Large Rock Mass Research Articles

Coupling stress and transmissivity to define equivalent directional hydraulic conductivity of fractured rocks

A DFN (Discrete Fracture Network) modelling approach is developed to couple stresses with fracture transmissivities and to evaluate large scale rock mass hydraulic conductivity. The transmissivity-stress coupling relies on a negative exponential correlation between normal stress acting on a fracture and fracture transmissivity, bounded by residual and maximal apertures. The remote stresses and the local stress fluctuations induced by the fractures themselves are combined in a semi-analytical approach to compute the normal stress acting on each fracture of a DFN. Directional equivalent hydraulic conductivities are numerically computed in all directions from a spherical permeameter setup. The resulting properties are first a cloud of points, where each point defines a direction and an equivalent hydraulic conductivity. The distribution of equivalent hydraulic conductivities is analyzed to define mean values, preferential directions and anisotropy ratio. The entire workflow is developed in the numerical platform DFN.lab. The capacity of the method to investigate the impact of the in-situ stresses on the rock mass hydraulic conductivity is illustrated for fracturing and in-situ stress conditions similar to the conditions at the Forsmark site in Sweden. We find that the stress fluctuations induced by the fractures have a significant impact on the resulting hydraulic conductivity field. They limit the anisotropy ratio to values close to a factor of 3 while the transmissivity distribution is correlated to orientations and spans several orders of magnitude. Sensitivity analyses, performed by changing the parameters of the transmissivity-stress law, show quantitatively how the directional hydraulic conductivities are rather controlled by the orientations of the in-situ stresses or by the underlying connectivity structure of the DFN.

Deconstruction of the Franciscan Complex Central Terrane Mélange and re-evaluation of Franciscan mélanges and architecture of the northwestern San Francisco Bay Area, California, USA

Various mélange types occur within the Franciscan accretionary Complex of western California. The largest mélange body, called the Central Belt Mélange (or similar names) served earlier as the type example for the orogen-long, subduction channel model, yet in the northwestern San Francisco Bay Area the name does not accurately reflect the geology. The mélange designation was commonly applied where resistant exotic and native blocks of rock are scattered across a relatively smooth terrain. Detailed mapping shows that many blocks experienced post-accretion transport. Areally large rock masses previously designated as Central Belt Mélange consist of multiple units and less than 30% of the tectonostratigraphy is mélange. Weakly metamorphosed sandstone–mudrock broken to dismembered formational units and similarly deformed sandstone–mudrock submarine fan facies dominate the tectonostratigraphy. Subordinate mélanges of the northwestern San Francisco Bay Area are of tectonic or sedimentary origin. The sedimentary bodies represent submarine mass flow deposits. Tectonic mélanges mark Mesozoic subduction-zone faults or Cenozoic strike-slip faults. Discriminating between mélange types and their origins, and reconstructing tectonostratigraphic columns for major fault blocks, clarifies the primary accretionary complex architecture and reveals significant along-strike variations in the Franciscan subduction accretionary Complex.

Deterioration mechanisms of tuff with surface fractures under freeze–thaw cycles

In practical engineering, the development of surface cracks is one of the most important reasons for the destruction of the rock mass, and the development of complex morphology fractures on the rock mass surface significantly influences rock mass mechanics. This paper addresses the freeze–thaw damage issue in rock mass containing surface fractures in cold regions. Tuffs and a control group are selected as research samples, with the control group being prefabricated surface jointed specimens with an inclination angle of 70° and a fracture depth ratio d (crack depth) /t (sample width) of 0.26. The study analyzes the mass, wave velocity loss, macro-microcosmic fracture damage morphology, and mechanical properties of the two specimen groups through laboratory freeze–thaw cycle tests, uniaxial compression tests, and scanning electron microscopy examinations. The results show an overall decrease in mass, wave velocity, and uniaxial compressive strength as the cycle number increases, with the prefabricated jointed group samples showing more significant changes. However, the two specimen groups exhibit different macroscopic failure fracture states. In addition, scanning electron microscopy images illustrate that after freeze–thaw cycles, the large rock mass particles break into smaller fragments, resulting in looser particle arrangements and a transition from initial surface cementation to point contact., which weakens the compressive strength of the rock mass. The paper also explains the mechanism of the diminishing impact of freeze–thaw cycles on the strength of the rock mass after a certain number of cycles. The research outcomes hold significant reference value for engineering construction in cold regions.

