The 17 February 2006 Guinsaugon rock slide-debris avalanche, Southern Leyte, Philippines: deposit characteristics and failure mechanism

The Guinsaugon rock slide-debris avalanche was the most catastrophic single landslide event in Philippine history, with 14–18 M m³ of debris instantly burying an entire village. Hummocky topography, pressure ridges and other internal structures suggest that the landslide deposit was emplaced as a debris avalanche and debris flow. Susceptibility to planar and wedge failures as well as to toppling due to rock discontinuities were demonstrated using kinematic analysis and SMR. Limit equilibrium analysis on planar failures yielded factors of safety ranging from 0.8 to 1.5. The study showed that pore pressure on discontinuities had a more significant effect on the slope stability than seismicity. For wedge failures, there is a sudden drop in the factor of safety at pore water pressures of 258–306 kPa. At the site, the pore water pressure may have been as high as 490 kPa. The possibility of such a landslide event in the future is discussed.      

Characteristics and dynamic analysis of the February 2021 long-runout disaster chain triggered by massive rock and ice avalanche at Chamoli,Indian Himalaya

A massive rock and ice avalanche occurred on the western slope of the Ronti Gad valley in the northern part of Chamoli, Indian Himalaya, on 7 February 7, 2021. The avalanche on the high mountain slope at an elevation of 5600 m above sea level triggered a long runout disaster chain, including rock mass avalanche, debris avalanche, and flood. The disaster chain had a horizontal travel distance of larger than 17,600 m and an elevation difference of 4300 m. In this study, the disaster characteristics and dynamic process were analyzed by multitemporal satellite imagery. The results show that the massive rock and ice avalanche was caused by four large expanding discontinuity planes. The disaster chain was divided into five zones by satellite images and field observation, including source zone, transition zone, dynamic entrainment zone, flow deposition zone, and flood zone. The entrainment effect and melting water were recognized as the main causes of the long-runout distance. Based on the seismic wave records and field videos, the time progress of the disaster was analyzed and the velocity of frontal debris at different stages was calculated. The total analyzed disaster duration was 1247 s, and the frontal debris velocity colliding with the second hydropower station was approximately 23 m/s. This study also carried out the numerical simulation of the disaster by rapid mass movement simulation (RAMMS). The numerical results reproduced the dynamic process of the debris avalanche, and the mechanism of long-runout avalanche was further verified by parametric study. Furthermore, this study discussed the potential causes of disaster and flood and the roles of satellite images and seismic networks in the monitoring and early-warning.     

Assessment of concrete quality using non-destructive techniques,Ghatghar project,Maharashtra, India

The Ghatghar Pumped Storage Scheme involves the construction of two roller compacted concrete dams. Cracks were observed when the 14.5m × 478 m dam across the river Pravara near Ghatghar village, Maharashtra, India was about 4.1 m high on the right side and 3.3 m high on the left side. A total of 1,206 measurements were made using seismic refraction, sonic tomography and ultrasonic testing to assess the competency of the dam, covering a volume of 5029.86 m³. The ultrasonic testing conducted on five RCC cores and an equal number of rock cores recovered from the body of the dam and site indicated a velocity of 4,050–4,250 and 3,900–4,100 m/s, respectively. The velocities obtained from the seismic refraction and tomographic survey ranged between 3,375 and 4,625 m/s and from the ultrasonic survey 3,800–4,300 m/s. The velocity range obtained from both the seismic (refraction and tomographic) and ultrasonic methods indicates good to excellent quality concrete and the results show the visible cracks have not affected the integrity of the dam.      

Hydrogeological behaviour of an unsaturated waste rock pile: a case study at the Golden Sunlight Mine,Montana, USA

Parent geology, mining operation, construction practice and weathering processes govern the hydrogeological behaviour of waste rock piles. Variable heterogeneity in such earth structures requires site specific correlations. Based on field investigation and laboratory characterization, this paper developed a physical model for the unsaturated East Pile at the Golden Sunlight Mine in Montana, USA. Results indicate that the pile had interfingered dipping beds characterized by a matrix-supported structure in the fine grained layers and a clast-supported structure in the coarse grained layers. Waste rock with at least 45% sand retained water (ψ _a = 2–4 kPa, ψ _r = 20–40 kPa, k _sat = 3.5 × 10⁻³ cm/s, k _unsat = 2–3 orders of magnitude lower at 100 kPa) whereas materials with less than 45% sand drained rapidly (ψ _a < 1 kPa, ψ _r < 10 kPa, k _sat = 1 × 10⁻¹ cm/s, k _unsat > 6 orders of magnitude lower at 10 kPa).      

