Geniş çaplı kazıklarda yükleme deneyi ve sonuçlarının değerlendirilmesi
Load tests on big diameter piles
- Tez No: 21993
- Danışmanlar: PROF. DR. REMZİ ÜLKER
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1992
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 85
Özet
ÖZET Bu tez kapsamı içinde, her cins zemindeki Çeşitli tipte kazıtın taşıma gücünün belirlenmesinde ve kazığın gelecekteki davranışı hakkında gerçeğe çok yakın bilgiler veren yükleme deneyleri üzerinde açıklamalara gidilmiştir. Sağlıklı sonuçlar verebilecek ve şartlara uygun hazırlanmış bir deney için gereken tüm bilgiler bu Çalışma içinde sunulmuştur.Günümüzde geçerli olan norm ve şartnamelerin hepsi toplu halde ayrıca açıklanmıştır. Kazıkların taşıma gücünün bulunmasında en güvenilir yol olan yükleme deneyleri, statik ve dinamik formüllere göre daha gerçekçi sonuçlar verirler. Kazık yükleme deneyinin amacı, kazığın nihai taşıma gücünü belirlemenin yanında, kazığın statik ve dinamik formülerle bulunan servis yükünü taşıyıp taşıyamayacağını kontrol etmektir. Gerekli olan bütün bilgiler, kazığın yük-oturma diyagramından elde edilir ve uygulanan yük neticesinde oluşan plastik ve elastik oturmalar esas alınır. Yalnız burada önemli olan, yük-oturma eğrisinin hatasız elde edilme sidir. Gerçek plastik ve elastik şekil değiştirmeler hakkında bilgi sahibi olabilmek için yükleme deneyi sırasında boşaltma ve tekrar yüklemeler yapılmalıdır. Boşaltma sırasında meydana gelen kabarma, kazığın ve zeminin elastik kısalmasını, o noktadaki toplam oturma dan bu değerin çıkarılması ise plastik şekil değiştirme yi verir. Yükleme deneylerinin güvenilirliği ve uygulamada faydalı sonuçlarının sağladığı ekonomi, bu deney için harcanan para ve kaybedilen süreden daha önemlidir. Çalışmanın sonunda günümüzde yapılan yükleme deneylerinden örnekler verilmiş ve Çeşitli şartnamelere ve normlara göre raaksimun taşıma yükü ve servis yükleri bulunmuştur. Bu değerlerin içinden kazık ve zemin cinsine göre en uygun olan seçilmeye çalışılmıştır.
Özet (Çeviri)
SU*Ö*ARY LOAD TESTS ON BIG DIAHETER PILES The purpose of a loading test may be either to deterraine the ultimate bearing capacity of a pile ör to check whether a pile can.safely carry its desîgn load as determined by öne of the pile formulae. Provided the test is well recorded and carefully interpreted, the load which a single pile can support without excessive settlement may be used as an indication is required regarding the elastic and plastic settlements caused by the applied load. The applicability of pile load test is confined to cohesionless ör primarily noncohesive soils. A load test on a pile in ör underlaid by cohesive strata cannot obtain its full settlement until after soil consalidation which may take years. I f the pile is in such soil the ultimate compression cannot be tested; the shearing valeu can be. Furthermore, the settlement of a small loaded area of a cohesive soil would have no relation to the much greater settlement which would occur under the same pile if it were öne of many under the entire structure. it is impossible to evaluate tests unless adequate boring records present a complete picture of the under- ground. Satisfactory pile load tests can be made in any soil through which water can escape freely in the voids. The test load shall be applied in seven increments equal to one-half, three-fourths, öne, öne and one-fourth öne and one-half, öne and three-fourth and two times the proposed working load. Readings of settlements and rebounds shall be referred to a constant elevation bench mark and shall be recorded to one-thousandth of a foot för each increment ör decrement of load. The rebound shall be recorded after each decrement is removed. The test loads may be applied by direct load from a platform on which heavy weights are placed, by direct load from a platform on which water tanks are placed, by jacking against a loaded platform, by jacking against an existing structure, thus reducing the amount of load needed. Alternativly the test pile may be driven in by hydraulic jack bearing against a rigid beam supported on two firmly driven anchor piles. The anchor piles should vibe at least 150 cm. away from the test pile. Whichever method of loading is used it should be possible to load the pile gradually and to reraove the load completely after each inerement has been applied. Two different loading procedures can be used, mainly maintained loading (ML) and constant rate of penetration (CPR). At maintained loading (ML) the load is applied in increments and at each load increment, the settlement of the pile head is