Surface Excavation Research Articles

Variation of the land surface temperature field in rare-Earth ore mining areas based on temperature downscaling

During the mining process of ionic rare earth elements (REE), mining disturbances, such as land surface excavation, stripped vegetation, injection holes, and tailings discharge, have led to large-scale vegetation degradation and land desertification, ultimately resulting in land surface temperature (LST) differentiation. The surface thermal anomaly is an important ecological parameter, and its spatiotemporal variation has become a powerful tool for identifying surface ecological disturbance. Because the REE mining areas have the characteristics of scattered ore and small areas, it is of great value to obtain LST data with strong practicality and high spatial resolution for sustainable ecological environment monitoring. In this study, the Lingbei mining area in Dingnan County, Ganzhou, China was selected as the study area. Via the use of Landsat and GaoFen-1 (GF-1) remote sensing images, and based on data fusion and the mixed-pixel decomposition method, the temperature downscaling with image fusion and spectral unmixing (TDIFSU) model and the temperature downscaling with data fusion and spectral unmixing (TDDFSU) model were constructed. In addition, they were compared with the commonly used temperature-downscaling disaggregation procedure for radiometric LST (DisTrad) model to explore the accuracy and applicability of different downscaling models for REE mining areas. Finally, based on remote sensing data from the past 20 years, a suitable downscaling model was selected and the temperature difference index (TDI) was used to analyze the spatiotemporal evolutions of ecological disturbances caused by REE mining. The results showed TDDFSU model had the highest accuracy and the smallest mean absolute error (MAE) and root mean square error (RMSE), which were 1.062 K and 1.386 K in February and 0.877 K and 1.094 K in October, respectively, but it had limitations in spatiotemporal study. The accuracy of TDIFSU model was the second, and TDIFSU model based on Landsat data has more advantages in long time series research. DisTrad model has the lowest accuracy. The most suitable model can be selected according to the time span and accuracy; The LST obtained by downscaling can reflect the actual land surface in more detail, and the boundaries between different ground objects were clearer; The high-temperature areas were mainly concentrated in the vicinity of long-term ore occurrences covered with a large amount of tailings. Medium-temperature areas were mainly bare soil and in situ leaching vegetation areas, and low-temperature areas were mainly natural and reclaimed vegetation areas; During the monitoring of the LST in Lingbei mining area for nearly 20 years, the temperature differences caused by different mining activities were revealed, and the land surface disturbance situation has improved after the state actively carried out REE mining environmental control.

Fracture mechanics of spallation

The in-situ spalling strength (stress at which spallation or, at a larger scale rockburst starts) is reported to be lower than the uniaxial compressive strength obtained in the laboratory; this difference has long been a puzzle. We hypothesise that the spallation is caused by extensive (wing) crack growth parallel to the excavation surface with subsequent buckling of the separated-out rock layers. The wing crack is initiated from a pre-existing defect (crack or pore) under compression. In uniaxial compression such a crack is not capable of extensive growth. In biaxial compression, the intermediate principal stress as low as 5–8.5% of the maximum principal stress was sufficient to make wings sprouting from an initial defect straighten and grow into a large crack comparable to the size of the sample and parallel to the lateral faces of the sample. The intermediate principal stress is invariably present at the excavation wall or face and the biaxial load ratio usually exceeds the critical value, which ensures extensive wing crack growth parallel to the excavation surface and finally spallation. We report new detailed observations of the stages of wing crack growth in biaxial compression. Based on these observations, a model of the wing crack growth and interaction with the free surface (excavation surface) allows relating the spalling strength to the uniaxial compressive strength if the initial cracks causing spallation are sufficiently small. In the case of large initial cracks, the obtained model involves uniaxial compressive strength of the rock mass of the corresponding scale.

