A Comparison of Local Site Conditions with Passive and Active Surface Wave Methods

This study encompasses dynamic soil characterization and seismic hazard mapping of the Plio-Quaternary and especially Quaternary alluvial sediments of the Çubuk district and its close vicinity that is situated towards the north of Ankara. The project site is located at a region which has a potential of being seriously affected by a possible earthquake occurring along the Çubuk Fault Zone that is thought to be a continuation of the Dodurga Fault Zone and a sub-fault belt of the North Anatolian Fault System that is one of the most prominent fault systems in Turkey with significant earthquake potential. Non-invasive seismic methods were used to obtain a 1-D shear wave velocity profile of the subsurface at 41 sites and two measurements were taken at each site for passive and active surface wave methods. The Multichannel Analysis of Surface Wave Method (MASW) and the Microtremor Array Method (MAM) were used as active and passive surface wave methods, respectively. By combining these two techniques, the shear wave velocity profiles of the sites were obtained. Based on the results, site classes were assigned for seismic hazard assessment studies followed by a preparation of a seismic zonation map of the site utilizing GIS software

EVALUATION OF SITE CHARACTERIZATIONS AND SITE EFFECTS OF THE ANKARA BASIN, TURKEY

ABSTRACT The purpose of this study is to assess the in-situ site characteristics and to perform seismic hazard studies of the Upper Pliocene to Pleistocene fluvial and Quaternary alluvial and terrace deposits located towards the west of Ankara. Based on a general engineering geological, geotechnical and seismic characterization of the site, site classification systems were assigned for seismic hazard evaluations. Then, short-period noise recordings of the microtremor measurements at the ground surface have been used to estimate the site response of the site. This research mainly focuses on the development of a methodology to integrate the various components necessary for a regional multihazard seismic risk assessment that includes consideration of hazards due to local site effects. These tasks have been fulfilled through the development of an engineering database that was obtained from invasive and non-invasive explorations at the study area. Hence, the engineering geological and geotechnical site characterization studies have been compiled; and geophysical site characterization studies have been performed, particularly in the Quaternary sediments of the Ankara basin. By using all of these studies, hazard assessment maps (i.e., site classification map and site period map) and a seismic zonation map of Ankara basin, Turkey were developed along with discussing the consequences of the seismic hazards

Assessment of kinematic rock slope failures in Mudurnu Valley, Turkey

Slope instabilities are one of the most frequent natural hazards capable of causing severe failures both at regional and large scales. Mudurnu, which is settled on a steep valley, is affected by regional rock slope instabilities. These instabilities constitute a hazard and create an important risk to the community since they threaten human lives, settlement areas, and historically-important structures. In order to minimize the hazard and risk associated with slope instabilities, rock masses along the valley were characterized and the potential failure mechanisms were defined. The west side of the valley, which is the focus of the research, is characterized by Cretaceous pelagic discontinuous limestone, and is prone to complex failures. The aim of the study is to characterize the rock mass along the valley, divide the area into geomechanically-uniform sectors, define possible modes of failure (kinematics) and ultimately quantify the potential failure (kinetics) and the associated risk. For the study, in addition to the field work and scan-line survey measurements, an Unmanned Aerial Vehicle (UAV) was utilized to collect high-resolution images from problematic locations that were not accessible. Then, a point cloud of the area was generated. The images were interpreted and the resulting structural representation of the rock mass was compared with information gathered from the scan-line survey in the field. Afterwards, it was used to identify the possible modes of failure along the valley. Since seismic activity in the area is significant due to the proximity of the North Anatolian Fault Zone (NAFZ), which is the most active fault system in Turkey, dynamic loading was also considered for the stability analyses

Discontinuous rock slope stability analysis by limit equilibrium approaches - a review

Slope stability is one of the most important topics of engineering geology with a background of more than 300 years. So far, various stability assessment techniques have been developed which include a range of simple evaluations, planar failure, limit state criteria, limit equilibrium analysis, numerical methods, hybrid and high-order approaches which are implemented in two-dimensional (2D) and three-dimensional (3D) space. In the meantime, limit equilibrium methods due to their simplicity, short analysis time, coupled with probabilistic and statistics functions to estimate the safety factor (F.S), probable slip surface, application on different failure mechanisms, and varied geological conditions has been received special attention from researchers. The presented paper provides a review to limit equilibrium methods used for discontinuous rock slope stability analyses with different failure mechanisms of natural and cut slopes. The article attempted to provide a systematic review for rock slope stability analysis outlook based on limit equilibrium approaches

Discontinuous rock slope stability analysis under blocky structural sliding by fuzzy key-block analysis method

