Polimerle ile stabilize edilmiş kumların kayma mukavemetinin laboratuvar deneyleri iel belirlenmesi
Determination of shear strength of polymer reinforced sand by laboratory tests
Yazar: NEVAL UYSAL
Danışman: DOÇ. DR. AYKUT ŞENOL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Zemin Mekaniği ve Geoteknik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Bu çalışmada, İstanbul Silivri bölgesinden alınan sarı kumun kayma mukavemetinin belirlenmesi kapsamında, ağ yapılı kopolimer (KP) ve virgin homopolymer (VHP) katkısıyla içsel sürtünme açısının arttırılmasına yönelik bir deneysel çalışma yapılmıştır. Laboratuvar çalışmaları 2013 yılında İstanbul Teknik Üniversitesi, Ord. Prof. Dr. Hamdi Peynircioğlu Zemin Mekaniği Laboratuvarı'nda gerçekleştirilmiştir. Araziden elde edilen zemin numuneleri üzerinde gerçekleştirilen granülometri analizi sonucunda zemin sınıflandırılması yapılmış ve (SP) kötü derecelenmiş kum zemin sınıfı olarak belirlenmiştir. Dane birim hacim ağırlığını belirlemek için piknometre deneyi yapılmış ve kayma mukavemeti özelliklerinin belirlenmesi için de farklı rölatif sıkılıktaki numuneler üzerinde kesme kutusu deneyleri yapılmıştır. Rölatif sıkılık değerleri %20, %30 ve %40 olan katkısız zemin numunelerine ek olarak, kuru zemin ağırlığının % 0.50, % 1.00 ve % 1.50' si oranlarında kum-KP ve kum-VHP karışımları hazırlanmıştır. Böylece 21 farklı deney seti üzerinde kesme kutusu deneyi yapılmış, rölatif sıkılıkların ve katkı malzemelerinin kayma mukavemeti üzerine etkisi gözlemlenmiştir. Deneysel çalışmaların sonucunda, hazırlanan farklı rölatif sıkılıklardaki numunelerde sıkılığı fazla olan numunenin daha yüksek kayma mukavemetine sahip olduğu ve hazırlanan birleşimlerde katkı malzemesi oranı arttıkça kayma mukavemeti açısının da arttığı gözlemlenmiştir. 
Zemin numunesinin rölatif sıkılığının arttırılmasının zeminin kayma mukavemetini artırdığı gözlemlenmiştir. Numunelerin yalın hallerine kopolimer ve virgin homopolimer fiber katkı malzemelerinin katılmasının zeminin kayma mukavemetini arttırdığı gözlemlenmiştir. Deney numunelerindeki polimer fiber katkı malzemelerinin kütlece yüzde (%) oranlarının artmasının zeminin kayma mukavemeti açısını arttırdığı gözlemlenmiştir. Yapılan 21 set deneyde en düşük kayma mukavemeti açısı kum numunenin %20 rölatif sıkılıktaki katkı malzemesi katılmamış, yalın halinde 28º içsel sürtünme açısına sahip olduğu durumdur. En yüksek kayma mukavemeti açısı ise numunenin %40 rölatif sıkılıktaki durumunun kütlece %1.5 virgin homopolymer (VHP) fiber içerdiği 39º içsel sürtünme açısına sahip olduğu durumdur. Yapılan deneyler sonucunda oransal olarak kayma mukavemeti açısının en çok arttığı durumun rölatif sıkılığın %20 olduğu durumda %21'lik bir artışla gerçekleştiği gözlemlenmiştir.

Abstract:
All structures are generally built on the ground or inside the soil with a certain depth and they transfer their loads by help of their foundations. On the other hand, soil is able to be used as a material in the most of the areas such as dams and highway fills. Soil strength, permeability, compressibility and determination of these properties are very important to use for the geotechnical applications.In the civil engineering, the soil must be considered like a material for constructions such as concrete and steel materials. The information of the engineering properties of soils are obtained from the laboratory and the field tests. The features of concrete, steel, wood, soil and other materials are determined by the chemical composition and the physical state. The soil minerals are very complex but strength, rigidity, stability, resistance to erosion and irrigation can be determined with the various experiments.For the experiments, the identification and the classification of these materials, the physical properties are used. The grain size, shape, particle size distribution, specific gravity of soil is related to the load which is carried by the soil. The load bearing capacity can be calculated with experiments such as compression test, shear box test.The soil beneath the pavement, the fill or other landfill constructions should be controlled with the tests such as compaction to determine the ratio of mixing.

In this thesis, the experimental research was conducted to calculate the strength of the material in the ITU Soil Mechanics Laboratory. The samples having different relative densities were stabilized with different ratio of the polymers. In terms of the laboratory program, all engineering properties of soil used in experiments were firstly determined by laboratory tests. Then, the samples were prepared with the certain relative density and the additive materials were added inside it with a percentage of the weight. The shear box tests were performed with the plain and mixed samples to determine the internal friction angle. The aim of the thesis is to determine the changes of the shear strength of a sand soil reinforced with a type of polymer.Soils are used for many different purposes as a construction material since human existence. Nowadays, soil can be used as a material for the highway and the airport transportation system, dams and the construction of surface coating of aerospace vehicles. Soils should be selected according to the aim of usage. For instance, the permeability of the fill dams desired to be very low.The soil improvement applications in the geotechnical engineering increase the shear strength and reduce the compressibility, the settlement and the permeability.The soil formations could be considered as a combination of four main types: gravel, sand, clay, and silt. It generally has significant shear strength and its characteristics may depend strongly on the environmental conditions (e.g. dry versus wet). On the other hand, the stabilization consists of incorporating certain materials with some desired properties within other materials having lack properties. Therefore, the soil stabilization is defined as a technique to improve the engineering characteristics of the soil in order to develop the parameters such as shear strength, compressibility, density and hydraulic conductivity.

