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Assessments on the stability of natural slopes prone to toe erosion, and man-made historical semi-underground openings carved in soft tuffs at Zelve Open-Air Museum (Cappadocia, Turkey)

Kaşmer T. | Ulusay R. | Geniş M.

Article | 2013 | Engineering Geology158 , pp.135 - 158

The Zelve Open-Air Museum, consisting of three valleys, is one of the oldest historical semi-underground settlements in the Cappadocia Region of Turkey which was designated as a World Heritage Site in 1985 by UNESCO. Particularly in the first valley, there are a lot of underground openings of different sizes carved in a soft tuff next to the valley cliffs used for cliff settlement in the past and several antique churches with some geo-engineering problems. In addition, steep natural slopes in this valley are prone to toe erosion resulting in stability problems. In this study, it is aimed to investigate engineering characteristics of . . . the surrounding tuff and factors affecting them, and to assess the effect of rate of toe erosion on the stability of steep valley slopes and structural stability of some selected typical underground openings with large spans subjected to spalling. For these purposes, some observational, experimental and numerical modelling studies were conducted. Experimental results indicate that strength and deformability properties of the weak tuff surrounding the openings drastically reduce when it becomes wet or saturated. This situation suggests that possibility of occurrence of failures is expected to be higher in rainy seasons due to increase in water content of the tuff. Experimental results also suggest that spalling commonly observed in the valley is related with freezing-thawing and wetting-drying cycles in nature and that the process of freezing and thawing accelerates further the degradation of the rock. The long-term measurements at selected locations suggest that erosion in the tuff is important, which increases particularly in winter and spring seasons and results in the loss of support accelerating the occurrence of further slope failures. The 2-D numerical solutions indicate that no significant change in shear and tensile stresses in steep valley slopes prone to toe erosion would be expected after 100. years. However, the solutions obtained from the 500- and 1000-year scenarios suggest that failure zones due to the tensile stresses would develop in the form of slabs with thicknesses of 50-60. cm and 90-100. cm, respectively, which would break off from the slope and fall down. The results from 3-D numerical solutions indicate that failure (yield) zone resulting from tensile stresses around the semi-underground openings will develop parallel to the sidewalls. These results confirm the observed spalling of the tuff in the form of slabs parallel to the walls of the openings. © 2013 Elsevier B.V Daha fazlası Daha az

The stability of an underground congress center in soft tuffs through an integrated in-situ monitoring, experimental, analytical and numerical methods (Cappadocia,Turkey)

Ulusay R. | Aydan Ö. | Geniş M. | Tano H.

Conference Object | 2012 | Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics , pp.1141 - 1146

Avanos municipality (Cappadocia, Turkey) planned to utilize a hill remnant from an abandoned quarry as an underground congress center in 1980s. The rough excavation of the congress center was done. However, the construction has not been completed due to financial problems. The in-situ investigations revealed that there are some new fracture formation and propagations at several locations in the underground halls as well as at the perimeter of the hill. The rock is a very soft tuff and it is susceptible to degradation due to process of cycles of wetting-drying and freezing and thawing and creep. An integrated experimental, analytical . . . and numerical analyses and in-situ monitoring program has been undertaken. This program still continues and this paper describes the preliminary findings. © 2012 Taylor & Francis Group, London Daha fazlası Daha az

An integrated approach for the prediction of subsidence for coal mining basins

Unlu T. | Akcin H. | Yilmaz O.

Article | 2013 | Engineering Geology166 , pp.186 - 203

In this study, land subsidence caused by underground mining activities was investigated by means of a new subsidence prediction approach (ISP-Tech) which takes into account the most important parameters contributing subsidence development such as coal production methods, depth, mining sequence and other geomechanical characteristics of underground rock strata, etc. ISP-Tech can be applied to operating mines to keep land subsidence under control as well as virgin coal sites to predict surface subsidence prior to mining activities. In the method, geological information gathered from the geographic information system (GIS) and the mini . . .ng information system (MIS) are utilised to obtain geological cross-sections which are used in finite element models for mesh building. Then, a number of two dimensional finite element modelling analyses are carried out to determine land subsidence occurring due to mining operations. Finally, land subsidence predicted from modelling studies is compared to the GPS and/or differential interferometry synthetic aperture radar (DIn-SAR) measurements. If incompatibility of the results is detected, finite element meshes should be optimised, and then reanalysed to obtain more compatible results. In the study, two different case studies were given as examples of the application of ISP-Tech. Results of the case studies showed that ISP-Tech can successfully be applied to complex mine subsidence problems. The proposed approach gives more accurate results than those obtained from other classical subsidence prediction methods. © 2013 Elsevier B.V Daha fazlası Daha az

A comparative study of the determination of rock mass deformation modulus by using different empirical approaches

Aksoy C.O. | Geniş M. | Uyar Aldaş G. | Özacar V. | Özer S.C. | Yilmaz Ö.

Article | 2012 | Engineering Geology131-132 , pp.19 - 28

The increase in rock engineering projects over the last decade, has made an increase in the importance of the determination of the rock mass parameters. Although properties of rock material are usually determined at laboratory, it can also be determined by special in situ tests. These in situ tests are both expensive and time consuming. Therefore, empirical equations are developed to estimate rock mass properties by several researchers. In numerical modelling, rock mass properties are important. Furthermore controlling the results of models, making back analysis and taking the feedback are very important. Comparison of different emp . . .irical equations of deformation modulus of rock mass suggested by different researchers by using field displacement measurements and numerical modelling results is aimed in this study. © 2012 Elsevier B.V Daha fazlası Daha az

Stability assessment of avanos underground congress centre (cappadocia, turkey) in soft tuffs through an integrated scheme of rock engineering methods

Ulusay R. | Aydan O. | Geniş M. | Tano H.

Article | 2013 | Rock Mechanics and Rock Engineering46 ( 6 ) , pp.1303 - 1321

The Cappadocia Region is one of the seven sites in Turkey included in the World Heritage List in 1985 by the United Nations Educational, Scientific and Cultural Organization (UNESCO) and includes structures carved into thick and soft tuffs that have survived and kept their integrity for a number of centuries. Besides existing ancient structures, new underground constructions have been undertaken. Considering the historical characteristics of the region, the construction of an underground structure was planned by the Municipality of Avanos Town to utilize a hill remnant from an abandoned quarry as an underground congress centre in th . . .e 1980s, but its construction has not yet been completed due to financial problems. In this study, integrated experimental, analytical and numerical analyses and an in situ monitoring program were undertaken to assess the stability conditions of the congress centre, which was carved into a soft tuff susceptible to long-term degradation processes. The experimental results indicate that the surrounding rock is quite vulnerable to cyclic freezing-thawing and wetting-drying processes. The strength of the rock is drastically reduced under saturated conditions, and the processes of freezing and thawing further accelerate the rock degradation under such conditions. Simple short-term stability analyses clearly show that some tensile cracking may take place and that the opening may suffer from some cracking problems 28-30 years after excavation. The analyses carried out for the long-term safety of the structure indicate that the most critical condition exists for the widest opening and that some supports at the middle of the widest opening may be necessary. Nevertheless, further studies on the long-term characteristics of this tuff are necessary to check this conclusion. The in situ monitoring clearly showed that some further crack propagation will occur, especially after rainy and freezing-thawing periods. © 2013 Springer-Verlag Wien Daha fazlası Daha az

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