Scanline Surveys Research Articles

The assesment of rockfall analysis near a railroad: a case study at the Kızılinler village of Eskişehir, Turkey

Rockfalls from basaltic lava flow hills and the rockfall hazard for the railroad passing along the Kizilinler village (Odunpazari/Eskisehir) were investigated in this study. Rockfalls are detected between 14 + 000 and 18 + 750 km on the Eskisehir-Kutahya railroad. This part of the railroad is controlled daily in case of rockfall, and the falling blocks on the railroad are cleared by workers. The rapid weathering of the tuff litology under the basaltic lava flows is the cause of the rockfalls. As a result of the weathering tuff unit, the basalt rock particles fall along the discontinuity surfaces due to the gravity forces. The geology of the rockfall region, the properties of the falling rock blocks, and the length to the railroad were investigated during the field study. During field studies, the rock blocks, greater than 5 m diameter that had passed to the other side of railroad, were recorded. In order to define the geologic properties of the rock mass and joint properties, two scan-line surveys were performed in the study area. A series of the rock block falling simulation studies were held with a computer program. The hazard for the train railroad was determined. A series of simple regression analysis was carried out between the fall height, the horizontal length of the rockfall, and the volume of falling rock blocks, and new empirical equations were determined. The evaluation of the estimation performances of some existing empirical equations for the determination of the runout distance of the rockfall using this study data was also performed. However, the prediction performance of the equations proposed in this study and the previous studies was not significant, except empirical equations derived between the fall height and the horizontal length of rockfall. The Rockfall Risk Rating system was applied at the selected slope sections along the study area. Consequently, the study area was classified as under medium risk. Active and passive protective measures were suggested for the study area.

3D rock slope data acquisition by photogrammetry approach and extraction of geological planes using FACET plugin in CloudCompare

Structure from motion (SfM) permits a fast and inexpensive way to obtain data necessary for geotechnical characterization of rock slope. Unlike scanline survey, a traditional technique, SfM can reduce the risk, time, cost, bias in measurement and improve the accessibility, quantity and quality of data collection. A small and low cost Unmanned Aerial Vehicle (UAV), DJI Phantom 4 Pro mounted with 20 megapixels camera is utilized to capture high quality images in this study with Real-Time Kinematic Global Positioning System (RTK-GPS) being used to obtain coordinates of 10 Ground Control Points (GCP) distributed evenly on the rock slope. Images registered and aligned with GCP render better accuracy results compared to images aligned without GCP. With photogrammetry software, dense point cloud, digital surface model (DSM) and orthophotos can be generated. 3D dense cloud reconstructed in the setting of high accuracy, with millions of points of a rock surface, can be imported into CloudCompare to extract the geological planes using FACET plugin. The major discontinuity sets can be observed and the orientation (dip/dip direction) of the discontinuity sets obtained from the algorithm is accurate and reliable for future geotechnical work such as rock slope stability analysis.

Geostatistical analyses of exfoliation and tectonic joint set spacing in alpine granites (Aar Valley, Switzerland)

Joint set spacing is a fundamental parameter in the determination of rock mass quality and can be measured in situ by means of, e.g., scanline surveys and/or by remote sensing techniques, such as photogrammetric analyses. In many Alpine areas, rock mass outcrops are not easily accessible, and geomechanical propexrties can be measured only in a few unevenly distributed locations, which are often separated by large distances (in the order of hundreds of meters). Geostatistical techniques have been explored to achieve a reliable estimate of rock mass properties in unreachable zones. This work aims to estimate joint set spacing of outcropping rock masses and the associated uncertainty, using photogrammetric models and geostatistical modeling, in an area of about 30 km2, located in the Aar Massif of the Swiss Central Alps. Since the joint set spacing is strongly related to fracture genesis, joints were subdivided according to their type and age into three younger exfoliation joint sets and older tectonic joint sets. Each fracture set spacing was analyzed by variography and its spatial distribution was estimated using Sequential Gaussian Simulations. The present research proves that photogrammetric techniques combined with geostatistical modeling can be satisfactorily applied to develop predictive maps of joint spacing, providing that the geological processes governing the formation of joints are taken into account. Moreover, predictive maps must be associated with the corresponding uncertainty maps. Finally, in mountainous area, whenever a full three-dimensional approach is not feasible due to the absence of subsurface data, at least the ground altitude, besides latitude and longitude, has to be included in the geostatistical modeling.

