İzmir Deniz Bostanlısı arazi ve laboratuvar ve yükleme deneyleri gözönüne alınarak kazıkların taşıma gücü tayini

Abstract

İzmir bölge olarak kompleks ve -farklı tektonik koşulların hüküm sürdüğü zonlar içinde yer almaktadır. Jeolojik yapısından anlaşılacağı gibi doğu-batı ve bağlı doğrultularda -faylarla kesilerek kırıklı bir yapıya sahiptir. İzmir ve çevresi i. derece deprem kuşağında yer almaktadır. Deniz Bostanlısı olarak adlandırdığımız etüd alanı, İzmir körfezi çökelme ortasında, oluşumu günümüzde devam eden ve 4. zaman alüvyonlarının oluşturduğu Gediz deltasının uzantısının içinde yer atmaktadır. Bediz delta birikintilerinin SO - H5 m. derinliklere kadar devam ettiği görülür. Bu yönüyle taşıma gücü ve özellikle oturma kriteri açısından problem arz eder. Arazinin geoteknik yapısının, her alanda ayrıntılı zemin etüdlerinin yapılmasıyla belirlenmiştir. 7 Adet kazık çakım deneyi yapılmıştır. Bundan çakma kriterleri için ön değerler belirlenmiştir. Kazıkların sınır yükü tespiti ve dolayısıyla servis yükünün saptanması amacıyla yükleme I, II, III deneyleri bizzat benimde bulunduğum halde yapılmıştır. İ. T. Ü. Yapı Ve Deprem Uygulama Araştırma Merkezi tarafından yürütülen tüm bu çalışmalarda çakma kazık ile fore kazığın avantajları birleştirilmeye çalışılmıştır. Zemine vibrasyonla, itme kapasitesi çok yüksek bir özel çakma aleti kullanılarak çakım gerçekleştirilmiştir. Çakım sırasında forajdan oluşan zemin katmanlarındaki de-formasyon minimuma indirilmiştir. Deneylerde servis yükünün tatbikatında oturmalar 5 mm. 'nin altında ; sınır -yükü olan 150.0 ton civarında yükün tatbikatı sırasında oturmalar S cm. altında kalmıştır. Yaptığımız 7 adet çakma deneyi sonuçları da değerlendirilerek saptadığımız servis yükünü sağlayacak çakma kriterleri saptanmıştır. Böylece kazık servis yükünü 75.0 ton olarak belirlenmiştir.

Izmir is a region which is on the zones conposed of deifferent techtonic conditions. Izmir is placed on west -east alighed faulting line whose placement area is the 1 st degree of earthquake region. The research area, called Deniz Bostanlisi,is in the "Delta" which has been formed by aluvions of 4 th age. The beach consists of soft clay, very fined sandy silt and clay mixtures. Those sediments are of low bearing capacity; cansettle to much in case of loading. This sediments can be seen to the depth of 20-25 m. therefore, a lot of settlement problem are faced. Today ; old Gediz Delta is in the appearance of march, and this area has been filled gravelly material so high bearing capacity was abtained. The other buildings and structures will be established on this filled area. For this construction purposes some soil investigations will be made. The two main groups of investigation geophysical and geotechnical surveys, will be achieved. The geotechnical surveying is consisted of 36 boring, 19 Holland boring and some loading tests for piles. So the ultimate bearing capacity of piles will be obtained and the value will be used in calculations. In addition to these, this summary was improved by; founction of piles, use of piles, load transfer, loading tests and interpretations of loading tests, negative skin friction, installing test piles and vibrodeplacement piles. The previously driven piles that are 35*35 and 40*40 square cross-sectioned have been driven with hammer. Although the average loads are between 35 t and 40t; the test loads are between 29 t and 78.6 t. There are some differantial settlement greater than 2 cm. among piles and pile group H is not possible to deter mind the penetration of the piles onto firm soil due to the different pile lengthn. vii a = 0.55 and b = 0,50 and -from aquation that log N = a - b M i 5 resulted M = 4.7 According to bulding age of 50 years in Izmir. It is offered that the largest eartquake magnetud M is 7.5 and a = 0.5 q It is appropriate that acceleration value is chosen minimum SO % in dynamic calculations. According to this, it is obtained that a = 0.20 g max On the other hand eartquake behaviour spektraswich had been determined on the soil surface is shown on fig 2."/ and 2.8 soil governing period, is prudenced between 1.5 and 4.0 seconds. It is mode 36 soil drillings whose depths changes between 35 and 55 meter. During the soil drillings it is especially determined these subjects : Soil layers., layer boundary depths, geotechnic properties of the layers. Including this in some borings ; pressiometre, Vane and SPT experiments, unmistreated and representative soil samples had been taken. We can summerije that SPT results are as follows ; N = 1 - 3 between 0.00 - SE.O m. N = 15 - 20 after 23.0 and 24.0 m. vm Vane experiments had been done between the depths o-f 12.0 - 15.0 - 18,0 - 21.50 m. and determined undrainage slide resistances, Cu is between 0.16 - 0.45 kg/cm2. At mentioned depths above according to the determined value, it is determined that soil consolidation under itself weight of soil still continues and observed that it isnot finishedyet. We can summarize pressiometer -field experiment results are as follow 5 At the top layers o-f soil. A-fter than 19 m of soil surface, specific some values had been obtained. Horizontal deformation modül value E varies between 32 - 113 kg/cm2. N et limit pressures P* varies between 3.09 - 15.64 'kg/cm2 ( App.5) CPT, conic penetration experiment had been done as an Holland drilling in 19 points if had been observed that the results were similior with the results of SPT and labaratuary experiments. Experiments had been finished when the end resistance wasbigger than 200 kg/cm2 and continuous. I» If we make a profitable use of field tests essencially ; In cohesionless bases -the SPT, stroke number of qualified transporter horiHons is found N = 25 this gives us the peculiarity of a stiddle dense stratum. In cohesionless base between SPT and cone penetration test the values of q MN tip is an acceptable water in general. Therefore