measured. The pile can be unloaded önce ör twice during the test. The pile may also be loaded cyclically at the established allowable load and at 1.5 and 2 times the estimated allowable load. The disadvan- tage with the (ML) method is the relatively long time that is required for each test and high costs involved. However, öne advantage with the (ML) method is, that öne can get some concept of the magnitude of the creep and its effect on the ultimate capacity. When the penetration rate is kept constant during a load test (the CR? metod) the corresponding force is measured. The constant-rate-of-penetration method (CPR) is the reverse to the (ML) metod. in the (CPR) test, the pile head is forced to settle at a predetermined rate, normally 0.02 in./min (0.5 mm/rain) and the force that is required to achieve the penetration is recorded. The test is carried out to a total penetration of 2 in. ör 3 in. (50 mm. ör 75 mm.) ör to the maximura capacity of the reaction arrangment, which means that the test is completed within about 2 hr.- 3 hr. The CRP metod has the advantage that a load test can be carried out rapidly and that the ultimate load for friction piles in cohesive soils is in general well defined. But it is not possible to get some information of the magnitude of the creep with the CRP metod. The CPR test will provide some important information, when carried to failure from the shape of the load-movement curve, the behavior of the pile as an end-bearing, a friction-pile in sand with more ör less end-bearing resistance, ör a friction-pile in clay can be evaluated. Movement at the pile head is caused by elastic deformation of pile and soil and plastic deformation of soil. The last caused undue settlement of structures and must be guarded against. This is the value which is the significant öne to be obtain from load test, and not primaraly the total downwards movement of the head of the pile under the test load. it is important to determine the ratio between elastic compression of the pile and plastic deformation of the soil. If each increment of load is allowed to act until movement has ceased and vii.removed before the next increment is applied the permanent set or plastic settlement can be measured. The theoretical elastic deformation in the case of an end-bearing oile unrestrained by friction can be computed from the formula 5 = Ql/AE and will be a straight line, and for other condition, the theoretical elastic deformation of the pile can be computed by assuming the location of the center of resistance and considering 1 (length of pile) as distance down to this point. By substituting for (5) in the formula the elastic deformation read from the curve obtained from the cyclic loading tests, values of (1) may be obtained which show the location of the center of resistance to that load. The resistance of the soil to the applied loading may be assumed to originate from depth defined by (1). When the depth is compared with the soil profile obtained during the site investigation the strata which are concerned in developing resistance can be Identified. A simpler tuetod of carrying a loading test is to plot each increment of load against the settlement reached when movement ceases. Each increment being applied without removal of load. The ultimate load which the pile will carry may then be shown by the flattening slope curve. A load factor of two or three can then be applied to determine the working load. To extract more information concerning the resisting capacities of the individual strata, piles may be driven to different depths and tested by static loading. In this way reliable indications can be obtained of the strength of the different groupings of strata, and hence, by difference, of the strengths of individual layers. Load test are exceedingly helpful. However, the results should be exeamined carefully before they are depended upon and before conclusions, because of the following reasons : 1. The soil condisions throughout the site may not be the same as those at the locations of the test piles. When the results from a load test are evaluated it has to be borne in mind that a test reflect only the conditions at the point of execution of the test. The ground conditions can vary within an area. It is important that the time between the installation and the load test is sufficent, particularly for friction piles in clay. In this case the change of the bearing capacity with time can be large, especially for normally consalidated clays with a high sensitivity ratio. viii2.The test may yield few ör no data that enable öne to estimate the reduction of safe load that should be applied to the results of the test because of the group effect of the large number of piles to be used near together in the actual substructure. 