Nokta Yükleme Deneyi ile İlgili Uygulamada Karşılaşılan Problemler

Abstract

Nokta yükleme deneyi, iki konik uç arasına yerleştirilen kayaç örneğinin kırılması esasına dayanmaktadır. Yenilme yükü ve örnek boyutları kullanılarak bulunan nokta yükleme dayanım indeksi çeşitli amaçlarla mühendislik jeolojisi çalışmalarında kullanılmaktadır. Bu makalede, nokta yükleme deneyi ile ilgili uygulamada karşılaşılan aletsel ve kullanıcıyı ilgilendiren problemler tartışılmıştır. Yazarın uygulamada elde ettiği deneyimleri sonucu, standart deney formuna kayacın "D”' boyutu, kırılma zamanı ve yüzde olarak yenilme yüzeyindeki süreksizliğin ve kayaç dokusunun kontrolü hakkındaki bilgilerin eklenmesi önerilmiştir. Tek eksenli sıkışma dayanımı (σc)- nokta yükleme dayanım indeksi (Is(50)) oranının (k) değişik kayaçlar için çok geniş bir aralıkta değişmesi nedeniyle, mühendislik projelerinde bu oran ayrıca belirlenmelidir. Bu çalışmada, tüfler için kullanılabilecek yüksek korelasyon katsayısı veren (<σc)-(Is(50)) ilişkisi sunulmuştur.

Keywords

• K-Değeri
• Mühendislik Jeolojisi
• Nokta Yükleme Dayanim Indeksi
• Tek Eksenli Sikişma Dayanimi
• Tüf

Problems Faced in The Applications of The Point Load Index Test

Abstract

The point load index test is based on the principle that rock sample is broken between two conical platens. Failure load and specimen dimensions are used to calculate the point load strength index and this index is used in engineering geological studies. In this paper, the problems related to the point load testing device and the common mistakes of the users are discussed. Based on the experience of the author, a proposal for including "D’ " dimension of the rock, failure time, and textural and structural information of the failure surface of rock in the point load test form is given, k-value, defining the ratio between the uniaxial compressive strength (soc) and the point load strength index (Is50), varies significantly for different rocks. Therefore, k-values for different rocks should be assessed for engineering projects. In this study, a linear relationship with high correlation coefficient between (σc) and (Is(50)) is given for tuff's.

Keywords

• Engineering Geology
• K-Value
• Point Load Strength Index
• Tuff
• Uniaxial Compressive Strength.

References

1. Abbs. F.A., 1985. The use of the point load index in weak carbonate rocks. ASTM Special Technical Pub. 883 (R.C., Chaney and K.R., Demars), Strength Testing of Marine Sediment, Laboratory and In-situ Measurements, 4 13-421pp.
2. Al Jassar. S.H., and Hawkins, A.B., 1979. Geotechnical properties of the Carboniferous limes¬ tone of the Bristol area-the influence of petrography and chemistry. 4th. Conference on International Society for Rock Mechanics, Montreoux, 1, 3-14pp.
3. Anıl, M., Kılıç, A., Kahraman. S., Sandıkçı, M., ve Akyıldız, M., 1996. İscehisar (Afyon) mermerlerinin petrografik ve mekanik özellikleri. KTÜ Jeoloji Mühendisliği Bölümü 30. Yıl Sempozyumu, Cilt 1, 436-447s.
4. Anon, 1972. The preparation of maps and plans in terms of engineering geology. Quarterly Journal of Engineering Geology, 5, 293- 382pp.
5. Beawis, F.C., Roberts, F.L, and Minskaya, L., 1982. Engineering aspects of weathering of low grade metapelites in an arid climatic zone. Quarterly Journal of Engineering Geology, 15, 29-45pp.
6. Bell, F.G., 1992. Engineering properties of soils and rocks. Butterworth-Heinemann, Oxford, 345 p.
7. Bieniawski, Z.T., 1975. The point-load test in geotechnical practice. Engineering Geology. 9, 1-11pp.
8. Bieniawski, Z.T., 1989. Engineering rock mass classifications. Wiley, New York. 264 p.

