Jet Grout Kolona Soketli Fore Kazığın çalışma Performansının Araştırılması

Abstract

Zayıf zemin üzerine gelecek yüzeysel temellerin taşıma gücü yetersizliği, büyük oturmalar, vb… gibi nedenler ile zeminin yetersiz kaldığı durumlarda çözüm olarak derin temeller ve/veya zemin iyileştirme yöntemleri kullanılması düşünülür. Son 60 yıldır teknolojinin de gelişimiyle farklı makine ve ekipman tasarımlarıyla istenilen derinliklerde ve amaçta çeşitli derin temel sistemi uygulamaları yapılmaktadır. Özellikle derin temel sistemleri içerisinde sıkça kullanılan kazık temeller, pek çok mühendislik yapısının elverişsiz zeminde yapılmasına olanak sağlamaktadır. Kazıklı temellerin kullanılamaması durumunda zeminin ıslah edilmesi tercih edilebilir. Jet grout tekniği ile ıslah yönteminin amacı; yüksek basınçla zemine çimento şerbeti enjekte ederken, belli hızla yukarı çekilen enjeksiyon borusunun aynı zamanda belli hızla döndürülmesi ile bir çimento – zemin karışımı (soilcrete) oluşturmaktır. Bu işlem sonucunda herhangi bir donatı kullanılmadan daha dayanımlı ve yeni bir zemin kütlesi oluşturulmaktadır. Tez çalışması sırasında, derin temel sistemlerinden biri olan kazıkların tasarım kriterleri üzerinde durulmuş, imalat aşamaları açıklanmış ve kazıklı temellerin tercih edilme nedenleri irdelenmiştir. Aynı zamanda zemin ıslah yöntemlerinden biri olan jet grouting yönteminin işletim parametreleri, imalat aşamaları, yöntemin avantajları ve sınırlamaları üzerinde durulmuştur. Tezin uygulama kısmında ise imalatı 2009-2011 yılları arasında tamamlanmış Zonguldak Çatalağzı Termik Santrali projesi imalatları üzerinde durulmuş olup; imalatta uygulama sırasında karşılaşılan anakayanın farklı derinliklerde olması ve üstteki yumuşak birimin borusuz kazık imalatına müsaade etmemesi nedeniyle kazık ve anakaya arasındaki mesafeye jet grout kolonu imalatı yapılması ile problemin çözülmesi anlatılmıştır. Jet grout kolona soketlenen fore kazık performansını değerlendirmek için KSS/159 nolu kazık üzerinde kazık yükleme deneyi yapılmış ve sonuçlar tez kapsamında verilmiştir. Bu tez kapsamında zemin ıslah yöntemlerinden biri olan jet grout yöntemiyle bir derin temel sistemi olan kazık temelin birlikte çalışma prensibi irdelenmiş; bu kombine sistemin seçilmesine sebep olan nedenler, sistemin imalat aşamaları anlatılmıştır. Sistemin uygulanabilirliğinin ve performansının anlaşılması için Zonguldak Çatalağzı Termik Santrali projesi incelenmiştir. Bu kapsamda mühendislik çözümlerinde farklı sistemlerin birlikte kullanılabilirliğinin düşünülmesi amaç edinilmiştir.

When the ground is insufficient such as bearing capacity problems of shallow foundations on weak soils, large setting etc.., deep foundations and/or soil improvement methods are considered for solving the problems. Many constructions of deep foundation have been made desired depth and purpose with different machine and equipment since 60 years. Especially pile foundations commonly used the purpose of the main function is to transfer the load to lower levels in the ground which are capable of sustaining the load with an adequate factor of safety. Soil improvement methods can be preferred to when pile foundations can not be used. The purpose of the jet grouting, uses a high-pressure jet of fluid to break up and loosen the soil at depth in a borehole and to mix it with a self-hardening grout to form columns in the ground. At the end of this proses more strength and new soilcrete is occured without reinforcement. Jet grouting systems define that a special drill bit with horizontal and vertical high speed water jets to cut soils and constructed hard impervious columns by pumping grout through the nozzles. Jet grouting systems is not depend on grain size distrubitions. There are three fluid systems and can make coulums in any soils. The advantages of jet grouting systems can be listed below: § It is more economical and efficient than the other injection methods. § Je grout columns can be made different geometry. § Jet grout columns can be made any depths which is desired. § Application of columns are easier than other methos of improvement methods. The purpose of pile foundations is to transfer the loads that are from superstructure to lower levels which are capable the sustaining the loads with factor of safety without setting and has bearing capacity. Pile foundations are used when the soil under the foundation has not bearing capacity and/or not capable the loads with factor of safety with setting. During this situations, mat foundation and spread footings can not be used with factor of safety on this soils. There are four type piles which are listed below: § Frictions piles § End – bearing piles § Compactions piles § Anchor piles Different kind of piles have been discussed. Before choosing of pile types, economical situations and factor of safety of design use. According to material used in their installation can be classified below: § Concrete piles § Steel Piles § Timber piles During the design methods of pile foudation, pile loads can be divided in three groups. This loads are listed below: § Dynamic formulas § Static formulas § Load tests Pile load test method is the most certain method to determine the bearing capacity of piles. Testing a pile for failure make sure that valuable information about pile setting and bearing capacity to design engineer. The static pile load test is common method of testing to considered capacity of piles. It is applicaple to all kind of pile types and it involves the direct measurement of pile heads displacement. Pile load test have three objectives: § To establish load-deflections relationships in the pile-soil systems § To determine capacity of the pile-soil system § To determine load distrubition in the pile-soil system Three types of loading for a static load tests are given below: § The quick load test § The incremental static load test § The constant rate of penetration test The static load test was conducted in general accordance with ASTM-D1143. During the this thesis; design criteria of pile foundations, construction phases and the reasons what designer uses pile foundation are explained. Additionaly, operating parameters of jet grouting which is a soil improvement methods, construction phases, advantages and limitations of the methods are explained. In the application part of thesis, Zonguldak Catalagzi Power Plant project was given for an example. Site investigations and labrotary works were completed before the design phase. Totally 11 pieces boreholes were done and from these application disturbed and undisturbed samples collected. At the end of the site investigation phase of design were completed. During the construction of Coal Stock Area, some problems were occurred. The problems that are bedrock is different depth in area and the soil on the bedrock is weak, during the drilling can be use casing. So this problem was solved with jet grouting that was constructed between bedrock and end of pile. After the construction of jet grout columns (dia. 80cm), pile (dia. 100cm) was applied in jet grout column which is socketed in 3 meters in improvement area that was made with jet grout columns. Jet grout columns under the pile was constructed 9 columns with intersects 10cm to create a unit improvement area. Hereby an improvement area was created to socketed the pile foundations. Then the pile load test performed on the pile that is named KSS/159 and the results were given in thesis to determine the bearing capacity of pile and setting value. During the pile load test on number of KSS/159 test pile, the pile was installed on 150% of the service load of pile. According to results of static load test amount of displacement was measured at 4mm. In this thesis, jet grouting which is a soil improvement method and pile foundation, which is a deep foundation method, are investigated and told construction phases of two methods. For understanding of applicability and performance of combined system, Zonguldak Catalagzi Power Plant project is investigated. The purpose of the thesis, different systems can be used together.