Improvement of Soft Soil Using Linear Distributed Floating Stone Columns under Foundation Subjected to Static and Cyclic Loading

A stone column is one of the soil improvement methods that are mainly used for improving the geotechnical behavior of soft soils. For deep improvement of soft soil, the floating stone columns are considered the best and effective economically which provide lateral confinement and drainage and longitudinal skin friction. In this study, six tests were carried out on the natural soft soil of undrained shear strength of 5.5 kPa improved by single and two linear distributed floating stone columns. The stone column dimensions are 30 mm in diameter and 180 mm in length and the stone column material is sand of high internal friction angle of 48°. The natural and improved soil samples are tested under isolated raft foundation of dimensions 120×120 mm subjected to vertical static and cyclic loading of frequency 2Hz and continued for 50 seconds. The results showed a significant improvement in soil bearing capacity when reinforced with stone columns despite the small area replacement ratio, where the bearing capacity of improved soil increased by 120 to 145%. The compressibility of improved soil decreased by 57 to 86% in comparison with that of natural soft soil. Also, the floating stone columns reduced the porewater pressure, where the stone columns considered efficient in providing short drainage pathways. This can be one of the reasons why soil reinforced with floating stone columns hold higher cyclic and static stresses regardless the end bearing of stone columns

Improvement of Geotechnical Properties of Cohesive Soil Using Crushed Concrete

Some natural resources such as gravel are not renewable, therefore, it is necessary to reduce the use of such resources and replace them with other recycled, economic, and environmentally friendly materials. Recycled crushed concrete aggregates demolished from old buildings and blocks of waste concrete can be used to replace the natural aggregates. The present study focused on using recycled crushed concrete in improvement the chemical and geotechnical properties of soft soil having undrained shear strength of 6.78 kPa. The soft soil samples were mixed with 5, 10, and 15% of crushed concrete. The blocks of waste concrete are grinded by mills to get crushed concrete which passing sieve no. 4. Such aggregates are lighter than natural aggregates and provide a good deformation modulus when mixed with soil. In Iraq, there are hundred thousand tons of concrete blocks used as fences and now considered wastes after removing these security fences, so it’s important to interest from recycling of such materials to be used in the improvement wide region of soft soils in Iraq. The results of tests showed increasing the undrained shear strength of soft soil by 175-193.5% and reduced the compressibility of soft by 25-31% measured in terms of compression index

Numerical Evaluation of Foundation of Digester Tank of Sewage Treatment Plant

In the present study the foundation of digester tank, main part of sewage treatment plant, is reanalyzed analytically and numerically to check the adequacy of such foundation to support superstructure loading. The foundation of digester tank consists of raft foundation and bored piles. The diameter of raft is 33 m and thickness of 1 m, while the piles are bored type of diameter 0.6 m and length 15 m. After testing eleven working piles, it is found that three piles cannot support a load of 1.5 times the working load (1305 kN) safely or in other words the factor of safety of these failed piles is less than 1.5. The results of filed pile tests are reanalyzed using two well-known methods, Davisson’s method and Brinch-Hansen method to check the ultimate carrying capacity of tested piles. Also, this paper includes analysis of previous soil investigation report and conducting additional soil investigation by drilling three boreholes to secure the soil parameters used in the analytical and numerical analysis of digester tank foundation. SAFE 12 software is used to analysis the foundation of structure as piled-raft instead of pile group to interest from the interaction between soil and raft foundation. The results of analysis showed that the piles failed in the tests can support its share of the superstructure load by a factor of safety 1.8 and the piles success in the field tests can support its share of the superstructure load by a factor of safety not less than 2.86. Also, the settlement under structure will be less than 100 mm, where using piled-raft analysis reduces the settlement to be within allowable limits