Research on a Space-Time Continuous Sensing System for Overburden Deformation and Failure during Coal Mining.

Underground coal mining can cause the deformation, failure, and collapse of the overlying rock mass of a coal seam. If the mining design, monitoring, early warning, or emergency disposal are improper, in that case, it can often lead to mining disasters such as roof falls, water inrush, surface collapse, and ground fissures, seriously threatening the safety of mine engineering and the geological environment protection in mining areas. To ensure the intrinsic security of the entire coal mining process, aspace-time continuous sensing system of overburden deformation and failure was developed, which breaks through the limitations of traditional monitoring methods that characterize the evolution process of overlying rock deformation and ground subsidence. This paper summarizes the classification of typical overburden deformation and failure modes. It researches the space-time continuous sensing of rock-soil mass above the coal seam based on Distributed Fiber Optic Sensing (DFOS). A multi-range strain optical fiber sensing neural series from micron to meter was developed to achieve synchronous sensing of overburden separation, internal micro-cracks, and large rock mass deformation. The sensing cable-rock mass coupling test verified the reliability of the optical fiber monitoring data. The sensing neural network of overburden deformation was constructed using integrated optical fiber layout technology on the ground and underground. Different sensing nerves' performance and application effects in overburden deformation and failure monitoring were compared and analyzed with field monitoring examples. A physical model was used to carry out the experimental study on the overburden subsidence prediction during coal mining. The results showed that the optical fiber monitoring data were reliable and could be used to predict overburden subsidence. The reliability of the calculation model for overlying rock subsidence based on space-time continuous optical fiber sensing data was verified in the application of mining subsidence evaluation. A systematic review of the shortcomings of current overburden deformation observation technology during coal mining was conducted, and a space-time continuous sensing system for overburden deformation and failure was proposed. This system integrated sensing, transmission, processing, early warning, decision-making, and emergency response. Based on the fusion of multi-parameter sensing, multi-method transmission, multi-algorithm processing, and multi-threshold early warning, the system realized the real-time acquisition of space-time continuous information for the overburden above coal seams. This system utilizes long-term historical monitoring data from the research area for data mining and modeling, realizing the prediction and evaluation of the evolution process of overburden deformation as well as the potential for mining subsidence. This work provides a theoretical reference for the prevention and control of mining disasters and the environmental carrying capacity evaluation of coal development.

Stabilization of Deep Roadways in Weak Rocks Using the System of Two-level Rock Bolts

Large rock mass deformation around deep roadways in the weak rocks was a significantproblem in mining activities in Vietnam and other countries. The excavation of roadways leads to highreleasing stress, which exceeds the peak strength of spalling surrounding rock and causes it to enter thepost-failure stage. Tensile failures then initiate and develop around the roadways, which causes thefragmentation, dilation, and separation of surrounding rock. The capacity of the primary support systemis low, which results in a severe contraction in the whole section of roadways, which requires findingsolutions to prevent the deformation of rock mass around roadways and technical solutions fromstabilizing for deep roadways. To stability analysis of roadways can be applied analytical, experimental,semi-experimental, and numerical methods. This paper introduces the prevention mechanism of largedeformation of rock mass around roadways using 2-level rock bolts. The research results show that usingthe system of two-level rock bolts can reduce the values of tensile stress on the boundary of roadwaysrange from 10 to 15% compared with only one. The importance of the total displacement of rock mass onthe boundary of roadways will be reduced from 3.47 to 13.85% using six long cable bolts.