Uncovering the Islamic Governmental Citadel of Shahdezh in Isfahan, Iran

The magnificent architectural complex known as Shahdezh Citadel is a defensive compound with an area of over 15 ha, sitting atop Soffeh Mountain, close to the city of Isfahan, Iran. It is a unique historical complex due to its majesty, impregnability, and strategic significance, however, studies on the Citadel are limited to a few historical documents and reports on its visible relics. It is for this reason that the present authors began archaeological investigations at this site in the summer of 2004. The main aim of the research was to determine the distribution and function of the architectural remains, as well as the construction and usage periods of the huge complex. To this end, topographic maps were prepared, followed by systematic surface survey and excavation of parts of the castle that were deemed most important. The findings of this research strongly suggest that the Shahdezh Castle was originally constructed in the Sassanid era (224–651 AD) and was later restored and reused by Saljuq rulers (1037–1194 AD) in the Islamic period. Its existence as a governmental citadel located near the Saljuq capital of Isfahan strengthens the authors’ proposition that Saljuq kings settled the royal family at the Shahdezh Citadel and ruled over the country from there.

High-Resolution Mining-Induced Geo-Hazard Mapping Using Random Forest: A Case Study of Liaojiaping Orefield, Central China

Mining-induced geo-hazard mapping (MGM) is a critical step for reducing and avoiding tremendous losses of human life, mine production, and property that are caused by ore mining. Due to the restriction of the survey techniques and data sources, high-resolution MGM remains a big challenge. To overcome this problem, in this research, such an MGM was conducted using detailed geological exploration and topographic survey data as well as Gaofen-1 satellite imagery as multi-source geoscience datasets and machine learning technique taking Liaojiaping Orefield, Central China as an example. First, using Gaofen-1 panchromatic and multispectral (PMS) sensor data and Random Forest (RF) non-parametric ensemble classifier, a seven-class land cover map was generated for the study area with an overall accuracy (OA) and Kappa coefficient (KC) of 99.69% and 98.37%, respectively. Next, several environmental drivers including land cover, topography (aspect and slope), lithology, distance from fault, elevation difference between surface and underground excavation, and the difference of spectral information from PMS multispectral data of different years were integrated as predictors to construct an RF-based MGM model. The constructed model showed an excellent prediction performance, with an OA of 98.53%, KC of 97.06%, and AUC of 0.998, and the 85.60% of the observed geo-disaster that have occurred in the predicted high susceptibility class (encompassing 2.82% of the study area). The results suggested that the changes in environmental factors in the high susceptibility areas can be used as indicators for monitoring and early-warning of the geo-disaster occurrence.

Late Pleistocene microlithic industries in the Ayodhya Hills, Purulia, West Bengal: insights from geoarchaeological exploration

Abstract New evidence from the Ayodhya Hills, located in the western upland of West Bengal, has expanded knowledge of Late Pleistocene microlithic technology spanning 42–25 ka in South Asia. Continuous exploration for the past two decades has resulted in substantial information on technology, distribution of sites and the colluvial context. It is now clear from surface exploration and excavations that there are localized differences in the formation of the colluvial context. At the Mahadebbera and Kana sites, which have yielded optically stimulated luminescence (OSL) dates, the in situ occurrence of artefacts in the excavated sections confirm their association with the colluvial context. The occurrence of microliths for a prolonged period (25–34 ka) at Mahadebbera indicates that the colluvial deposition must have followed a slower rate during the course of occupation at the site. At Khududih-Chauniya, a site currently being investigated, excavation and surface exploration indicate that the artefacts are mostly scattered over the regolith surface capping the bedrock; much of the colluvial material from the site has been eroded and transported downslope, exposing the lithic artefacts over the regolithic badland surface. Added interest in this site ensues from recent finds of Middle Paleolithic cores and a Lower Paleolithic core from the badland rain gullies. This promises to complement the already published results from the region, which has emerged as an important zone in understanding the behaviour patterns of anatomically modern humans in South Asia.

Assessment of Ground-Borne Vibration Impact on Nearby Underground Facilities Induced by Ground Surface Excavation

AbstractHydraulic breakers are used widely in construction activities such as rock excavation, building demolition, and pavement crushing. High-level ground-borne vibrations generated by hydraulic ...

