Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Gypseous soil


Behavior of Piled Raft Foundation Model Embedded within a Gypseous Soil Before and after Soaking

N.A. Ab-dullah; M.R. Mahmood; H.H. Baqir

Engineering and Technology Journal, 2017, Volume 35, Issue 5, Pages 445-455

The paper explain an experimental study to show piled raft system behavior when embedded within gypseous soil in three different stats (dry, socking for 1 day and placing a bearing layer of dense sand below the gypseous soil when socking for 1 day). A small-scale “prototype” model of steel box with dimension of (60cm length x 60cm width x 75cm heights) was used for carried out the model tests. Two different lengths of reinforced concrete pile models (40cm and 45cm) of 2.0cm dia. were used to keep the same imbedded length ratio during testing piled raft and piles only. Three different configurations of pile groups (single, three and six piles) were tested in the laboratory in two ways, first; the raft does not contact with the soil and the second; the raft is in contact with the soil. In dry state, the gypseous soil showed a very high carrying capacity with reduction in settlement. Piled raft foundations show an efficient in dry state, where the load carrying capacity increased and the settlement decreased. The improvement ratios in the load carrying capacity were about 16% for single piled raft and 39% for group of three-piled raft, while settlement reduction ratios were about 18% for single piled raft and 45% for group of six-piled raft. When the gypseous soil socked with water for 1 day, the ultimate bearing capacity of foundations is generally reduced by about (69%-83%) compared with dry state for all model configurations. The improvement ratios in ultimate bearing capacity due to using piled raft in soaking state was about (11% -50%) whilst the reduction settlement ratios was about (16% -44%).

Study Shear Strength Characteristics of Gypseous Sandy Soil Using Additives

Hussein H. Karim; T. Schanz; Maha H. Nasif

Engineering and Technology Journal, 2013, Volume 31, Issue 8, Pages 1431-1446

The present study investigated the possibility of enhancing collapsible gypseous soil of Al-Qarma site (with relatively high gypsum content around 50%), which is located in Al-Anbar Governorate, using kaolinite and bentonite as additives. The essential idea is concentrated in mixing these additives with natural soil using different percentages (5, 10, 15 and 20% by soil dry weight) to investigate soil shear strength enhancement. The effect of such additives on soil shear strength parameters, cohesion (C) and angle of internal friction (Φ), and their behavior were studied using direct shear test. The results showed that shear strength parameters of soil sometimes increased and then decreased with increasing additives. Generally, higher shear strength parameters have been obtained from bentonite mixed soil than that of kaolinite mixed soil for the same percentages of additives. It was concluded that bentonite was much more effective in increasing C and reducing Φ than kaolinite. While, kaolinite was much more effective in reducing C than bentonite. It was also concluded that gypseous soil shear strength is improved using such additives (with only 5% kaolinite or with only 20% bentonite) which provide cohesion strength to the soil mass and also acts as a binder agent material.

Improving Collapsibility and Compressibility of Gypseous Sandy Soil Using Bentonite and Kaolinite

Hussein H. Karim; T. Schanz; Maha H. Nasif

Engineering and Technology Journal, 2012, Volume 30, Issue 18, Pages 3141-3153

The sandy soil which covers the surface layer for the investigated area consists of
high gypsum content (50%). The soil was found to be a “collapsible” soil. Thus
bentonite and kaolinite have been used as an improving agents for such soil. The
essential idea of this study represents an investigation of the possibility of using
these materials as additives with different percents (5%, 10%, 15%, and 20%) to
enhance these soils. A testing program was conducted on 9 models of untreated and
treated gypseous soil specimens to study the behavior of such mixes as well as their
effects on physical properties, collapsibility and compressibility characteristics. It
was concluded that a significant reduction in collapsibility reaching 80 to 82 % for
the 10 percent mixed kaolinite and bentonite respectively. Lowest compression
index (Cc) and recompression index (Cr) have been obtained using the same
percentages of mixed additives. Generally, best improving results have been
obtained using bentonite additive (specially the ratio 10%) for its finer grains than
those of kaolinite.

Improvement of Gypseous Soil by Clinker Additive

Mohammed A. Mahmoud Al-Neami

Engineering and Technology Journal, 2010, Volume 28, Issue 19, Pages 5822-5832

In this paper, mechanical properties were studied for gypseous soil
brought up from Al-Axandria region, Babylon Governorate. Gypsum
content is equal to (40%). Many tests were employed on disturbed and
undisturbed samples collected at depth (1-1.5) m.
Clinker material used in cement was chosen as additive to study its
effect on improvement of gypseous soil by using three crushed percentages
(2, 4, & 6) %.
The results marked that (4) % clinker decreases the collapsibility
sharply; more than 73 % of improvement in collapse potential has been
achieved at this percent of clinker. Also, compressibility decreases with
increase of clinker percentage. The compression index decreased from 0.17
to 0.1 (29 – 41% reduction with increases of clinker).
The shear strength parameters of the treated soil determined by
direct shear test are more those than for natural soils due to increase in the
cohesion and decrease in angle of internal friction.

