Rock Ridge Research Articles

Simulation Analysis of Single-tooth Rock Breaking Process

In this paper, the rock breaking process of the cutting teeth is analyzed, firstly, based on the rock constitutive model and damage law, the simulation model is established by finite element software, and the cutting load of the cutting teeth in the plane rock, rock ridge and rock ridge root is analyzed, and on this basis, the load of the rock and the cutting tooth during scraping is analyzed through the cloud map. The effects of camber angle, depth and cutting speed on cutting force and crushing ratio were analyzed.

A Study on the Rock-Breaking Characteristics of an Arcing-Blade Cutter under Different Cutting Parameters

To analyze the rock-breaking characteristics of an arcing-blade cutter in cutting red sandstone, a two-cutter cutting model was established based on the finite element method. Then, the cutting processes of the arcing-blade cutter at penetrations of 2 mm, 4 mm, and 6 mm with different cutter spacings were investigated, and the changing rules of the rock-breaking load, rock crushing state, and rock-breaking efficiency were obtained. Subsequently, the obtained simulation results were validated through linear cutting experiments. The research results showed that, as the penetration of the arcing-blade cutter increased, the rock-breaking load also increased; specifically, under 2 mm penetration, the rock-breaking load remained stable, irrespective of the cutter spacing. However, under 4 mm and 6 mm penetration, the vertical and rolling force increased and then stabilized with an increase in the cutter spacing, while the lateral force decreased and then stabilized, attributed to the synergistic effect between the cutters. At 2 mm penetration, the absence of interaction between the cutting of two cutters in sequence resulted in two separate crushed areas on the rock surface. However, at 4 mm and 6 mm penetration, the rock ridge could be crushed under a smaller cutter spacing. Meanwhile, with an increase in the cutter spacing, the synergistic effect between the cutters diminished, causing the rock ridge between two cuttings to remain uncrushed. The specific energy at the 4 mm and 6 mm penetrations decreased initially with an increase in the cutter spacing, then increased, and eventually stabilized. The optimal cutter spacings at these penetrations were determined as 50 mm and 60 mm, respectively. Conversely, at 2 mm penetration, the specific energy remained almost unchanged with an increase in the cutter spacing, maintaining at a high level and resulting in a low efficiency in cutting rock.

Experimental modal and FEM analysis of a historical building

The CEDRAV building in Cerreto di Spoleto, originally a monastery, was built in the 14th century on the top of a rock ridge. The two seismic events that occurred on September 26th, 1997, with magnitude Ms=5.4 and Ms=6, respectively, caused some damages to it, but the event occurred on 14 October 1997 caused the main damages. This study includes analyses mainly related to the part of the data acquired corresponding to tests and configurations using temporary deployments. The building is very complex and rigid. In fact, translational and torsional frequencies are close to one another, coupling occurs and damping ratio is low. Coupling of the frequencies and the low damping are two factors that cause beating effect when shaking is strong enough. For example, the approximate beating period is computed for the June 28th 2000 earthquake as (taking T1 = 1/9.7 = 0.104 s, and T2 = 1/10.4 = 0.096 s) Tb = 2.5 s, observable in the time history plots. On the basis of the experimental results obtained by means of temporary arrays, a permanent network was designed and installed, which recorded several seismic events. A preliminary analysis in frequency domain, based on the determination of auto and cross power spectral density, has been first performed; subsequently the modal structure identification by means of the Ibrahim time domain technique and the Frequency Domain Decomposition technique in the frequency domain, have been carried out. A frequency domain analysis of the structure has also been performed by means of the Frequency Response Function (FRF) analysis. The experimental results have been finally compared with those obtained from a FEM.