Size and mineral composition of airborne particles generated by an ultrasonic humidifier

This study describes the size distribution and concentration of particles expelled by a portable, 3‐L ultrasonic humidifier. The ultrasonic humidifier was filled with waters of varying mineral content and hardness. Aerosol size distributions were measured during 8 hours of humidifier operation in a typical bedroom. Humidifiers produced approximately 1.22 × 10¹⁰‐2.50 × 10¹⁰ airborne particles per milliliter of water consumed, resulting in airborne particle concentrations of 3.01‐5.91 × 10⁴ #/cm³, with modes ranging between 109 and 322 nm in diameter. The emission rate of particles varied by water type from 1.02 × 10⁹ to 2.27 × 10⁹ #/s. Lower mineral waters produced fewer, smaller particles when compared to higher mineral waters. Chemical analyses of particles collected with a cascade impactor indicated that the minerals in emitted particles had the same relative mineral concentrations as the fill water. Our results demonstrate that ultrasonic humidifiers should be considered a source of inhalation exposure to minerals dissolved in water, and that the magnitude of exposure to inhalable particles will vary with water quality.     

Landslide dams triggered by the Wenchuan Earthquake,Sichuan Province,south west China

At 14:28 (Beijing time) on 12 May 2008, the catastrophic Ms 8.0 Wenchuan earthquake occurred just west of the Sichuan basin, China, causing severe damage and numerous casualties. It also triggered a large number of landslides, rock avalanches, debris flows etc. Some of the landslides formed natural dams in the rivers, with the potential secondary hazard of subsequent flooding. Through the interpretation of a series of aerial photographs and satellite images, 256 landslide dams were identified, although because of limited access, relatively detailed data were available for only 32. The paper presents statistical analyzes of the distribution, classification, characteristics, and hazard evaluation of these 32 dams. A case study of the 2.04 × 10⁷ m³ Tangjiashan landslide dam and the emergency mitigation measures undertaken is discussed.     

Drip sealing of tunnels in hard rock: A new concept for the design and evaluation of permeation grouting

This paper presents a new pre-excavation grouting concept to prevent dripping and reduce the inflow into a railway tunnel. For this purpose, the tunnel’s roof was drip-sealed using colloidal silica and the walls and invert of the tunnel were grouted with cement. The grouting design process followed a structured approach with pre-investigations of core-drilled boreholes providing parameters for the layout. Water pressure tests and pressure volume time recordings were used for the evaluation. Results showed that the design was successful: the total transmissivity was reduced from 4.9 × 10^?08 m²/s to the measurement limit (1.6 × 10^?08 m²/s), and the dripping was reduced to eight spots from the roof. Improved rock characterisation showed that the grout hole separation was within the transmissivity correlation length and that grouting efficiency depends to a large extent on the dimensionality of the flow system of the rock mass.     

Exposure to fine,ultrafine particles and black carbon in two preschools in nur-sultan city of kazakhstan

Children in preschools were studied as an exceptionally vulnerable group to lung diseases due to their immature immune system. Few data are available in the literature addressing the exposure of children in preschools to ultrafine (>10 nm) particles. Exposure of children to fine, ultrafine (10 nm–1 µm) particles and black carbon particles present inside and near two preschools in Nur-Sultan, Kazakhstan, during Fall 2019 was investigated. For Preschool I, the average daily (6 h) indoor (outdoor) PM₁, PM_2.5, and PM₁₀ concentrations over three-week measurements were 15.0 (SD 12.5) µg/m³, 34.6 (SD 35.1) µg/m³, and 47.2 (SD 45.2) µg/m³, respectively. Average indoor UFP concentrations (>10.0 nm) including candle burning events were 5.20 × 10³ (SD 8.80 × 10³) particles/cm³, with the background UFP concentration to be 3.30 × 10³ (SD 1.80 × 10³) particles/cm³. In Preschool II, the average UFP concentration (>30.0 nm) in the morning and afternoon was 3.94 × 10³ (SD 5.34 × 10²) and 3.36 × 10³ (SD 1.90 × 10³) particles/cm³, respectively. Indoor black carbon (BC) concentrations were correlated with the outdoor smoking activity. The major sources of the indoor particles in the preschools were dust resuspension, candle burning, and infiltrated outdoor particles.     

