الفهرس 
Research ObjectivesOnly 14 pages are availabe for public view
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Abstract
The calcareous soil is extensively found near the coastal areas of Egypt, such as the
northern coast on the Mediterranean Sea. Due to its structural weakness, its performance
is usually connected with different interdependent problems, such as crushability,
compressibility and chemical dissolving. Furthermore, the aforementioned problems
affect development of projects; such as soil replacement, excavation works for water
channels, roads and railways. In earth works applications, the calcareous soil is unable
to respond effectively to the imposed stresses and has become a dominant factor
responsible for structure damages. Therefore, calcareous soils with such conditions need
stabilization to be suitable as a construction material. Therefore, the main goal of the
present study is to explore the feasibility of applying a treatment approach in the
improvement of calcareous soils toward mixing the calcareous soil with Kaolinite clay.
Additionally, the effects of salinity on geotechnical properties of the carbonate soil were
investigated through investigating the effect of different types of water (e.g. fresh and
sea water) used in compacting the soil.
An extensive experimental program was performed. Whereas, the laboratory tests
included chemical analysis (to evaluate some predominant chemical characteristics, e.g.
carbonate content and The lower the power of hydrogen “pH”); mechanical tests on
compacted material (to reveal the geomechanical behavior, e.g. shear parameters by
triaxial test) after different soaking periods in fresh water (0, 4 and 90 days), and
compaction tests, in addition to the California Bearing Ratio-(CBR) and hence, some of
geotechnical aspects (modulus of subgrade reaction “Ks” and modulus of elasticity “E”)
estimated from California Bearing Ratio-(CBR) are investigated . Additionally, physical
tests (to ascertain the soil physical properties, e.g. particles gradation). To explore the
crushability analyses, sieve and hydrometer analyses were applied on three different
states of loading and soaking in fresh water. Thus, the first state is “natural state
whether without soaking in fresh water or without applying compaction test” (NS); the
second state is “after applying compaction with fresh water test only” (CS); and the
third state is “after applying both of soaking in fresh water for three months and
compaction test” (SCS). These tests are complemented by permeability test to
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investigate the effect of Kaolinite added on the coefficient of permeability. Whereas, it
is important in evaluating the relative influences of the treated calcareous soil
formations on the stability and serviceability of earth slopes of excavated water
channels.
The results of the experimental study have shown that a gradual increase in maximum
dry density (ɤ dry max) of Kaolinite - carbonate sand mixtures was shown by increasing
the Kaolinite content “from 3% to 9%”, which the increase ratio becomes more
significant in the state of sea water. Accordingly, a gradual decrease in optimum
moisture content (O.M.C) of Kaolinite - carbonate sand mixtures was shown due to the
lubrication phenomena, wherein the planar-shaped clay minerals are helping the sand
grains to slip against each other and also, Kaolinite exhibits low quantities required for
both of absorption and adsorption properties, which are due to the low surface charge on
the particle. Moreover, The CBR values of the all treated mixtures, whether in the
unsoaked state or after soaking in fresh water whether for four days or three months, are
higher than it in the pure carbonate sand. In short term of soaking in fresh water “after
four days soaking”. Both of the modulus of subgrade reaction “Ks” and the modulus of
elasticity “E” take the same trend of California Bearing Ratio-(CBR) because they
proportional directly with it.
Cohesion strength of Kaolinite - carbonate sand mixtures compacted with sea water is
generally lower than it in the same mixtures but compacted with fresh water.
Furthermore, friction angle of Kaolinite - carbonate sand mixtures compacted with sea
water is generally higher than it in Kaolinite - carbonate sand mixtures compacted with
fresh water. However, in long term of soaking in fresh water “after ninety days
soaking”, cohesion strength of Kaolinite - carbonate sand mixtures compacted with sea
water is generally higher than it in the same mixtures but compacted with fresh water.
On the other hand, a gradual decrease in the permeability was shown by increasing the
Kaolinite content “from 3% to 9%” which the decrease ratio became more significant
when the Kaolinite content is equal to three percent. Particle breakage is reduced by
increasing the Kaolinite content to the calcareous sand up to 9%.