The formation of fan‐deltas in mountain lakes: Findings from Zelené Kežmarské Lake (Slovakia)

AbstractFan‐deltas are formed in mountain lakes, contributing to changes in shorelines' shapes and filling lake basins with sediments. Factors that condition sediment delivery to the lakes and the formation of fan‐deltas are not fully understood. This study aims to identify processes forming fan‐deltas in mountain lakes based on the sedimentary architecture of a fan‐delta filling Zelené Kežmarské Lake (Slovakia). Our study is based on ground‐penetrating radar and seismic refraction surveys conducted over the lake and debris‐flow fans in its vicinity, and grain‐size analyses of the surface deposits. The internal structure of the fan‐delta comprises foreset deposits representing the fan‐delta lobes. Mouth bars were identified in the near‐shore zone. The fan‐delta is built of sands and silty sands whereas an alluvial debris‐flow dominated fan west of the lake contains gravels. A general trend of downslope fining of the fan surface sediments, disturbed by zones of coarse gravels, was identified in the surficial sediments forming the fan. The fan‐delta was formed by depositional events in humid periods, alternating with dry periods featured with a small or no deposition. The lake‐level steadily rose in the humid periods and remained stable in dry periods. The contrast between the coarse sediments forming the alluvial debris‐flow dominated fan, and sands forming the fan‐delta was caused by a selective deposition. Coarse gravels in the fan were mobilized in humid periods but did not reach the lake‐shore. The reason was a basement rock ridge situated parallel to the lake shore. Sands were delivered to the fan‐delta in humid periods owing to frequent high‐energy flows. A deposition of silts took place in dry periods. The studied fan‐delta might preserve the sedimentary record of three humid periods from the last 200 years. However, further studies are needed to establish the timing of the fan‐delta formation.

A New Linear Cutting Experimental Machine for Disc-Cutter Rock Breaking with High-Pressure Water Jets Assisted

Aiming at the low rock-breaking efficiency of TBM disc cutters in tough rock environments, A new experimental machine combined with the high-pressure water jet rock-breaking method was designed. It can flexibly change the cutting parameters of the water jet, such as spray position, spray height, pressure, etc. Moreover, the three-direction load of the disc cutter during the rock-breaking process can be obtained accurately by strain testing. The rock-breaking experiment reached the following conclusions. The experimental machine can meet the design function. In this study, the normal and rolling forces when the disc cutter breaks rock are significantly lower than the traditional, 26.90% and 28.39%, respectively. The lateral force increased slightly, about 31.17%. Although the energy consumption of water-jet-assisted is higher than the traditional rock-breaking method, the volume of broken rock per unit of time is approximately 5.85 times that of the traditional. It is feasible to increase the energy cost to increase the excavation speed. On the rock surface after the water jet experiment, a rock ridge appears on the rolling trajectory of the disc cutter, which is not conducive to further breaking the rock. The cutting depth of the water jet needs to be adjusted to reduce the height of the rock ridge.

Peculiarities of the Magnetic Field of Geothermal Systems of the Pauzhetsky Area (South Kamchatka)

Based on many years of research, maps of magnetic field anomalies ΔTa for large geothermal systems of the Pauzhetsky region of South Kamchatka were constructed. Magnetic fields have both general characteristics and individual features for each research object. In the area of Nizhne-Koshelevsky steam-dominated geothermal field identified a system of linear negative magnetic field anomalies, confined to thermal controlling discontinuous tectonic disturbances. Pauzhetsky geothermal field is characterized by a heterogeneous structure of the anomalous magnetic field ΔTa: NW region is marked by a quiet weakly negative magnetic field, indicating the predominance in this part of the field lateral spreading of hydrotherms from the upper aquifer; SE – a large number of alternating magnetic anomalies of high intensity, confined to subvolcanic bodies of acidic to moderate composition. The South Kambalnaya group of thermal fields is characterized by a lower magnetic induction modulus T as compared to the Pauzhetsky and Lower Koshelevsky geothermal fields, indicating a more intense alteration of the Kambalnaya Ridge rocks by hydrothermal-metasomatic processes, apparently as a result of long-term exposure to convective heat flow.

