The Institute of Mining and Metallurgy and E. Hoek and J. W. Bray “Based on Rock Slope Engineering (third edition, ) by. Dr Evert Hoek and Dr John be downloaded (free) from sibacgamete.gq This program. pdf. Rock Slope Engineering Civil and mining 4th edition Duncan C. Wyllie and “Based on Rock Slope Engineering (third edition, ) by Dr Evert Hoek and .. clearly presents well-proven methods to design rock slopes, Hoek and Bray's. Fhwa - Hoek Y Bray - Rock Slopes Engineering - Free ebook download as PDF File .pdf), Text File .txt) or read book online for free.
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Hoek Bray Rock Slope Engineering 1 - Ebook download as PDF File .pdf) or read book online. Stabilnost kosina stijena. Evert Hoek. D. Sc(Eng). Principal John Bray. Ph. D(Eng). 'Reader in Roe ~ t- 1echanics, Imperia! College of Science and Technology, Maximum slope height - slope angle relationship for excavated slopes. Role of discontinui ti es in. The purpose of rock slope engineering is to produce a slope that is stable for the duration of its working life (see Vol. XIV: Slope Stability Download entry PDF . See Hoek and Bray () for a comprehensive text and relevant references.
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Examples of infrastructure built on potentially paraglacial unstable rock slopes are rare Duvillard et al. At least three infrastructure are known to have been affected by paraglacial rock slides during the last two decades: the Gletscherbahn Moosfluh cable-car near the Aletsch glacier in Switzerland Kos et al. This study focuses on the Pilatte hut 2, m a.
Initial damage to the hut, in the form of small cracks, was observed in the late s, but the opening of a large crack in the hut foundations and walls in the early s was of great concern to its managers.
The rock slope on which the hut is built, adjacent to the Pilatte glacier, has been monitored since with ground-based surveying techniques and more recently with high-resolution topographic imagery. To test the hypothesis that the subsidence behind the damage to the Pilatte hut is a result of paraglacial slope adjustment, this research project aims to study the geometry and the dynamics of the rock mass movement and its relationship with the lowering of the Pilatte glacier surface.
It is mainly frequented by hikers and, to a lesser extent, by alpinists climbing Les Bans 3, m a. B The hut above the glacier and the main fracture line dashed red line. A wooden hut was first built here in and is presently used as the winter hut. In , the growth of mountain activities led to the construction of a larger hut with cemented stone walls. A reinforced concrete extension on the west side was built in to increase the number of beds and to improve the comfort and privacy of the hut keepers.
Permafrost is absent in the surroundings of the hut because of the relatively low elevation of the area and an unfavorable geomorphological context Marcer et al. The Pilatte Glacier The hut is separated from the glacier by a very steep and partly overhanging m-high rock wall, which has progressively deglaciated since the end of the Little Ice Age LIA. The till around the hut is relatively recent and was deposed during the LIA Vivian and Bergeret, The glacier length has decreased by c.
The surface area of the glacier decreased by Methods Three different methods were used over different time periods following an initial structural and geological survey of the rock outcrop: i annual crack measurements were done from to , and the results analyzed to detect and study the rock dynamics in progress directly beneath the Pilatte hut, ii Terrestrial Laser Scanning TLS surveys were carried out in and to assess the volume of unstable rock and to monitor any substantial geomorphological activity over that 2 year period, and iii Structure for Motion SfM photogrammetry from historical aerial photographs was carried out to measure elevation changes of the glacier surface from to This became more severe between and ; in particular vertical cracks appeared in the north and south facades 1—2.
Pilatte hut damage with main cracks shown. A The hut and the main fracture line dashed red line. B South wall of the Pilatte hut and location of the fracture delimiting the back of the unstable rock mass in August Since , the evolution of the cracks and damage to the hut has been monitored by two structural engineering companies initially CEBTP and then CEBEA with 20 Saugnac crack-meters—a simple tool which uses a millimetric paper grid.
Crack surveys are carried out three to four times during the period of opening of the hut, i. Data from just four gauges numbered 7, 10, 16, and 17 were used to reconstruct the dynamic processes. These gauges had been ideally positioned, perpendicular to the main fracture line from the floor to the ceiling, and as such were deemed the most relevant. In July , a field visit was carried out to study the local structural context of the rock slope and to locate and choose the main cracks to measure annually.
The major fracture lines delimiting the unstable rock mass were also surveyed annually using crack-meters Figure 3. The main crack close to the hut, on the north side, was surveyed once or twice a year from to by CEBTP.
In , we added 8 sets of two crack-meters at the back 1 , northern 2 , possible downhill 3 , and southern 4 limits of the rock mass which previous structural analysis had identified as being unstable crack openings: Three sets of cracks were equipped with three sets of crack-meters to measure the potential slippage and rotational dynamic of the rock mass.