PRINCIPLE AND APPLICATION OF CONTROLLABLE GROUTING OF CEMENT-SODIUM SILICATE SLURRY IN LARGE LOOSE ROCK MASS DUE TO MINING CAVING

Loose rock mass is a kind of common rock mass structure in mining,tunnel,underground space and other projects. It has the characteristics of low strength and poor stability. Grouting reconstruction is one of the important technologies to enhance its integrity and strength in site. To meet the special needs of the plugging project of the main ore pass with large-scale collapse under the condition of full rocks in Hebei provincial Xingshan Iron Mine,the concept of the controllable grouting of cement-sodium silicate slurry in the large loose rock mass is adopted. Based on the experimental study of cement-sodium silicate slurry grouting in the large volume loose rock mass,the grouting process was divided into the following five stages. They are vertical dominant seepage with macrovoid,circumjacent seepage with macrovoid,superior seepage stone,splitting and seepage of the first layer and splitting and seepage of the nth layer. According to the spatiotemporal propagation of slurry,the controllable grouting problem was divided into the one-dimensional vertical dominant seepage of cement-sodium silicate slurry and the circumferential spatiotemporal diffusion of single-stage grouting. and the mechanism of its occurrence was revealed that there is an exponential function with base e between the diffusion distance and the time of the one-dimensional vertical dominant seepage of cement-silicate slurry in the loose rock mass. On the basis of the above experimental results,the technology of the controllable grouting of cement-silicate slurry in the loose rock mass was applied to the plugging project of the main ore pass fully filled with large-scale collapsed rocks in the Xingshan Iron Mine,and good engineering performance were achieved.

Stability mechanism recognition and failure risk assessment on a high slope by synthesizing different analysis methods

The studied slope is located in the middle reach of the Yalong River in the eastern margin of Qinghai-Tibet Plateau in Southwest China. A large hydropower station is planning to be built near the slope. Understanding the stability mechanism of the slope is important for dam site design. Under a combination of tectonic activity, unloading and weathering, the bedrock mass was fractured. On the basis of field investigation, the GSI classification system and Barton criterion were introduced to determine the strength of the rock mass. The kinematic, limit equilibrium and discontinuum modeling methods were carried out to comprehensively understand the stability of the slope. The kinematic analyses show that only wedge mode is possible for large rock mass failure. However, limit equilibrium analyses show that both wedge failure and circular slip are not expected for rock mass. The slope rock mass is now in the surface rebalance stage. The potentially unstable part is the covering deposit. The 40 million m3 surface deposit is now nearly in a limit equilibrium state. The possibility of failure reaches 41%. Mitigation measures must be put into effect on the deposit to assure the stability of the slope. The results indicated that the failure mechanism of the slope was not controlled by the discontinuities in the rock mass at present but depended on the stability of the surface deposit.

Cave radon exposure, dose, dynamics and mitigation

Many caves around the world have very high concentrations of naturally occurring 222Rn that may vary dramatically with seasonal and diurnal patterns. For most caves with a variable seasonal or diurnal pattern, 222Rn concentration is driven by bi-directional convective ventilation, which responds to external temperature contrast with cave temperature. Cavers and cave workers exposed to high 222Rn have an increased risk of contracting lung cancer. The International Commission on Radiological Protection (ICRP) has re-evaluated its estimates of lung cancer risk from inhalation of radon progeny (ICRP 115) and for cave workers the risk may now (ICRP 137) be 4–6 times higher than previously recognized. Cave Guides working underground in caves with annual average 222Rn activity > 1,000 Bq/m3 and default ICRP assumptions (2,000 workplace hours per year, equilibrium factor F = 0.4, dose conversion factor DCF = 14 µSv/(kBq h m-3) could now receive a dose of > 20 mSv/y. Using multiple gas tracers (d13 C--CO2, Rn and N2O), linked weather, source gas flux chambers, and convective air flow measurements a previous study unequivocally identified the external soil above Chifley Cave as the source of cave 222Rn. If the source of 222Rn is external to the cave, a strategy to lower cave 222Rn by passively decreasing summer pattern convective ventilation, which draws 222Rn into caves, is possible without harming the cave environment. A small net annual average temperature difference (warmer cave air) due to geothermal heat flux produces a large net annual volumetric air flow bias (2–5:1) favoring a winter ventilation pattern that flushes Rn from caves with ambient air. Rapid anthropogenic climate change over decades may heat the average annual external temperature relative to the cave temperature that is stabilized by the thermal inertia of the large rock mass. Relative external temperature increases due to climate change (Jenolan Caves, 2008–2018, 0.17°C) reduces the winter pattern air flow bias and increases Rn concentration in caves.

