Theses supervised by Prof. Dr. Ali Fırat Çabalar
13 theses · Gaziantep University, Hasan Kalyoncu University
Laboratory evaluation of the geotechnical characteristics of two waste materials: Stone powder blends with brick dust
Rapidly increasing urbanization and industrialization are results of the demand generated by the growing human population, and hence leads to a large amount of waste materials. Recycling of waste materials have become an important issue worldwide, due to reasons such as limited natural resources, increasing harmful greenhouse gas emissions, increasing landfill and disposal costs. Based on this, the geotechnical characteristics of the two major waste materials, stone powder (SP) and brick dust (BD), were investigated. In this study, geotechnical properties of mixtures obtained by adding 5%, 10%, 20%, 30%, 40% and 50% (by total dry weight of mixture) brick dust to waste stone powder were examined. This study was conducted with a comprehensive test program. The addition of brick dust has a dramatically reducing effect on compression index (cc) and swelling index (cs). It was observed that the particle size of the brick used in the California Bearing Ratio (CBR) tests have a critical role on the experiment results. The results of the direct shear test showed that cohesion is the main parameter that increases the shear strength. In general, the maximum dry density decreased with the addition of brick dust, while the optimum moisture content increased. SP blend with addition of 5% BD had the highest unconfined compressive strength value while SP blend with addition of 30% BD had the lowest value. Lastly, the use of waste materials has significantly reduced the cost of base course construction compared to traditional natural aggregate.
Effect of the waste glass on engineering properties of a bentonite
This thesis presents some engineering properties of bentonite-glass mixtures. The waste glass (WG) with two different sizes (Fine WG-FWG and Coarse WG-CWG) was mixed with bentonite at ratios of 0%, 10%, 20%, 30%, and 40%. A series of laboratory tests including compaction, fall-cone, consolidation, direct shear, crumb, double hydrometer, viscosity, unconfined compression (UC), and bender element (BE) tests were performed on the specimens. Testing results showed that WG additions increased the maximum dry unit weight (γdmax) of bentonite. Consolidation testing results showed decrement in void ratio with WG additions. Maximum unconfined compressive strength (qu) value of the specimens was obtained at bentonite-30% CWG mixture. Angle of internal friction of bentonite increased until 30% WG content and then decreased. The dynamic viscosity and dispersion potential of bentonite decreased with WG additions. Shear wave velocity (vs) and compressional wave velocity (vp) values of bentonite increased with WG additions. The vp to vs ratio of the specimens varied between 2.0 and 2.5, thus, yielding Poisson's ratios (υ) from 0.33 to 0.40. Effect of a medium plastic silt (ML) at 0%, 10%, 20%, 30%, 40%, and 50% mixture ratios on the triaxial behavior of a sand were also presented. The undrained triaxial tests (CU) tests showed that addition of ML decreased the deviatoric stress of Narlı sand. Furthermore, mixtures with the ML showed more contractive behaviour.
Filter design for a dispersive soil stabilized by various additives
This thesis presents a series of empirical studies to define dispersibility of a base soil and its stabilization to prevent dispersibility to be able to be used as a filter. A low plastic clay (CL) with intermediate dispersibility was used as a base soil during the experimental studies. An environmentally-friendly biopolymer xanthan gum (XG) and bentonite were separately added to the base soil with the ratios of 0.5, 1, 2, 3 % by dry weight. These specimens were tested at the end of 0, 7, 14, 28 days in the pinhole, crumb and double hydrometer tests. Furthermore, narli sand (NS) and crushed sand stone (CSS) were also used in the permeability tests in order to understand the effect of different particle shape on the filter design. XG and tire waste powder (TWP) at the contents of 0%, 1%, 3% by dry weight were separately added to the NS and CSS samples in order to decrease the permeability values. The specimens were tested at the end of 0, 7, 28, 56 day curing time using the constant head permeability test. Eventually, CL type base soil with intermediate dispersibility was stabilized by using the XG. It was also found that XG and TWP additives decreased the permeability values of the sand samples substantially. XG was found to be strongly effective on the results of both testing series
Improving geotechnical properties of silty sand by using xanthan gum and waste brick
This study presents change the engineering properties of silty sand altered by the addition of xanthan gum and brick which is a waste material. The samples were prepared by mixing silty sand at various proportions by dry weight of xanthan gum biopolymer (0, 0.5, 1, 3%) and dry weight of waste brick (%10), and then tested at the end of different curing times (0, 7, 28, and 56 days). To understand the effect of waste material and biopolymer on silty sand, a series of laboratory tests carried out such as specific gravity test, Atterberg limit test, fall cone test, vane shear test, compaction test, falling head permeability test, California bearing ratio (CBR), oedometer test (consolidation), unconfined compression test (UCS). According to the results of all experiments it was determined that the best efficiency would be obtained when 0.5% XG was added to a mixture of silty sand and 10% waste brick for soil improvement.
