Kazık yükleme deneylerinde göçme yükünün tahmin edilmesi
Başlık çevirisi mevcut değil.
- Tez No: 55491
- Danışmanlar: PROF.DR. AHMET SAĞLAMER
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 92
Özet
ÖZET Bu tez kapsamı içinde, kazığın taşıma gücünün belirlenmesinde ve kazığın gelecekteki davranışı hakkında gerçeğe çok yakın bilgiler veren kazık yükleme deneyleri üzerinde açıklamara gidilmiş ve bu kazık yükleme deneylerinde göçme yükünün doğru olarak tahmin edilmesi için araştırmalar yapılmıştır. Eksenel basınç, çekme ve yanal yükleme etkisinde kalan kazıkların göçme yükü araştırılarak, limit değerler bulunmuştur. Farklı göçme yükü tahminlerinin birbirlerine ve uygulanan kazık yükleme deney yöntemlerine göre değerlendirilmesi yapılmıştır. Böylelikle kullanılan kazığa ve kazık yükleme deney yöntemine göre en doğru göçme yükünü veren yöntemler belirlenmiştir. Günümüzde en çok kullanılan ve geçerliklerini koruyan, norm ve şartnameler (ASTM, DÎN, BSI, TSE) incelenerek, kazık yükleme deneylerinin doğru uygulanması için gerekenler açıklanmıştır. Çalışmanın sonunda yine günümüzde yapılan kazık yükleme deneylerinden örnekler verilmiş ve çeşitli yöntemlere göre göçme yükü bulunup bu kazıklar için limit değerler saptanmıştır. Bu yöntemlerin birbirlerine göre değerlendirilmesi yapılıp, gerçeğe en yakın tahminler belirlenmiştir. Eksenel basınç altındaki kazıklar için, göçme yükünün belirlenmesinde sekiz değişik yöntem verilmiş ve bunların günümüzdeki dört kazık yükleme deneyi üzerinde uygulanabilirliği tecrübe edinilmiştir. Eksenel çekme ve yanal yükleme etkisindeki kazıklar için göçme yükünün belirlenmesindeki kriterler açıklanmıştır. Göçme yükünün doğru saptanması için kazık yükleme deneylerinden yük yer değiştirme eğrisi hatasız olarak elde edilmelidir. Bunun için, kazık yükleme deneylerinin büyük bir itina ile ve şartnamelere uygun olarak yapılması gerekir. Bir kazık için göçme yükü, kazığın dalmasıdır. Dalma büyük yer değiştirmelerden sonra meydana gelir. Bu zemin ile kazık sisteminin kabul edilebilir şeklini aşmasıdır. Bir başka deyişle uygulanan yük, arttırılmadan kazığın yer değiştirmesine devam etmesidir. Bu, yük yer değiştirme eğrisinde belirgin şekilde fark edilmelidir. Yükleme deneylerinin güvenilirliği ve uygulamada faydalı sonuçlarının sağladığı ekonomi, bu deney için harcanan para ve kaybedilen süreden daha önemlidir. xii
Özet (Çeviri)
THE DETERMINE OF THE ULTIMATE FAILURE LOAD FOR THE PİLE LOAD TESTS SUMMARY The main function of bearing piles is to transfer the load to lower of the ground which are capable of sustaining the load with an adequate factor of safety and without settling at the working load by an amount detrimental to the structure that they support. When friction piles are installed in a deep deposit of fairly uniform consistency in order to transfer the foundation pressure to the lower levels, they should be long enough to ensure a substantial advantage over a shallow foundation. In these circumstances it should be borne in mind that for the same superficial area of pile surface, a few long piles forming a piled foundation are more effective and will support the load with smaller settlements than many short piles. Piles should be installed to the prescribed depth, resistance or set per blow without damage to the pile shafts or the bearing stratum and records of the installation process should be maintained. The piles should be able to carry their design loads without exceeding the permissible working stresses in the material of the pile, but the stresses during driving may exceed these. The stresses during pitching and handling should be within the safe bending stresses prescribed in the design. An investigation of the ground should be carried out by competent and experienced persons. Boring should reach depths adequate to explore the nature of the soil both around and beneath the proposed piles, including all strata likely to contribute significantly to settlement. It is important that the nature and occurrence of groundwater should be investigated. If the standing levels vary from stratum to stratum or if there is a water table gradient between boreholes this should be noted. Groundwater or soil may contain harmful constituents in amounts sufficient to cause damage to Portland cement concrete or buried metals. Chemical analysis of samples of the groundwater and soil should be undertaken to assess the necessity for special precautions. On sites where the soil conditions, do not permit point bearing at econimical depth, the available point resistance and skin friction should be determined separately at various depths before the pile foundation is designed. The bearing capacity of a pile is dependent on the size, shape and type of pile and on the properties of the soil in which it is embedded. The ultimate bearing capacity is the load at which the resistance of the soil becomes fully mobilized. At a load greater than the ultimate bearing capacity the soil undergoes shear failure, allowing the pile to xiiio When the pile behaviour during installation is below the critical bound which has been anticipated from the site investigation and previous experience. Generally, load and settlement test data are plotted. The plotted settlement could either be gross (the total movement of pile butt under full test load) or the net (the distance the pile has permanently moved after it has rebounded upon removal of the test load). These plotted data are then used to estimate the failure load so that allowable pile capacity can be calculated. For the axial compression pile load tests, the ultimate failure load for a pile is defined as the load when the pile plunges or the settlements occur rapidly under sustained load. Plunning, however, may require large movements that may exceed the acceptable range of the soil pile system. Other failure definitions consider arbitrary settlement limits such as the pile is considered to have failed when the pile head has moved 10 percent of the pile end diameter or the gross settlement of 38 mm. and net settlement of 19 mm. occurs under two times the design load. Many engineers define the failure load at the point of intersection of the initial tangent to the load movement curve and the tangent to or extension of the final portion of the curve. All these definitions for defining failure are judgemental. Methods of determining failure load from compression pile load tests calculated eight way. The following interpretation methods have been used in the past for various load tests. First, these methods are reviewed and their applicability for different pile types discussed. 