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Slope Stability
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
Naturally-eroded slopes are created by the movement of ice, surface water and the sea. Glacial erosion produces U-shaped valleys (Fig. 3.41) whose over-steepened sides became over-stressed when the glaciers melt and the lateral support to them provided by the glaciers is gradually removed. Such slopes eventually fail. Glacial erosion is facilitated by the generation of joint sets a small distance below the base of a glacier: similar joints develop in the rock adjacent to the sides of a glacier. These joints are an addition to those existing prior to glaciation and by stress-relief of the valley sides occurring after glaciation (see Fig. 14.14b), and are thought to be produced by the drag of ice against the rock walls and base of a valley. It is common for them to be filled with rock-flour (p. 55) and clay; in this condition they have a low shear strength and are often the surfaces on which slope failure may commence. The lower slopes of many glaciated valleys are covered by glacial deposits which conceal such surfaces (Fig. 3.41) and cut slopes of excavations into the bedrock, these can fail on clay filled joints, causing slope instability that may extend over a large area.
Jimmie Creek run-of-river project—geohazard and seepage control design of intake structure
Published in Jean-Pierre Tournier, Tony Bennett, Johanne Bibeau, Sustainable and Safe Dams Around the World, 2019
The project area is located within the Elaho Range of the southern British Columbia Coast Mountains. Repeated glaciations throughout the Quaternary Period (past 2.6 Ma) have been the primary morphological process shaping the area slopes. The resulting terrain is characterized by steep-sided, U-shaped valleys that grade from upper steep rock slopes and hanging valleys into broad and gently sloping valley floors.
A novel spectral index for mapping blue colour-coated steel roofs (BCCSRs) in urban areas using Sentinel-2 data
Published in International Journal of Digital Earth, 2023
The spectral profiles of BCCSRs (BCCSRl and BCCSRd) have obvious characteristics, which are different from typical land cover types such as vegetation, water and bare soil. The BCCSR drops from the blue band (490 nm) to the red band (665 nm), then rises again to the near-infrared (NIR) band (842 nm) and reaches its highest reflectance at the short-wave infrared (SWIR) band (2190 nm). The reflectance peak of the BCCSR appeared in the blue and NIR bands, and the absorption peak appeared in the red band. Therefore, the BCCSR presents an obvious ‘U-shaped valley’ between the blue and NIR bands (Guo et al. 2018). The BCCSR and ISA-ha have high reflectivity in blue, NIR and SWIR bands. The BCCSR has strong absorption of vegetation, water bodies, ISA-ma and ISA-la in the green and red bands, and strongly reflects of vegetation in the NIR band. In addition, the reverse-colour peak of RRB occurs near the NIR band, but its absorption peak occurs near the blue band. BS is similar in shape and size to the reflected spectrum of water, and has low reflectance at blue, green and red bands. In addition, the UGPC and BCCSR reflectance spectra are very similar in shape and size. As a result, BCCSR seems to be difficult to distinguish from UGPC, especially BCCSRl.
Hydraulic fracturing: a main cause of initiating internal erosion in a high earth-rock fill dam
Published in International Journal of Geotechnical Engineering, 2021
Morteza Salari, Ali Akhtarpour, Amin Ekramifard
The Bidvaz dam is a high earth-rock fill dam with a thin and inclined clay core constructed on the Bidvaz River in northeast of Iran. The dam has been constructed on a narrow and U-shaped valley. About 7 and a half years after the start of the first impounding of this dam, a subsidence was observed on the upstream face of the dam body. Dam monitoring relying on data recorded by the installed instruments confirms the occurrence of internal erosion in the lower levels of the core near the left abutment. Given the geometrical specifications and compressibility of materials in the dam body and the foundation, hydraulic fracturing phenomenon can be hypothesised as a main cause of initiating internal erosion (with concentrated leaks mechanism) in the dam. Accordingly, the main purpose of this research is to evaluate the possibility of hydraulic fracturing in the core of the Bidvaz dam using 3D numerical modelling as well as theoretical and empirical equations.
Cryogenian glaciomarine megaclasts of the MacDonald Corridor, Bimbowrie Conservation Park, Olary Region, South Australia
Published in Australian Journal of Earth Sciences, 2020
At Old Boolcoomata Homestead, approximately 3 km east of the fault-controlled eastern margin of the MacDonald Corridor, the Old Boolcoomata Conglomerate Member onlaps granite of the Kalabity Inlier (Figures 4 and 5). The conglomerate was first noted in print by Mawson (1912) and discussed and shown in plan by Campana and King (1958). Recently Preiss (2006) indicated that the vast majority of conglomeratic debris was derived from the adjoining and underlying two-mica Bimbowrie Suite granite, and also that bedding within the conglomerate dips steeply to the south. The granite lying unconformably below conglomerate shows crazing presumably due to frost shattering. Preiss (2006, 2014) interpreted the morphology of the conglomerate/granite contact to be consistent with the profile of the northern flank of a broad glacial U-shaped valley (Figures 5 and 12).