Research on rock breaking characteristics of impact hob of hard rock excavator

During hard rock excavation in the process of tunnel construction, the hard rock excavator wears seriously and quickly and reduces its excavation efficiency. Aiming at this problem, this paper proposes a composite rock breaking method by impact rolling and cutting as a solution. In this paper, the composite rock breaking characteristics of impact hob are studied. The impact cutting load of the hob was analyzed, and the hobbing force equation and the rock crushing volume equation were established. The effects of different impact frequencies and impact loads on the cutting force and rock crushing characteristics of the hob were analyzed by experiments. The results show that under a certain thrust and hob spacing, with the increase of the impact frequency, the rock ridge between the two hobs gradually decreases, while the crushed volume of the rock increases gradually. Under the same axial load and cutter spacing conditions, with the increase of the impact frequency, the hob shear force decreases significantly. Under a certain axial load and impact frequency, with the increase of impact load, the crushing volume of rock and the hob shear force decrease significantly. These test results are of great significance for guiding the efficient excavation of hard rock tunnels.

Erosion of Coastal Slope in the Zelenka locality, Northern Black Sea Coast of Bulgaria

The study covers a coastal slope along the northern Bulgarian Black Sea coast near Cape Kaliakra, Zelenka locality. The slope is composed of Miocene (Sarmatian), unconsolidated aragonite sediments with limestone interbeds (Topola Formation) and a steep limestone rock ridge (Karvuna Formation). Water flows along the surface of the slope, attached to the karstified and cracked limestones of the two formations. An assessment was made of the material eroded from the slope, composed of aragonite sediments of the Topola Formation, for the period from September 2018 to October 2022. The quantities of this material were measured and laboratory tests of the aragonite sediments were carried out. Their classification characteristics have been determined - grain size composition and plasticity index. Geotechnical studies and mapping of the coastal slope showed that erosion processes in the studied area represent a real geological hazard and can affect the stability of the slope, as well as the integrity of the road.

Mt. Rainier Sanctification

Mt. Rainier Sanctification

Sensitivity analysis of factors controlling earth fissures due to excessive groundwater pumping

Aseisimic earth fissures are complex consequences of groundwater withdrawal and natural hydrogeologic conditions. This paper aims to improve the understanding of the mechanism of earth fissuring and investigate the relative importance of various factors to fissure activity, including bedrock geometry, piezometric depletion, compressibility and thickness of the exploited aquifer. For these purposes, a test case characterized by an impermeable and incompressible rock ridge in a subsiding basin is developed, where stress/displacement analyses and fissure state are predicted using an interface-finite element model. Three different methods for global sensitivity analysis are used to quantify the extent of the fissure opening to the aforementioned factors. The conventional sampling based Sobol’ sensitivity analysis is compared to two surrogate based methods, the general polynomial chaos expansion based Sobol’ analysis and a feature importance evaluation of a gradient boosting decision tree model. Numerical results indicate that earth fissure is forming in response to tensile stress accumulation above the ridge associated to pore-pressure depletion, inducing the fissure opening at land surface with further downward propagation. Sensitivity analysis highlights that the geometry of bedrock ridge is the most influential feature. Specifically, the fissure grows more when the ridge is steeper and closer to the land surface. Pore pressure depletion is a secondary feature and required to reach a certain threshold to activate the fissure. As for this specific application, the gradient boosting tree is the most suitable method for its better performance in capturing fissure characteristics.

Modeling of the 1783 Tsunami Event in Scilla Generated by Landslide

In 1783, an event that has gone down in history as the great seismic crisis in Calabria began, during which two major earthquakes occurred, affecting the Calabrian ridge from the Strait to the north. Between 6 and 7 February in Scilla a tsunami occurred that caused the greatest number of victims in Italy: 1500 people. The mechanism that triggered the tsunami was the detachment of a ridge of rock due to a violent earthquake that affected the area; this detachment caused a subaerial landslide which, by sliding, then deposited the rock on the seabed a few kilometers from the coast, immediately generating the tsunami event. The objective of this study is to perform numerical simulations for tsunami events that occurred in history and use models that perform the propagation of a tsunami, using the best possible bathymetric and topographic data and the historical data to compare the validity of the results. In this way, one can obtain the validation of a model that can be used to simulate possible events of this magnitude on the Calabrian coasts and therefore be able to develop a reliable early warning tsunami system; it also has the advantage of perfectly combining computational burdens and the validity of results.