Prediction of an environmental impact of tunnel blasting using ordinary artificial neural network, particle swarm and Dragonfly optimized artificial neural networks

Blasting is an intrinsic component of surface and underground excavation but it is associated with adverse environmental effects that can threaten the safety of lives and property. This study, therefore, proposed artificial intelligence (AI) based models for predicting the air overpressure (Aop) in the tunnel blasting. Three AI models which are ordinary artificial neural network (ANN), particle swarm optimized artificial neural network (PSO-ANN) and Dragonfly optimized artificial neural network (DA-ANN) are proposed. The input parameters into the models are the charge per delay (Cd), the number of holes (Nh), distance from the measuring station to the blasting point (Dm), and the rock mass rating (RMR) while the Aop is targeted output. The model parameters were obtained through field measurements and laboratory experiment. The performance of the models was evaluated using the coefficient of determination (R2), mean-squared error (MSE), mean absolute percentage error (MAPE), and the variance accounted for (VAF). Out of the different model simulations, the PSO-ANN model with 4-15-15-1 architecture performed best with R2 of 1, 0.984, 1, 0.9985, MSE of 0.0004, 0.125, 5.5E-0.6, 0.018, MAPE of 0.004, 0.152, 0.002, 0.025, and VAF of 99.996, 98.29, 1, 98.85 for the respective training, testing, validation and overall datasets. The selected model was compared with the MLR model and empirical model predictions. The proposed model outperformed them. Hence, the proposed model can predict Aop with a high degree of accuracy.

Study of Rock Mass Rating (RMR) and Geological Strength Index (GSI) Correlations in Granite, Siltstone, Sandstone and Quartzite Rock Masses

A comprehensive understanding of geological, structural geological, hydrogeological and geotechnical features of the host rock are essential for the design and performance evaluation of surface and underground excavations. The Hungarian National Radioactive Waste Repository (NRWR) at Bátaapáti is constructed in a fractured granitic formation, and Telfer Gold Mine in Australia is excavated in stratified siltstones, sandstones and quartzites. This study highlights relationships between GSI chart ratings and calculated GSI values based on RMR rock mass classification data. The paper presents linear equations for estimating GSI from measured RMR89 values. Correlations between a and b constants were analyzed for different rock types, at surface and subsurface settings.

Stress Inversion in a Gelatin Box: Testing Eruptive Vent Location Forecasts With Analog Models

AbstractAssessing volcanic hazard in regions of distributed volcanism is challenging because of the uncertain location of future vents. A statistical‐mechanical strategy to forecast such locations was recently proposed: here, we further develop and test it with analog models. We stress a gelatin block laterally and with surface excavations, and observe air‐filled crack trajectories. We use the observed surface arrivals to sample the distributions of parameters describing the stress state of the gelatin block, combining deterministic crack trajectory simulations with a Monte Carlo approach. While the individual stress parameters remain unconstrained, we effectively retrieve their ratio and successfully forecast the arrival points of subsequent cracks.

The influence of rock mass fracturing on splitting and contour blasts

ABSTRACT Splitting and contour blasting are aimed to achieve suitable profiles by cutting along a surface, while common blasting is intended to detach and to fragment relevant rock volumes by increasing the fracturing state. These techniques are adopted in both underground works (tunnels, caverns, quarries) and also for surface excavations (quarries, mines, rock slopes engineering). Contour blasts are widely used techniques in mining and civil engineering to enhance performance while maintaining the safety of personnel and infrastructure. Splitting blasts are mainly used in dimension stone mining to obtain intact blocks of valuable ornamental stone. The parameters of controlled blasting (geometry, charge, blast agent) require an accurate selection using optimised blasting patterns and explosive properties; most of the proposed methods are limited and unsatisfactory due to insufficient consideration of rock mass properties. A quick but effective comparison and analysis of the different characteristics of the rock mass and its heterogeneities is presented, as it indicates a better strategy to determine a tailored blasting design for a given site, thus significantly improving the contour blasting quality.

Mineralogical and sample selection implications for geomechanical properties of intact heterogeneous and veined rocks from the Legacy skarn deposit

