Rock Face Research Articles

Face destressing blast design for hard rock tunnelling at great depth

Destress blasting of development headings is a construction technique in deep tunnels, whereby explosives are used to fracture the rock in such a way that strain energy is dissipated from the rock mass, with minimal deformation. This is intended to reduce the frequency and severity of violent stress-driven face or floor instability. Effective destressing relies on shear mechanisms of rock mass failure. For this to occur, the length and directionality of blast-induced radial fractures must be sufficient to generate fracture continuity between adjacent explosive charges. Natural rock structure must also be weakened by blasting. The blast-induced fracture network characteristics are largely dependent upon the explosive properties, rock mass strength, natural structural characteristics, as well as the magnitude, orientation and anisotropy of the principal stresses. This paper presents a destress blasting design concept consisting of a series of symmetrical rows of destressing charges which are sub-parallel, yet almost oblique to the major principal stress. When detonated, these rows of charges are intended to create a series of continuous fracture planes which may deform in shear, transitioning the rock face to a post-peak loading condition. The blast design and related damage zones have been examined numerically using the Hybrid Stress Blasting Model. The modelling results guide the blast design parameters, such as borehole diameter, burden, spacing, explosive charge properties and alignment of the borehole rows relative to the major principal stress. It is suggested that the optimal destressing charge consists of a collar primed, fully confined and coupled explosive.

Technical note: In situ measurement of flux and isotopic composition of CO<sub>2</sub> released during oxidative weathering of sedimentary rocks

Abstract. Oxidative weathering of sedimentary rocks can release carbon dioxide (CO2) to the atmosphere and is an important natural CO2 emission. Two mechanisms operate – the oxidation of sedimentary organic matter and the dissolution of carbonate minerals by sulfuric acid. It has proved difficult to directly measure the rates at which CO2 is emitted in response to these weathering processes in the field, with previous work generally using methods which track the dissolved products of these reactions in rivers. Here we design a chamber method to measure CO2 production during the oxidative weathering of shale bedrock, which can be applied in erosive environments where rocks are exposed frequently to the atmosphere. The chamber is drilled directly into the rock face and has a high surface-area-to-volume ratio which benefits measurement of CO2 fluxes. It is a relatively low-cost method and provides a long-lived chamber (several months or more). To partition the measured CO2 fluxes and the source of CO2, we use zeolite molecular sieves to trap CO2 “actively” (over several hours) or “passively” (over a period of months). The approaches produce comparable results, with the trapped CO2 having a radiocarbon activity (fraction modern, Fm) ranging from Fm = 0.05 to Fm = 0.06 and demonstrating relatively little contamination from local atmospheric CO2 (Fm = 1.01). We use stable carbon isotopes of the trapped CO2 to partition between an organic and inorganic carbon source. The measured fluxes of rock-derived organic matter oxidation (171 ± 5 mgC m−2 day−1) and carbonate dissolution by sulfuric acid (534±16 mgC m−2 day−1) from a single chamber were high when compared to the annual flux estimates derived from using dissolved river chemistry in rivers around the world. The high oxidative weathering fluxes are consistent with the high erosion rate of the study region. We propose that our in situ method has the potential to be more widely deployed to directly measure CO2 fluxes during the oxidative weathering of sedimentary rocks, allowing for the spatial and temporal variability in these fluxes to be determined.

Key factor analysis and model establishment of variation of rock face temperature in a deep open-pit mine

In recent years, with the increase of the depth of open-pit mining, the pollution level has been on the rise due to harmful gases and dust occurring in the process of mining. In order to accelerate the diffusion of these air pollutants, the distributed regularity of the rock face temperature which is directly related to the air ventilation in deep open-pit mines should be studied. Here, we establish the key factors influencing the rock face temperature in a deep open-pit mine. We also present an empirical model of the rock face temperature variation in the deep open-pit mine, of which the performance is interestingly high compared with that of the field test. This study lays a foundation to study the ventilation thermodynamic theory in the deep open-pit mine, which is of great importance for theoretical studies and engineering applications of solving air pollution problem in deep open-pit mines.

