The Setting of Strength Parameters in Stability Analysis of Open-Pit Slope Using the Random Set Method in the Bełchatów Lignite Mine, Central Poland

The slopes of open-pit mines are often at risk of failure. To identify this hazard, stability analyses are performed. An important element of these stability analyses is the reliable selection of input parameter values for the calculations. This selection is difficult because the slopes of the open pit are disturbed by mining activities. In such conditions, rheological processes, intensified by weathering, develop in open-pit slopes. This study is aimed at setting the strength parameters for the stability analysis of open-pit slopes with a developed slide process, using the random set method. The study was performed on the example of the open pit of the Bełchatów lignite mine, central Poland. A four-stage methodology, according to the random set method, was proposed. The methodology covered the following: site investigation, sensitivity analyses, shear strength reduction (SSR) analyses using numerical calculations, and probability analyses of the factor of safety (FoS) calculation results. The setting of the input parameters took into account the peak and residual strength parameters for each lithological unit in the physical model of the open-pit slope. Samples for laboratory tests were taken from the cores of nine test boreholes. The sensitivity analysis included all peak and residual strength parameters for each lithological unit in the body. As a result of the sensitivity analysis, specific strength parameters were adopted that would have a great impact upon the results of the calculations. Selected sets of parameter values were then used for the FoS calculations. The resultant FoS values revealed the probable slide planes. The positions of the slide planes were consistent with the interpreted slide surfaces based on the control boreholes and terrain observations. Knowledge of the slide planes positions and the values of the strength parameters enabled the designing of a securing approach for this landslide, and the taking of preventive measures to reduce this risk.

Introduction to the cartographic and sedimentological study of the coverage of the TAHANAOUT BASIN (HIGH ATLAS, MOROCCO)

This study is carried out on the northern edge of the High Atlas of the MARRAKECH basin. The TAHNAOUT DOUAR SOUR basin belongs to the Atlasic domain which is structured by the Hercynian orogeny, taken up and elevated by the Alpine orogeny, our main goal in this studying is to map the TAHNAOUT DOUAR SOUR basin and to characterize all these geological formations, For this purpose we analysed sedimentary tectonic structures ,made lithostratigraphic sections with description and draw a geological map at scale 1/25000 on a topographic background by used MapInfo platform. As final results, our studying of the TAHANOUT basin consists of two main lithological units: the basement formed by conglomeratic and turbidite deposits (alternating sandstone and pelites), and the lithological unit that forms the cover of the TAHNAOUT basin formed by a red detrital material and, carbonate deposits in some cases depending on the deposition environment, The TAHNAOUT basin is also affected by tectonic activity at the basement and Meso-Cenozoic cover levels [1-2]. Magmatic activity is absent and no trace has been recorded.

Exploration for limestone deposit at Onigbedu, South–Western Nigeria

The Onigbedu limestone deposit was investigated using the aeromagnetic data, resistivity soundings and borings with the aim of characterizing the limestone deposit and estimating its reserves. The subsurface structural features and depth to basement were identified with the analysis of aeromagnetic data. Twenty nine boreholes were drilled for subsurface appraisal and correlation of the limestone deposit. Eighty nine Vertical Electrical Sounding (VES) were acquired using the Schlumberger array. The results showed NE-SW trending lineaments that segmented the limestone. Depth to basement varied from 144.2 m to 1090 m. The VES results showed four to six layers indicating the topsoil (7-315 Ωm), clay (2-25 Ωm), shale (6-31 Ωm), limestone (20-223 Ωm), sandstone (>200 Ωm) and sandy materials. The VES results correlated well with the lithological unit delineated from the borehole. The overburden thickness ranged from 3.3 m to 28 m, while the limestone thickness varies between 18.1 m and 48.3 m. The limestone reserve was estimated at 1.9 × 109 t. This study concluded that the study area had vast occurrence of the limestone deposits, which would be of economic importance, if exploited.

The Mesoproterozoic ‘seismite’ at Laiyuan (Hebei Province, E China) re-interpreted

A 1-million m3 breccia near Laiyuan (Hebei Province, E China) occurs as a block-like lithological unit between dolo-stones of the 1.55-1.45 Ga (Early Mesoproterozoic) Wumishan Formation. It has previously been interpreted as a seismite, but it appears not to fulfil any of the commonly accepted criteria that jointly are considered diagnostic for seis-mites. Its presence in a graben-like structure with almost vertical bounding fault planes rather indicates an origin as a (submarine) valley fill. As the valley originated by tectonic activity in the form of faulting, the breccia can be considered as a secondary effect of seismic activity, but it does not represent a seismite.