This study presents a fuzzy logical decision-making algorithm based on block theory to effectively determine discontinuous rock slope reliability under various wedge and planar slip scenarios. The algorithm was developed to provide rapid response operations without the need for extensive quantitative stability evaluations based on the rock slope sustainability ratio. The fuzzy key-block analysis method utilises a weighted rational decision (multi-criteria decision-making) function to prepare the 'degree of reliability (degree of stability-instability contingency)' for slopes as implemented through the Mathematica software package. The central and analyst core of the proposed algorithm is provided as based on discontinuity network geometrical uncertainties and hierarchical decision-making. This algorithm uses block theory principles to proceed to rock block classification, movable blocks and key-block identifications under ambiguous terms which investigates the sustainability ratio with accurate, quick and appropriate decisions especially for novice engineers in the context of discontinuous rock slope stability analysis. The method with very high precision and speed has particular matches with the existing procedures and has the potential to be utilised as a continuous decision-making system for discrete parameters and to minimise the need to apply common practises. In order to justify the algorithm, a number of discontinuous rock mass slopes were considered as examples. In addition, the SWedge, RocPlane softwares and expert assignments (25-member specialist team) were utilised for verification of the applied algorithm which led to a conclusion that the algorithm was successful in providing rational decision-making

Application of the modified Q-slope classification system for sedimentary rock slope stability assessment in Iran

Abstract(#br)The Q-slope system is an empirical method for discontinuous rock slope engineering classification and assessment. It has been introduced recently to provide an initial prediction of rock slope stability assessment by applying simple assumptions which tend to reflect different failure mechanisms. This study offers a correlation relationship between Q-slope and slope stability degree using case studies of sedimentary rock slopes from 10 regions of Iran. To this end, we have investigated 200 areas from these regions, gathered the necessary geotechnical data, have classified the slopes from a Q-slope perspective, and have estimated their stability relationships. Based on artificial intelligence techniques including k-nearest neighbours, support vector machine, Gaussian process, Decision tree, Random-forest, Multilayer perceptron, AdaBoost, Naive Bayes and Quadratic discriminant analysis, the relationships and classifications were implemented and revised in the Python high-level programming language. According to the results of the controlled learning models, the Q-slope equation for Iran has indicated that the stability-instability class distributions are limited to two linear states. These limits refer to the B-Line (lower limit) as

Lined waste containment systems: A method for design and performance evaluation

The objective in designing lining systems for the containment of the leachate generated within a landfill is the prevention of contamination of groundwater and surface waters. The technology involving the design of these systems has progressed to a point that the integrity of the containment can be relied on over the long term. Double-lined systems provide the additional benefit of being able to quantify the performance of the lining system through the detection of leakage through the upper liner. The difficulty, however, lies with the qualitative evaluation of the system. This paper addresses this issue and offers a practical approach for the design and evaluation of double-lined systems and the leakage that is detected

Shear strength of cement-grout borehole plug

The theoretical normal stress and shear strength distributions along the plug-rock interfaces of axially loaded expansive cement-grout borehole plugs cast in rock cylinders, determination of interfacial shear strength parameters, and experimental analyses of plug-rock mechanical interactions are presented as a function of uniform curing and testing temperature and of borehole size. The results of the back analysis show that the angle of internal friction along the plug-rock interface remains almost constant with increasing temperature. The cohesion slightly decreases going from ambient temperature to 70 degrees C. A pronounced reduction in cohesion occurs at 90 degrees C, which is attributed to high pore pressures and deterioration of the structural properties of the cement gel and of the cement plug-rock interface at high temperatures. In-situ experiments on larger radius plugs are recommended to assess the validity of the laboratory-scale shear strength determined in this study

Geotechnical characterization and performance assessment of bentonite/sand mixtures for underground waste repository sealing

The objective of this study is to assess the performance of a bentonite/sand mixture for the sealing of underground waste repositories through performing geotechnical laboratory tests such as compaction and flow tests. Swelling, mechanical and shear strength tests along with analyses of seal/rock mechanical interactions of an axially loaded seal in rock have been conducted to recommend an optimum compacted bentonite/sand mixture and a suitable bentonite/sand seal length-to-radius ratio (L/a) as a function of water load. The bentonite used in this study was a natural sodium based non-treated bentonite possessing a high swelling potential and containing at least 90% montmorillonite. The results of the compaction permeameter tests led to a recommendation to select a mixture with a bentonite content of about 30% since it possessed the lowest hydraulic conductivity. Analysis of seal/rock mechanical interaction to reduce the possibility of seal slip was performed as a function of the axial load generated from a water column on the seal for seal length-to-radius ratios (L/a) ranging from 2.0 to 20

Strength Parameters of Cement Borehole Seals in Rock

Sealing of penetrations (e.g. boreholes, shafts, mine drifts and tunnels) may be required for a variety of reasons. Penetrations of and near a high-level nuclear waste repository need to be sealed reliably to retard any radionuclide migration to the accessible environment (US Nuclear Regulatory Commission, 1983, 1985). Design of seals may also be required in (1) water dams, barriers, water wells, mine drifts or shafts, to prevent flooding of underground operations (e.g. Garrett and Campbell Pitt, 1961; Loof-bourow, 1973), (2) diversion tunnels for the construction of hydroelectric power plants (e.g. Mitchell, 1982; Kinstler, 1983; Moller et al., 1983; Pett-man, 1984), (3) mine openings in order to control mine effluents (e.g. Mining Waste Study Team 1988; Einarson and Abel, 1990), (4) oil, gas and chemical disposal wells (e.g. Smith, 1976; Calvert, 1980; Halliburton Services, undated), and (5) blasthole stemming studies (e.g., Konya, Otounye and Skidmore, 1982; Otuonye, Konya and Skidmore, 1983)