

      A significant decrease in percent swell and swell pressure were obtained for increase of percentage of lime up to 4% the lime fixation percentage. Addition of 2%NaCl enhanced the swell caracteristics but addition of 3%NaCl with lime reduced the swell characteristics.

      The order of swell characteristics for different combinations of lime and NaCl are

      Natural soil > Natural Soil +2%lime +3%NaCl > Natural Soil +2%lime > Natural Soil +2%lime +2%NaCl > Natural Soil +4%lime +2%NaCl > Natural Soil +4%lime

      +3%NaCl

    4. Effect on SWCC Parameters

      The SWCC parameters of the stabilized soil depend on the interaction between different combinations of lime and NaCl. Generally on addition of the higher percentage of stabilizing agents, the slope of SWCC, residual suction and air entry value increases.

      For soil+2% lime the residual suction and air entry value are lesser than the natural soil. The slope of SWCC of soil+2% lime and soil+2% lime +2% NaCl are greater than the other values of slope.

      Addition of lesser percent of lime (lesser than lime fixation point) increased the slope desaturation zone, which made the soil to attain residual state at lower suction value. Addition of higher percentage of stabilizing agent reduced the slope of desaturation zone and the residual states are attained at higher suction value. More data are required to propose the order of variation in the SWCC parameters.

    5. Relation between Suction and Swell Properties

      The relationship between suction and swell are different for soil and soil stabilized with a different stabilizing agent. The relationship between the suction and swell of both soil and stabilized soil are different for different initial states. The interaction of stabilizing agent with soil is different at different initial water content.

      The order of suction value at which the natural soil and natural soil with different combinations of stabilizing agent exhibited swell properties are give below

      1. SWCC at Initially Liquid State

        Natural soil > Natural soil + 4%lime+3%NaCl

        > Natural soil + 2%lime > Natural soil + 4%lime, and >

        Natural soil + 2%lime+2% NaCl

      2. SWCC at Initially Plastic State

        Natural soil > Natural soil + 2%lime+2% NaCl > Natural soil + 4%lime+3% NaCl > Natural soil + 4%lime > Natural soil + 2%lime.

      3. SWCC at Initially Solid State

    Natural soil > Natural soil + 2%lime > Natural soil + 2%lime+2% NaCl > Natural soil + 4%lime+3% NaCl > Natural soil + 4%lime.

    From the above statement is concluded that the stabilized soil exhibits different suction- swell relation if its initial water content at liquid state. The suction swell relationship of stabilized soil is same if it is initially in plastic state and solid state.

    VI. REFERENCE

    1. Anand Puppala P.,Koonnamas Puthutaecha and sai vanapalli K.(2006) Soil Water Charateristics Curves of stabilized Expansive soils, Journal ofGeotechnical and Geoenviromental Engineering, Vol.132, pp.736-751.

    2. Anand Puppala, Aravind Pedarla, Laureano R.Hoyos,ClaudiaZapata,Tejo V.Bheemasetti (2016) A semi empirical swell prediction model formulated from clay minerology and unsaturated soil properties, An International Journal of Engineering Geology,vol.200,pp.114-121.

    3. Delwyn Fredlund G., Daicho Sheng and Jidong Zhao (2011) Estimation of soil suction from the soil-water characteristic curve, Journal of Canada Geotechnical, Vol. 48, pp. 186-198.

    4. ErdalCokca and Altay Birand (2012) Suction-Swelling Relations, American Society of Civil Engineers, Vol.8, pp.379- 392.

    5. Ikeagwuani Chijioke Christopher, Nwonu Donald Chimbi (2018)Emerging trends in expansive soil stabilization, Journal of Rock Mechanics and Geotechnical Engineering.

    6. Janardhan Tahasildar and B.Hanumanatha Rao (2016) Determination of Swelling characteristics using soil water characteristics curve parameter, Indian Geotecnical Journal

    7. Gueddouda M K., Gaul I., Lamara M., Smaida A. and Mekarta K (2011) Chemical stabilization of expansive clays from Algeria, Journal of Global Reserahes in Engineering. Vol.11, No.5, pp.36-51.

    8. Mohamed Khemissa and Abdelkrim Mahamedi (2014) Cement and lime mixture stabilization of an expansive overconsolidated clay, An International journal on the Application and Technology of Clays and Clay Minerals.

    9. Tyagaraj T., Sudhakar Rao M., Sai Suresh P. and Salini U. (2012) Laboratory studies on stabilization of an expansive soil by lime precipitation technique, Journal of, material in Civil engineering, Vol.24, No.8, pp.899-1561.

    10. Susan Rafalko D., Thomas Brandon L., George Filz M. and James Mitchell K. (2008) Rapid Chemical Stabilization of Soft Clay Soils, Journal of Transportation Research Board of the National Academies, Washington, Vol.2026, pp.39-46.

    11. Thamer H Al-Yaquob, Jafarali Parol, Dobroslav Znidarcic (2017) Experimental investigation of volume change behavior of swelling soil, An International journal on the Application and Technology of Clays and Clay Minerals, vol.137, pp.22-29.

    12. Tamadher Abood T., Anuar Bin Kasa and Zamri Bin Chik (2007) Stabilization of silty clay soil using chloride compounds, Journal of Engineering Science and Technology, Vol. 2, No. 1, pp.102-110

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