Geotechnical investigation of reclaimed asphalt pavement and xanthan gum treated silty sand
This thesis conducts a comprehensive investigation into the impact of recycled waste construction material and an eco-friendly biopolymer on the stabilization of local soil. The laboratory-based experimental program focused on silty sand (SM) soil treated with 10% reclaimed asphalt pavement (RAP) and Xanthan gum (XG) concentrations (0%, 0.5%, 1%, and 3% by total dry weight) across curing periods of 0, 7, 28, and 56 days. Results indicate distinct effects on soil properties: RAP reduced liquid limit, plastic limit, and optimum water content (OMC) while increasing maximum dry density (MDD). Conversely, XG elevated these parameters and decreased MDD. In 7-day cured specimens, the inclusion of 10% reclaimed asphalt pavement (RAP) significantly enhanced compressive strength. The initial strength of 2983 kPa for the clean soil rose to 3464.9 kPa with the addition of RAP. Incremental changes were observed at rates of 0.5%, 1%, and 3% XG, resulting in compressive strengths of 4754.9 kPa, 6189.6 kPa, and 7999.1 kPa, respectively. Curing effects on strength were partially positive, peaking at 28 days. The biopolymer positively influenced shear strength but exhibited a paradoxical outcome in consolidation and California bearing capacity tests, increasing consolidation while decreasing bearing capacity. In summary, this study highlights the multifaceted effects of XG on soil behaviour, emphasizing the need for a nuanced exploration of the intricate interplay between XG and water in soil systems.
Use of construction and demolition materials to improve geotechnical properties of a clay
A study was conducted to explore the various effects of construction and demolition materials (CDMs), which are considered to be solid waste materials (SWMs), on the geotechnical properties of clay. The properties of the mixed samples were investigated by adding crushed brick pieces (CBPs), dumped asphalt pieces (DAPs), and crushed concrete pieces (CCPs) into clay. The laboratory tests included the testing of consistency limits, California bearing ratio (CBR), unconfined compressive strength (UCS), swelling, consolidation, and direct shear. A series of plate loading tests on clay with 10% CDMs was also carried out in a specially-designed model box made of reinforced concrete with a dimension of 2.0m diameter and depth of 1.5m to gain a deep understanding of the samples. The results show that when the CDMs percentages were 20%, there were decreases of about 15% and 25% in liquid limit and plasticity index of clay, respectively. Small increases of about 3% in γdrymax for the clay were noticed when the DAPs and CCPs content was increased from 5% to 20%. A reduction of about 35% of wopt for clay was shown by increasing the DAP percentage to 20%. The CBR and UCS strength values of the clay were increases by around 25% by increasing the CDMs percentage from 5% to 20%. In the direct shear test, 10% of all CDMs additions gave out the maximum angle of internal friction. In the plate load test, the addition of 10% CDMs increased the ultimate bearing capacity of clay by about 50% to 75%. The oedometer characteristics, including the swelling and consolidation of CDMs-clay mixtures, were controlled mainly by the type and content of CDMs in the clay. Using Plaxis 2D for the program, a remarkable matching of the results of the numerical simulation and the plate load test was observed (R2=0.97).