First mammals from the Paleocene Porcupine Hills Formation of southwestern Alberta, Canada

Although mammals of Paleocene age are well known from Alberta, their record is largely restricted to one lithological unit, the Paskapoo Formation (a record that includes mammals from the Cochrane area erroneously attributed to the Porcupine Hills Formation). We report here the first occurrence of Paleocene mammals from the Porcupine Hills Formation at exposures near the western edge of the city of Calgary. The assemblage, termed the Bearspaw local fauna, documents a diversity of multituberculate and eutherian mammals, including new species of the pentacodontid Aphronorus bearspawensis sp. nov., the mixodectid Eudaemonema bohachae sp. nov., the hyopsodontid Promioclaenus thnetus sp. nov., and a new genus and species of multituberculate (Alopocosmodon hadrus gen. et sp. nov.) tentatively referred to the Microcosmodontidae. The Bearspaw local fauna also details the first Canadian occurrences of several taxa, including Ptilodus wyomingensis, Aphronorus fraudator, Bryanictis microlestes, Elpidophorus minor, and possibly Goniacodon. Preliminary biostratigraphic analyses suggest that the Bearspaw local fauna is middle Torrejonian (To2) in age, correlating most closely with near-coeval Gidley Quarry of Montana and Rock Bench Quarry of Wyoming. In addition to improving the depauperate record of Torrejonian mammals in western Canada, the new fauna is important in documenting a mammal assemblage from a lithological unit that is thought to have been deposited in semi-arid conditions, rather than the wetter and more humid conditions of the Paskapoo Formation. Further, the Bearspaw localities, along with several other recently discovered localities in the Calgary and Cochrane areas, closely bracket the 27n–26r chron boundary and as such will be important in detailing the Torrejonian–Tiffanian transition in western Canada.

Mechanical control of a lithological alternation on normal fault morphology, growth and reactivation

This paper presents an analysis of the control of lithological variation on normal fault morphology, growth and reactivation. We study a normal fault population contained within an inter-bedded sequence of marly-limestones and clay rich layers. The analysis of cross sectional and bedding plane exposure of faults reveals that the plastic clay layers act as barriers to vertical fault propagation. Only the long vertically restricted normal faults (i.e. confined between two clay layers) are later reactivated and show extensional-shear mode of deformation. The likelihood of reactivation of the faults was probably favoured by the small plastic strength of the clay rich layers. We discuss the extensional-shear mode in terms of structural context, reactivation and rock rigidity. Displacement profile analysis of only isolated non-reactivated faults allows us to distinguish the faults mechanically influenced by the rheological discontinuities from those that are contained within the same lithological unit. Using both cross-sectional observations and displacement-length data of the fault population we estimate the average aspect ratio (length/height ~ 2) of the faults contained within the same lithological unit. A 3-D displacement-length scaling law that integrates post yield fracture mechanics (PYFM) and the principal fault dimensions (length and height) reveals the importance of the low rigidity of the marly-limestone on the displacement of the faults contained into a same lithological unit. A comparison of our displacement-length data with those compiled from the literature suggests that the displacement-length variability is strongly related to the rock mechanical properties and contrasts in layered rocks. The bulk of our analysis, based on field observations and theory, shows that: (i) fault shape, (ii) fault ability to be reactivated, (iii) shear mode, and (iv) displacement-length values are strongly sensitive to the lithological contrasts, and are therefore dependent on the fault dimension relative to the thicknesses of the sedimentary bodies. Therefore, regardless the variety of fault initiation processes, our analysis confirms that both fault morphology and fault growth are not self similar in heterogeneous layered rocks from centimetre to kilometre scale.

Autochthonous granodiorites north-west of Frederikshåbs Isblink, Fiskenæsset region

The gneiss complex immediately north-west of Frederikshåbs Isblink is composed mostly of amphibolite facies, grey, streaky, quartzo-feldspathic, biotite and hornblende gneisses. Subordinate amphibolites, homblendites, thin anorthosites, peridotite lenses up to 200 m across, rare concordant marble bands and associated calc-silicate gneisses and kyanite and sillimanite gneisses make up the bulk of the remainder, and the whole has been complexly deformed. Occupying the higher ground within the complex, and comprising the largest single lithological unit there is a considerable volume of massive weathering, porphyroblastic granodiorite and granodiorite gneiss. Field relationships show this to be unquestionably autochthonous and almost certainly of palingenetic origin and while on a small scale the 'contact' with the surrounding gneisses may be locally discordant, overall it follows closely the large scale structure and this suggests its control by preexisting lithology.