The Homeric Formula ἐπ’ εὐρέα νῶτα θαλάσσης and Its Reception: Adaptation and Reinterpretation in the Aeneid

The article examines the reception of the Homeric formula ἐπ’ εὐρέα νῶτα θαλάσσης “on the broad back of the sea” in Greek and Latin poetry, and reconstructs (on the basis of scholia and lexical glosses) how Alexandrian exegesis evaluated this expression. Special attention is given to Vergil’s adaptation of this formula in the Aeneid: in one context Vergil translates the expression neutrally, reproducing Homer’s usage of εὐρέα νῶτα θαλάσσης to speak of the open sea, but omitting the metaphor of the sea’s back (Aen. 7, К рецепции гомеровской формулы ἐπ’ εὐρέα νῶτα θαλάσσης… 47 808–811); in another context, he faithfully reproduces the image, but applies it to the ridge of rocks on which Trojan ships were nearly wrecked (Aen. 1, 108–110).

Paleo-Tethys subduction induced slab-drag opening the Neo-Tethys: Evidence from an Iranian segment of Gondwana

The Iranian plateau has a more straightforward relationship between the Paleo-Tethys and Neo-Tethys, than other regions in the Tethyan realm and is an ideal place to test the genetic connection of how the Paleo-Tethys affected the Neo-Tethys. Moreover, there is no consensus on how Paleo-Tethyan evolution influenced the Neo-Tethyan Wilson cycle. We studied the petrology , geochemistry , and metamorphic age of an eclogite suite at Rasht in northern Iran from the Paleo-Tethyan suture. The eclogitic protolith was a typical mid-ocean-ridge basalt and achieved its peak metamorphic condition of 2.7 GPa and 590 °C at 353 ± 8.9 Ma. Reconstructed pressure-temperature-time path of the eclogite-facies rocks suggests that the eclogitic protolith entered the trench at 356 ± 8.9 Ma. Mid-oceanic ridge rocks formed at ~380 Ma at the Rasht region and other places along the Alborz Mountain strike. A ~ 25 million years (Myr) period from the birth of oceanic crust to subduction at Rasht region implies that the mid-ocean-ridge was close to the trench. We propose that the Paleo-Tethyan mid-ocean-ridge was trench-parallelly subducted beneath the Eurasian boundary in northern Iran. This ridge-subduction propagated from east to west between 380 and 355 Ma. 47–27 Myr after ridge consumption, subduction of the remaining Paleo-Tethyan oceanic crust exerted a continuous extensional stress of ~0.1 GPa on the passive margin of Gondwana since the late Carboniferous. The drag-force eventually detached the Central Iranian Block from Gondwana, and opened the Neo-Tethyan ocean during the middle-late Permian .

Rockfall Analyses at Km 13+550 in the New Road of Vlora, Albania

Rockfall dynamics is a complex function of the location of the detachment point and the geometry and mechanical properties of both the block and the slope. Theoretically, knowing the initial conditions, the slope geometry, and the relationships describing the energy loss at impact or by rolling, it should be possible to compute the position and velocity of a block at any time. Nevertheless, relevant parameters are difficult to ascertain both in space and time, even for an observed event. Usually, the geometrical and geomechanically properties of the blocks (size, shape, strength, fracturing) and the slope (gradient, length and roughness, longitudinal and transversal concavities and convexities, grain size distribution, elastic moduli, water content, etc.), and the exact location of the source areas are unknown. In this paper, the sources of potential rock fallings involve a rocky area including between km 13+550 and km 13+600 in the new road of Vlora city in Albania. The area is characterized by a rock ridge, shaped like a dome, located few tens of meters above the design road. The purpose of this paper is the rock slope analysis. This analysis consists mainly of defining the sources of falling rocks, estimating the causes (by toppling, rock slides, single blocks) the size, the geometry, and type of blocks, the structural arrangement of joints, etc.

