Explosive Excavation Research Articles

Changes in Crater Morphology Associated With Volcanic Activity at Telica Volcano, Nicaragua

AbstractVolcanic summit craters are typically noted to form by roof collapse into a depressurized magma chamber or by explosive excavation. Recent examples of effusive activity (e.g., Kilauea Volcano, Hawai'i) allowed specifically for quantification of the collapse process. However, small spatiotemporal morphologic change related to background mass wasting and low‐level explosive activity has not been well quantified in volcanic craters. Telica volcano, Nicaragua, is a persistently restless basaltic‐andesite stratovolcano. Telica's persistent restlessness is caused by a long‐lived magmatic‐hydrothermal system with high‐temperature crater fumaroles and low‐frequency seismicity, punctuated by subdecadal, low‐explosivity (VEI 1–2) phreatic eruptions. We use photographic observations (1994 to 2017) and structure‐from‐motion point cloud construction and differencing (2011 to 2017) to analyze changes at Telica in the context of summit crater formation and eruptive precursors. Crater wall retreat (up to 40 m) spatially correlates with long‐lived high‐temperature fumaroles in the crater walls, whereas eruptions eject material (>5 m) from the crater floor through vent formation and/or clearing. These processes sustain a morphology similar to that of pit craters but without a shallow depressurized magma chamber. Our observations indicate system‐wide sealing prior to eruption by viscous magma in the conduit and eruption of a dome in 2017 and hydrothermal mineralization, not from vent covering talus; though, vent covering talus can redirect the shallow conduit. This study shows promise for photogrammetric techniques in correlating morphologic change with summit crater formation and volcanic activity and the power of long‐term visual observations in understanding active volcanic processes.

On energy relationships between explosive rupture and extraction processes at quarries

The article deals with the links between mineral extraction processes. The most universal characteristic of the process is its energy intensity. Production process cycles are considered in the relationship between their energy characteristics, taking into account the extraction in the working face over time. This approach has been largely determined by earlier studies in the direction of studying the energy intensity of technological processes. However, the relationship between explosive rupture energy and excavation has not been established, although the link between explosive preparation and the performance of the excavation equipment was stated in the technical literature multiple times. The presented material analyzed previously published materials on establishing relationships between drilling and explosive rupture processes of rock massif. The energy characteristics of excavation works and explosive rupture were considered. Prospective direction of technological links study was proposed. Attention is drawn to the fact that the approach to relationships definition between processes may not always be monotonous, because it is sometimes difficult to express physical meaning in a flat system.

Shallow magma diversions during explosive diatreme-forming eruptions

The diversion of magma is an important mechanism that may lead to the relocation of a volcanic vent. Magma diversion is known to occur during explosive volcanic eruptions generating subterranean excavation and remobilization of country and volcanic rocks. However, feedbacks between explosive crater formation and intrusion processes have not been considered previously, despite their importance for understanding evolving hazards during volcanic eruptions. Here, we apply numerical modeling to test the impacts of excavation and subsequent infilling of diatreme structures on stress states and intrusion geometries during the formation of maar–diatreme complexes. Explosive excavation and infilling of diatremes affects local stress states which inhibits magma ascent and drives lateral diversion at various depths, which are expected to promote intra-diatreme explosions, host rock mixing, and vent migration. Our models demonstrate novel mechanisms explaining the generation of saucer-shaped sills, linked with magma diversion and enhanced intra-diatreme explosive fragmentation during maar-diatreme volcanism. Similar mechanisms will occur at other volcanic vents producing crater-forming eruptions.