The soil reinforcement using discrete randomly distributed fibers has been widely investigated over the last 30 years. The mechanical behavior of clean sands was investigated firstly by Coulomb in the 18th century (Coulomb 1776). The studies of the mechanical behavior of pure clays were reported only approximately 150 years later (Terzaghi 1925). Lots of models were recommended to estimate the improvement by various fibers to increase the shear strength of soils. The objectives of this thesis are to supplement the data available on the behavior of fiber-reinforced sands affected the shear strength of fiber-reinforced sands.

The geosynthetics are the planar products manufactured from polymeric materials used for soil, rock, or other geotechnical related materials as a of a civil engineering project or system. In 1970, there were only five or six geosynthetics available, while today more than 600 different geosynthetic products are sold throughout the world. The worldwide annual consumption of geosynthetics is approximately close to 1,000,000,000m^2. Last 30 years, the geosynthetics have been innovated in many aspects of the practices. In some applications, they have entirely replaced the traditional construction material. In many cases, the use of the geosynthetic can significantly increase the factor of safety, improve the performance, and reduce the costs in comparison with the conventional design.

ASTM has defined the geosynthetics as a planar product manufactured from a polymeric material used with the soil as an integral part of a geotechnical engineering application. A type of geotextiles is a permeable geosynthetic made from the synthetic textile materials. The geogrids are primarily used for the reinforcement. They are formed by a regular network of the tensile elements with the apertures of sufficient size to interlock with the surrounding fill material. The geomembranes are low permeable geosynthetics used as the fluid barriers. The geotextiles and related products such as nets and grids can be combined with the geomembranes and the other synthetics to take advantage of the best attributes of each component. These products are called geocomposites and they may be composites of geotextile-geonets, geotextile-geogrids, geotextile-geomembranes, geomembrane-geonets, geotextile-polymeric cores, etc...

The use of fibers in reinforced soils is widely used particularly with regard to the applications involving the stabilization of the slopes and the steep cover systems for the fills. In addition, the fiber-reinforced soils are currently being used to recycle and reuse shredded and fibrous inorganic wastes in the geotechnical engineering applications and as alternate backfills and improved pavement materials. The design of geotechnical systems involving fiber-reinforced soils is typically based on empirical experience or available models developed from the laboratory tests on the composite fiber-reinforced soils samples.The safe and the economical design of the geosynthetic-reinforced soil structures, such as retaining walls, slopes, and embankments require the information of the behaviour of the soil–reinforcement interface. The mobilization of the internal friction angle between the soil and the reinforcement material is an important factor governing the stability analysis for the design.In this research thesis, a sand soil taken from Silivri region in Istanbul and a type of copolymer fiber (CP) and a type of virgin homopolymer (VHP) were used. The aim is to increase the shear strength of the relevant sand soil by use of the additive materials such as the copolymer and the homopolymer. The grain-size analysis performed on the clean sand and it has been classified as poorly graded sand (SP). The tests were performed to determine the shear strength of the samples having the different relative density values. With the relative density values of 20%, 30% and 40%, the CP ratios and the VHP ratios of 0.50%, 1.00% and 1.50% by the weight of dry sand-CP and sand-VHP mixtures were prepared. Then the shear box tests were done as the 21 different experiments set. It shows that how different relative density values and the additional materials effect the shear strength. The result of the tests improved that the shear strength values are higher when the ratio of the relative density and additional materials are getting higher percentage.Consequently, in this study which is consist of experiment researches done in laboratory environment, the calculations of shear strengths are made by adding polymer additive material to the sands of different relative density according to their masses.At the end of the experiments, soil classification is carried out, then the highest and the lowest void ratio is calculated, lastly relative density is calculated.

The phases of the study carried out can be listed as; selecting the sand which is going to be used as the main material; doing experiments to determine the engineering properties of the selected sand; selecting polymer filter materials which is going to be used as additive material for the sand; determining soil weights which are going to be placed in shear box; doing trial experiments to determine the range of the values which experiments will be done with; doing shear box experiments when materials, datum, the range of the values and ratios are decided and prepared.This study is presented as a thesis which is consist of five main phases. In the first section, the details of the purposes and the goals of this study are explained.In the second phase of this thesis, the shear strengths of soil, the factors which affects the shear strengths and the methods which are adopted to calculate these are introduced.The detailed research of literature is made in the third phase of this thesis. The main materials, additive materials, ratios of these which were used earlier studies are reported and examined. Following this, the experimental results of these studies are presented with their details in tables.In the fourth phase, the studies which are done in the Istanbul Technical University Ord. Prof. Dr. Hamdi Peynircioğlu Soil Mechanics Laboratory, how the studies are carried out, the sand used and the properties of additive materials are presented. The results of the experiments done in this study are presented with the help of figures and table; and the details of the evaluation of these results and the comparison of the results are also presented.At the last section, general results and recommendations are presented.