Numerical Modelling of Steep Slopes in Open Rock Quarries

ABSTRACT The key question regarding steep rock slopes along rock quarries is their stability because a rock slope failure can have critical results. In this study, the aim is to investigate the areas with potential risk for jointed karstic limestones in a rock quarry. First, to determine rock mass properties, scan-line surveys were performed, and the major orientations of discontinuities were analyzed using stereographic projection. Then, the physico-mechanical properties of the slope-forming rock were determined in the laboratory, and geomechanical properties of the rock mass were determined using an empirical failure criterion. Finally, the quarry slope stability was assessed in accordance with numerical modelling. According to the results obtained, the numerical modelling of steep rock slopes can be efficiently evaluated by using finite element method. Beside this, the presence of joints intersecting the main discontinuity sets, the filling materials of discontinuities resulting from weathering of limestone and surface deposits, surcharge load due to mine waste dumped on the slopes and excavation blasting during construction of quarry area play a key role when modelling the steep rock slopes by using finite element method.

Geotechnical Investigations - A Tool for Deciding Mining Method for Chromite Deposits in Odisha State, India

The Chromite deposits of Sukinda valley, Odisha, India are of strategic importance for the development of ferro-alloy industries. Around 90% of the India’s chromite ore production derived from two important chromite bearing belts, namely the Baula-Nuasahi belt and Sukinda valley ultramafic complex deposit. In terms of rock strength properties, the host rocks and ore body at Baula – Nuasahi chromite belt are hard and compact, with some structural defects such as joints, faults and dykes. After extracting the chromite ore by surface mining up to the economic pit bottom, the remaining reserves were being mined by underground method. In the Sukinda valley chromite deposits, both the wall rocks and ore body are weak, highly weathered. These mines were operated by opencast method. As most of the working mines in Sukinda valley reached their economic pit limit and there is no further scope to extract the ore by opencast mining. Since the chromite ore bodies are having considerable mineable strike length, width, and depth persistence, there is no option except to convert them into underground mines to increase the life of the mines. The chromite ore bodies were proved up to depth of 270m by exploratory drilling. Some major mining companies are planning for underground mining operations, due to constraint of limited space available for waste dumping, working with common lease boundary, slope instability, high volume of stripping ratio. To overcome such problems, the basic step is to conduct the detailed geo-technical investigations to avoid any unexpected consequences during mine development and stoping operations. The geo-technical investigations comprised of geotechnical mapping of existing mined out benches using scan line surveys, geo-technical drilling and logging of cores for the estimation of RQD, structural discontinuities, testing of cores for material properties followed by performing numerical modeling to evolve a suitable stoping method and excavation geometry. The paper deals with the results of the geo-technical investigations carried out for the planning and design of underground mine workings, design of stope parameters based on the geo-mining conditions.

Assessment of Excavatability, Abrasivity and Slope Stability in a Sandstone Quarry in Istanbul, Turkey

ABSTRACT The Cebeci region is characterized by outcrops of Carboniferous sandstone, including diabase dykes. This region is very important area for aggregate production in Istanbul, Turkey. The aim of this study is to determine the engineering geological properties of sandstones to assess the excavatability, abrasivity and stability of cut slopes in a quarry site. Firstly, the sandstone samples were used to determine their petrographical and mineralogical characteristics. Then, physico-mechanical tests were performed on these samples. In order to determine rock mass properties, scan-line surveys were performed, and the major orientations of discontinuities were analyzed through the stereographic projection technique. Kinematical analyses were also made to determine the potential failures at the quarry site. According to the results obtained, excavatability is changed from easy ripping to hard ripping on sandstones; the carbonated sandstone is less abrasive than other sandstones. Based on the field studies and stability analyses of the cut slopes, optimum slope geometry and necessary support measures, such as wire mesh and rock fall barriers, are suggested.