Volcanic Geoheritage of Landslides and Rockfalls on a Tropical Ocean Island (Western Samoa, SW Pacific)

Landslides and rockfalls on volcanic islands in tropical climate are characteristic landscape shaping features. Their common formation poses potential hazard for island communities; hence, understanding their formation and recognition on modern landscapes are vital element of educating local communities and providing mitigation strategies for future events. As landslides and rockfalls are continuously shaping tropical islands’ landscapes, they contribute significantly to the volcanic geoheritage of those islands. Rockfall and landslide hazards are commonly associated with the Fagaloa Formation and Salani Formations of Western Samoa in the SW Pacific. Four case studies (Mauga-o-Fao, Mauga-o-Vaea, Fagaloa Bay, and Leagi’agi Hill) are reported here, based on highly populated areas which are predicted to be vulnerable in generating rockfalls and landslides in the future. Field observations and interpretation of aerial photographs and satellite images were used to identify landslide and rockfall hazards in the region. The lack of records and previous studies related to rockfalls and landslides in the region is the major challenge for this investigation. Commonly, rockfall and landslide scenarios in Western Samoa are associated with the presence of high angle faults, highly weathered, extensively jointed, and fractured rocks. Surface and groundwater could expand the size of the joints, and existing fault scarps trigger the rock face to become more unstable by losing its support. There are two networks of jointing patterns commonly occurring in both old (3 Ma to 800 ka) and young (200 ka to 3 ka) volcanic rock formations: parallel and perpendicular with lava flow axis. These joint networks would increase the instability of tabular lava flows especially nearby to fault scarps and thick columnar jointed lavas. It is suggested that the major faults on the main islands almost running perpendicular to the central volcanic rift (elongated north east to south west) could be other main drivers of the rockfall and landslide hazards in the region.

Crossing the East River of New York in the Era of Mixed Face Tunneling

Research Article| May 23, 2018 Crossing the East River of New York in the Era of Mixed Face Tunneling David M. Cregger David M. Cregger 1 AECOM Technology, 250 Apollo Drive, Chelmsford, MA 01824 1Corresponding author email: david.cregger@aecom.com Search for other works by this author on: GSW Google Scholar Author and Article Information David M. Cregger 1 AECOM Technology, 250 Apollo Drive, Chelmsford, MA 01824 1Corresponding author email: david.cregger@aecom.com Publisher: Association of Environmental & Engineering Geologists First Online: 30 Nov 2017 Online Issn: 1558-9161 Print Issn: 1078-7275 © 2018 Association of Environmental & Engineering Geologists Environmental & Engineering Geoscience (2018) 24 (2): 137–141. https://doi.org/10.2113/EEG-1982 Article history First Online: 30 Nov 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David M. Cregger; Crossing the East River of New York in the Era of Mixed Face Tunneling. Environmental & Engineering Geoscience 2018;; 24 (2): 137–141. doi: https://doi.org/10.2113/EEG-1982 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Engineering geology and case history experience have been relied upon as predictors for several historical East River tunnel crossings, as shown in Figure 1. Differing rock types were crossed, consisting of gneisses, schist, and limestone or dolomite nearly vertical in orientation and part of a complex tightly folded sequence, but deeply weathered along faults parallel to the river. Each crossing had vertical grade requirements, forcing the alignment through known geologic hazards of poor-quality rock and mixed face. The presence of decomposed and highly crushed zones at depth and glacial or man-made deposits further complicated the mixed face conditions for... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Kindia (Pavetteae, Rubiaceae), a new cliff-dwelling genus with chemically profiled colleter exudate from Mt Gangan, Republic of Guinea.