Crack-meter location and TLS survey positions around the Pilatte hut.
A Crack surveying at C4. B The rock slope below the Pilatte hut from P2 July All the crack-meters were also mapped in July by dGPS with 2 cm to 5 m accuracy due to mask effect and low precision on the rock wall below the Pilatte hut.
TLS Surveys Laser ranging is based on the transmission-reception of infrared light signals with very low spatial dispersion and high temporal precision Slob and Hack, ; Telling et al. For geomorphological purposes, TLS can be used for mapping, geometry assessment or monitoring Jaboyedoff et al. Regarding the latter, some studies have been conducted in high mountain environments Oppikofer et al.
TLS is a very effective study method, despite certain limitations including the weight 14 kg counting the case, tripod, rotating base, laptop and generator and cost of the equipment. Two TLS surveys were carried out from the glacier surface to measure the entire volume of unstable terrain and to monitor the morphodynamics rockfalls, slide over a 2-year period. In order to carry out a kinematic survey of the rock wall below the Pilatte hut, it was scanned in July and August from two distinct positions on the glacier to avoid occlusions resulting from the complex micro-topography.
To assess the unstable volume, the upper part of the rock knoll around the hut was scanned in August from six positions. In reality, few points are acquired beyond — m because of poor reflectivity, skewed rays, or high brightness.
Our scanning was done at a maximum distance of c. Precision in measuring a point at m, and therefore the precision of the model obtained, is 7 mm for distance and 8 mm for position.
Ten characteristic points such as boulders or hut corners were surveyed by dGPS in August to georeference the 3D model. The accuracy was 2—50 cm due to the masking effect of the terrain or the roof of the hut. Cloud point alignment and georeferencing were processed using CloudCompare 2.
V2 software Girardeau-Montaut, Meshing, mapping, computing potential rock sliding volume and rockfall volumes between and were carried out with 3DReshaper software MR1 version. All the points were used for each meshing, and these were generated by a chordal deviation process with a maximum length of triangle edge of 3.
In cases where holes remained in the model, the mesh was hand built to match the recognized topography. The furthest back crack of the potential sliding rock mass was defined by intersecting the main fractures planes.
The zones most poorly covered by TLS, which were also interpolated during the meshing process, were not taken into account during the volume computation because they were situated outside of it. Aerial SFM Photogrammetry SfM photogrammetry allowed us to measure changes in thickness in the Pilatte glacier over the last few decades from historical aerial photographs.
This method has recently become popular Kappas, ; Marcer et al. Some other studies have combined terrestrial photogrammetry and TLS data for the reconstruction of detached rock volumes in high mountain environments Curtaz et al.
The workflow described by Smith et al. The different steps of the workflow are summed up in Figure 4. Snow and cloud free aerial images were aligned to create large 3D models of the upper Pilatte basin Table 1. SfM point clouds were generated through 2 main procedures: 1 the alignment of the images according to the camera view points and 6 ground markers which had not been georeferenced, 2 the building of large dense point clouds.
The different SfM point clouds were then cut out and only those of the study area were retained Pilatte hut area with a c. Then, to ensure that the clouds were perfectly aligned, each SfM model was cut out between the likely stable part of the rock slope i. Work flow of the SfM and TLS processing procedures, from the creation of point clouds to the drawing of polylines on the glacier surface example with image.
Aligning and scaling each part independently compensated for the fact that no ground control points had been directly provided for PhotoScan.
The 3D model from was used as the base on which the other models were aligned because of its high resolution and matching of the TLS point cloud. Polylines representing the contact level between the glacier surface and the rock wall from to were generated from SfM point clouds drawn onto the TLS model, and completed with the TLS point cloud.
The upper one is also cut by four sub-vertical fractures. Delimitation of the unstable rock mass and evolution of the monitored fracture lines over the period — View from the glacier A,B and aerial view C,D. D: rockfall detected when comparing the TLS 3D models of and Based on the structural data, we chose the positions of the crack-meters in order to optimize our understanding of the mechanism of the rock mass movement.
The upper rock mass was surveyed each year with one crack-meter placed at the Pilatte hut since , and with four more crack-meters since or Table 2. During the two last decades, the back cracks have been very active, ranging from an increase in width of 2—3 mm at the north end C5 since to 9 mm on the upper part C6 since Then, probably between September and August , a contraction and probably a small rotation toward the south of at least the upper rock mass occurred in connection with the closing movement of four sub-vertical cracks C1, C2, C3, and C4 and also the closing movement of the southern crack C8.
Cumulative movement monitored by crack-meters.