1) Davisson's method (1972) 2) Chin's method (1970, 1971) 3) De Beer's method (1967) 4) Brinch Hansen's 90 percent criterion (1963) 5) Brinch Hansen's 80 percent criterion (1963) 6) Mazurkiewicz's method (1972) 7) Fuller and Hoy's method (1970) 8) Butler and Hoy's method (1977) Mazurkiewicz's method is way the acceptable and applicability failure load for different pile types. This method consists of the following steps: a) Plot the load movement curve. b) Choose a series of equal pile head movements and draw vertical lines that intersect on the curve. Then draw horizontal lines from these intersection points on curve to intersect the load axis. c) From the intersection of each load, draw 45 line to intersect with the next load line. d) These intersections fall approximately on a straight line. The point which is obtained by the intersection of the extension of this line on the vertical (load) axis is xvithe failure load. Methods of determining failure load from pullout pile load tests vary depending on the tolerable movement of the structure. In general, failure load for pullout test is more easily defined when compared with the axial compression load test data because the available pullout resistance generally decreases more distinctly after reaching failure. The generally accepted interpretation methods, in practice, for estimating ultimate pullout load is the lowest of the following three criteria. 1. Failure load may be taken as the load value that produces a net upward pile butt movement of 6.25 mm. 2. The upward failure load is at the point of intersection of tangents on the load movement curve. 3. The upward failure load is the value at which upward movement suddenly increases disproportionately (the point of sharpest curvature on the load movement curve). Methods of determining failure load from lateral pile load tests vary depending on the tolerable movement of the structure supported by the piles. The generally accepted criteria for estimating the ultimate lateral load is the lower of the following two methods: 1. Failure load may be taken at 6.25 mm. lateral movement or deformation. 2. Failure load may be considered at the point of intersection of tangents on the load- movement curve. In this thesis author proposes to state the methods of predicting the failure load on the pile loading test, so that the current pile capacity can be calculated. XVIIo When the pile behaviour during installation is below the critical bound which has been anticipated from the site investigation and previous experience. Generally, load and settlement test data are plotted. The plotted settlement could either be gross (the total movement of pile butt under full test load) or the net (the distance the pile has permanently moved after it has rebounded upon removal of the test load). These plotted data are then used to estimate the failure load so that allowable pile capacity can be calculated. For the axial compression pile load tests, the ultimate failure load for a pile is defined as the load when the pile plunges or the settlements occur rapidly under sustained load. Plunning, however, may require large movements that may exceed the acceptable range of the soil pile system. Other failure definitions consider arbitrary settlement limits such as the pile is considered to have failed when the pile head has moved 10 percent of the pile end diameter or the gross settlement of 38 mm. and net settlement of 19 mm. occurs under two times the design load. Many engineers define the failure load at the point of intersection of the initial tangent to the load movement curve and the tangent to or extension of the final portion of the curve. All these definitions for defining failure are judgemental. Methods of determining failure load from compression pile load tests calculated eight way. The following interpretation methods have been used in the past for various load tests. First, these methods are reviewed and their applicability for different pile types discussed. 1) Davisson's method (1972) 2) Chin's method (1970, 1971) 3) De Beer's method (1967) 4) Brinch Hansen's 90 percent criterion (1963) 5) Brinch Hansen's 80 percent criterion (1963) 6) Mazurkiewicz's method (1972) 7) Fuller and Hoy's method (1970) 8) Butler and Hoy's method (1977) Mazurkiewicz's method is way the acceptable and applicability failure load for different pile types. This method consists of the following steps: a) Plot the load movement curve. b) Choose a series of equal pile head movements and draw vertical lines that intersect on the curve. Then draw horizontal lines from these intersection points on curve to intersect the load axis. c) From the intersection of each load, draw 45 line to intersect with the next load line. d) These intersections fall approximately on a straight line. The point which is obtained by the intersection of the extension of this line on the vertical (load) axis is xvithe failure load. Methods of determining failure load from pullout pile load tests vary depending on the tolerable movement of the structure. In general, failure load for pullout test is more easily defined when compared with the axial compression load test data because the available pullout resistance generally decreases more distinctly after reaching failure. The generally accepted interpretation methods, in practice, for estimating ultimate pullout load is the lowest of the following three criteria. 1. Failure load may be taken as the load value that produces a net upward pile butt movement of 6.25 mm. 2. The upward failure load is at the point of intersection of tangents on the load movement curve. 3. The upward failure load is the value at which upward movement suddenly increases disproportionately (the point of sharpest curvature on the load movement curve). Methods of determining failure load from lateral pile load tests vary depending on the tolerable movement of the structure supported by the piles. The generally accepted criteria for estimating the ultimate lateral load is the lower of the following two methods: 1. Failure load may be taken at 6.25 mm. lateral movement or deformation. 2. Failure load may be considered at the point of intersection of tangents on the load- movement curve. In this thesis author proposes to state the methods of predicting the failure load on the pile loading test, so that the current pile capacity can be calculated. XVII
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