Artificial Neural Networks Analysis of Treatment Process of Gypseous Soils

Mohammad M. Al-Ani; Mohammad Y. Fattah; Mahmoud T. A. Al-Lamy

Engineering and Technology Journal, 2009, Volume 27, Issue 9, Pages 1811-1832

Artificial Neural Networks (ANNs) are used to relate the properties of gypseous soils
and evaluate the values of compression of soils under different conditions. Therefore, onelayer
perception training using back propagation algorithm is used to assess the validity of
application of ANNs for modelling the settlement ratio for wetting process, (S/B)w, and the
settlement ratio for soaking process, (S/B)s.
It was found that ANNs have the ability to predict the compression of gypseous soil
due to soaking, washing process with high degree of accuracy. Also, performance of ANNs
showed that one hidden layer with one hidden nodes is practically enough for the neural
network analysis.
The sensitivity analysis indicates that the viscosity and specific gravity have the
most significant effect on the predicated settlement ratio and the density of injection material
and void ratio have moderate impact on the settlement ratio. The results also show that the
initial gypsum content, stress and time have the smallest impact on settlement ratio.
It was concluded that the artificial neural networks (ANNs) have the ability to
predict the settlement ratio for wetting process (S/B)w, and settlement ratio for soaking
process (S/B)s of gypseous soil with high degree of accuracy. The equations obtained using
(ANNs) for (S/B)w, and (S/B)s showed excellent correlation with experimental results where
the coefficients of correlation are (0.9541) and (0.991), respectively.

Long -Term Deformation Of Some Gypseous Soils

Mohammed Y. Fattah; Yousif J. al-Shakarchi

Engineering and Technology Journal, 2008, Volume 26, Issue 12, Pages 1461-1483

Time-dependent deformation and stress relaxation in soils are important in a variety of
geotechnical problems where long-term behavior is of concern.
Previous studies on soils showed that the magnitude of delayed compression
(creep) is controlled by compressibility and soil sensitivity in addition to
preconsolidation.
In this paper, the time-dependent behavior of gypseous soils is investigated. The
soils used in this study were brought from three locations at Al-Tar region west of Al-
Najaf city in Iraq. These soils had gypsum content of (66%, 44% and 14.8%). The
mineralogical and chemical properties of the soils were determined.
Two series of tests were performed. In the first, collapsibility characteristics were
investigated for a long period (60 days) by conducting single and double oedometer
tests. In the second series, the effect of relative density on collapse with time was
investigated. The samples were compacted to 40%, 50% and 60% relative density and
then tested. The results of collapse tests showed that the relationship between the
strain and logarithm of effective stress has two vertical lines. The first one represents
the collapse settlement taking place within 24 hours, while the second one represents
the long-term collapse. The collapse potential in both single and double oedometer
tests increases when the gypsum content increases from (14.8%) to (66%) and when
the initial void ratio increases.
The results of double oedometer tests showed that the relationship between the
collapse potential and logarithm of time, for samples loaded to 800 kPa for 60 days,
consist of three distinct segments. The first segment is represented by a curve concave
downward in which the compressibility gradually increases. The second segment is a
straight line with a higher increase in the strain. The third segment which refers to
creep collapse depends on the gypsum content. Gypseous soil with low gypsum
content (14.8%) exhibited significant decrease (5.21% at 24 hours to 7.16% at 60 days)
in collapse potential with time.

CONTRIBUTION OF LIQUID ASPHALT IN SHEAR STRENGTH AND REBOUND CONSOLIDATION BEHAVIOUR OF GYPSEOUS SOIL

SAAD I. SARSAM; SALAH W. IBRAHIM

Engineering and Technology Journal, 2008, Volume 26, Issue 4, Pages 484-495

Abstract
This paper deals with the effect of stabilizing gypseous soil using two liquid Asphalt
types (cutback and emulsion) on its behavior in shear strength and rebound
consolidation.
Soil-Asphalt specimens had been constructed using various percentages of both liquid
Asphalt types. One group of such specimens were tested in the direct shear box
apparatus to determine the effect of liquid Asphalt on shear strength, cohesion and
angle of internal friction using the unconsolidated un drained test.
Another group of the specimens were subjected to one dimensional confined
compression test using both dry and saturated testing conditions in the consolidation
apparatus.
The effect of liquid Asphalt on the behavior of mixes in consolidation and rebound
consolidation was studied.
It was concluded that gypseous soil is usually stiff in the dry condition, but it is weak
and had a collapsible behavior when saturated. The addition of liquid Asphalt provides
cohesion strength to the soil mass and also acts as a waterproof agent. It creates a type
of elastic properties and reduces the total strain.