Evidence for an explosive origin of central pit craters on Mars

Kilometer-scale pits are nested in the centers of many impact craters on Mars as well as on icy satellites. They have been inferred to form in the presence of a water–ice rich substrate; however, the process(es) responsible for their formation is still debated. Previous models invoke origins by either explosive excavation of potentially water-bearing crustal material, or by subsurface drainage of meltwater and/or collapse. If explosive excavation forms central pits, pit-derived ejecta should be draped around the pits, whereas internal collapse should not deposit significant material outside pit rims. Using visible wavelength images from the Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) instruments and thermal infrared images from the Odyssey Thermal Emission Imaging System (THEMIS) instrument, we conducted a survey to characterize, in detail, the global population of central pits in impact craters ⩾10km in diameter. We specifically examined the morphology and thermophysical characteristics of the pits for evidence of pit ejecta. Our analysis of thermal images suggests that coarse-grained materials are distributed proximally around many central pits on the floors of their host craters. The decrease in average grain size with distance from pit rims is consistent with pit-derived ejecta. These observations and interpretations better support an explosive origin for central pits on Mars than they do an origin of subsurface meltwater drainage and collapse of the overlying substrate. A major weakness to previous explosive central pit formation models is the inability for them to form pits late enough in the impact process to be preserved. To address this, we present an alternative “melt contact model” where a central uplift brings ice-bearing substrate into contact with impact melt to generate steam explosions and excavate central pits during the impact modification stage. Theoretical calculations show that more than enough thermal energy is available via impact melt from the host crater to form central pits by steam explosions, and such explosions would require only a modest amount (2–6% by volume) of uplifted water–ice. We therefore propose that central pits on Mars could have formed explosively by the interaction of impact melt and subsurface water–ice.

Numerical Analysis on Minimal Safe Distance between Two Opposite Excavation Faces of Deep-Buried Tunnel

When the distance between two opposite excavation face is too small, the explosive load of one excavation face may causes rock failure of the other excavation face and result in engineering accidents. In this paper, the dynamic response of rock pillar between two opposite excavation faces during one explosive excavation cycle is investigated. An aftereffect function is adopted to reflect the viscoelastic properties of deep rock mass, and the explicit difference scheme of stress field is derived and then implemented by Matlab programs. The transient stress field of rock pillar is computed by coupling the initial stress field and the explosive waves. The analogies between the minimal safe distance and those influence factors such as explosive excavation load, rock mechanical properties, in-situ stresses, are fulfilled by this method. The back analysis results of a real case indicate that the results of presented method agree well with the actual situation.

Eruption of kimberlite magmas: physical volcanology, geomorphology and age of the youngest kimberlitic volcanoes known on earth (the Upper Pleistocene/Holocene Igwisi Hills volcanoes, Tanzania)

The Igwisi Hills volcanoes (IHV), Tanzania, are unique and important in preserving extra-crater lavas and pyroclastic edifices. They provide critical insights into the eruptive behaviour of kimberlite magmas that are not available at other known kimberlite volcanoes. Cosmogenic 3He dating of olivine crystals from IHV lavas and palaeomagnetic analyses indicates that they are Upper Pleistocene to Holocene in age. This makes them the youngest known kimberlite bodies on Earth by >30 Ma and may indicate a new phase of kimberlite volcanism on the Tanzania craton. Geological mapping, Global Positioning System surveying and field investigations reveal that each volcano comprises partially eroded pyroclastic edifices, craters and lavas. The volcanoes stand <40 m above the surrounding ground and are comparable in size to small monogenetic basaltic volcanoes. Pyroclastic cones consist of diffusely layered pyroclastic fall deposits comprising scoriaceous, pelletal and dense juvenile pyroclasts. Pyroclasts are similar to those documented in many ancient kimberlite pipes, indicating overlap in magma fragmentation dynamics between the Igwisi eruptions and other kimberlite eruptions. Characteristics of the pyroclastic cone deposits, including an absence of ballistic clasts and dominantly poorly vesicular scoria lapillistones and lapilli tuffs, indicate relatively weak explosive activity. Lava flow features indicate unexpectedly high viscosities (estimated at >102 to 106 Pa s) for kimberlite, attributed to degassing and in-vent cooling. Each volcano is inferred to be the result of a small-volume, short-lived (days to weeks) monogenetic eruption. The eruptive processes of each Igwisi volcano were broadly similar and developed through three phases: (1) fallout of lithic-bearing pyroclastic rocks during explosive excavation of craters and conduits; (2) fallout of juvenile lapilli from unsteady eruption columns and the construction of pyroclastic edifices around the vent; and (3) effusion of degassed viscous magma as lava flows. These processes are similar to those observed for other small-volume monogenetic eruptions (e.g. of basaltic magma).