4D quantification of alpine permafrost degradation in steep rock walls using a laboratory‐calibrated electrical resistivity tomography approach

ABSTRACTThe warming of rock permafrost affects mechanical stability and hydro‐cryostatic pressures in rock walls. The coincident decrease in slope stability frequently affects infrastructure by creep and subsidence and promotes the generation of rockfalls and rockslides. The increasing hazard posed by warming permafrost rock walls and the growing exposure of infrastructure and individuals create a demand for quantitative monitoring methods. Laboratory‐calibrated electrical resistivity tomography provides a sensitive record for frozen versus unfrozen bedrock, presumably being the most accurate quantitative monitoring technique in permafrost areas where boreholes are not available. The data presented here are obtained at the permafrost‐affected and unstable Steintaelli Ridge at 3100 m a.s.l. and allow the quantification of permafrost changes in the longest electrical resistivity tomography time series in steep bedrock. Five parallel transects across the rock ridge have been measured five times each, between 2006 and 2019, with similar hardware. Field measurements were calibrated using temperature‐resistivity laboratory measurements of water‐saturated rock samples from the site. A 3D time‐lapse inversion scheme is applied in the boundless electrical resistivity tomography (BERT) software for the inversion of the data. To assess the initial data quality, we compare the effect of data filtering and the robustness of final results with three different filters and two time‐lapse models. We quantify the volumetric permafrost distribution in the bedrock and its degradation in the last decades. Our data show mean monthly air temperatures to increase from −3.4°C to −2.6°C between 2005‒2009 and 2015‒2019, respectively, while simultaneously permafrost volume degraded on average from 6790 m3 (±640 m3 rock in phase‐transition range) in 2006 to 3880 m3 (±1000 m3) in 2019. For the first time, we provide a quantitative measure of permafrost degradation in unstable bedrock by using a temperature‐calibrated 4D electrical resistivity tomography. Our approach represents a fundamental benchmark for the evaluation of climate change effects on bedrock permafrost.

Temperature distribution in a permafrost-affected rock ridge from conductivity and induced polarization tomography

SUMMARY Knowledge of the thermal state of steep alpine rock faces is crucial to assess potential geohazards associated with the degradation of permafrost. Temperature measurements at the rock surface or in boreholes are however expensive, invasive, and provide spatially limited information. Electrical conductivity and induced polarization tomography can detect permafrost. We test here a recently developed petrophysical model based on the use of an exponential freezing curve applied to both electrical conductivity and normalized chargeability to infer the distribution of temperature below the freezing temperature. We then apply this approach to obtain the temperature distribution from electrical conductivity and normalized chargeability field data obtained across a profile extending from the SE to NW faces of the lower Cosmiques ridge (Mont Blanc massif, Western European Alps, 3613 m a.s.l., France). The geophysical data sets were acquired both in 2016 and 2019. The results indicate that only the NW face of the rock ridge is frozen. To evaluate our results, we model the bedrock temperature across this rock ridge using CryoGRID2, a 1-D MATLAB diffusive transient thermal model and surface temperature time-series. The modelled temperature profile confirms the presence of permafrost in a way that is consistent with that obtained from the geophysical data. Our study offers a promising low-cost approach to monitor temperature distribution in Alpine rock walls and ridges in response to climate change.

Vibration failure and anti-vibration analysis of an annular-grooved PDC bit

To extend the service life of drill bits through reducing various drilling vibrations, this paper presents a fundamental analysis of the root cause of failure for polycrystalline diamond compact (PDC) bits during the drill-based process of vortex generation. In this work we develop a new type of PDC drill bit, namely the annular-grooved PDC bit, which can form one or more annular convex rock ridges at the bottom of the hole, having a raised ring that can limit transverse vibration. Our experimental results confirm that the accelerations of the annular-grooved PDC bit in axial, tangential, and radial directions are smaller than that of a conventional PDC bit. More specifically, acceleration declines by 33.5%, 21.6%, and 25.9% in tangential, axial, and radial direction, respectively. Our experimental investigation also shows that, as the weight on bit and the rotation speed increase, bit vibration intensifies, and the impact load on bit increases which can worsen bit stability. However, as the height and the width of the rock ridge increase, the drilling vibrations in three directions can decline. Therefore, the developed annular-grooved PDC bit can reduce bit vibration and improve bit’s drilling stability.