Structural controls on carbonate-hosted Pb–Zn mineralization in the Dongmozhazhua deposit, central Tibet

Fault zones control the locations of many ore deposits, but the ore-forming processes in such fault zones are poorly understood. We have studied the deformation and ore textures associated with fault zones that controlled the lead–zinc mineralization of the Dongmozhazhua deposit, central Tibet, ∼100km southwest of Yushu City. Geological mapping shows that the structural framework of the Dongmozhazhua area is defined by NW–SE-trending reverse faults and superposed folds that indicate at least two stages of deformation. The first stage is characterized by tight nearly E–W-striking folds that formed during the closure of the Jinshajiang Paleo-Tethyan Ocean in the Triassic. The second stage of deformation produced NW–SE-trending reverse faults and related structures of the Fenghuoshan–Nangqian fold-and-thrust belt associated with India–Asia collision in the late Eocene to Oligocene. Scanline surveys along the ore-controlling fault zones show an internal structure that comprises a damage zone, a breccia zone with clasts that have become rounded, and a breccia zone with lenticular clasts, and this complex architecture was formed during at least two compressional substages of deformation. The Pb–Zn mineralization in the Dongmozhazhua area occurs exclusively close to NW–SE-trending reverse fault zones. Microtextural observations reveal that mineralization occurred as veinlets and disseminated blebs in limestone clasts, and as continuous bands and cements in fractured rocks. Cataclastic sulfide grains also can be seen in the matrix of some fault zones. The types of mineralization differ with structural position. The fillings of the ore-bearing veinlets typify the products of hydraulic fracture and both types of mineralization took place concurrently with regional contraction. We consider, therefore, that the ore-bearing fluids in the Dongmozhazhua deposit were concentrated in fault zones during regional compression and that the ore minerals were precipitated during hydraulic fracturing of host rocks. Subsequent fault activity pulverized some pre-existing sulfide material into cataclastic grains in the matrix of a tectonic breccia that developed in the same faults.

Mechanical stratigraphic controls on natural fracture spacing and penetration

Fine-grained low permeability sedimentary rocks, such as shale and mudrock, have drawn attention as unconventional hydrocarbon reservoirs. Fracturing – both natural and induced – is extremely important for increasing permeability in otherwise low-permeability rock. We analyze natural extension fracture networks within a complete measured outcrop section of the Ernst Member of the Boquillas Formation in Big Bend National Park, west Texas. Results of bed-center, dip-parallel scanline surveys demonstrate nearly identical fracture strikes and slight variation in dip between mudrock, chalk, and limestone beds. Fracture spacing tends to increase proportional to bed thickness in limestone and chalk beds; however, dramatic differences in fracture spacing are observed in mudrock. A direct relationship is observed between fracture spacing/thickness ratio and rock competence. Vertical fracture penetrations measured from the middle of chalk and limestone beds generally extend to and often beyond bed boundaries into the vertically adjacent mudrock beds. In contrast, fractures in the mudrock beds rarely penetrate beyond the bed boundaries into the adjacent carbonate beds. Consequently, natural bed-perpendicular fracture connectivity through the mechanically layered sequence generally is poor. Fracture connectivity strongly influences permeability architecture, and fracture prediction should consider thin bed-scale control on fracture heights and the strong lithologic control on fracture spacing.

