Bulletin of Engineering Geology and the Environment

This paper describes the cut slope stability problems of southern engineered slopes along 57 km long Mersin-Tarsus Motorway. While the northern slopes were slipping during and following construction, the stability problems occurred at southern slopes after heavy rains in December 2001. The most recent slope stability problem took place on chainage at the km 10+800 embankment on 9 April 2009. About 3.62 × 106 m3 soil materials have currently slipped at 60 different location. After the occurrence of slides, different remedial methods (reshaping slopes, soil improvements, etc.) have been applied to stabilize the slipped slopes. The slope stability studies were carried out using back analysis to determine the slope failure mechanisms and to estimate effective shear strength parameters. Pore water pressures increase following intense rainfall events and cause reduced resistance to shear strength at the engineered slopes. In addition, the affects of the static and dynamic parameters to analyse the state of the slope after excavation were investigated and possible remedies to improve the state (toe rockfill and retaining wall) were assessed for motorway slopes through determining the slope stability with water parameter and seismic loading, separately and together. The results of the stability analysis have exhibited that a good drainage system and retaining wall prevents the motorway slope slides.

Radioactive materials are widely used in mining, manufacturing, medicine, and agricultural processes. The waste products from these materials are hazardous and should be appropriately dumped. As a result, a proper radiation shielding barrier is required to avoid the contamination of the surrounding environment. Clay soil is an efficient and eco-friendly radiation shielding material, which is commonly used to cap the hazardous and radioactive landfills. In this research, the effects of basalt fiber additive in four percentages, including 0.5, 1, 2, and 5 on the bentonite clay radiation shielding performance, were investigated using experimental and simulation methods. Also, the permeability of the mixtures is controlled to be in the acceptable range as a vital parameter for radioactive disposal barriers. Chemical and microstructure analyses were conducted on the utilized material, using energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). Linear attenuation coefficient (μ), representing the material radiation shielding performance, was evaluated using the HPGe spectrometer detector, MCNP simulation code, and XCOM web program on the three commonly used gamma-ray energy levels of 137Cs (661.6 keV) and 60Co (1173.5 and 1332.5 keV). An acceptable agreement was observed between experimental and simulation results, revealing that adding basalt fiber improves the shielding performance due to a higher linear attenuation coefficient (μ), where 2% of basalt fiber leads to the highest values of 12.3 m−1, 10.14 m−1, and 8.5 m−1 obtained for 661.6 keV, 1173.2 keV, and 1332.5 keV energy levels, respectively. The results concluded that, due to radiation shielding performance, workability, and permeability limitations, the 2% basalt-bentonite mixture could be a new candidate covering low-level radioactive waste disposal.

The high-temperature swelling and subfreezing frost heave of the tunnel surrounding soil are indispensable parts in analyzing the tunnel stability in swelling soil. In this paper, the physico-mechanical properties of paleosol and loess in the Loess Plateau were compared, and the temperature distribution of the surrounding soil and interior wall of the tunnel in the swelling paleosol layer was measured. The temporal and spatial distributions of high and low temperatures in surrounding soil during construction were compared using the numerical model, and the sensitivity of surrounding soil temperature was discussed. The results show that the Q1 paleosol has the largest dry density, liquid-plastic limit, clay content, clay mineral content, and mechanical strength compared with the loess from the Q3 to Q1 strata. The swelling pressure of the Q1 paleosol gradually decreases with increasing water content, but increases with increasing temperature. During the tunnel excavation in the thick paleosol layer, with the decrease in water content, the surrounding soil temperature and the duration of high-temperature swelling increase under the influence of high-temperature shotcrete, but the surrounding soil temperature and the time to enter subfreezing frost heave decrease under the influence of subzero-temperature air. In analyzing the time required for the surrounding soil temperature to vary to a specific value, the influence of water content should be given priority if the values are 80, 0, and − 10 °C, and the influence of air temperature should be given priority if the values are 60 and 70 °C.

This paper presents a new geotechnical database for the soils of Quito, Ecuador. The geotechnical database is then used to investigate the best fit probability distributions for the key geotechnical parameters contained in the database. Using the Akaike information criteria for best fit selection, SPT (N), plasticity index, Vs30, peak friction angle (direct shear), and apparent cohesion (triaxial) are best represented by a Weibull distribution. The peak friction angle (triaxial) is best fitted with a truncated normal distribution. The database is also used to develop transformation models to allow for the estimation of more complex geotechnical parameters from intrinsic ones. This analysis shows that the transformation model between Vs30 and SPT (N) has high coefficients of determination and is statistically significant. Finally, the systematic collection of information in the database is used to investigate the assumption, based on engineering judgement by local practitioners, that soil derived from volcanic deposits and volcano-lacustrine sediments in the northern part of Quito has different geotechnical properties with respect to the southern zone of the city beyond the value of shear wave velocity whose difference is embedded in the soil classification map of the seismic code.

Detailed subsurface modeling, help safe and cost-effective operations. The proposed model by integration of geological data, petrophysical data, and geomechanical model allowed for better reservoir characterization, development, and management. Well data such as leak-off test or mini-frac and image logs are found essential for constructing the geomechanical model. Since these data are rarely available, the geomechanical unit (GMU) concept is used in this study to cover such a gap. Based on facies index (percentage of grains, cement, dolomite, matrix, or microporosity), uniaxial compressive strength (UCS), and porosity, the studied formation was divided into five GMUs. From GMU1 to GMU5, the amount of cement and dolomite, UCS, cohesion, friction angle, fracture toughness, and brittleness increase, whereas porosity, bioclasts/grains, and clay content decrease. Optimization of geomechanical model by GMU concept was caused to show a good correlation between GMUs distribution and breakouts and breakdowns of the studied well. The GMU1 and GMU2 were found more susceptible to breakout, the GMU4 and GMU5 more susceptible to breakdown, while the GMU3 contains both breakdown and breakout zones. For a safe drilling in the studied formation, the highest breakout pressure (11.5 ppg) was observed for the GMU1 and GMU2 and the lowest (8 ppg) was seen for GMU4 and GMU5. The results of this study may help in designing, based on optimized geomechanical units, and safe mud weight window for drilling in heterogeneous reservoirs.

Peat is an organic soil type with properties of high compressibility and high water content. Peat deposits are often unsuitable for supporting structures of any kind due to their susceptibility to cause a number of geo-engineering problems, such as settlement, slope instability and soil amplification. There are peatlands in Turkey, although these are not so extensive as in other countries, such as Canada, where peatlands are very common. One of the peat deposits in Turkey is located close to the city of Kayseri (Central Anatolia), and industrial structures have been built on these deposits. This paper focuses on one part of a comprehensive research project conducted by the authors on various geo-engineering aspects of the peat deposits in this industrial site, with the main aims to investigate and assess some of the dynamic properties of the peat deposits in this area, to determine and assess their seismic site response and to compare them with the design spectra recommended in the current seismic codes of Turkey and Europe. In the study shear wave velocities of the peat deposits were determined with seismic measurements, and some dynamic properties of the peat were obtained from the resonant column and torsional shear tests. Then site response analyses were carried out and the results were compared with the design spectra recommended for loose-soft soils by the Turkish Seismic Design Codes and European Construction Design Codes. The comparisons suggest that the response spectra of the investigated peat deposits are greater than those recommended in the Turkish Seismic Codes and that at periods of > 0.3–0.5 s the peat will cause an increase in amplification. Although the response spectra of the peat tested show a better agreement with those recommended in the European codes, they show differences at periods of > 1 s.