Influence of reservoir water level variations on slope stability and evaluation of landslide tsunami

Reservoir filling and water level variations are important factors that induce slope failures near the reservoir banks. Once a landslide occurs, a tsunami might form which can result in a far greater disaster. This study provides insight and a method for analyzing the disaster chain of a landslide near the reservoir water by taking a slope near the bank of A’lagou reservoir in Xinjiang, China, as an example. The instability mechanisms of the slope are studied based on the field investigation and numerical analysis. The results show that there are two factors that increase the process of slope instability: the rock structure of the slope, which is an important internal factor, and the reservoir filling, especially the rapid drawdown which is an important external factor. Then, a numerical simulation that is based on SPH-DEM coupling method is used to evaluate the landslide tsunami process. The quantitative analysis of the tsunami indicates the initial wave height is about 22 m, the tsunami run-up on the opposite slope is about 44 m high, the maximum overtopping flow is about 1.35×10⁴ m³/s, the maximum velocity is about 9 m/s, the maximum overtopping depth is about 7 m, and the erosive velocity on the downstream slope of the dam is > 20m/s. The results of this study will be useful for preventing and mitigating landslide hazards in reservoirs.

     

Hydraulic conductivity of bentonite-polymer geosynthetic clay liners to coal combustion product leachates

Hydraulic conductivity of seven geosynthetic clay liners (GCLs) to synthetic coal combustion product (CCP) leachates were evaluated in this study. The leachates are chemically representative of typical and worst scenarios observed in CCP landfills. The ionic strength (I) of the synthetic CCP leachates ranged from 50 mM to 4676 mM (TCCP-50, LRMD-96, TFGDS-473, LR-2577, HI-3179 and HR-4676). One of the GCLs contained conventional sodium bentonite (Na–B) and the other six contained bentonite-polymer (B–P) mixture with polymer loadings ranging from 0.5% to 12.7%. Hydraulic conductivity tests were conducted at an effective confining stress of 20 kPa. The hydraulic conductivity of the Na–B GCLs were >1 × 10⁻¹⁰ m/s when permeated with all six CCP leachates, whereas the B–P GCLs with sufficient polymer loading maintained low hydraulic conductivity to synthetic CCP leachates. All the B–P GCLs showed low hydraulic conductivity (<1 × 10⁻¹⁰ m/s) to low ionic strength leachates (TCCP-50, I = 50 mM and LRMD-96, I = 96 mM). B–P GCLs with P > 5% showed low hydraulic conductivity (<1 × 10⁻¹⁰ m/s) up to HI-3179 leachates. These results suggest that B–P GCLs with sufficient polymer loading can be used to manage aggressive CCP leachates.     

Estimating geometrical and mechanical REV based on synthetic rock mass models at Brunswick Mine

This paper uses a case study from Brunswick Mine in Canada to determine a representative elementary volume (REV) of a jointed rock mass in the vicinity of important underground infrastructure. The equivalent geometrical and mechanical property REV sizes were determined based on fracture systems modeling and numerical experiments on a synthetic rock mass. Structural data collected in massive sulphides were used to generate a large fracture system model (FSM), 40 m×40 m×40 m. This FSM was validated and subsequently sampled to procure 40 cubic specimens with a height to width ratio of 2 based on sample width from 0.05 to 10 m. The specimens were introduced into a 3D particle flow code (PFC3D) model to create synthetic rock mass (SRM) samples. The geometrical REV of the rock mass was determined based on the number of fractures in each sampled volume (P₃₀) and the volumetric fracture intensity (P₃₂) of the samples. The mechanical REV was estimated based on the uniaxial compressive strength (UCS) and elastic modulus (E) of the synthetic rock mass samples.The REV size of the rock mass was determined based on a series of statistical tests. The T-test was used to assess whether the means of the samples were statistically different from each other and the F-test to compare the calculated variance. Finally, the coefficient of variation, for the synthetic rock mass geometrical and mechanical properties, was plotted against sample size. For this particular site the estimated geometrical REV size of the rock mass was 3.5 m×3.5 m×7 m, while the mechanical property REV size was 7 m×7 m×14 m. Consequently, for engineering purposes the largest volume (7 m×7 m×14 m) can be considered as the REV size for this rock mass.     