A new genus Kindia (Pavetteae, Rubiaceae) is described with a single species, Kindia gangan, based on collections made in 2016 during botanical exploration of Mt Gangan, Kindia, Republic of Guinea in West Africa. The Mt Gangan area is known for its many endemic species including the only native non-neotropical Bromeliaceae Pitcairnia feliciana. Kindia is the fourth endemic vascular plant genus to be described from Guinea. Based on chloroplast sequence data, the genus is part of Clade II of tribe Pavetteae. In this clade, it is sister to Leptactina sensu lato (including Coleactina and Dictyandra). K. gangan is distinguished from Leptactina s.l. by the combination of the following characters: its epilithic habit; several-flowered axillary inflorescences; distinct calyx tube as long as the lobes; a infundibular-campanulate corolla tube with narrow proximal section widening abruptly to the broad distal section; presence of a dense hair band near base of the corolla tube; anthers and style deeply included, reaching about mid-height of the corolla tube; anthers lacking connective appendages and with sub-basal insertion; pollen type 1; pollen presenter (style head) winged and glabrous (smooth and usually hairy in Leptactina); orange colleters producing a vivid red exudate, which encircle the hypanthium, and occur inside the calyx and stipules. Kindia is a subshrub that appears restricted to bare, vertical rock faces of sandstone. Fruit dispersal and pollination by bats is postulated. Here, it is assessed as Endangered EN D1 using the 2012 IUCN standard. High resolution LC-MS/MS analysis revealed over 40 triterpenoid compounds in the colleter exudate, including those assigned to the cycloartane class. Triterpenoids are of interest for their diverse chemical structures, varied biological activities, and potential therapeutic value.

3D mapping of discontinuity traces using fusion of point cloud and image data

A new methodology is presented for 3-D automated mapping of joints that are exposed primarily as traces in a rock face as opposed to planar facets. The method identifies 3-D points in a photogrammetry or a LiDAR derived point cloud that corresponds to the traces of the joints as observed in image data. First, the 2-D trace texture is extracted from image data using a hybrid global and local threshold method and integrating a series of image-processing algorithms. Second, data matching links the pixel locations corresponding to the identified traces in an image to the 3-D coordinates in the point cloud. This matching is accomplished by a coordinate transformation between the image coordinates and point cloud coordinates. Finally, a 3-D discontinuity trace map is acquired by analysing the 3-D spatial features of the traces. A case study of a rock slope along a highway is presented using the proposed method. The results demonstrate that the fusion of image data and point cloud data improves the mapping of discontinuities that primarily appear as traces in outcrops versus that achieved by existing methods that rely only on point cloud data.

Life history and chemical ecology of the Warrior wasp Synoeca septentrionalis (Hymenoptera: Vespidae, Epiponini).

Swarm-founding ‘Warrior wasps’ (Synoeca spp.) are found throughout the tropical regions of South America, are much feared due to their aggressive nest defence and painful sting. There are only five species of Synoeca, all construct distinctive nests that consist of a single sessile comb built onto the surface of a tree or rock face, which is covered by a ribbed envelope. Although locally common, research into this group is just starting. We studied eight colonies of Synoeca septentrionalis, a species recently been described from Brazil. A new colony is established by a swarm of 52 to 140 adults that constructs a colony containing around 200 brood cells. The largest colony collected containing 865 adults and over 1400 cells. The number of queen’s present among the eight colonies varied between 3 and 58 and no clear association between colony development and queen number was detected. Workers and queens were morphologically indistinguishably, but differences in their cuticular hydrocarbons were detected, particularly in their (Z)-9-alkenes. The simple cuticular profile, multiple queens, large size and small number of species makes the ‘Warrior wasps’ an excellent model group for further chemical ecology studies of swarm-founding wasps.

SOME TOOLS TO SUPPORT TEACHING PHOTOGRAMMETRY FOR SLOPE STABILITY ASSESSMENT AND MONITORING

Abstract. This paper describes the use of some tool to help training of photogrammetry for applications in the field of landslide and slope stability assessment and monitoring. These tools have been used in classes of the MSc on Civil Eng. for Risk Mitigation at Politecnico di Milano university, Lecco (Italy). The first tools are hardware facilities. The first one consists of a ‘Landslide Simulator,’ where shallow landslides may be reproduced at small scale. Simulations are also used here for active-learning purpose. In particular, here the use of digital images to obtain multi-temporal information is presented. The second tool is a ‘Rock face 3D Modelling Simulator.’ This is used by students to learn how a photogrammetric block should be designed in order to reconstruct rock slopes using Structure-from-Motion photogrammetry. The last to tools are software packages (CloudCompare and LIME) devoted to point cloud analysis (including change detection/ deformation analysis) and advanced visualization, respectively. The combination of these tools together with datasets from either lab and the real field, has been successfully tested to provide efficient training to students in an active-learning fashion.