Scale effect of shear mechanical properties of non-penetrating horizontal rock-like joints

From the perspective of macroscopic scale, the majority of natural rock mass should be categorized as non-penetrating jointed rock mass. The existing researches in the field of scale effect of joint properties were mainly implemented on penetrating joints, which contradicts engineering practice, and is of high possibility to make the strength estimation of large natural jointed rock mass inaccurate, leading to serious loss of life and property. In response to such case, a series of numerical calculations of direct shear test on non-penetrating horizontal rock-like joints with different scales were carried out by PFC in this paper, to investigate the scale effect of shear mechanical properties of non-penetrating horizontal rock-like joints. First, the model microparameters were calibrated by three physical experiments to guarantee the precise reproduction of the mechanical performances of target rock and joint. Next, the particle parameters (average particle size dave and radius ratio μ) of model were changed, the effect of particle size on joint strength was studied by direct shear calculation, and the determining method for the values of dave and μ was suggested. Then, based on two distribution forms of non-penetrating horizontal rock-like joint (type I and type II joints), the numerical shear tests were conducted on jointed rock models with different persistence rations and model scales, and the variations of shear stress displacement curve and strength characteristics were analyzed. The results indicate: The lower the persistence ration λ of the joint, the more obvious the negative scale effect of joint shear strength. Besides, the scale effect of shear strength gradually decreases when λ > 0.5 for type I joints while λ > 0.8 for type II joints and the scale effects of joint strength parameters only emerge in the case of λ < 0.2.

Analysis of Blast Induced Ground Vibration under Varying Controlled Blasting Parameter

Mining activity plays a major role for economic development of any nation. The drilling and blasting are the two key operations in the mining industry. The execution of these operations generates some disturbances to the environment, like noise and vibration. Blasting is the process of reducing large rock mass into the smaller fragments for our convinces of further processing. In this study the blast induced vibrations are monitored in the form of peak particle velocity (PPV) for the different cases of varying hole spacing. In this study, the PPV was measured for the three different directions, namely, transitional, vertical and longitudinal and it was observed that the PPV for in transitional direction is decreasing with the increment in the hole spacing between two consecutive rows. Further, it was observed that peak vector sum (PVS) having an inverse relation with the hole spacing.

Investigation of Dimension Stone on the Island Brač—Geophysical Approach to Rock Mass Quality Assessment

A site located on the island of Brač is known in history for world-famous architectural stone and stone mining, dating all the way back to ancient Greek and Roman times. The most famous building constructed from the stone from Brač is the Diocletian Cesar Palace in the town Split. Prospective new locations for quarries are still required because the demand for the stone from the island is still high. This paper presents a review of undertaken geophysical investigations, as well as engineering geologic site prospection, with the purpose of determining if the rock mass quality is suitable for the mining of massive blocks needed for an architectural purpose—dimension stones. Several surface noninvasive geophysical methods were applied on the site, comprising of two seismic methods, multichannel analysis of surface waves (MASW) and shallow refraction seismic (SRS) electrical methods of electrical resistivity tomography (ERT), as well as electromagnetic exploration with ground penetrating radar (GPR). Results of geophysical investigations were compared to the engineering geologic prospection results, as well to the visible rock mass structure and observed discontinuities on the neighboring existing open mine quarry. Rock mass was classified into three categories according to its suitability for dimension stone exploitation. Each category is defined by compressional and shear seismic velocities as well as electrical resistivity. It has been found that even small changes in moisture content within the large monolithic rock mass can influence measured values of electrical resistivity. In the investigated area, dimension stone quarrying is advisable if the rock mass has values of resistivity higher than 3000 Ωm, as well as compressional seismic velocities higher than 3000 m/s and shear wave velocities higher than 1500 m/s. Georadar was found to be a good tool for the visual determination of fissured systems, and was used to confirm findings from other geophysical methods.