if we limit the pile cowl deformation our limit is q > 100 Kg /cm2 in cohesionless bases, the out set limit of transporter base is up to natural water contents and plastic limit. They have to be close to each other. IX Being C > 1 r is the most better condition we must be more careful in cohessionless soil while we are evaluating the results of SPT test. For SPT stroke number î N > 10 - 12 and if it is in drainageless cohesion C > 0.75 kg/cm* u it gives as the outset limit of a qualified bearing Unexhausted and representative potterns was taken from the 36 boring pits which were bored un the area for the aim that to make the laboratory tests of Izmir Deniz Bostanlisi index properties that was found 3tb '« Natural water contents is generally neorby liquid limit values at upper soil layers. But at bearing qualified cohesive soils the values are found near to plastic limit right consistency. Right consistency limits have been examined according to connected soil classification. And also it has found that soils take place into the class of CH - MH. Particile distribution was made on the cohesiontess soil pattern. From the contents it has determined that silt ratio is high and also it comprise, sand and clay. Unreserved pressure and triaxial pressure tests were performed to define. The result of unreserved pressure ; q >_ 1.35 Kg /cm2 u And the result of triaxial pressure test is ; Cohesion s C = 0.00 kg/cm2 cd Shear strength angle : = £6 - 29 cd (with consolidation and drainage ) Load transfer I - End bearing piles When a pile is driven through material with little or no penetration resistance to frim bearing on or a short distance into a relatively hard soil or a rock -formation it is said to be en bearing Under these conditions the pile functions -for all practical purposes as a column. It is assumed to derive no vertical support.from the material in which it is embadded and to deliver its full load, undiminished, to the bearing material at the tip. However, it is customary to assume that the material surrounding the pile provides significant lateral support and that, in calculating column strength, the usual rules relating to buckling can be disregarded. Endbearing piles are usually characterized by a fairly constant cross section rather than being tapered like friction piles. II - Friction piles The designation friction pile implies that all or the major part of the loading on the pile is transmitted to the soil through friction at the pile surface with a friction pile, load transfer is accomplished gradually over the full lenght of the pile. The compressive stress in the pile itself there fore decreases with depth and use of tapered piles can be justified on this basis. If may be noted that- skin friction evidenced itself not on in providing a means of support for static loading but also as a factor which affects penetration resistance.during driving resistance, in fact is widely used as an index of the capaifity of a pile to support static loading. xx Skin frictionm and/or adhesion at the pile surface can develop an extremely effective bond between the pile and the soil. The supporting capacity of a -friction pile does not depend solely on the development of adequate skin friction and shearing strentgh in the soil surrounding the pile A further ; requirement is that the material beneath, the pile tips must have adequate bearing capacity. Loading tests The purpose of a loading test may be either to determine the ultimate bearing capacity of. a pile or the check whet her a pile can safety carry its desing bad as determined by one of the pile formulae. Provided the test is well recorded and carefully interpreted, the dead which a single pile can support without exessive settlement may be used as an inication of the safe working bad the fullest possible information is required regarding the elastic and plastic settlements caused by the applied load. Test loads may be applied in the form of kentledge placed directly on a platform on top of the pile, or indirectly at the end of a lever. Alternatively the test pile may be driven in by a hydraulic jack bearing against a rigid beam supported on two firmly driven anchor piles. The anchor piles should be 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 remove the load completely after each increment has been applied. When a load is applied to a pile the resulting settlement is made up of the elastic compression of the pile and partly of plastic deformation of the soil It is important to determine the ratio between these two deformations. If each increment of load is allowed to act until movement has ceased and removed before the next increment is applied the permanent set or plastic settlement can be measured. The resistance of the soil to the aptied loading may be assumed to originate from the depth defined by i when this depth is compared with the soil profile obtained during the site investigation the state which are concerned in developing resistance can be identified. A simpler method of carr ying a loading test is to plot each increment of load against the settlement reached when movement ceases. Each increment beeing applied without removal of load. The XI i ultimate load which the pile will carry may then be shown by the.flattening slope o-f the curve. A load -factor of two or there can then 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 may reliable indications can be obtained of the strength of the different groupings of strata, and hence, by difference, of the strengths of individual layers. Interpretation of loading tests The data obtained by careful study of the elastic and plastic load / settlement diagrams furrish a reasenably accurate estimate of ultimate of ultimate bearing capacity in cohesionless soils. Ip chesive soils, however, the data must be troated with caution These load / settlement diagrams relate only to short - term loading ; hence