The Research on Tunnel Surrounding Rock Classification Based on Geological Radar and Probability Theory

In order to effectively classify the surrounding rock types of tunnels, a multi-factor tunnel surrounding rock classification method based on GPR and probability theory is proposed. Geological radar was used to identify the geology of the surrounding rock in front of the face and to evaluate the quality of the rock face. According to the previous survey data, the rock uniaxial compressive strength, integrity index, fissure and groundwater were selected for classification. The related theories combine them into a multi-factor classification method, and divide the surrounding rocks according to the great probability. Using this method to classify the surrounding rock of the Ma’anshan tunnel, the surrounding rock types obtained are basically the same as those of the actual surrounding rock, which proves that this method is a simple, efficient and practical rock classification method, which can be used for tunnel construction.

Effect of Geological Structure on Flyrock Prediction in Construction Blasting

Blasting is sometimes inevitable in civil engineering work, to fragment the massive rock to enable excavation and leveling. In Minyak Beku, Batu Pahat also, blasting is implemented to fragment the rock mass, to reduce the in situ rock level to the required platform for a building construction. However, during blasting work, some rocks get an excessive amount of explosive energy and this energy may generate flyrock. An accident occurred on 15 July 2015 due to this phenomenon, in which one of the workers was killed and two other workers were seriously injured after being hit by the flyrock. The purpose of this study is to investigate the causes of the flyrock accidents through evaluation of rock mass geological structures. The discontinuities present on the rock face were analyzed, to study how they affected the projection and direction of the flyrock. Rock faces with lower mean joint spacing and larger apertures caused excessive flyrock. Based on the steoreonet analysis, it was found that slope failures also produced a significant effect on the direction, if the rock face failure lay in the critical zone area. Empirical models are often used to predict flyrock projection. In this study five empirical models are used to compare the incidents. It was found that none of the existing formulas could accurately predict flyrock distance. Analysis shows that the gap between predicted and actual flyrock can be reduced by including blast deign and geological conditions in forecasts. Analysis revealed only 69% of accuracy could be achieved if blast design is the only parameter to be considered in flyrock projection and the rest is influenced by the geological condition. Other causes of flyrock are discussed. Comparison of flyrock prediction with face bursting, cratering and rifling is carried out with recent prediction models.

Failure of the threaded region of rockbolts in underground coal mines

HSAC 840 steel rockbolts were examined, all of which had failed in service through the threaded region exterior to the rock face by brittle fracture transverse to the bolt axis. The bolts had been in service in an Australian coal mine in which the groundwater had a pH of 7·5–8·5 and a relatively high bicarbonate level of 515–2200 mg l−1. All failures had occurred within the region comprising the domed washer and the end plate. The majority of the bolts showed a small thumbnail-shaped discoloured region 1.5-4.5 mm in length at the fracture origin, as is characteristic of stress corrosion cracking (SCC) in rockbolts. In half of these bolts, SCC had initiated immediately at the root of the thread, but in the other half of the bolts, SCC had initiated from a small pre-existing crack that had been produced in the thread as a result of a prior bending load.

English

In a mining operation, any noticeable instability can pose a catastrophic threat to the lives of workers. Slope instability can also disrupt the chain of production in a mine, resulting in a loss to the business. Due to the potential threat associated with rock mass movement, it is necessary to be able to predict the time of slope failure. In the past couple of decades, innovations in slope monitoring equipment have made it possible to scan a broad rock face in a short period of time with sub-millimeter accuracy. The data collected from instruments such as Slope Stability Radar (SSR) are commonly used for slope failure predictions, however, it has been challenging to find a method that can provide the time of failure accurately. The aim of this paper is to demonstrate the use of different methods to optimize slope failure predictions. Various methods investigated for research presented in this article include: Minimum Inverse Velocity (MIV), Maximum Velocity (MV), Log Velocity (LV), Log Inverse Velocity (LIV), and Spline regression (SR). Based on the different methods investigated, the Minimum Inverse Velocity method provided the most consistent and accurate results. The use of MIV method resulted in about 75% better predictions than the other methods.   Key words: Monitoring, slope failure, slope instabilities, slope movement, rock failure.