Estimates of particulate matter inhalation doses during three-dimensional printing

Harmful emissions including particulates, volatile organic compounds, and aldehydes are generated during three-dimensional (3D) printing. Ultrafine particles are particularly important due to their ability to penetrate deep into the lung. We modeled inhalation exposure by particle size during 3D printing. A total of six thermoplastic filaments were used for printing under manufacturer's recommended conditions, and particle emissions in the size range between 10 nm and 10 μm were measured. The inhalation exposure dose including inhaled and deposited doses was estimated using a mathematical model. For all materials, the number of particles between 10 nm and 1 μm accounted for a large proportion among the released particles, with nano-sized particles being the dominant size. More than 1.3 × 10⁹ nano-sized particles/kgbw/g (95.3 ± 104.0 ng/kgbw/g) could be inhaled, and a considerable amount was deposited in respiratory regions. The total deposited dose in terms of particle number was 3.1 × 10⁸ particles/kgbw/g (63.6% of the total inhaled dose), and most (41.3%) were deposited in the alveolar region. The total mass of particles deposited was 19.8 ± 16.6 ng/kgbw/g, with 10.1% of the total mass deposited in the alveolar region. Given our findings, the inhalation exposure level is mainly determined by printing conditions, particularly the filament type and manufacturer-recommended extruder temperature.     

Design considerations for an underground room in a hard rock subjected to a high horizontal stress field at Rana Gruber,Norway

Rana Gruber AS is an iron mining company in the North of Norway, and it operates Kvannevann mine 30 km east of Mo i Rana. The Kvannevann mine is located in a foliated gneiss host rock, with an ore body about 70 m wide and more than 300 m deep. The mine has been in operation for many years using sublevel stoping, and is now changing to sublevel caving. Experience from past mining activity in the infrastructure preparation for the new mining method indicates that the mine is located in a hard, brittle rock mass with high horizontal stresses. Stress measurements have been made from time to time. The measurement results indicate a major principal stress of 20 MPa perpendiculars to the strike of the ore, and a minor principal stress of 10 MPa parallel to the strike of the ore, which is 10–15 times higher than the theoretical vertical stress caused by gravity at the measured location. In addition to the high horizontal stress, lessons learned regarding failure and rock support during the underground excavation need to be considered for designing and excavating a new canteen room (B × H = 9 × 8 m) at the mine. Numerical modelling is utilised to be able to include all of the adverse conditions for consideration.     

TCE and PCE diffusion through five geomembranes including two coextruded with an EVOH layer

Aqueous diffusion of trichloroethylene (TCE) and tetrachloroethylene (PCE) is examined for high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polyurethane/urea, and two polyethylene (PE) geomembranes coextruded with ethylene vinyl alcohol (EVOH). Additionally, the diffusion of benzene, toluene, ethylbenzene, and xylenes through polyurethane/urea geomembrane is examined. Permeation coefficients for HDPE, LLDPE, and polyurethane/urea range from 0.4-1.2 × 10⁻¹⁰ m²/s for TCE and 1.0-2.5 × 10⁻¹⁰ m²/s and for PCE. Experiments using the coextruded geomembranes have not reached equilibrium at 500 days, however parameters for the EVOH layer are deduced using data from these experiments. Using the parameters of the individual layers, single layer parameters were calculated. These single layer parameters range from 0.37-2.2 × 10⁻¹² m²/s for TCE to 0.28-0.93 × 10⁻¹² m²/s for PCE. Two hypothetical vapour intrusion cases are modelled using the parameters developed for the five geomembranes, and the calculated airspace concentrations decrease depending on the choice of vapour barrier in the following order: no barrier >0.75 mm LLDPE >1.5 mm polyurethane/urea >1.5 mm HDPE >0.75 mm LLDPE/EVOH/LLDPE >1.5 mm HDPE/EVOH/HDPE.     

Ceiling-jet thickness and vertical distribution along flat-ceilinged horizontal tunnel with natural ventilation

A series of fire tests was conducted in a 10.0 m (L) × 0.75 m (W) × 0.45 m (H) model tunnel with a rectangular cross section, and detailed measurements were taken of the temperature and velocity within a quasi-steady state fire-driven ceiling-jet running along the centre of a ceiling.The ceiling-jet thickness was defined as the distance from the tunnel ceiling to the point where the temperature and/or velocity dropped to half of their maximums. Correlations to represent the variation in the ceiling-jet thickness along the tunnel axis were developed with the aid of a theoretical approach. The coefficients included in these correlations were determined based on the experimental results obtained. It was found that the ceiling-jet thickness derived from the temperature was 1.17 times greater than that from the velocity in the tranquil flow region.In the tranquil region, both the velocity and temperature showed top-hat distributions, with a bulging shape from the apex of the distribution towards the tunnel floor. A cubic function and coordinate transformation were applied to develop empirical formulae for the temperature and velocity distributions, which were represented by the dimensionless distance from the tunnel ceiling and dimensionless temperature rise and/or velocity at a given distance from the fire source. The correlation developed for the temperature distribution was compared with the results of large- and full-scale tunnel experiments, which verified its applicability.     