The Cause of Instability and Reinforcement of the Complicated High Slope Drawing near a Deep-Founding Pit

The combination of a single row of artificially-dug-up piles and pre-stressed anchor rope was adopted to the foundation pit as the retaining structure,and anchor-plate retaining structure and rubble retaining wall were used as the bracing system for the complicated building slope. In the process of excavation, monitoring has been done to see if any horizontal displacement, deformation of deep soil and crack width take place or any technical data and code dispatch from the demand. Monitoring results show that deformation in some parts of the tops of support structure is larger than the designed warning value some times and the deformation continue to increase in the process of the excavation, and this result in twice dangerous situations in the support structure of the slope. In this paper, the geologic construction of the slope and the situations of the designed support structure and monitoring condition were depicted. The mechanism of the instability of the slope was explained on the basis of comprehensive analysis of deformation monitoring datas. It is concluded that the over-excavation, explosive excavation, rainfall and so on were the factors affecting the stability of the slope. Corresponding emergency measures and reinforcement measures,such as unloading and pre-stress rope, were proposed, which were proved to be highly effective.

Origins and energetics of maar volcanoes: examples from the ultrapotassic Sabatini Volcanic District (Roman Province, Central Italy)

Maar volcanoes represent a common volcano type which is produced by the explosive interaction of magma with external water. Here, we provide information on a number of maars in the ultrapotassic Sabatini Volcanic District (SVD, Roman Province) as young as ∼90 ka. The SVD maars are characterised in terms of crater and ejecta ring morphologies, eruptive successions and magma compositions, in light of the local substrate settings, with the aim of assessing magma–water interaction conditions, eruption energetics and genetic mechanisms. Feeder magmas spanned the whole SVD differentiation trend from trachybasalts–shoshonites to phonolites. From the ejected lithic fragments from aquifer rocks, the range of depth of magma–water explosive interaction is estimated to have been mostly at ∼400–600 m below ground level, with a single occurrence of surficial interaction in palustrine–lacustrine environment. In particular, the interaction with external water may have triggered the explosive behaviour of poorly differentiated magmas, whereas it may have acted only as a late controlling factor of the degree of fragmentation and eruption style for the most differentiated magma batches during low-flux ascent in an incipiently fragmented state. Crater sizes, ejecta volumes and ballistic data allow a reconstruction of the energy budget of SVD maar-forming eruptions. Erupted tephra volumes from either monogenetic or polygenetic maars ranged 0.004–0.07 km3 during individual maar-forming eruptions, with corresponding total magma thermal energies of 8 × 1015–4 × 1017 J. Based on energy partitioning and volume balance of erupted magmas and lithic fractions vs. crater holes, we consider the different contributions of explosive excavation of the substrate vs. subsidence in forming the SVD maar craters. Following available models based on crater sizes, highly variable fractions (5–50%) of the magma thermal energies would have been required for crater excavation. It appears that subsidence may have played a major role in some SVD maars characterised by low lithic contents, whilst substrate excavation became increasingly significant with increasing degrees of aquifer fragmentation.

Geomorphology of snow avalanche impact landforms in the southern Canadian Cordillera

Snow avalanche impact landforms (SAILs) are typically elliptical‐shaped depressions bounded by an arcuate ridge located at the base of avalanche paths. The geomorphology of these features is controlled by the topography of the avalanche path, the availability of unconsolidated debris in the impact area and the ability of the avalanche impacts to displace the available debris in the direction of avalanche flow. Ground‐based snow avalanches move debris by bulldozing, and airborne snow avalanches move sediment by excavation on impact.This paper reports on the geomorphology, and surface age and stability of three SAILs in the southern Canadian Cordillera. Dendrochronology and lichenometry were used to date geomorphic activity at the sites. Evidence of present SAIL stability suggests they result from episodic, high‐magnitude avalanche impact events over many hundreds of years. All three landforms share common morphologies: a water‐filled bowl‐shaped depression distally bounded by an arcuate ridge‐oriented transverse to the avalanche path. Despite sharing many attributes, field investigations revealed that the origin of each SAIL was a function of the local variations in snow avalanche path topography and availability of unconsolidated debris in the impact area. The snow avalanche path associated with the Blackhorn site has a gentle gradient, which suggests that this SAIL is a result of ground‐based avalanches. The SAIL at Spoon Lake appears to be a consequence of a resistant geologic feature that focuses snow avalanches in the impact area and results in explosive excavation. The morphology of the snow avalanche track at Peyto Lake causes large snow avalanches to become airborne prior to impacting and excavating an impact pool. All three SAILs examined in this paper are historically persistent landforms and these observations support previous findings indicating that SAILs require hundreds of years to develop.

