GEOTECHNICAL CHARACTERIZATION OF THE ANTALYA KARSTIC ROCK MASSES Dr. Evrim Sopacı Consulting Engineer/Temelsu
T U R K E Y The city of Antalya is built on and surrounded by one of the largest (600 km 2 ) and thickest (up to 250 m) deposits of tufa (i.e. calcium carbonate precipitated from cool-water springs) in the Mediterranean region, or elsewhere. Tufa, rather than the more traditional travertine, which is reserved for hotspring deposits (>20C), derives from Tophus, originally used by Pliny to describe a porous rock. 2
Geotechnical Characterization of the Antalya Karstic Rock Masses 3
Why is Tufa significant in the field of engineering geology? missing geotechnical database unknown controlling parameters of the strength and the deformability characteristics of the Antalya tufa rocks an engineering classification pertaining to the Antalya tufa rocks is missing in the literature the engineering classification to produce rock specific design parameters (i.e., shear strength parameters, deformation modulus, etc.). 4
Geotechnical Characterization of the Antalya Karstic Rock Masses b- c- d- e- a- a- PHYTOHERM FRAMESTONE b- MICROCRYSTALLINE c- PHYTOHERM BOUNDSTONE d- INTRACLAST e- PHYTOCLAST 5
Geotechnical Characterization of the Antalya Karstic Rock Masses Laboratory and field tests Uniaxial Compressive Strength Test Seismic Refraction Tomography Triaxial Compressive Strength Test Pressuremeter Test Indirect TensileStrength Test Unit weight and Porosity determination 6
Results of Lab Tests of the Antalya tufa rock types Uniaxial compressive strength test Brazilian tensile strength test Tufa types σ c (MPa) E (GPa) ν σ t (MPa) No. of Std. Mean Mean Std. Mean Std. No. of Std. Mean sample dev. dev. dev. sample dev. Microcrystalline 10 18.56 7.94 8.44 4.57 0.09 0.04 11 3.10 1.20 Intraclast tufa 3 4.66 1.34 1.54 0.61 0.29 0.23 - - - Phytoherm framestone 13 7.76 5.35 4.41 2.99 0.11 0.05 9 1.40 0.80 Tufa type Porosity (%) Unit weight (kn/m 3 ) Mean Std. Dev. Mean Std. Dev. Microcrystalline tufa 10.6 3.9 20.9 1.3 Phytoherm framestone 14.0 5.6 20.8 0.9 Intraclast tufa 14.0 5.9 18.6 2.4 7
Results of Lab Tests of the Antalya tufa rock types P-wave velocity (m/s) S-wave velocity (m/s) To (s) Type / Parameters Mean ± St.d. Mean ± St.d. Mean ± St.d. Intraclast 1836 ± 496 693 ± 210 0.33 ± 0.09 Phytoherm framestone 2350 ± 443 930 ± 71 0.23 ± 0.02 Microcrystalline tufa 2299 ± 437 1234 ± 311 0.21 ± 0.04 Tufa type c (MPa) φ ( ) m i Mean Std. Dev. Mean Std. Dev. Mean Std. Dev. Microcrystalline tufa 3.41 2.51 37.8 12.1 15 9 Phytoherm framestone 3.21 1.12 33.1 18.4 6 3 Phytoclast 1.57 0.52 31.6 10.9 9 5 8
Results of Lab Tests of the Antalya tufa rock types Borehole Location Depth (m) Lithology PL (kpa) PLn (kpa) E (MPa) BH-4 Lara 2.50 785 627 5.70 BH-4 Lara 10.0 2000 2000 99.5 BH-4 Lara 13.0 Intraclast tufa 2000 2000 43.2 BH-7 Lara 8.00 588 431 5.54 BH-8 Konyaaltı 1.50 2452 1978 59.6 BH-2 Lara 3.50 1569 1215 12.3 BH-2 Lara 9.50 2000 2000 95.3 BH-3 Lara 2.50 Phytoherm framestone 2000 2000 86.4 BH-3 Lara 6.00 1765 1411 14.2 BH-6 Lara 1.50 2059 1603 98.4 Mean ± one standard deviation Intraclast tufa 1565 ± 826 1407 ± 805 42.7 ± 39.6 Phytoherm framestone 1878 ± 207 1646 ± 351 43.6 ± 43.3 9
Controlling parameters In regards to the factor(s) controlling the Antalya tufa rock strength or behavior, porosity has been observed to be the most probable candidate responsible for the variations Analyzing the regression results of the geomechanical parameters, it seems that the Antalya tufa rock may be better characterized by using strength parameters, namely, uniaxial compressive and tensile strength, together with index parameters such as unit weight 10
GSI 75 ± 5 40 ± 5 30 ± 5 20 ± 5 20 ± 5 Microcrystalline tufa Phyotherm framestone Phyotherm boundstone Phytoclast tufa/intraclast tufa 11
Rock Mass Parameters Microcrystalline tufa Phytoherm framestone Phytoclast tufa Intact rock strength (MPa) 18.56 7.76 5.50 Hoek-Brown constant, mi 15 6 9 Geological Strength Index 75±5 40±5 20±5 Intact rock modulus, Ei (GPa) 8.44 4.41 2.26 Hoek-Brown constant, mb 6.142 0.704 0.517 Hoek-Brown constant, s 0.0622 0.0013 0.0001 Constant, a 0.501 0.511 0.544 Deformation modulus (GPa) 6.899 0.704 0.103 Mohr-Coulomb fit c (MPa) 1.576 0.277 0.146 φ ( ) 41.34 23.49 20.68 12
Thank you... 13