Fast automatic registration of range images from 3D imaging systems using sphere targets

The use of 3D imaging systems (e.g., laser scanners) in construction has grown significantly in the past decade. Range images acquired with such systems often require registration. This paper describes an automatic method to rapidly locate spheres and perform a registration based on three pairs of matching points (centers of fitted spheres) in two range images. The proposed method is directly applicable for regularly gridded datasets obtained with instruments that are typically used for construction applications and whose maximum ranges are greater than 50 m. A lab was scanned from two locations at three different scan densities. Four spheres were located in the lab, and the total number of points hitting the four spheres was a small fraction (< 0.01%) of all the points in the dataset. At the highest scan density, the registration of two datasets with 6.4 × 10⁶ and 3.4 × 10⁶ points is obtained in less than 30 s. At the medium scan density, two range images with 1.6 × 10⁶ and 0.8 × 10⁶ points can be registered in less than 2 s.     

2-D and 3-D resistivity in the area of the Menkaure Pyramid Giza, Egypt

An area 47 × 26 m adjacent to the Queens’ pyramids near the Menkaure Pyramid, Giza, was examined using 14 parallel Wenner-Schlumberger profiles at 2 m intervals with a 1 m electrode spacing. Most of the inverted 3-D models show moderate resistivity values at shallow depths. However, in two places higher resistivity values identified two elongate features. One may correspond to a 2 × 8 m solar boat placed near the pyramid while the other may indicate a 5 × 20 m N–S room with a mud brick roof.      

Municipal solid waste management and practices in coastal cities of the Eastern Black Sea: a case study of Trabzon City, NE Turkey

Each day some 400–450 ton solid waste is dumped on land and in the sea and rivers in the coastal cities of the eastern Black Sea, creating serious environmental problems. The paper reports the engineering geological studies of a proposed landfill site for Trabzon, a major city in the region. Fieldwork included scan-line and seismic surveys as well as boreholes and in-situ testing. Water absorption tests indicated permeabilities in the order of 10⁻⁸ m/s.      

Size‐resolved fluorescent biological aerosol particle concentrations and occupant emissions in a university classroom

This study is among the first to apply laser‐induced fluorescence to characterize bioaerosols at high time and size resolution in an occupied, common‐use indoor environment. Using an ultraviolet aerodynamic particle sizer, we characterized total and fluorescent biological aerosol particle (FBAP) levels (1–15 μm diameter) in a classroom, sampling with 5‐min resolution continuously during eighteen occupied and eight unoccupied days distributed throughout a one‐year period. A material‐balance model was applied to quantify per‐person FBAP emission rates as a function of particle size. Day‐to‐day and seasonal changes in FBAP number concentration (N_F) values in the classroom were small compared to the variability within a day that was attributable to variable levels of occupancy, occupant activities, and the operational state of the ventilation system. Occupancy conditions characteristic of lecture classes were associated with mean N_F source strengths of 2 × 10⁶ particles/h/person, and 9 × 10⁴ particles per metabolic g CO₂. During transitions between lectures, occupant activity was more vigorous, and estimated mean, per‐person N_F emissions were 0.8 × 10⁶ particles per transition. The observed classroom peak in FBAP size at 3–4 μm is similar to the peak in fluorescent and biological aerosols reported from several studies outdoors.     

Geostructural and geognostic survey for a stability analysis of the calcareous cliff of Ispica (Hyblean plateau, southeastern Sicily)

The paper reports a geostructural and geognostic survey to evaluate the stability conditions of the highly fractured calcareous cliff where the Monastery of the “Frati Minori” of Ispica is located. A large number of fractures affect the whole cliff, resulting in dangerous conditions. In addition to a careful inspection of the slope to measure the structural discontinuities and identify rock blocks larger than 1 m³, cored boreholes were extended to a depth of 30 m. The rock quality designation indicated that the rock quality varies from poor to fairly good. In this steep, vegetated area, the use of different investigation methods was necessary to determine the physical, mechanical and geometric parameters necessary to plan the remedial works and measures to reduce the risk of rocks falling.