Delineating ore-forming rock using a frequency domain controlled-source electromagnetic method

Several magmatic Ni-Cu deposits associated with Permian-Triassic mafic-ultramafic intrusions have been discovered during the last three decades in the southern part of the Central Asian Orogenic Belt, the northeastern margin of Tarim, and the margin of the North China Craton. The accurate delineations of the large resistive rock masses are crucial for locating potential ore bodies when they are located beneath rock masse. The controlled-source electromagnetic method (CSEM) is an important tool for investigating resistivity contrast in earth subsurface. In this study, we present a comprehensive example of using frequency domain CSEM survey to delineate the resistive rock masses that are related to the forming of orebody. The horizontal electric field, which is more sensitive to resistive target than the other components, is used in our study. We first built a geophysical model of the survey area based on prior confirmed geophysical and geological information. Then, both forward and inverse modeling were performed in order to assess the detectability of the resistive ore-forming rock masses in the model. Finally, this study acquired field data in the Kalatongke Ni-Cu Deposit, which is located in the Kalatongke District of the southern section of the Central Asian Orogenic Belt, and is specifically part of China’s southern Altai Orogenic Belt. The resistive ore-forming rock masses were successfully identified during the survey process and further verified by the drilling results. It was observed that both the synthetic and field examples indicated that the adopted frequency domain CSEM method successfully measured the electrical fields, and could be utilized to explore deeply buried resistive targets in future prospecting activities.

Detioracja kamiennych obiektów budowlanych - główne czynniki i procesy

Deterioration of stone buildings – main factors and processes. A b s t r a c t. The condition of stone building objects is determined by many physicochemical factors and destructive processes. All stone materials are subject to natural aging, losing many of their primordial properties. The destructive processes and decline of the stone quality are termed the “deterioration” (Latin: deterior – worse). This definition is close to that of rock weathering. However, weathering and deterioration are two different concepts.Weathering is a large-scale process related to large rock masses located in a geological environment. By contrast, deterioration refers to processes destroying a stone material, which has already been treated with stonework. The most known field of research for the deterioration processes are all historical old monuments. It is assumed that the deterioration reaches such a depth as those influenced by changes that take place on the stone object surface during the adsorption of solar radiation and deep penetration of oxygen and carbonated water, coming from infiltration of atmospheric precipitation or surface water. The most prominent factors of deterioration are caused by temperature changes, crystallization pressure of salts dissolved in water, gaseous pollutants and dust contained in the air, wind, hail and snow action, adsorption of acidic chemical substances, and dust particles, activity of microorganisms, fungi and lichens living on surfaces of monuments.

Removing of a large unstable rock mass on the national highway slope with road blocked

Removing of a large unstable rock mass on the national highway slope with road blocked

Technology Focus: Stimulation (June 2019)