Characterizing fractures to mitigate inrush of water into a shaft using hydrogeological approaches

The inrush of water during excavation is one of the most difficult challenges in modern underground engineering. Studies of the permeability of a rock mass, and especially potential paths for the flow of groundwater, are important for mitigation. This study considers a ventilation shaft for a twin-bore four-lane highway tunnel, and applies hydrogeological approaches to characterize the site, and to propose corresponding plans for mitigating water inrush. Based on detailed descriptions on outcrops, a scanline survey, and the interpretation of scanned images of four boreholes with a total length of 480m that were obtained using a televiewer, more than 3400 data concerning the attitudes and locations of fractures are acquired to classify the strata close to the study site as terrace alluvium, regolith and fractured rock masses. Five predominant fracture sets, with corresponding parameters of their respective spatial distributions that are determined by stereographic projection analysis and statistical analysis, are characterized to establish a model to characterize the fractures of fractured rock masses. Taking into account the locations where high equivalent hydraulic conductivity are identified, this study presumes a model that provides potential paths of groundwater that flows to the shaft, including specific locations, scopes and directions of groundwater flows. Another model that is inferred based on the conventional Qlogging method is also provided for comparison. Two plans for mitigating water inrush during shaft construction are proposed based on the models of the spatial distribution of fractures and potential paths of flowing groundwater to the shaft. The adopted plan involves grouting in the regolith stratum to form a water-proof curtain that is applied in the ground surface or inside the shaft, radial grouting in the fractured rock masses that is applied inside the shaft, and the installation of pumping wells at the ground surface to draw down the groundwater table.

A stability assessment of the rockfall problem around the Gökgöl Tunnel (Zonguldak, Turkey)

The stability of rock slopes is an important area of interest in civil and mining engineering. This study investigated rockfall occurring around the Gokgol tunnel along the Zonguldak-Ankara roadway. Extensive field studies, including determination of geological description of the rock mass, scan-line surveys on discontinuities, identification of slope profiles, measurement of actual fallen block dimensions, and sampling procedures, were carried out. The study area and its surroundings are part of a Lower Carboniferous limestone formation. The assessments based on field studies indicated that two joint sets and a bedding plane were the main types of discontinuity. Two slope profiles were then created by considering the most frequently encountered rock fall events. The present study aimed to investigate the rockfall potential in this area by means of numerical analyses. For this purpose, RocFall software based on the lumped-mass method was utilized. Based on these analyses, traffic safety is threatened by potential rockfall. In Case I, a 30 % portion of the falling blocks reached the side of the main road, while about 70 % of them remained on the slope. However, falling blocks reached the end of the road in Case II. The study area requires some protection measures, such as the construction of retaining barriers and steel mesh to hold small size rock blocks. As a result, barrier heights to hold falling blocks were calculated as 0.5 m and 4 m for Case I and Case II, respectively. Barrier heights sufficient to hold falling rocks were determined using numerical analysis. In Case II, from such analyses, the energy required for a protection barrier for 1000 kg was found to be 200 kJ.

Assessment of rock slope stability at Cham-Shir Dam Power Plant pit using the limit equilibrium method and numerical modeling

There is global concern about the stability of rock slopes in open pit mines while the limit equilibrium technique used for modeling complex geometries and forces fails to provide a complete understanding of the behavior of rock slopes due to its inherent shortcomings. However, numerical approaches to modeling complex rock structures have improved the general understanding of these slope structures. In this study, geological and geotechnical data were obtained from both exploration drill holes and laboratory tests using face mapping and scanline surveys to reveal three major joint sets related to the regional tectonic history at the Cham-Shir dam power plant pit in Iran. The joints play an important role in the slope stability of the open pit, notably in terms of planar and wedge failures. Moreover, both the limit equilibrium technique and the discrete element method were employed to analyze the stability of the Cham-Shir dam power plant pit in an attempt to evaluate its behavior under both supported and unsupported conditions in the three modes of continuous rock mass, rock mass with two joint sets, and rock mass with three joint sets. Results show that the rock mass is stable in the continuous mode. The possible failure must, therefore, be due to the structure type and the joint sets at the site. To address the requirements and to resolve the problem, a simulation study was conducted. Based on the findings, stage by stage excavations are recommended for the study site.