Simulation the Behavior of Passive Rigid Pile in Sandy Soil

This research studied the behavior of a rigid pile driven into sandy soil and subjected to soil movement. The behavior of the pile was simulated in two cases: loaded and unloaded. The modeled piles were made of aluminum and had a diameter (D) of 10 mm. Embankment loads were applied at three different distances from the face of the pile (2.5, 5, and 10) D. Strain gauges were fixed at four points along the pile shaft using a half-bridge configuration to measure the strains resulted from the lateral movement of the soil. The results obtained from the physical model were the lateral and vertical movements at the surface of the soil and the bending strain along the pile shaft. These results were analyzed numerically to calculate the bending moment, pile rotation, pile deflection, shear force, and soil reaction profiles. Some of these results were measured experimentally and others were calculated theoretically based on the measured strains. The maximum deflection of the axially loaded pile was more than that in the unloaded pile by 26%, 108%, and 159%, with the embankment at distances (2.5, 5, and 10) D, respectively. The rigid pile provided more resistance to the pressure generated from the soil movement.

Investigation of the Impacts of Fuel Oil on the Geotechnical Properties of Cohesive Soil

The present study investigates the impacts of fuel oil (MFO) on the chemical, physical and mechanical properties of cohesive soil. The contaminant is fuel oil disposed as byproduct from the fuel feeding the electricity power plant at the campus of University of Baghdad in Baghdad/Iraq. The soil sample are obtained from the same site of electricity plant and classified according to unified soil classification system (USCS) as silty clay of low plasticity (CL). The soil samples are artificially contaminated with two percentages of fuel oil, 10 and 20 % in relative to the dry weight of soil. The soil samples were mixed by hands with fuel oil and left for 4 days to allow chemical reactions between soil particles and contaminant. A series of laboratory tests are conducted on both intact and artificially contaminated soil samples to measure the effects of fuel oil on the chemical, physical and mechanical properties of soil samples. The results of tests showed that the fuel oil has significant impacts on the mechanical properties of soil and slight effects on the chemical and physical properties of soil. Increasing the percentage of contaminant causes a slight decrease in the liquid limit and particle size distribution, on the other hand it causes a considerable decrease in the consolidation and shear strength parameters. The results of direct shear tests showed decreasing the cohesion of soil by 44 and 66 %, but the angle of internal friction decreased by 18 and 33 % for soil samples contaminated with 10 % and 20 % of fuel oil respectively.The present study investigates the impacts of fuel oil (MFO) on the chemical, physical and mechanical properties of cohesive soil. The contaminant is fuel oil disposed as byproduct from the fuel feeding the electricity power plant at the campus of University of Baghdad in Baghdad/Iraq. The soil sample are obtained from the same site of electricity plant and classified according to unified soil classification system (USCS) as silty clay of low plasticity (CL). The soil samples are artificially contaminated with two percentages of fuel oil, 10 and 20% in relative to the dry weight of soil. The soil samples were mixed by hands with fuel oil and left for 4 days to allow chemical reactions between soil particles and contaminant. A series of laboratory tests are conducted on both intact and artificially contaminated soil samples to measure the effects of fuel oil on the chemical, physical and mechanical properties of soil samples. The results of tests showed that the fuel oil has significant impacts on the mechanical properties of soil and slight effects on the chemical and physical properties of soil. Increasing the percentage of contaminant causes a slight decrease in the liquid limit and particle size distribution, on the other hand it causes a considerable decrease in the consolidation and shear strength parameters. The results of direct shear tests showed decreasing the cohesion of soil by 44 and 67%, but the angle of internal friction decreased by 20 and 32% for soil samples contaminated with 10% and 20% of fuel oil respectively

Remediation of clay soil contaminated with lead nitrate using washing-enhanced electrokinetic technique