Improving some of geo technical properties of an organic soil using crushed waste concrete
Many urban areas are now struggling with the high volume of solid wastes, especially the construction and demolition materials. In this study, the crushed waste concrete (CWC), which is considered as one of the biggest components of solid waste, was used to improve some geotechnical properties of an organic soil. The CWC at the ratios of 5%, 10%, 15%, and 20% were added to organic soil in order to conduct an intensive series of experimental tests. The laboratory tests included the consistency limits by fall cone, modified compaction, unconfined compressive strength (UCS), and swelling percentage. The results show that when the CWC percentages were increased to 50%, there were decreases of about 30% and 60% in liquid limit and plasticity index of clay, respectively. Increase of about 35% in γdrymax for the organic soil was noticed when the CWC content was increased from 10% to 50%. A reduction of about 50% of wopt for organic soil was shown by increasing the CWC percentage to 50%. The UCS values of the organic silt increases by around 25% by increasing the CWC percentage up to 50%. The swelling percentage increased by adding CWC up to 30%, and then decreased with the addition of CWC up to 50%.and increasing the CWC proportions has a positive effect on the consolidation features of organic soil. CWC decreased the consolidation of organic soil by decreasing the compression index (Cc) and the time of consolidation for organic soil was decreased due to the increasing of the coefficient of consolidation (Cv) and coefficient of conductivity (k) for organic-CWC mixtures
Effects of size and shape of sand grains on some engineering properties of a clayey soil
This thesis presents an experimental research studying in the effect of shape and size of sand grains on some geotechnical properties of a clayey soil using unconfined compression and triaxial compression machines equipped with a pair of bender elements. The materials used in this study were low plasticity clay, Narli Sand and Crushed Stone Sand. Three different gradations of the sands (0.6-0.3, 1.0-0.6, and 2.0-1.0) mm were chosen. Five contents of clay-sand (90-10, 80-20, 70-30, 60-40 and 50-50) by dry weight were investigated. Series of bender elements (BE) tests were carried out on clay-sand mixtures to measure small strain shear modulus (Gmax). Unconfined compression (UC) tests were conducted on these mixtures to have a correlation between Gmax and unconfined compressive strength (qu). Gmax and qu increased with increasing roundness and sphericity of sand grains. The qu values decreased, and the Gmax values increased when sand content in the mixture increased. As size of sand grains increased, Gmax and qu values increased. For the results that obtained from triaxial compression machine equipped with bender elements tests, the deviatoric stress increased with increasing content, size, roundness and sphericity of sand grains. The pore water pressure decreased as sand content increased and it is increased as size, roundness and sphericity decreased. The effective cohesion (c') decreased and effective angle of friction (ϕ΄) increased as sand content increased. A correlation between Gmax, voids ratio and effective stress were developed for rounded and angular sand of clay-sand mixtures.
Use of sewage sludge ash for soil improvement
This study presents the application of incinerated sewage sludge ash (SSA) as a soil stabilizing agent. The ash used in this study was obtained from Gaziantep wastewater treatment plant, and had fine particles passing through 0.425 mm sieve. The SSA was mixed with a clay at different percentages (0%, 5%, 10%, 15%, 20%, and %30), and an extensive laboratory study was employed including Atterberg's limits, standard Proctor, unconfined compressive strength (UCS), California bearing ratio (CBR), vane shear, consolidation, fall cone, falling head permeability, and plate load tests. The testing results showed about 30% increment in liquid limit and plasticity index of clay as the SSA percentage increased. A decrease about 2% in maximum dry unit weight for the clay was observed by increasing SSA content up to 30%. An increment about 40% in optimum water content for clay was observed by increasing the SSA percentages up to 30%. The CBR performance of the unsoaked samples was found to be increased up to 6 times greater than the untreated clay, while those of the soaked samples was found to be increased up to 4 times greater than the clean clay. Curing periods have a varying effect on the UCS as well as the CBR testing results. The UCS values was observed to be increased up to 3 times higher than the clean clay samples. In the plate loading tests, the SSA addition increased bearing capacity of clay up to about 75%. The oedometer characteristics of SSA-clay mixtures were controlled mainly by the SSA content. A reinforced circular model box, which has a diameter of 2.0 m and a depth of 1.50 m and a 40 t loading capacity frame, was also constructed to perform plate loading tests in order to investigate bearing capacity of the samples. The results of the plate loading tests showed that the SSA addition increased the bearing capacity, and that the mixtures with SSA had a less settlement than the untreated clay. The laboratory testing results reported in this research showed that the SSA can be used as an alternative soil stabilizing agent. Keywords: Sewage sludge ash, clay, geotechnical properties
Improving some geotechnical properties of organic soil by using waste stone powder
In general, improving the quality of life and the progress of industrial revolution adversely affect the urban environment. Recycled waste materials are now widely utilized in geotechnical usage, particularly in soil improvement fields. In this study, stone powder (SP) was used to investigate its effects on the stabilization of organic soil. The waste powder was blended with organic soil at different percentages of 10%, 20%, 35% and 50% by dry weight of mixture. A series of tests such as fall cone test, modified compaction test, unconfined compressive strength test and consolidation test have been performed on the mixtures. The results showed that the liquid limit, plastic limit and plasticity index decreased with the addition of stone powder. For compaction test, the maximum dry density increased by the addition of 50 % of SP and the optimum moisture content has decreased with adding 50% of SP. In addition, the unconfined compressive strength increased with adding stone powder with comparing to untreated soil and the maximum obtained value of unconfined compressive strength was at using 10% of SP. The compression index (cc), swelling index (cs) and the initial void ratio decreased with increasing SP ratio. The volume compressibility mv decreased with adding more SP. Inversely, the consolidation coefficient (cv) increased with the SP addition.