Evaluation of rock slope stability for a touristic coastal area near Kusadasi, Aydin (Turkey)

The study area, which will be open to tourism in Kusadasi (Aydin), has steep and high cliffs on the Aegean coast in Turkey. Flysch is the main lithological unit and consists of alternating sandstone–claystone–marl sequences. Some sliding and rockfall problems have occurred in the area in the past, so potential geological hazards need to be investigated to ensure the safety of tourists. The aim of this study is to mitigate geological hazards by recommending engineering solutions, which will ensure the continuation of the nature-friendly appearance of the slopes. To accomplish these tasks, a geological survey was performed. It involved gathering information on rock discontinuities by means of scan-line surveys and collection of rock samples. Furthermore, in situ and laboratory tests were also carried out. The data collected from the field and laboratory test results were used to perform slope stability and rockfall (2-D and 3-D) analyses for different slope conditions along 43 profiles. Based on the analyses, rockfall was found to be the main slope instability problem in the study area. Under the light of these studies, rock removal, drainage, greening (vegetation), filling of caverns, protective wall building and erosion prevention are offered as remedial measures.

가중치를 이용한 국내 석회동굴 발달 방향성 해석법 개발에 관한 연구

다양한 원인에 의해 형성된 석회동굴 내 주굴과 가지굴 등은 일정한 방향성을 가지고 발달하게 된다. 이러한 원인은 주변에 분포하고 있는 층리나 절리, 단층 등과 같은 불연속면의 영향을 받고 형성된다고 알려지고 있다. 석회동굴에 발달된 방향성은 구간별로 어떤 불연속면의 영향을 받고 있는지는 확인이 가능하지만, 전체적으로 주된 영향을 준 불연속면과 발달 방향성을 방향을 명확히 파악하기는 어렵다. 본 연구는 이러한 석회동굴의 발달 방향성을 전체적으로 파악하기 위하여 연장성에 가중치를 적용하는 평균 폭 비율법(Average Span Ratio Method)과 개별 발달 비율법(Individual Development Ratio Method)을 새롭게 제안하여 분석하였다. 새로운 분석법을 적용하기 위해 국내 석회동굴 9개를 임의 선정하여 분석하였다. 분석 결과, 발달 방향성 분포만을 해석한 것보다 두 가지 방식을 적용한 해석기법이 동굴 발달 방향성을 더욱 명확하게 해석할 수 있음을 확인하였다. 석회동굴의 주 층리각과 평균 폭의 연관성 분석을 통해 주 층리의 경사각이 저각일수록 석회동굴 폭 확장에 더 많은 영향을 주고 있음을 확인할 수 있었다. 현장자료를 이용하여 RMR 분석을 수행함으로써 각 석회동굴의 지반안정성을 분석하였다. Limestone caves that consist of main passages and branches are formed by a variety of processes, and have the characteristic of developing with a preferred orientation controlled by discontinuities such as bedding, joints, and faults around the cave. However, it is difficult to analyze a representative orientation from various orientations. To interpret the overall development orientation of limestone caves, this study proposes new development orientation analysis methods, termed the Average Span Ratio Method (ASRM) and the Individual Development Ratio Method (IDRM), using the weighting of persistence. Nine limestone caves in Korea were randomly selected for testing the new methods. The methods show a stronger development orientation for limestone caves than that obtained by traditional methods, which consider only the distribution of development orientations. Based on an analysis of the relationship between the average span and the dip angle of bedding, it is confirmed that shallowly dipping bedding is a major contributor to the expansion of span in limestone caves. In addition, using scan-line survey data acquired in the field, we perform an RMR analysis of stability of the ground around limestone caves.

Evaluation of rock falls in an urban area: the case of Boğaziçi (Erzincan/Turkey)