Technology Focus The fourth industrial revolution is taking the oil and gas business by storm. Many companies have increased resources for developing and using big-data analytics and machine learning to catch the wind that could bring the fragrance of the new economy. In a conversation with management of a major service company, I learned that the downturn made them want to shift from a position as a capital-intensive stimulation service provider to that of a higher-profit-margin data-service provider. Though no one sees the actual physical oilfield services—such as pumping, measurement, and chemicals—as in decline, technology development in these areas may take a back seat to artificial intelligence. That said, technological innovation is not a privilege exclusive to scientists and high spenders in research and development but is often the work of good engineers. Integrating and applying existing (or even old) technologies to do the things we know how to do better is our operational model in many ways in this low- price environment. If we do not feed the right data to the machine-learning process, we are not doing justice to the smart machines we build. An example of the right data is downhole pressure, particularly during acid fracturing. We do not know whether we routinely conduct high-rate matrix acidizing or acid fracturing unless we have reliable downhole pressure data. Otherwise, we may dissolve a large rock mass in an undesirable manner and location, failing to optimize stimulation design. The other technology area to improve in stimulation is the measure of diversion. We have been using particulate diverters for ages. Now, we need such products to function under more-challenging conditions. Instead of diverting from matrix, we want them to divert from fractures. Advanced experimental equipment and testing procedures are necessary to gain better quantitative information to determine what size diverter pill is appropriate to build sufficient pressure for inducing new fractures. Matrix-stimulation techniques predominantly rely on chemicals to attack the rock and mechanical tools to place the chemicals. The aspect of physics-enhanced chemical reactions has not caught many eyes, though it has been around for a while. Some oil-production increases have been reported after earthquakes. Geophysicists provided plausible reasons, but petroleum engineers only explored such applications superficially. Not every well can be hydraulically fractured nor every rock dissolved by acids. We need all the help we can get in this kind of situation. Combining acoustic waves with chemicals for stimulation definitely should be studied more. It is encouraging to see people persevere in pursuing continuous improvements in stimulation technologies by going back to the shelf. Recommended additional reading at OnePetro: www.onepetro.org. SPE 191981 Introduction of Real-Time Flow Measurements Opens New Paths To Overcome Challenges Encountered During the Acid Stimulation of Extended-Reach Wells by Laurie Duthie, Saudi Aramco, et al. SPE 192069 Development and Application of Key Equipment of CO2 Waterless Fracturing by Lichen Zheng, PetroChina, et al. SPE 193723 Effective Matrix Acidizing Based in Chelating Agents: A Case Study in Romanian Heavy-Oil Reservoirs by Emil Panait, OMV Petrom, et al.

Analysis of stress evolution characteristics during TBM excavation in deep buried tunnels

Full-face tunnel boring machines (TBMs) are widely used in tunnel engineering projects as an efficient, safe and economical tunneling method. However, TBM excavation causes stress near the tunnel boundary that is disturbed and redistributed under high in situ stress. The changing stress of the surrounding rock can lead to rock failure and cause machinery damage, owing to large rock mass deformations. Research on the impact of TBM excavation on the surrounding rock has mostly focused on the stress magnitude, while the influence of the variation of stress orientation has not been considered. In this study, the practical simulation of a double-shield TBM (DSTBM) construction process was conducted using a three-dimensional (3D) numerical simulation. The rock mass stress changed intensely with the rotations of the principal stress axes as the tunnel face passed through the rock monitoring section during the tunnel excavation. Additionally, the significant influence of stress variation is discussed in qualitative terms, and the analysis results of the stress path are presented. Moreover, using a new self-developed laboratory apparatus, the actual stress path of the surrounding rock is proposed under conditions of a changing principal stress magnitude and changing rotation of the principal axis during the process of TBM excavation.

Monitoring of Tempi Valley Critical Rock Masses: Establishment of Special Monitoring Network and Procedures in Aegean Motorway S.A. Concession Project

The paper aims to describe the installed monitoring network of critical rock masses stability and deformations and the procedures that are followed by the Concessionaire in order to ensure the safety of users along the National road in Tempi Valley. The road runs between the mountains of Olympus and Ossa in a canyon characterized by steep rock slopes on both sides, parallel to Pinios River that streams through it. The intense discontinuity systems of the rock slopes could activate planar slide of large rock masses, rock wedges as well as individual rockfall events concluding on the pavement during the roadway operation and therefore could cause accidents and damages on the infrastructure. The concessionaire Aegean Motorway S.A. (AMSA) is responsible for the Operation and Maintenance of this road. For this reason, an extensive rockfall protection and stabilization design for the mitigation of rockfall risks along the National road through Tempi Valley was realized in the years 2009 and 2010. A procedure was established as outlined in detail in the Rockfall Protection Inspection and Maintenance Manual (RIMM) setting out the necessary actions for the continuous inspection of the areas of increased rockfall risks within the Concession Project and for the operation and maintenance of the rockfall protection systems. All rockfall measures as well as rock slopes of the valley are being inspected systematically with any new rockfall event and/or damage to the protection measures documented in designated forms. Moreover, a special geodetic monitoring network has been established in critical rock masses with specific warning and alarm thresholds. The monitoring system of critical rock masses in Tempi Valley is enhanced with grout bridges applied to rock discontinuities where movement is supposed to occur prior to failure. All the collected data are the subject of interpretation by rockfall experts in line with the established procedure.

