soil improvement by thermal treatment

1. Soil Improvement by
Temperature Control
Aodai A. Ismail
Engineering college - Tikrit university

2. Methods based on temperature control
are classified as:
1. Heat treatment method 2. Ground freezing method

3. Heating and Engineering Properties of Soil
• Kerstetx (1949), Carter (1951) and Scott (1961)
investigated the specific heat, latent heat and
thermal conductivity of soils.
• Winterkorn (1947), Rollins et al. (1954) and
Hutcheon (1958) studied the movement of moisture
under a thermal gradient.
• Eichler and Kazda (1965) studied temperature
gradients in soils using a theoretical analysis and
laboratory measurements.
• DuBose (1953) and You et aI (1961) reported that
optimum water content increaued while dry
density decreased with decreased temperature and
both liquid limits and plastic limits decreased with
increasing temperature.
• The variations in volume, pore pressure, soil
strength, shearing resistance, creep behavior,
swelling and effective stress with temperature
variations had been studied.
Compressive Strength of three soils as a function
of Temp. (After Sayles, 1966)

4. Temperature influence on soil properties.
 Heating would cause permanent changes in the soil
making the soil harder as well as durable. Treatment
at 300OC to over 10000Cwould..
1. Decrease in compressibility
2. Increase in cohesion
3. Increase in Internal friction angle
4. Increase in modulus of elasticity
 It has been experimented and found that heat was
able to change an expansive clay into an essentially
none- expansive material.
 Boreholes of 0.15-0.20 m diameter, stabilized zones
of 1.3-2.5 m after treatment for 10 days.

5. Heating method
 Temperature control methods based on :
 Thermal conductivity of the soil
 Heat capacity of the soil
 Heat of fusion
 Heat of vaporization

6. Thermal conductivity of the soil
 The amount of heating passing through
a unit cross sectional area of soil under
a unit temperature gradient.
KT = q / (A (T2 –T1) /L)
 Thermal conductivity increases with
water content and dry density

7. Heat capacity of the soil
 The amount of the heat required to
raise the temperature by 1°C or 1°K.
Q = CMΔT
 Heat capacity of Water Cw = 4.2 kj/kg°C

8. Latent heat of fusion (LF)
 The change in thermal energy when
water freeze or ice melt.
 To melt a mass of 1 cubic meter f ice ..
Q = LF M
 For 1 cubic meter of soil with water
content LF s = pd w LF

9. Heat of vaporization of water
 The energy required to boil water
from liquid state to gaseous state.
 Heat of vaporization of water
LV = 2026 MJ/Kg

10. Heat treatment of soils
 Used with clay soils.
 Give pronounced changes in
engineering properties at 400 °C
 Energy extensive

11. Applications of Thermal Stabilization of Soil
The usage of heating for thermal stabilization of soil is mainly employed in U.K, U.S.S.R
and eastern Europe… It is used in:
 Landslide stabilization
 Improving soil undergoing collapsing
 Mat foundation construction
 Forming vitrified piles in place
 Reduction lateral stresses on retaining walls

12. Heating soil in situ
 Ground surface
 Heating through boreholes
 Thermal piles
 Thermally stabilized building block

13. Heating soil in situ
 Combustion to electrical
 microwave drying
 laser beam

14. Thanks….
for your
attention