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4. PROPOSED REMEDIES FOR GYPSEOUS SOILS
The invenitable geotechnical problems associated with the aban-
dance of gypseous soils in Iraq create real challanging issues.
Based on that proposals were made for treatment of soils focus-
sing on controlling the settlement and reducing the coefficient of
permeability or preventing any contact of water between the
foundation soil and any source of water. All the proposed treat-
ments are based on elemt tests and not verified by field applica-
tions
4.1.
Chemical treatment
The treatment materials proposed are basically cement, lime and
petroleuum products
4.1.1.
Treatment with cement
(Khattab1986) reported that sulphate resisting cement improved
the unconfined compression strength of granular gypsified soil,
but a substaintial amount of reduction in strength and stiffness
upon immersion in water.
4.1.2.
Treatment with lime
Al-Obaidy 1992 and Al-Zory 1993 showed that mixing 5 -7 %
lime with gypsous soil of 43 % gypsum content exhibited an in-
crease in strength and high resistance to leaching. It is reported
that the soil became practically impermeabile after 28 days cur-
ing.
4.1.3.
Treatment with petroleum products
Various types of petroleum products such as kerosene, automo-
bile oil ,fuel oil and bitumenous materials such as S-125 and R-
250 were proposed as improvement agents for gypseous soils.
(Saleam 1988) found that treating soil of gypsum content be-
tween 40-50 % with kerosene caused a decrease in compressi-
bility and permeability by delaying the removal of gypsum.(Al-
Aqaby 2001) observed a reduction in cohesion of soil of gypsum
content between 30 -67 % upon immersion in water or kerosene.
The angle of internal friction was reduced by 6 degrees upon
soaking in kerosene.
(Al-Kaisi 1997) found that 4 % automobile oil caused a re-
duction in the coefficient of permeability by not less than ten
folds.
(Al–Hassany 2001)perfromed consolidation tests on two
samples of gypsum content 26 % and 51% treated with fuel oil.
The fuel oil tends to to fill the pores of soil and prevent water
perculation and hence reduce the permeability. The presence of
fuel oil also reduced the copmressibility and collapsibility.
Bitumenous materials S-125 and R-250,emulsified asphalt,
Cut-Back MC-30 were used by (Al-Morshedy 2001 and many
others). Gypseous soils treated with one of the above materials
showed reduction in coefficient of permability as well as com-
pressibility and collapsibility.
4.2.
Physical treatment
(Al-Khafaji 1997) developed simple and quick equations for es-
timating the optimum water content and maximum dry unit
weight to control field compaction of soils with gupsum content
ranging between 0.5 -50 %.
5. CONCLUSIONS
Inspite of the abandant data collected concerning the
the geotechnical properties of gypsefeous soils and the attempts
to investigate and understand the behaviour of gypseous soils
under different stresses and environmental conditions.The
challanges still exist due to the scarceyt and complexity of such
natural material. No real firm solution or a general improvement
technique can be proposed. It is advised that geotechnical engi-
neers must investigate each case seperatly depending on the type
of structure, characteristics of site, environmental conditions
coupled with the engineering judgement of the consultant.
6. REFERENCES
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of
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