Disasters caused by events such as earthquake, flooding, rock falls, landslides are often encountered. However, generally, the reasons for the destructive and devastating effects of these nature events are that settlement locations were chosen without site investigation studies, or that available studies were inadequate. Such inadequacies in the field are related to inappropriate settlement location and the resulting damage caused by rock falls. This study evaluated rockfall risk in a settlement that developed in a similar manner. The study was carried out in Bogazici village of Kemah (Erzincan/Turkey), which is located in a very important tectonic zone. The study site is located on the lower sections of an area with very steep cliffs and 50–75° slopes. This cliff, which is the source of rockfalls, has a slope dip of approximately 90°. The cliff comprises 25–30 m high, fractured and cracked basaltic volcanic mass. To determine block size in the study area, scanline survey measurements and block size measurements were performed on blocks that loosened and fell from the cliff face. It was found that block sizes reached 6 m3. Rockfall analyses were performed along the selected profiles using the Rockfall V.4.0 software. Kinetic energy, bounce height, horizontal location of rock end-points, and velocity of the rocks along each section were evaluated separately for each profile. This data were used to produce distribution maps for each profile and the settlement was evaluated in terms of rockfall risk. The results indicate that the study area was at risk of future rockfalls and that it would be appropriate to relocate one part of the settlement.

MATLAB script for analyzing and visualizing scanline data

Scanline surveys consist of directional and qualitative measurements of rock discontinuities. These surveys are used in geologic and engineering investigations of fractured rock masses. This paper introduces a new MATLAB script developed for visualizing results from scanline surveys as traces in 2D and disks in 3D. The script is also able to cluster orientation data and to present statistical summaries and to reflect the change in degree of rock brokenness along the scanline. Advantages of this new script are that it can present undulating discontinuities as wavy surfaces and different discontinuity properties using color codes. An intensity rose diagram is utilized to visualize interdependency of certain properties and orientation. This new script has a potential for preprocessing vast amounts of scanline and oriented drill core logging data before using it in 3D discontinuity network modeling. The script is demonstrated using data concerning rock fracturing gathered from a dimension stone quarry in Southern Finland.

From fractures to flow: A field-based quantitative analysis of an outcropping carbonate reservoir

Fractures can play an important role in the fluid storage–migration properties of fault damage zones. In this present contribution, we document the role exerted by fractures on fluid flow in carbonate damage zones of hydrocarbon-bearing, km-long, oblique-slip normal faults with 10's of m-throw. The carbonate fault damage zones were analysed by mean of scan line surveys conducted in both tar-free and tar-rich outcrops. In this way, the relationships among the individual fracture characteristics (length, spacing, aperture, orientation, connectivity and distance from slip surfaces pertaining to small faults of the fault damage zones) and hydrocarbons have been established. Data obtained by scan line surveys were also used to compute the amount of fracture porosity, the degree of fracture connectivity and, based upon simple assumptions, the orientation of the local σ hmax at times of faulting. Additionally, scan line surveys were also carried out along outcrops exposing unfaulted carbonate host rocks. The results of our computation are consistent with a carbonate host rock made up of a quite isotropic fracture array comprised of isolated and coupled fractures, in which individual fracture sets have negative exponential spacing distributions. In terms of fluid flow, the fracture array of the carbonate host rock enhances the fluid storage. Conversely, the fracture array of the fault damage zones is characterized by a pronounced anisotropy due to interconnected fractures, which enhance the fluid migration. Fractures in the fault damage zones include those inherited from background deformation and others related to the faulting processes. The latter fracture sets are characterized by power law spacing distributions. In conclusion, counter-intuitively, both fracture length and fracture spacing do not have any correlation with hydrocarbons in the fault damage zones. On the contrary, fracture anisotropy, fracture spread and fracture orientation are positively correlated with hydrocarbons.