The remediation of clay soil contaminated with lead nitrate has been investigated in details by using the electrokinetic technique enhanced by using purging solutions, mid compartment, and washing technique. The intact soil samples are obtained from Al-Ahdab oil field located in the southeast of Iraq. The soil samples are contaminated synthetically with two different percentages of lead nitrate (6.67 and 20g/kg) and kept for 30 days. The mid compartment is used to reduce the existing paths of contaminants from the soil. Purging solutions in the anode, mid, and cathode compartments are used to control the pH value, while the activated carbon is used to prevent the reverse electroosmotic flow from cathode to anode. The main results of electrokinetic experiments, such as variations of electrical current and pH with time, and the accumulated volume of electroosmotic flow are presented and discussed. It is shown that increasing of the concentration of lead causes increase of the electrical current generated during the remediation process. As a consequence, the intensity of chemical reactions occurring in the anode, mid, and cathode compartments are also increased. The removal efficiency of lead from soil samples ranged between 12.4 and 21 %. The washing process is found beneficial in reducing the period of remediation but does not affect the removal efficiency

Studying the Effects of Contamination on Soil Properties Using Remote Sensing

The problem of soil contamination is increased recently due to increasing the industrial wastes such as petroleum hydrocarbon, organic solvents, and heavy metals as well as maximizing the use of agricultural fertilizers. During this period, wide development of data collection methods, using remote sensing techniques in the field of soil and environment applications appear and state the suitable technique for remediation. This study deals with the application of remote sensing techniques in geoenvironmental engineering through a field spectral reflectance measurements at nine spots of naturally hydrocarbons contaminated soil in Al-Daura Refinery Company site which is located to the south west of Baghdad using radiometer device to get standard curves of wavelengths and analyzing the satellite imagery of the site to get the spectral reflectance curves using GIS technique and EARDAS software package which help in producing thematic maps for the spatial distribution and concentration of contaminants. The comparison of results showed a good correlation between the spectral reflectance from field measurements and the spectral reflectance obtained from analyzing the satellite imagery. The study also improves a method to save cost, time, efforts and staff

GEOTECHNICAL PROPERTIES OF SANDY SOIL CONTAMINATED WITH INDUSTRIAL WASTEWATER

The present work is devoted for studying the geotechnical and chemical properties of intact and contaminated sandy soil samples. The soil samples were obtained from Al-Kufa city that is located in the south-west of Iraq. The contaminant is a by-product industrial wastewater disposed from the refinery that supplies fuel for the thermal electricity power plant. The intact sandy soil samples were contaminated in the laboratory with four percentages of 10, 20, 40 and 100% of the weight of distilled water used in the soaking process and the soaking process continued for thirty days. The results of tests showed a slight increase in both liquid limit and particle size and a significant increase in the optimum moisture content with increasing the percentages of the contaminant. However, with increasing the percentages of the contaminant, there was a slight decrease in the specific gravity and maximum dry unit weight. In addition, there was a considerable decrease in the angle of internal friction and the coefficient of permeability. The angle of internal friction of contaminated soil samples decreased by 18 to 26% with increasing the contaminant percentage from 10 to 100%. The cohesion of soil samples decreased by 7 to 33% with increasing the contaminant percentage, this conclusion is limited to the soil samples contaminated with 10, 20 and 40%, but the cohesion of soil sample contaminated with 100 % of industrial wastewater increased by 7%

Experimental Pullout Capacity of Screw Piles in Dry Gypseous Soil

Screw piles are widely used in supporting structures subjected to pullout forces, such as power towers and offshore structures, and this research investigates their performance in gypseous soil of medium relative density. The bearing capacity and displacement of a single screw pile model inserted in gypseous soil with various diameters (D = 20, 30, and 40) mm are examined in this study. The soil used in the testing had a gypsum content of 40% and the bedding soil had a relative density of 40%. To simulate the pullout testing in the lab, a physical model was manufactured with specific dimensions. Three steel screw piles with helix diameters of 20, 30, and 40 mm are used, with a total length of 500 mm. The helix is continuous over the pile's embedded depth of 400 mm. The results of tests revealed that decreasing the length to diameter (H/D) ratio resulted in a higher pullout capacity of screw piles and a lower corresponding displacement