Anatomy of a cascading hazard: the flood part of the 7 February Uttarakhand event

<p>The 7 February Chamoli, Uttarakhand singularity imposed a severe geomorphic crisis. While remote sensing imagery quickly identified a major rock avalanche as its origin, there is a fundamental lack in high precision temporal information on the kinetics of this event about when, how, and why it evolved from a slope failure into a channel-confined mass wasting process, and ultimately into a debris laden flood. Furthermore, while the initial rock slide could be detected and located by global seismic networks, it was the flood which caused most of the destruction and fatalities. Yet, that part of the process cascade remained elusive in global seismic data sets.</p><p>Here, we present a detailed anatomy of the hazard cascade, with emphasis on the flood part. Using information from a dense seismic network, we explore the limits of detection and constrain its propagation velocity. By jointly inverting two physical models that predict spectral signal properties of floods, we estimate important hydraulic and sediment transport metrics. These information are key for designing any future early warning infrastructure.</p>

Analysis of Rock Dynamic Stresses During the Drilling by Polycrystalline Diamond Compact Bits

In view of shortening the development period of polycrystalline diamond compact (PDC) bits, the finite element method was adopted to simulate the dynamic stress of rocks. By employing drilling related theories, the three dynamic principal stresses of rock were analysed and the dynamic rock-breaking criterion was established. Second, the drilling model of PDC core bit was constructed, and the stress was simulated and calculated. Finally, laboratory tests were carried out to verify the simulation results. The analytical results demonstrate that the two obvious stages in the rock-breaking process are the initial rock-breaking stage and the normal one. The dynamic rock-breaking stress in the normal drilling stage varies from 66.3 to 99.6 MPa, which is lower than 278.4 MPa in the initial rock-breaking stage. During spud drilling, the axial force and the tangential force are 1.85 and 1.60 kN, respectively. During normal drilling, the axial force ranges from 0.2 to 0.9 kN, and the tangential force from 0.15 to 0.6 kN. The load of normal drilling is lower than the spudding load, and the bit is more likely to be damaged during spudding. The bit is normally worn during normal drilling.

Economic efficiency of preconcentration with X-ray fluorescence separation

Introduction. A promising direction in mineral processing development is the combination of preconcentration and deep processing. For that purpose, X-ray fluorescence separation (XFS) is highly effectively used. A feature of the technology is the availability of the procedures of crushing and screening of the initial rock into machine and unsortable classes, and separation in machine classes. The efficiency of preconcentration complex depends on the quality of granulometric composition forming procedures. Methodology. X-ray radiometric washability of polymetallic ore samples has been assessed, schemes and equipment for preconcentration with the use of X-ray fluorescence separation of the rock mass with various granulometric composition have been selected, and technical and economic assessment has been made. Results. Economic indicators of X-ray fluorescence separation application for preconccentration have been determined for polymetallic ore of various granulometric composition. The possibilities for significant improvement of the economic effect by means of forming the granulometric composition of the processed rock mass have been revealed. Summary. X-ray fluorescence separation in polymetallic ore preconcentration is highly effective. Optimization of blasted rock mass granulometric composition by means of specific organization of drilling and blasting operations and selecting specific modes of crushing and screening results in the growth of the economic effect from XFS by 2.1–2.7 times.

A Study on the Heat Transfer of Surrounding Rock-Supporting Structures in High-Geothermal Tunnels

The temperature distribution is one of the most vital parameters which should be fully considered in high geothermal tunnel design. For the purpose of studying the impact of temperature disturbance caused by construction on temperature distribution of surrounding rock and lining structure in a high geothermal tunnel, a new finite difference model for temperature prediction was proposed. Based on the abundant field test results, forecast analysis for the research of a high geothermal tunnel in this paper is made. The results indicate that the temperature of the surrounding rock near the tunnel sidewall decreases obviously in the first 14 days while that of the surrounding rock far away is stable after tunnel excavation, and the rock temperature showed three ways of change: undulate type (<2 m), decline type (2–5 m) and stable type (>5 m). There is a linear relationship between the initial rock temperature and the released heat of the surrounding rock. The radius of the heat-adjusting layer and the initial rock temperature presents a quadratic function relation. The lining concrete actually cures under the variable high-temperature environment and the real curing temperature decreases with time and becomes stable seven days later. The results would contribute to providing support for high geothermal tunnel research and design.

Effective Mechanisms to Relate Initial Rock Permeability to Outcome of Relative Permeability Modification

Excessive water production is becoming common in many gas reservoirs. Polymers have been used as relative permeability modifiers (RPM) to selectively reduce water production with minimum effect on the hydrocarbon phase. This manuscript reports the results of an experimental study where we examined the effect of initial rock permeability on the outcome of an RPM treatment for a gas/water system. The results show that in high-permeability rocks, the treatment may have no significant effect on either the water and gas relative permeabilities. In a moderate-permeability case, the treatment was found to reduce water relative permeability significantly but improve gas relative permeability, while in low-permeability rocks, it resulted in greater reduction in gas relative permeability than that of water. This research reveals that, in an RPM treatment, more important than thickness of the adsorbed polymer layer ( e ) is the ratio of this thickness on rock pore radius ( e r ).