Evidence for igneous activity and implications for the origin of a fretted channel in southern Ismenius Lacus, Mars

Northern Arabia Terra, Mars is characterized by a complex landscape that includes fretted terrain, fretted channels, completely closed canyons, shallow troughs, and fracture‐bounded depressions. The importance of ground ice in the initiation and development of these features, and of large impact structures in controlling channel courses, has long been recognized. The development of the fretted channel systems, including the integration of closed canyons, craters, and surface depressions into throughgoing channels, has previously been attributed primarily to mass‐wasting processes. The two channel systems in southern Ismenius Lacus quadrangle, Mamers Valles and Ismeniae Fossae, incorporate craters of probable impact origin, but both also include irregular crater‐like features and scalloped channel reaches that have characteristics not consistent with an impact origin. Some of these are, by analogy with morphologically similar features on Earth and elsewhere on Mars, reasonably interpreted as of volcanic origin. The detailed morphologies of a few diagnostic features associated with Ismeniae Fossae suggest a hydrovolcanic origin, an inference supported by the probable presence of abundant ground ice or groundwater at the time of their formation. The evidence described here for hydrovolcanism supports the inference that, in addition to mass‐wasting processes, explosive excavation, intrusion‐driven sublimation, subsurface erosion, and erosion by running water may have played important roles in channel formation and evolution as well. All of these processes are consistent with magma interacting with groundwater or ground ice.

TRACING ESTUARINE SEDIMENTS BY NEUTRON ACTIVATION

Tracing the movement of dredged sediments in north San Francisco Bay was accomplished jointly by the San Francisco District of the U.S. Army Corps of Engineers, Explosive Excavation Research Laboratory (now the Explosive Effects Division of the Weapon Effects Laboratory, U.S. Army Waterways Experiment Station), and the Stanford Research Institute. The study involved developing a technique which would permit the longterm tracing of fine sediments dredged from Mare Island Strait after disposal at the Carquinez Strait disposal site; application of the tracer; disposal of the tagged sediment for the February-March 1974 dredging of Mare Island Strait; sampling bottom sediments throughout the study area for a 10-month period; and, quantitative analysis of the collected samples.

Project Trinidad : Explosive excavation tests in sandstone and shale. Figs, Refs. US Army Eng. Waterways exper. Stat. Corps Eng. Report. AD-762-174, July, 1972, 107P

Project Trinidad : Explosive excavation tests in sandstone and shale. Figs, Refs. US Army Eng. Waterways exper. Stat. Corps Eng. Report. AD-762-174, July, 1972, 107P

Recent developments in explosive excavation technology : TRANS. AMER. NUCL. SOC. V15, N2, 1972, P624

Recent developments in explosive excavation technology : TRANS. AMER. NUCL. SOC. V15, N2, 1972, P624

Annotated bibliography of explosive excavation related research : DEP. NAT. TECH. INF. SERV. EERL-TR-E-72-32, JULY, 1972

Annotated bibliography of explosive excavation related research : DEP. NAT. TECH. INF. SERV. EERL-TR-E-72-32, JULY, 1972

Ten Years of High Explosive Cratering Research at Sandia Laboratory

Ten years of cratering research at Sandia Laboratory are reviewed and related, along with the work of others, to the development of explosive excavation technology.Single-charge experiments gave em...