Severe Historical Droughts Carved on Rock in the Yangtze

AbstractThe White Crane Ridge (WCR) Rock Fish, now submerged under the backwater of the Three Gorges Reservoir in the Yangtze River, are affirmed as one of the earliest hydrologic observations ever made in any large river in the world. The usually in-water monument provides highly valuable historical records of severe droughts in the upper Yangtze over the last 1,200 years. This article updated the historical drought chronology previously developed based on the WCR inscriptions, which can be applied in assessment of extreme climatic and hydrological risks, and also made a preliminary analysis of changes of the severe drought frequency during the last thousand years in the upper Yangtze. The analysis shows that the severe droughts occurred more frequently during the Medieval Climate Anomaly (MCA), relatively less so during the Little Ice Age (LIA), and once again more often under the background of modern global warming. It was suggested that a generally warmer Euro-Asian continent during the MCA was in favor of the stronger East Asian summer monsoon, and the resulting less precipitation and more severe droughts of the Yangtze and the lower water level at the Three Gorges area on the centennial scale, and vice versa for the period of the LIA. The results would help in understanding the causes and mechanisms of the regional climate change and variability, and also in taking measures in the fields of the watershed management to cope with the long-term change in climatic and hydrologic droughts.

Tectonic evolution of the Grenville Orogen in the central Appalachians

Remnants of the Grenville Orogeny—a globally pervasive tectonothermal event resulting from the amalgamation of the supercontinent Rodinia between ca. 1.3 and 1.0 Ga—are exposed throughout eastern North America for ca. 3000 km from Labrador to Alabama. Although tectonic models for the development of the Grenville have historically been based on observations from the large and well-exposed Canadian Grenville Province, recent investigations suggest that initial continental collision occurred proximal to the Appalachian Blue Ridge. Mesoproterozoic rocks within this portion of the orogen are exposed within a series of allochthonous terranes that were extensively reworked during Paleozoic orogenesis. To better understand the tectonic history of this critical region, we utilized garnet and monazite geochronology to reconstruct the metamorphic history of eleven samples of ortho- and paragneiss from the Appalachian Blue Ridge Province.The resultant dates, together with new results from trace element thermobarometry, define a prolonged record of high temperature metamorphism coincident with the timing of continent–continent collision as recognized in the northern portion of the orogen. Initial garnet and monazite growth commenced between 1100 and 1065 Ma with peak granulite-facies conditions (750–900 °C, 0.55–0.85 GPa) occurring from 1050 to 1010 Ma. Burial and heating of the paragneisses progressed rapidly with peak metamorphism occurring ∼20–30 Myr after deposition of the sedimentary protoliths. Local hydrothermal alteration followed peak metamorphism and occurred at 1000–990 Ma with later cooling through ∼660 °C between 980 and 935 Ma (3 ± 2 °C/Myr). The metamorphic history outlined here, together with insights from previous studies, is consistent with formation of the Blue Ridge rocks within a continental suture zone that had an orogenic architecture comparable to that of the Himalayan-Tibetan orogen.

The anthropic landscape imprint around one of the largest Roman hydraulic gold mines in Europe: Sierra del Teleno (NW Spain)

This study explores the information gathered from the landscape transformation that occurred during the intense period of Roman hydraulic gold mining activity in northwest Spain. The Sierra del Teleno and its surroundings are characterised by the presence of Quaternary glacial and periglacial deposits and, locally, Neogene alluvial sediments, which were intensely mined by the Romans. However, the mining debris often obscures natural deposits, making their identification and description a challenging task. The aim of this study is to determine the existence of specific geomorphological features that can improve the identification of anthropic elements related to mining activity. River captures and widened drainage systems are among the most outstanding structures remaining, due to the extent and complexity of the work involved. However, other mining elements, such as anthropic modification of alluvial fans, moraine deposits and rock ridges are also evident in the landscape. In many cases, these remains are linked to the hydrologic infrastructure found in the area, which mainly comprises an extensive system of natural and man-made channels and distribution water-tanks. Difficulties arise in areas where no such structures are found. Thus, the use of geomorphic elements and patterns can help to distinguish natural and anthropic landforms. Using this approach, therefore, we have performed the first systematic and detailed analysis of the morphological imprint of Roman hydraulic gold mining activity on the landscape. These data will help piece together the puzzle of how the landscape was transformed by Roman mining activity, and can contribute to discussions surrounding the new epoch: The Anthropocene.