Analysis of microseismic signals collected on an unstable rock face in the Italian Prealps

Analysis of microseismic signals collected on an unstable rock face in the Italian Prealps

The numerical study of seismic behavior of gravity retaining wall built near rock face

The numerical study of seismic behavior of gravity retaining wall built near rock face

Mechanizmy i uwarunkowania rozwoju progów morfologicznych Gór Stołowych = Mechanisms and controls of escarpment evolution in Poland’s Stołowe Mountains

The Stolowe Mountains,situated in the Middle Sudetes, form Poland’s only tableland, which is underlain by an alternating succession of sedimentary rocks, all of Permian and Late Cretaceous age. The morphology of the Stolowe Mountains is characterised by the presence of isolated mesas and plateaus. Nearly-level summits are bounded by precipitous escarpments up to 300 m tall. These are bipartite in profile, with stronger sandstones forming vertical cliffs and less-resistant marls and mudstones being truncated by concave slope sections. There seems to be general agreement that long-term escarpment retreat is the dominant pathway by which this tableland evolved geomorphically. However, ideas on the processes contributing to the scarp recession vary. Since the early 20th century, the dominant concept has ascribed a major role to catastrophic mass movements. Łozinski (1909) for example pointed to rock falls, and linked their origin with intense mechanical weathering. For their part, both Czeppe (1952) and Dumanowski (1961, 1967) underlined the crucial importance of subsurface water flow at the point of contact between the permeable sandstones and impermeable fine-grained rocks. In their opinion, that phenomenon results in the undercutting and destabilisation of rock faces. Pulinowa (1972, 1989) was of a similar view and suggested that plastic deformations of underlying marls and mudstones caused subsidence and the toppling of marginal parts of the sandstone caprock. Although deep clefts are a prominent feature of Mt Szczeliniec Wielki, no significant movements have been recorded in recent decades (e.g. Cacon, 2008). Thus, from a present-day standpoint, the different outlooks mentioned above can be considered highly influenced by paradigms, while lacking in support where empirical data are concerned. In contrast, systematic study based on quantitative measurements has been engaged in recently by Duszynski and Migon (2015) and Duszynski et al. (2016). They reveal that non-catastrophic disintegration of cliff lines appears to be a much more common phenomenon than rock failure. An alternative scenario assumes that the marginal parts of plateaus are separating along joints, due to underground erosion and removal of rock residuum. In this way, after a long period of time, a once-solid rock face becomes a mess of joint-bounded blocks. Transport downslope is then more apparent than real as progressively lower topographical positions are occupied, while the lower escarpment slope recedes. Landslides in the middle and lower parts of the slope (Duszynski et al., 2017), block ploughing (Pulinowa, 1989; Duszynski and Parzoch, 2016) and erosional incision (Migon and Kasprzak, 2016) all do contribute to escarpment retreat, but their role is limited to single localities. Although our knowledge regarding the evolution of the Stolowe Mountains has improved greatly, we still lack chronological data, and are hence unable to pinpoint the environmental conditions proving particularly favourable to escarpment recession. There is also a need to determine whether the arenisation process often described in the foreign literature (e.g. Wray and Sauro, 2017) is actually responsible for the slow detachment of sand grains from quartz sandstone.