Liquefaction potential of sand with fines using Bender element test
This study aims to evaluate the maximum dynamic shear modulus (Gmax) based liquefaction potentials of sand with various fines using bender element test. The fines (CL) was added to two different particle gradations (0.15-0.30 mm and 1.0-2.0 mm) of clean sand having distinct shapes (rounded and angular) at mixture ratio of 5%, 10%, 15%, 20%, 30% and 40%. The results indicated that the Gmax values and liquefaction resistance were decreased up to 20% fines content then increased. The liquefaction resistance of the mixtures with coarse sand grains were found to be greater than those with fine sand grains at a given fines content.
Using sewage sludge ash and stone powder in soil stabilization and concrete mixtures
In this study, two different types of wastes (Sewage Sludge Ash SSA and Stone Powder SP)wereused as a stabilizer to improve some geotechnical properties of silty soil and as alternatives of cement and sand in concrete mixtures. Five different ratios (in weight percentage: 0%, 5%, 10%, 15%, and 20%) of SSA and SP admixtures are mixed with cohesive soil to make soil samples. Also the materials used with four different ratios (0%, 10%, 20%, and 30% in weight) in 1:2:4 (cement: sand: gravel) concrete mixtures. In order to understand the influences of admixtures on the soil properties, tests of Atterbeg limits, compaction, unconfined compressive strength, fall cone, laboratory vane shear, and primary swell were performed on those samples. Another test of compressive strength was performed to 28-days cured concrete samples. The study shows that the unconfined compressive strength of specimens with the SSA addition was improved and with the SP addition was reduced; furthermore the undrained shear strength obtained from fall cone and laboratory vane shear tests was increased in both SSA and SP addition. The strength of concrete samples contained SSA and SP was adversely affected with increasing the SSA and SP ratios in the mixtures. This suggests that SSA and SP have many potential applications in the field of geotechnical engineering and can used to reduce the cost of non-structural application such as road pavement, walkways, and floor works.
Soil behavior at the grain scale and its effect on macro scale
The objective of this study is to investigate soil behavior while taking into consideration its shape characteristics, and establishing a relationship between these characteristics and macro problems of soil. One of the key problems that will be looked at within the scope of this thesis is slope stability. When considering stability of slopes, the contribution of, if any, shape and size parameters to the calculation of shear strength of soils is not addressed in the literature. One may think that the reason for the absence of this particular topic in the literature could be that in slope stability, factor of safety generally provides us with enough safe room, leaving any further analysis especially anything that concerns micro mechanics of soil redundant. However, we argue that studying slope stability using only the continuum theories may not always be sufficient and that it could not allow us to leverage the full potential of strength of soil in our engineering designs. In soil mechanics, there are always many unknowns and even in slope stability there are still many topics yet to be researched. The brief literature review shows that micro mechanics of soil can have a significant effect on overall soil behavior. Although this study will be concerned with cohesion-less soils, we believe that it is still another step into understanding soil behavior in the context of slope stability.