Barajlardaki deformasyon ölçmeleri ve kullanılan aletler

Abstract

Günümüzde dünyanın pek çok yerinde bir çok büyük sanat yapıları yapılmak -tadır. Bunların yapımı için pek çok elemana, zamana ve paraya ihtiyaç olmaktadır. Bu yapıların yapılmasından sonra yapılacak ve bu büyük sanat' yapılarının yapımı kadar önemli bir konuda bu yapıların planlanması aşamasında düşünülen emniyet sınırları içinde varlığını sürdürüp - sürdürmediğidir. Diğer bir deyişle yapıda herhangi bir deformasyon olup olmadığının araştırılmasıdır. Büyük sanat yapılarındaki olası deformasyonlarm önceden belirlenmesi ve muhtemel kazalardan korunmak için deformasyon ölçmeleri yapılır. Bu ölçme sonuçlarına göre yapı da önlem alınır. Barajlarda yapılacak deformasyon ölçmeleri fiziksel ve jeodezik olmak üzere iki farklı yöntemle yapılır. Fiziksel yöntemde barajlardaki bağıl hareketler ölçülür. Bu gruptaki ölçmelerde kullanılan aletler deformasyonu belirlenecek yüzeyin içine veya üzerine yerleştirilir. Günümüzde deformasyonlar sürekli izlenebilir. Bilgisayar alanındaki gelişmeler bunu mümkün kılmıştır. Yapılan deformasyon ölçmeleri bir bilgisayara kaydedilerek veya elektriksel işaretlere dönüştürülerek bir ekrandan izlenebilmektedir. Deformasyonların sürekli izlenmesi ile ani olarak ortaya çıkan deformasyonlar ve tektonik hareketler sonucu ortaya çıkan yer kaymaları belirlenebilmektedir. Deformasyonların sürekli izlenmesi için kullanılan aletlerden en yaygın olanı Talyvel elektronik düzecidir. Jeodezik yöntemde ise lokal bir jeodezik deformasyon ağı kurulur ve yapıda jeodezik ölçmelerle ağın tümden mutlak hareketleri belirlenir. Yapılan ölçmeler matematik - istatistik yöntemlerle değerlendirilir. Deformasyon vektörleri elde edilir. Bu vektörlerin irdelenmesi sonucu o noktada deformasyon olup - olmadığı belirlenir. Bu çalışmada genelde deformasyon ölçme yöntemleri ve özellikle de fiziksel yöntemlerle bir barajdaki deformasyon ölçmeleri ve kullanılan aletler anlatılmıştır.

