Search

Safe design of surface coal mine slopes must be considered early in the mine planning stage and is required throughout the life of mining operation. The success and efficiency of such an operation depend primarily on the reliability and accuracy of stability assessments based on integrated geotechnical evaluations and hydrogeological assessment. The Isikdere lignite mine is one of the most recently operated large coal pits in Turkey since late 2009 and its depth will reach up to about 170 m. A few local failures experienced in the current pit and considerations on its maximum depth forced the mine operators to consider the redesign of the final pit wall slopes. The technical objectives of this study are to evaluate the stability of the final pit wall slopes considered in the initial pit project and to investigate and demonstrate the application of possible remedial measures to achieve safe conditions based on integrated geotechnical assessments and hydrogeological conceptualisation. To study the problem, a two-year collaborative program of geotechnical and hydrogeological investigations throughout the current pit and the area in the direction of advance of the pit in accordance with laboratory tests and analyses was commenced by the authors. The analysis results indicate that stability of the final pit slopes is sensitive to multi-planar failures and confined water in the coal seam is also a factor adversely affecting the stability. Problems associated with groundwater at the site were also assessed with the analyses of piezometric level and groundwater inflow. Remedial measures investigated suggest that at some parts of the pit, the initial pit project should be modified by flattening or shifting the final pit wall slopes towards the north or stripping them to a certain elevation.

Peats consist of the partly decomposed remains of vegetation, which have accumulated in waterlogged areas. They are often unsuitable for supporting structures of any kind due to their high water content, high compressibility, low shear strength and high degree of spatial variability. The paper reports a preliminary study on peats from industrial sites in the city of Kayseri, Turkey. The soils in the study area are classified as peat to muck. The peats are fibrous at shallow depth and become amorphous as they extend to some 8 m depth. The ranges of geo-engineering properties are generally consistent with those reported in the literature, with some variation due to their higher mineral soil contents. The behavior of the peats is essentially frictional, with high friction and relatively small cohesion. The direct shear tests yielded higher shear strengths than those from the triaxial tests, due to the fact that the peat specimens used in the direct shear tests were rich in fibers and mineral soils. Back analysis of the settlement of heavy rolls of metal wires laid on the peat generally confirmed the consolidation properties of the soil determined in laboratory.

One of the parameters which affect the uniaxial compressive strength (UCS) of rock materials is the length to diameter ratio (L/D) of test cores. ASTM recommends a ratio of between 2 and 2.5, and ISRM suggests 2.5–3:1. Research has shown that high UCS values are obtained for L/D ratios 2.5:1. In this study, the shape effect on the UCS of seven rocks was investigated by testing dry cores with L/D ratios from 1 to 2.5:1. Based on the results, a decrease in UCS with increasing L/D ratios up to 2.5:1 was measured for all the rocks except the tuff. By omitting the data from the tuff sample, a correction formula was determined for the rocks tested in this study and results obtained from the literature. However, further work is required on different types of rock to verify or modify this formula.

Recent examples show that strong earthquakes can cause damage to dams, notably tailings or hydraulic fill dams or relatively small earth fill embankments. Liquefaction is known to be one of the most dangerous consequences of the dynamic loading of an embankment dam and hence must be considered during the dam site selection and construction stages. This paper presents the liquefaction analyses undertaken for the Demirozu dam site in Northeast Turkey. The liquefaction assessments are mainly based on field-performance data using SPT- and CPT-based methods in conjunction with the results of the available cyclic triaxial tests. The presence of a very shallow groundwater table, loose sandy layers and the seismic features of the region result in a high susceptibility to liquefaction. The results obtained from the SPT- and CPT-based criteria for evaluating the liquefaction potential are generally consistent and show that the thickness of the liquefiable layers increases in the area between the left bank and the central part of the proposed dam. Further studies are required to evaluate the suitability and efficiency of measures which could be taken to avoid liquefaction-induced problems at the dam site.

Seismic micro hazard zonation for urban areas is the first step towards a seismic risk analysis and mitigation strategy. Essential here is to obtain a proper understanding of the local subsurface conditions and to evaluate ground shaking effects. In this study, present and future settlement areas of Yenisehir, which is located in the earthquake-prone Marmara Region of Turkey, were evaluated with respect to site amplification and site period. Borings in conjunction with in-situ penetration tests, seismic velocity measurements, resistivity surveys and microtremor studies were performed, and available data from previous investigations were complied to determine the variation of the soil profile as well as the characteristics of the soil layers within the study site. In addition, new empirical correlations between shear wave velocity ( V s ) and number of blows from standard penetration test (SPT -N ) were also developed to be used for the estimation of amplification factors. Site amplification was assessed using empirical methods based on estimated values of V s , 1-D site response numerical modeling program and microtremor measurements. Among the three methods employed, the numerical technique and microtremor method yielded considerably higher amplification factors when compared to those obtained from the empirical method. This situation is considered as a limitation of the empirical methods. The survey of site response suggests ground amplification. The microzonation map based on soil site amplification suggests amplification factors between 1.6 and 5 in the present settlement, while the areas at the north and south of the settlement generally amplify the motion 5 to 9 times. The site periods obtained from microtremor studies vary from 0.51 to 0.8 s throughout the settlement. In addition, the comparison between fundamental site periods and fundamental building periods, which were measured in a few buildings and estimated from an empirical expression, indicate that prime attention should be paid to resonance phenomena, particularly for the northern part of the settlement where high-rise buildings are still in construction.

Prediction of the ground shaking response at soil sites requires knowledge of the soil, expressed in terms of shear wave velocity. Although it is preferable to measure this dynamic soil parameter in situ, this is often not economic at all locations. Existing correlations between shear wave velocity and penetration resistance have been assessed in this study and compared with correlations with SPT values obtained based on geotechnical and geoseismic data collected from a first-degree earthquake zone in Turkey. The results obtained support the findings of earlier studies that blow-count is a significant parameter in these correlations while type of soil has no important influence. The regression equations developed in this study compare well with most of the previous equations and exhibit good prediction performance. It is noted that better correlations are obtained when uncorrected blow-counts are used.

Liquefaction-induced lateral spreading affects large areas and causes considerable damages to overlying structures and buried lifelines at shallow depths. In this study, the world-wide lateral spreading case studies compiled from literature and available records of some institutions were re-evaluated to assess the performance of the current empirical methods and to develop a new empirical method for predicting the magnitude of lateral spreading. The probability-based four empirical models were developed using the maximum likelihood methodology for predicting displacements of (a) a sloping ground, (b) a free face, of a ground (c) with and (d) without slope and free face, and their prediction performances were compared with those of the existing models.