9. Bowden, A. J. Lamoni Black. .1., and Ullyott, S., 1998. Point load testing of weak rocks with particular reference to chalk. Quarterly Journal of Engineering Geology. 31. 95-103pp.
10. Broch, E., 1983. Estimation of strength anisotropy using the point load lest. International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 20,181-187pp.
11. Broch, E., and Franklin, J.A., 1972. The point load strength test. International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 9, 669-697pp.
12. Brook, N., 1980. Size correction for point load testing (Technical Note). International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 17, 231-235pp.
13. Brook, N., 1985. The equivalent core diameter method of size and shape correction in point load testing. International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 22, 61-70pp.
14. BSI, 1981. Code of practice for site investigations BS 5930. British Standards Institution, 147 p.
15. Cargill, J.S., and Shakoor, A., 1990. Evaluation of empirical methods for measuring the uniaxial compressive strength of rock. International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 27, 495-503pp.
16. Carter, P.G., and Sneddon, M., 1977. Comparison of Schmidt hammer, point load and unconfined compression tests in Carboniferous strata. Proceeding Conference on Rock Engineering, Newcastle, UK, 197-210pp.
17. Cavagnaro, R.L., 1980. Geotechnical testing for Leigh Creek Coalfield. Proceeding 3rd. Australian and New Zealand Conference on Geomechanics., Wellington, 1, 237- 242pp.
18. Chau. K.T., and Wong, R.H.C., 1996. Uniaxial compressive strength and point load strength of rocks (Technical Note). International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 33, 183-188pp.
19. ELE, 1990, Point load test apparatus, Operating instructions, ELE International Ltd., 13 p.
20. Fookes, P.G., Gourley, C.S., and Ohikere, C., 1988. Rock weathering in engineering time. Quarterly Journal of Engineering Geology,21, 33-57pp.
21. Forster, I.R., 1983. The influence of core sample geometry on the axial point-load test (Technical Note). International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 20, 291-295pp.
22. Greminger, M., 1982. Experimental studies of the influence of rock anisotropy on size and shape effects in point-load testing (Technical Note). International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 19, 241-246pp.
23. Guidicini, G., Nieble, C.M., and Cornides, A.T., 1973. Analysis of point load lest as a method for preliminary geotechnical classification of rocks. Bulletin of International Association of Engineering Geology, 7,37-52pp.
24. Hagenaar, J., Sijlsma, H., and Wolsleger, A., 1984. Selection and use of piles for marine structures in coral formations and carbonate sediments. Conference on Piling and Ground Treatment. Institution of Civil Engineers. Thomas Telford. London. 77-86pp.
25. Hassani, F.P., Scoble, MJ., and Whittaker, B.N.,1980. Application of the point load index lest to strength determination of rock and proposals for a new size-correction chart. The Slate ol the Art in Rock Mechanics, Proceedings 21th. US. Symposium on Rock Mechanics. 543-553pp.
26. Hawkins. A.B., 1986. Rock descriptions. Site investigation Practice: Assessing BS 5930, Special Publication No.2. 59-72pp.
27. Hawkins. A.B., 1998. Aspects of rock strength. Bulletin of Engineering Geology and the Environment, 57(1), 17-30pp.
28. Hawkins, A.B., and Olver. J.A.G., 1986. Point load tests: Correlation factors and contractual use. An example from the Corallian at Weymouth. Site Investigation Practice: Assessing BS 5930, Special Publication No.2. 269-271pp.
29. ISRM, 1972. Suggested method for determining the point-load strength index. ISRM Committee on Field Tests, Document No. 1, 8-12pp.
30. ISRM,1985. Suggested method for determining point load strength. International Journal of Rock Mechanics, Mining Sciences and Geomechanical Abstracts, 22, 51-60pp.
31. Jenni, J.P., and Balissat, M., 1979. Rock testing methods performed to predict the utilization possibilities of tunnel boring machine. Proceedings of 4th. Int. Soc. Rock Mechanics, Montreoux, 2, 267-273pp.
32. Kahraman, S., 1996. Basınç direnci tahmininde Schmidt ve nokta yük indeksi kullanmanın güvenilirliği, KTÜ Jeoloji Müh. Bölümü 30.Yıl Sempozyumu. Cilt 1, 362-369s.
33. Leung, C.F., and Radhakrishnan, R., 1990. Geotechnical properties of weathered sedimentary rocks. Geotechnical Engineering, Thailand, 21, 29-48pp.
34. McFcat. S., and Tarkoy. P.J., 1979. Assessment of tunnel boring machine performance. Tunnels and Tunnelling, 11 (10), 33-37pp.
35. Norbury. D.R., 1986. The point load lest. Site Investigation Practice: Assessing BS 5930, Special Publication No.2, 325-329pp.
36. Pcltifer, G.S., and Fookes, P.G., 1994. A revision of the graphical method for assessing the excavalabilily of rock. Quarterly Journal of Engineering Geology, 27,145-164pp.
37. Rao, K.S., Venkatappa Rao, G., and Ramamurthy, T., 1987. Strength of sandstone in saturated and partly saturated conditions. Geotechnical Engineering, Thailand, 18, 99-127pp.
38. Read, J.R.L., Thornton, P.N., and Regan, WJML, 1980. A rational approach to the point load test. Proceedings 3rd. Australian and New Zealand Conference on Geomechanics, Wellington, 2, 35-39pp.
39. Robins, P.J., 1980. The point-load strength lest for concrete cores. Magazine of Concrete Research, 32, 101-111pp.
40. Rodrigues, J.D., and Jeremias, F.T., 1990. Assessment of rock durability through index properties. Proceedings 6th. International Congress IAEG.,4, 3055-3060pp.
41. Türk. N., 1988. Kayaçların nokta yükleme dayanımını bulmak için yeni bir yöntem. Mühendislik Jeolojisi Bülteni, 10. 25-3 İs. Türk, N., and Dearman, W.R., 1985. Improvements in the determination of point load strength. Bulletin of International Association of Engineering Geology. 31. 137-142s.
42. Türk, N., and Dearman. W.R., 1986. A new procedure for determination of point load strength in site investigation. Site Investigation Practice: Assessing BS 5930. Special Publication No.2. 406-41 Is.
43. Ulusay, R., Gökçeoğlu. C. ve Binal A., 1997. Kaya Mekaniği Laboratuvar Deneyleri. Ders Notları 39. Hacettepe Üniversitesi Yayın No.3, 53 s.
44. Ünal. E. ve Tutluoğlu, L., 1986. Kaya Mekaniği İlkeleri, Seminer no.6, ODTÜ Maden Mühendisliği Bölümü, 223 s.
45. Wiesner, E., and Gillate, S.J., 1997. An evaluation of the relationship between unconfined compressive strength and point load strength index. Bulletin of International Association of Engineering Geology, 56, 115-118pp.
46. Wijk, G., 1980. The point load lest for the tensile strength of rock. Geotechnical Testing Journal, 3, 49-54pp.
47. Wilson. L.C., 1976. Tests of bored and driven piles in Cretaceous mudstone al Port Elizabeth. South Africa. Geotech Nique, 26. 5-12pp.