Sulfides in Metamorphic Rocks of the Fore Range Zone (Greater Caucasus). A New Type of Mineral Container for Peak Metamorphism Mineral Assemblages

The rocks of the Armovka Formation (the Fore Range zone, Greater Caucasus) have undergone low-grade metamorphism that partially erased information about initial rock formation conditions. We discovered high-pressure mineral inclusions such as omphacite, phengite, garnet, and paragonite enclosed by pyrite and chalcopyrite. Mineral inclusions in sulfides may provide important information about metamorphic pressure−temperature conditions because they are shielded by the host minerals and isolated from significant low-grade overprinting. Calculations performed on phengite inclusions using the phengite Si-content barometry indicate a pressure ranging from 1.7 ± 0.2 to 1.9 ± 0.2 GPa for temperature of 600 ± 40 °C. These data are consistent with estimations obtained for eclogite bodies embedded in rocks of the Armovka Formation. Geothermobarometry of the latest yielded conditions of 680 ± 40 °C and a minimum pressure of 1.6 ± 0.2 GPa to upper pressure boundary at 2.1 GPa. This fact allows us to assume that the metamorphic rocks of the Armovka Formation were immersed in the subduction zone to the conditions of the eclogite facies of metamorphism, forming a coherent subduction complex together with eclogites.

Back-calculation of the 2017 Piz Cengalo-Bondo landslide cascade with r.avaflow

In the morning of 23 August 2017, around 3 million m3 of granitoid rock broke off from the east face of Piz Cengalo, SE Switzerland. The initial rock slide-rock fall entrained 0.6 million m3 of a glacier and continued as a rock(-ice) avalanche, before evolving into a channelized debris flow that reached the village of Bondo at a distance of 6.5 km after a couple of minutes. Subsequent debris flow surges followed in the next hours and days. The event resulted in eight fatalities along its path and severely damaged Bondo. The most likely candidates for the water causing the transformation of the rock avalanche into a long-runout debris flow are the entrained glacier ice and water originating from the debris beneath the rock avalanche. In the present work we try to reconstruct conceptually and numerically the cascade from the initial rock slide-rock fall to the first debris flow surge and thereby consider two scenarios in terms of qualitative conceptual process models: (i) entrainment of most of the glacier ice by the frontal part of the initial rock slide-rock fall and/or injection of water from the basal sediments due to sudden rise in pore pressure, leading to a frontal debris flow, with the rear part largely remaining dry and depositing mid-valley; and (ii) most of the entrained glacier ice remaining beneath/behind the frontal rock avalanche, and developing into an avalanching flow of ice and water, part of which overtops and partially entrains the rock avalanche deposit, resulting in a debris flow. Both scenarios can be numerically reproduced with the two-phase mass flow model implemented with the simulation software r.avaflow, based on plausible assumptions of the model parameters. However, these simulation results do not allow to conclude on which of the two scenarios is the more likely one. Future work will be directed towards the application of a three-phase flow model (rock, ice, fluid) including phase transitions, in order to better represent the melting of glacier ice, and a more appropriate consideration of deposition of debris flow material along the channel.

Downhole Transient Flow Field and Heat Transfer Characteristics During Drilling With Liquid Nitrogen Jet

As a novel jet technology, liquid nitrogen jet (LNJ) is expected to effectively break rocks and further provide a high-efficiency method for drilling, especially geothermal drilling. Using this technology, rocks can be broken down by the coupled effects of cryogenic cooling and jet impingement. In this study, transient downhole jet flow field and heat transfer during drilling with LNJ were simulated. Then, the distributions of temperature (including LNJ and ambient rock), velocity, and pressure at different times were analyzed. Finally, the effects of the parameters on jet impingement and rock cooling performance were discussed. Results indicated that cryogenic LNJ could be efficiently generated in the downhole region. The temperature of the rock surface remarkably decreased as the LNJ reached the bottomhole. The high-speed LNJ caused axial impingement and radial shear effects on the bottomhole rock. The rock cooling performance caused by the LNJ was influenced by the initial rock temperature. With the increase of the initial rock temperature, the drop amplitude of the rock temperature also increased. The impingement capability of the LNJ was improved by increasing the nozzle diameter and the nozzle pressure drop. With the increase of standoff distance, the wall pressure and the radial velocity of the bottomhole decreased while increasing the impingement scope. The confining pressure hardly influenced the rock cooling performance and jet impingement capability, thereby indicating that LNJ could work even at high confining pressure conditions.