the settlemen 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 loading applied to the soil it is possible to estimate probable final settlements but the deformations measured during the loading test are by themselves nosure guide. While the pile loading test is being fullfilled ; the vertical deformations are measured with 1 / 100 mm. presicion, but the extensiometer with 5 cm. mobility or leveling device with 0.3 mm. presicion are preferred, especially. We have some country regulations and specifications about loading and unbadihg. Most common wed of these are Din 1054 and ASTM - D - 1143. According DIN - 1054 ; for in-situ poured piles ; the bearing capacity of pile is the load that causes 2 cm. settlement in pile According to ASTM-D-1143 the servis load is determined with the load corresponding to 3.3 cm. settlement at load - total settlement curve. The underground water in our research area comprises harmful I materials and water level har been determined from analysis reports. X11I For this reason, it has been tought that to us trans cement and admixture material which increase the -fluidity of the concrete. The area appears marshy, It has been touhght that by -filling that area, soil improvement was obtained. In the design of light weight building', like ville and for the purpose of soil improvement ; preloading, waiting, vertical sand drains, improvement of soil by changing soil stratification were quest igated. Research has been conducted for the purpose of construction of piles of highrise buildings which is related to the pi!»?? applied beforehand and also related to offered type of pile As a result, a test pile has been driven into soil between S9 and 310 borings with CPT İ7 value. A steel pipe with 58 cm. drameter has been driven up to E7.60 m. depth. Allowable service load for pile is obtained as 70.0 t with respect to TS 3167 and Table 6.4 C313. Boring is a mesurement of a special end which is being forced into soil by pushing, driving or rotating. From these, we will use the push boring and Hol Ian borings. Vibrodeplacement piles t These piles are suitable when the condition pi the soil is not so soft that it has little resistance to the flow of the concrete. They btb particularly suitable when ground of low bearing value but adequate consistency to resist flow is encountered far «. considerable depth. The base has an enlarged rim that diminished the frictional resistance during driving. Method of forming. (a) A stell tube with a cast-iron shoe of slightly larger dimension is driven to the required. (b) The tupe is filled with concretem and concreted to the hammer by extracting links. The extraction of the tube an foundation of the pile are ©fleeted by the hammer, each upward blow being followed by a downward tamping blow, During the upward blow, the tube rises and the concrete moves out under the rim during the downward blow the friction of the tube on the concrete tamps it. (c) The finished concrete shaft.present a corrugated air face. XIV These piles are used extensively in Europe and the British Isles. Advantages of VibrDdeptacement piles s a) Since the strenght of poured concrete is quickly gained, a new pile aport -from theprevious one 4.5 - 5 m. can be constructed a few hours later without any damage to other pile. b) In the meantime of construction o-f vibrodeplacemet pile, due to the increase of pile diameter in some depth, the negative skin friction of soil is eliminated. c) In the construction internal 5 no liquefaction or no dşmage in the structure or in the texture soft clay is seen. d) Due to high energy in the vibrator, it is possible to reach any depth wanted. e) After vibratory driving : at tip of pile, compression occurs and the compression yields the increase at tip resistance. In the test piles, the 1 st, 2nd, 3 rd and 7 th drivings are performed only by driving and pulling out of piles. In the 4 th and 5 th piles the steel work that is reinforcement, is achieved, then concreting is done to be able to do the loading I and loading II At the 6 th pile, only driving is performed, but the pulling out of pipe wasnot done. Test results ; there is a parallelity between these test results and previously made controlled drivings. It is understood that ; in case we get suitable results from loading tests, driving criteria will be determined. Loading test and results 5 loading I and II tests are done by the method of dead load. Iron is used as dead load at the loading platform. The outmost compression numbers supporting that load are wall and concrete support and main supports comprises hot rolled steel bars. All these can be seen at figure 8.4. and 8.5.. The height of platform is i.80 m. and the necessary protection is. done aganist wind, fain and bad weather conditions. The pressure measurement device is hydraulic cricko press. xv The settlement is found under 5 mm. around the service load in loading I and II tests. At the max. allowable load, İ50 t, the total settlement is under S cm. All the curves of load - settlement and settlement - time are plotted by the time of tests. All loading test are achieved according to that ; each pile has lenght of 4 - 5 m. in the bearing soil.The heg.fr ict ion of piles is found as 7.0 - 9.0 tonne / length. As a result ; the safety factor is S and the service load or project load for pile is ; Q = 75.00 t 5 regstayins in the safeside. By taking care of the pile driven criteria values in side differences between the regions. The first 400 - 500 driven results willbe controlled continuesly. Therefore, the part differences between' the regions will be revised. When the driven pressure reach 130 - 140 bar in a first gear, it will be increased to the second gear. In the second gear when we are over 2' minute for 10 cm genetration. It will be on the third gear. It will be continued to the driving till that pile length will be minimum 3m. in a firm soil.