Deformation measurements are getting more important novadays. Because of the number of the big art buildingsare increasing. They must be measured at a certain moment whether there is a deformation or not. It is called deformation measurements to determine deformation in a big art building (dam, bridge, skyscraper v.b.) Deformation are examined different models according to the kinds of problem, the shape of problem, content and appl i eating measurement method. These are dynamics, kinetics and statick models. Prior to the design a dam, a topographic survey is made to determine the feasibility of the project, the approximate size of the r ezer voir, and the optimum location and height of the dam. To provide information for the design, a topographic survey of the size is made, similar in many respect to that for a bridge. Extensive soundings and borings are made, and topography is taken in detail sufficient to define not only the dam itself but also the appurtenant structures, necessary construction plant, roads, and perhaps a branch railroad. A property line survey is made of the are to be covered by, or directly affected by the proposed r ezer voi r. Prior to construction, a number of transit stations, sighting points, and bench marks are permanently established and referenced upstream and downstream from the dam, at advantageous locations and elevations for sighting on the various parts of the structure as work proceeds. These reference points are usually established by triyangulation from a measured base line on one side of the valley, and all points are referred to a system of rectengular coordinates, both in plan in elevation. To establish the horizontal location of a point on the dam, as for the purpose of setting concrete forms or of checking the alinement of the dam, simultaneous sights are taken from two transits set up at reference stations, each transit being sighted in a direction previously computed from the coordinates of the reference station and of the point to be established However, it may be established by setting off on one Of the transits the computed vertical angle, the height Of instrument being known. Deformation measurement methods two groups; can be seperated 1 -Geodetic deformation measurement- method, 2 -Physical deformation measurement method. Absolute movements are measured and determined in geodetic deformation measurement methods. Relative movements are measured and determined in physical deformation measurement methods. Engineering science and naturel sciences can be used casuring in the physical deformation measurement method. Obtaining results are relative characteristic and measurement can be done remote measuring technique- The instruments of measurement are placed on the ground or inside or outside of the buildings. Generally, measurement in a dam can be classified like that in the physical deformation measurement methods; l-)Measurements are done in order to determine the statement of the material of the trunk filling and base ground : In this group measurements can be lined up; a-) Measurements that vacuum water and base water : Piezometers and observation boreholes are used in order tp measure vacuum water. Height of water surface may be measured with refinement by piezometer or manometer, consisting of a graduated glass tube, which is connected in a vertical position to a pipe, the other end of which is in the flowing water, the top of the glass tube being above level of the water surf ace. Piezometers are seperated three groups; -Hydrolic piezometer, -Pneumatic (hydrometer) piezometer, -Electric piezometer, b-) Measurements of the trunk concrete deformation : The behaviourof the matters under pressure and shrinkage forces is to determine, before deformation modüle and poison coifficent of that matter must be known. Streynmeters are appropriate to determine this. Two kinds of streynmeter are used on dams. These are active and normal streynmeter. Acoustic streynmeter are placed concrete of dam by threes groups spaced 20-40 cm each other to fix regional tension of their avarage positions. Normal streynmeters are used to measure deformation of unpressed concrete that affect below the variation temperature and state of moisture. c-)Heat measurements in the trunk : Heat measurements are done by acoustic thermometer and telethermometer. Working principle of acoustic thermometer is based on same principle like streynmeter. Vibration of a wire streched two ends is changed to depend upon variation of wire temperature. This variation; VI 11 T - To = K * can be calculated this formulation, where. To =Beginning temperature, T = Acoustic temperature, Fo = Measured frequency at beginning temperature, F = Measured frequency at acoustic temperature, K - Is a coefficient to depend upon the lengt of wire, thickness and kind, 2-) Measurement s are to determine movement in the trunk and using instruments can be classified like that; a-) Measurements of rotation, bending, tension and pressure and horizontal movements : In this gruop measurements are done instruments such as teleformeter, telepresmeter, tenso-pick up. the scale of acoustic tension and pendelum. Pendelum is appropriate to measure horizontal movements in dams and base and it is simpler than theirs. b-) Measuring that derz and crack : In concrete dams measuring the space of derz is determined horizontal deformations of dam trunk on the different height. Jointmeter is a frame that is made of a 200 mm height aluminium or brass. A stick that is made of stell and can be opened side is attached an end of this frame. The amount of opening stell stick is measured by micrometer. c-) Measurements removing pressure is fixed instruments that measured pressure or acoustic instruments d-) Measurements of leakage. 3-) Measurements that is to determine exterior load and used instruments ; a-) Measurements that deformations of base rock : Deformeter is used to control 1 deformation of base rock. Basically, deformeter is simi liar jointmeter as a measurement instrument. A deformeter isn't only placed to measure deformation of base rock. Generally, two deformeter are placed. b-) Measurements that vertical rotation and bending of blocks : Inclination measured is used to measure vertical rotation of dam trunk and blocks and to fix whatever this kind of varitions. There are different kinds inclination measured. These are klinometer with wires. It is formed a stick and a weight that hang this stick and is placed in a cylindrical borehole. IX Inclinator is a mechanic instrument that is used to determine bending on vertical surfaces and small inclination d-)Measuring water levelling in the rezervoir : Water levelling in the rezervoir are done with mare graph. d-) Seismic measurements : Seismic measurements are done continuous stations that is set up surroundings of dam. Obtaining results are evaluated in the central. e-) Atmospheric measurements : Because of dam security, surroundings of dam, before dam hasn't been constructed an atmospheric observation station is set up. In these stations. Atmospheric temperature. Pressure, Moisture, The velocity of wind. Daily rain, measurings are done and are recorded. Geodetic control measurements are done certain moment. Therefore, geodetic measurements aren't determined to be formed instantaneous deformations. Deformations must be traced continious in order to determine instantaneous deformations. Using commonly measurement instruments to traced continious in the structure deformations those are ; a- Weggeber, b- Electronic Alinement, c- Automatic Hydrostatic Levelling, d- Electronic Levels. in this instruments, weggeber and electronic alinement, deformations are determined to be measured variations of lengt in the structures. In the automatic hydrostatic levelling deformations are determined to be measured variations of height. However, electronic levels, deformations are determined to be measured variations of inclination. Electronic levels are two groups that are electrolitic and pendulum in order inclination measures. Talyvel level is the most common kind of instrument in the pendulum in order inclination measures. We can also seperate two groups geodetic deformation measurement methods. 1 -Methods can be used that determining defermation in the horizontal direction; a Geodetic deformation network method, b Precision polygon method, c Mi nement method, x 2-Methods can be used that determining defermation in the vertical direction; a Precision geometric levelling method, b Precision trigonemetric levelling method, c Hydrostatic levelling method, Geodetic networks that are used to determine the deformations are local networks. This networks needn't depend upon whichever coordinates system. Jeodetic deformation network must be reached from mouth of a river to fountain and be contained critics points in order to be indicated the movements. In generally, there are four different characteristic points in a geodetic deformation networks ; a- Object ( deformation ) Points, b- Control Points, c- Orientation Points, d- Insurance Points In application, geodetic netvorks are met that aren't contained orientation and insurance points. In deformation analysis first of all, datas are subjected to a front balancing. Disdordant measurements are cleared. After that difference vectors are obtained in the object points one by one, d difference vector is, d-d + d + d 12 3 it is formed like three different components. These are; d4 - Likely deformation in the point, d2 - Local inclined in the point, d - It is a difference that is occured because of 3 the at random measurements errors. The basic aim in the interpretation is that : the cause and effects of deformations, the safety and decided researching object must be determined and to take measures aganist deformations and earths sliding in the structures e.t.c. can be arranged with the technic members of the other branches. There are a lot of advantage because of determining deformation three dimensions, different combination of the geodetic methods can be used according to conditions and alternatives in practice.