Sleeping in a Field, and: For Every Shadow

Sleeping in a Field, and: For Every Shadow Triin Paja (bio) Sleeping in a Field in a dream moths thud into my body taking me for light +the way to the water: a one-eared yellow cat, beach roses, swans like bones in the air. then it was only the hanging moss of your damp hair,the sea's painting of hysteria behind you. no one asking who will bring us water. no one stopping the soft prayer of your hands breaking up bread, oranges. we did not speak of her, though we saw faces of girlsin dusk-blushed rocks. only later, in a letter, did we say. Writing becomes memory. the wine bottle fellto form a bazaar of lanterns. What could we say? the sea wind eats our words, the way particles of lightbegin to fall into night's mouth. it didn't mean absence of thought. Someone touchingher long, unwashed hair. Like coarse wheat. [End Page 69] it was only something hushed in our village.a girl fell asleep in a field and then it was blood brushed on wheat, the sound of tractors humming,the white feathers of sunlight falling, and falling. For Every Shadow You taught me to love women, women who were prostitutesto the German occupiers and whose heads were shaved, who sold brown soap, wore clogs, women in legends,Medusa, Valkyries, women who bled making lace— We loved them, and I love you in a room which Chopinfills with rain, where your curls coil like ferns, and I tell you how, as a child, my feet were marredby wooden shoes. Each body wore stories like unwanted uniforms, soldiers sowing onthe Soviet emblem at night, blistered fingers spelling: Kõigi maade proletaarlased, ühinege!Proletarians of the world, unite. I loved the women with furrowed handswho carried bread to the store in bicycle baskets, mothers who fried potato peels, women who spat. (Dusk) We go to a cemetery, find tables by the graves,shot glasses in weeds: [End Page 70] a Slavic manner to drink with the dead.I do not believe oppression thins like morning mist. The memory of it alters into a habit, like the women I lovewho still slip their hair into florid scarves, who serve tea for ghosts,whose furrowed hands braid our hair with light. [End Page 71] Triin Paja Triin Paja is an Estonian living in a small village in rural Estonia. Her poetry has appeared or is forthcoming in the Adroit Journal, Portland Review, Entropy, and others. She also writes and publishes poetry in Estonian. Copyright © 2018 University of Nebraska Press

A 3D model for annular displacements of wellbore completion fluids with casing movement

During mud circulation and cementing operations, non-Newtonian completion fluids are injected along the wellbore annular space formed by the gap between the outer wall of the casing and the rock face. During such processes, these fluids displace each-other and follow a complex path given by pressure gradients, rheology and density contrasts, casing rotation and reciprocation and by the actual shape and orientation of the annulus. Muds and cement slurries also often exhibit a yield stress which may represent additional challenge for optimal fluid removal and cement coverage. This paper presents a novel approach to solving the 3D flow and displacement of completion fluids in the annulus. In particular, this work extends a model published in Tardy and Bittleston (2015) which solves the flow in the 2D axial-azimuthal plane, to now capture fluid distribution and velocity profiles across the gap width in the 3D axial-azimuthal-radial space. The new 3D model is derived using the so-called narrow-gap approximation for the momentum balance equations. This approximation provides a mean to solve the 3D velocity and concentration fields while solving a 2D-only elliptic pressure equation, which is significantly faster to solve than the original 3D pressure equation, and without suffering any significant loss of accuracy.

Validation of simulated temperature profiles at rock walls in the eastern alps (Dachstein)

AbstractWhile rock temperature is a key factor for many geomorphic phenomena in high mountains, assessing the small‐scale temperature distribution remains challenging. We adapted the program package WUFI®, originally designed to calculate energy and moisture fluxes in building walls, for modeling natural rock faces. We determined physical rock properties and local meteorological parameters as input data for the simulations at rock walls in the Dachstein Mountains, Austria, and calculated annual temperature fluctuations at the surface and at 3, 10, 30, 50 and 100 cm depth, including different elevations, aspects and slope angles. Thirty‐seven temperature sensors inserted into drillholes of different depths at ten locations (altitudes from 2300 to 2700 m) were used to validate the simulation. Additionally, surface temperatures were determined from infrared images; these were calibrated for surface emissivity using further temperature sensors. Simulated temperatures and sensor data show very good agreement, with a mean correlation coefficient of 0.94, and the validation of surface temperatures by thermal imaging also delivered good results (r > 0.9). This means that the WUFI software can be used to model complex temperature distributions in natural rock wall settings, thus making it a valuable tool for geomorphological investigations.

Bulbine dewetii, a New Cliff-Dwelling Bulbine Species (Asphodelaceae) from the Western Cape

Bulbine dewetii (Asphodelaceae) is named; it is an obligatory geophytic cremnophyte from the sheer rock faces of the lower southern slopes of the Heks River Mountains (Western Cape, South Africa). Bulbine dewetii usually grows solitary (rarely proliferating and forming small groups) with soft pendent leaves, flowering during the month of November (late spring, S. Hemisphere), the flowers open during the afternoon and remain open during the night. The description of this taxon forms part of an extensive survey of cliff-dwelling succulent and bulbous-succulent taxa in South Africa and Namibia.