3.The test load are applied för such a short time that no data are glven regarding the slow compaction and flow of the soil that may occur because of the future long-term loading of the area. 4.The settlement of the test piles to be used as that constituting practical failure is difficult to establish without being chosen arbitrarily. Perhaps the applicable building code specifies it, but that does not mean that it is correct. 5.it may be necessary to set some average load as that to be considered to cause this critical sett¬ lement i f the data obtained from the tests differ. 6.A safety factor should be applied to the ultimate bearîng capacity of the piles as deterrained by tests. Perhaps this should be 2, perhaps soraetimes larger, ör something smaller. Excellent engineering judgment is needed in making this decision. 7.it is probable that the raore nearly the piles act in end bearing, the raore reliable the results of the test will be, unless tips of the piles are under- lain by plastic ör other compresssible materials, ör soils that may flow. To be preferred are piles tests made in advance of the planning of the structures. Then, besides infor- mation indicating load-bearing of capacity, these test may yield valuable data regarding the best type of pile for a particular site, the length of pile needed, the pile driving equipment required, and whether jetting is necessary. Ali these will probably enable the designer to develop a safe and economical design for the structure The data obtained by careful study of the elastic and plastic load/settlement diagraras furnish a reasonably accurate estimate of ultimate bearing capacity in cohesionless soils. in cohesive soils, however, the data must be treated with cautiorı. These load/settlement diagrams relate only to short-term loading; hence the settlement which occurs under a pile carrying a static load for a long period cannot be estimated accurately from a loading test. From the immediate intensity of ixloading applied to the soil it is possibie to estimate probable final settlements but the deformations measured during the loading test are by themselves no sure guide. The safe bearig load on a single pile is variously given as: 1.Half the load causing a total settlement of 0.01 in. per ton of test load (without creep), 2.Half the load at which the rate of increase of total settlement exceeds 0.03 in. per ton of test load increment, 3.Half the load at which the total plastic settlement (which is not recovered after removal of load) is 0.25 in., 4.Two-thirds of the load causing a plastic creep of 0.01 in. per ton of test load in 24 hours, 5.One-half to one-thrid of the load causing settlement causing equal to 10 per cent of the diameter of the pile. it is sometimes difficult to convince an inex- perienced ovmer that the money spent for such test is a good investment. Too often he believes that the cost of getting equipment to the site making the test is wasted and unnecessary.
Benzer Tezler
- Numerical analysis of monopile foundations for offshore wind turbines
Açık deniz rüzgar türbinleri için tek kazıklı temellerin sayısal analizi
MARYAM MASSAH FARD
Doktora
İngilizce
2021
İnşaat Mühendisliğiİstanbul Teknik ÜniversitesiDeprem Mühendisliği Ana Bilim Dalı
PROF. DR. AYFER ERKEN
DR. ÖĞR. ÜYESİ BÜLENT ERKMEN
- Data-driven modeling of ultimate load capacity of closed- and open-ended piles using machine learning
Kapalı ve açık uçlu kazıkların nihai taşıma kapasitelerinin makine öğrenmesi kullanılarak veriye dayalı modellenmesi
EMİRHAN ALTINOK
Yüksek Lisans
İngilizce
2021
İnşaat Mühendisliğiİstanbul Teknik Üniversitesiİnşaat Mühendisliği Ana Bilim Dalı
DOÇ. DR. MEHMET BARIŞ CAN ÜLKER
- Baret kazıklı temeller ile ilgili hesap yöntemleri, imalat ve kalite kontrol hesapları
Calculation methods, installation and quality control principles for barrette piled foundations
HAKAN KÖPÜKLÜ
Yüksek Lisans
Türkçe
2015
İnşaat Mühendisliğiİstanbul Teknik Üniversitesiİnşaat Mühendisliği Ana Bilim Dalı
PROF. HÜSEYİN YILDIRIM
- Composite and aggregate production using high calcium fly ASH
Başlık çevirisi yok
KHALED ZEYAD S. RAMADAN
- Helisel kazıklarda tork korelasyon katsayısını etkileyen faktörlerin incelenmesi
Evaluation of factors affecting torque correlation coefficient in helical piles
TAYFUN GÜL
Yüksek Lisans
Türkçe
2017
İnşaat MühendisliğiKocaeli Üniversitesiİnşaat Mühendisliği Ana Bilim Dalı
PROF. DR. SAMİ ARSOY