A Novel Experiment to Study the Roll Motion Characteristics of a Sailing Ship in a Landslide‐Generated Wave in the Three Gorges Reservoir

Strong earthquakes, heavy rains, changes in reservoir water levels, and other external factors destabilize large rock masses causing them to fall into the water at high speed, thereby destroying the original ecological balance in the region. These occurrences cause fluctuations in water levels and form landslide‐induced waves, which behave similar to tsunamis upon reaching the shore, a dam structure, or ships. The impact invariably threatens residents’ lives and properties in the upper and lower reaches of the reservoir area. In the current study, we conducted orthogonal experiments of landslide‐induced impulse waves to assess their related hazards. To explore the effects of a landslide‐generated wave on the roll characteristics of a ship, experimental model tests were performed using different speed vessels, landslide bodies, and navigation positions. Accordingly, a reasonable optimization strategy was proposed to provide technical support for ship navigation safety in regions of landslide‐generated waves.

ROCK GLACIER MONITORING USING AERIAL PHOTOGRAPHS: CONVENTIONAL VS. UAV-BASED MAPPING – A COMPARATIVE STUDY

Abstract. Rock glaciers are creep phenomena of mountain permafrost. Typically, these landforms look like lava flows from a bird’s eye view. Active rock glaciers move downslope with flow velocities in the range of few centimeters to several meters per year. Thus, large masses of rock and ice can be gradually transported down-valley. In this paper we present a comparative study analyzing surface change for Tschadinhorn rock glacier, a relatively fast moving rock glacier located in the Hohe Tauern Range of the Austrian Alps. Aerial photographs (1954–2017) of both metric (conventional) and non-metric (UAV-based) aerial surveys were compared to derive multi-annual to annual flow vector fields and surface height change. For each time interval given we computed a single representative value for flow velocity and, if applicable, also for area-wide surface height change, i.e. volume change. The velocity graph obtained represents the temporal evolution of the kinematics of the rock glacier with good discrimination. Volume change was difficult to quantify since temporal changes were rather small and close to insignificance. The precision and accuracy of the results obtained were numerically quantified. Our study showed that for the Tschadinhorn rock glacier UAV-based aerial surveys can substitute conventional aerial surveys as carried out by national mapping agencies, such as the Austrian Federal Office of Metrology and Surveying (BEV). Thus, UAV-based aerial surveys can help to bridge the data gap between regular aerial surveys. The high accuracy of the UAV-derived results would even allow intra-annual change detection of flow velocity.

Development of Large Direct Shear Test Apparatus for Passive Bolt Reinforced Mass

Shear testing of large size rock mass in the laboratory is a tedious and challenging task. Difficulties further arise when testing is done with rock bolts. Complex interaction between intact blocks of mass, joint and bolts creates problems during shear testing. Hence, for testing of large rock mass with bolts, special technique and facilities are required. The present paper summarized the details of the development of a large sized direct shear testing facility for passive bolt—reinforced rock masses. A specially designed servo-controlled direct shear test apparatus having shear box of size 750 mm × 750 mm × 1000 mm has been fabricated in the Geotechnical engineering laboratory of IIT Roorkee. The normal loading capacity of the apparatus is 1500 kN while shear loading capacity is 2000 kN. To evaluate the performance of the apparatus, specimens of blocky mass were prepared and tested without and with bolts. The present paper discusses the details about the large direct shear apparatus and testing methodology.