Assessment of rockfall potential in the Kula (Manisa, Turkey) Geopark Region

The term Geopark is an interrelated phenomenon of geology, landscape, civilisation and society. One of the first Geopark areas in Turkey will be founded in the Kula district of Manisa. This region is an impressive area with its archaeological, historical and tourism-related features and its geological characteristics, such as cinders and maars, tectonic structures and earth pillars. Moreover, the earth pillars in the region present high-rockfall potential due to their geometric and lithologic peculiarities, formed by erosional processes. The present study aims in investigating the rockfall potential in this area by means of experimental investigation and numerical analyses. Extensive field studies including determination of earth pillar locations with rockfall potential, geological description of the earth pillars, scan-line surveys on discontinuities, identification of slope profiles, measurement of actual fallen block dimensions and sampling procedures were carried out. The eight earth pillar profiles were analysed to determine the run-out distances of basalt blocks and seven blocks were found to be capable of reaching the transportation line. For future protection purposes, barrier designs were suggested by computer analyses. Additional analyses were performed to determine rockfall-prone areas, taking into consideration the mapped rockfall source areas. Based on these analyses, the transportation line is threatened by potential rockfall. These results are in accordance with conclusions of the runout distance analyses. As a consequence, environmental aspects and rockfall phenomenon of the Kula Geopark Region must be taken into consideration during the planning process. It should also be pointed out that we have to own the values of geological heritages and to protect them based on the scientific and rational approaches.

Municipal solid waste management and practices in coastal cities of the Eastern Black Sea: a case study of Trabzon City, NE Turkey

Each day some 400–450 ton solid waste is dumped on land and in the sea and rivers in the coastal cities of the eastern Black Sea, creating serious environmental problems. The paper reports the engineering geological studies of a proposed landfill site for Trabzon, a major city in the region. Fieldwork included scan-line and seismic surveys as well as boreholes and in-situ testing. Water absorption tests indicated permeabilities in the order of 10−8 m/s.

The evolution of the damage zone with fault growth in sandstone and its multiscale characteristics

We document the formation and evolution of the damage zones associated with strike‐slip faults in porous sandstone, through detailed field and statistical studies of faults of increasing slip magnitudes. The faults initiate as sheared joints with discontinuous damage zone located primarily at fault tips and fault surface irregularities. With increasing slip, the damage zone develops by progressive fracture infilling and is organized into two components with different characteristics. The first of these components is the inner damage zone flanking the fault core with a high fracture frequency and a thickness scaling with fault slip. It contributes to the progressive widening of the fault core with increasing deformation. The second of these components is the outer damage zone with a larger and more variable thickness and a lower fracture frequency than the inner zone. The origin and evolution of the inner and outer damage zones are closely related to the history of fault development, as presented in a new conceptual model for damage zone evolution with fault growth. The statistical properties of the fault networks, determined by scan line surveys, evolve with fault growth. This is attributed to the progressive saturation of the fault networks. Well‐developed fault networks have multifractal properties with important consequences in forecasting and characterizing faults from limited data sets. The conceptual model and statistical data presented here may be used as predictive tools to better estimate the geometrical and statistical properties of the damage zones associated with large faults with remotely resolvable slip magnitude in the subsurface.

Engineering characteristics of Ankara Greywacke under the foundation of the Beytepe open air theatre, Ankara, Turkey

The construction of a large open air theatre having with an audience capacity of 7,000 is planned at the Beytepe Campus of Hacettepe University located near Ankara, Turkey, in the heart of Anatolia. The foundation of the open air theatre is composed of weak and heavily jointed Ankara Greywacke. An estimation of the strength and deformation of the Ankara Greywacke was required for assessments of short- and long-term stability. Accordingly, rock mass characterization of the Ankara Greywacke was investigated in detail by scan-line surveys and back-analyses of in situ tests performed on the excavated surface of the rock mass. The final version of the Hoek and Brown Criterion (Hoek et al., In: Proceedings of the north American rock mechanics society meeting, Toronto, Canada, pp 1–6, 2002) together with and improvements proposed by Sonmez and Gokceoglu (Int J Rock Mech Min Sci, 43:671–676, 2006) were considered together for the back analyses of small slope benches subjected to plate loading test loaded to failure. In addition, the plate loading test data were used with some well-known empirical equations for predicting of deformation modulus of rock masses to calculate ranges of values of the Geological Strength Index (GSI) The static and pseudostatic slope stabilities of the audience seating structures to be supported by benches excavated into the rock were also analyzed. The stability assessments revealed the unlikelihood of large rock mass failures for the short-term construction stages or for the long-term, as-constructed conditions under static or pseudo-static conditions. Additionally, the analyses showed that there was no need for anchors between the concrete seating structures and greywacke rock mass.