Abstract Predicting the geomechanical behaviour of rockmasses is key to the economic success and safety of rock engineering projects including surface and underground excavations. For these projects, unconfined compressive stress (UCS) laboratory testing provides fundamental geomechanical properties of intact rocks. It is currently standard practice for UCS testing to consider only homogeneous specimens that are free of defects and discard heterogeneous specimens such as those that contain intrablock structures (e.g. veins) or extra-granular defects (e.g. phenocrysts). Understanding the complexities of these heterogeneous rocks and rockmasses is critical for excavation projects such as deep cave mines where extensive tunnel networks, caves, and stopes are regularly excavated through heterogeneous rockmasses. This paper presents the test results and analyses of UCS tests conducted on 29 matrix-type and 21 veined drill core specimens from the Legacy Skarn deposit located in northern New Brunswick, Canada. These specimens are sorted into five lithological units: beige, red, and black varieties of quartz-plagioclase granodiorite, calcareous mudstone, and garnet-pyroxene skarn. Mineralogical compositions of these units are determined using field identification techniques and microscopic laboratory methods including petrographic thin section analysis, powdered X-Ray Diffraction, and micro-X-Ray Fluorescence. Significant effects of hydrothermal veining and phenocrysts on the UCS test results are discussed in this study to highlight the significant influence of mineralogy on the variability of geomechanical properties. For example, vein mineralogy dominated by calcite weakened the granodiorites but strengthened the calcareous mudstone. Vein mineralogy dominated by quartz in the skarn unit had a mixed influence on geomechanical properties. Vein thickness primarily influenced geomechanical properties of specimens with single veins, whereas vein density was more useful to characterize specimens that contained vein networks or stockwork. The effects of vein orientation only partially agree with the established Jaeger model for shear failure through critically oriented foliations. The disseminated alteration in the granodiorites (plagioclase phenocrysts) and skarn (garnet crystals) typically increased stiffness and strength as the large grains arrest crack propagation when under load. Lastly, the effects of sample selection on reported UCS test results using four sample selection methods are presented. The results demonstrate the importance of including heterogeneous veined specimens in UCS sample selection and testing programs to capture rock variability and improve the accuracy of numerical geomechanical design. Recommendations are made to improve geotechnical core logging and sample selection protocols when characterizing heterogeneous complex rockmasses.

Inscriptions from Panakton

Six inscriptions of the 4th and 3rd centuries B.C. recovered during surface survey and excavation at Panakton (the paleokastro above Prasino/Kavasala) are published here in full, four of them for the first time. The earliest, an arsenal inventory, preserves an archon date of 343/2 B.C.; three are ephebic texts of the Lykourgan era; one is a dedication by soldiers of the garrison in the second half of the 3rd century; one is a fragmentary heading. These inscriptions, the first found on this site, prove beyond doubt that this was the Athenian fortress of Panakton, and they provide new evidence for armaments, the ephebeia, and the history of Panakton among Attic garrison forts.

Ground stone tools from the copper production site Al-Khashbah, Sultanate of Oman

Archaeological research at Al-Khashbah, Sultanate of Oman, conducted by the University of Tübingen, revealed a large Early Bronze Age (3rd millennium BCE) site. During the intensive surface survey and excavations, several ground stone tools were found. Most of them came from the vicinity of monumental stone and mud-brick structures, so-called towers, and are clearly connected to copper-processing waste such as slag, furnace fragments and prills, i.e., droplets of molten copper. Therefore, it is assumed that these ground stone tools were used within the operational procedures of copper-processing. Interestingly, only the monumental towers from the first half of the 3rd millennium BCE, i.e., the Hafit period, feature larger quantities of ground stone tools as well as copper processing waste. Towers from the second half of the 3rd millennium BCE, i.e., the Umm an-Nar period, have none. Within the scope of this paper, the distribution of the different types of ground stone tools in Al-Khashbah as well as their find context will be presented. They are illustrated with drawings generated from 3D models created using digital photography processed with the software Agisoft Photoscan. Comparisons with other 3rd millennium BCE sites in Eastern Arabia show that there as well, copper-processing remains are often associated with ground stone tools. The overall variety of types seems to be rather homogeneous in the region.

APPLICABILITY OF THE GEOLOGICAL STRENGTH INDEX (GSI) CLASSIFICATION FOR THE TRUSMADI FORMATION AT SABAH, MALAYSIA

During the feasibility and preliminary design stages of a project, when very little detailed information on the rock mass and its geomechanic characteristics is not available, the use of a Rock Mass Classification Scheme (RMCS) can be of considerable benefit. Various parameters were used in order to identify the RMCS. The parameter comprised of Rock Quality Designation (RQD), Rock Mass Rating (RMR), Rock Structure Rating (RSR), Geological Strength Index (GSI), Slope Mass Rating (SMR), etc. In this paper, we present the results of the applicability of the Geological Strength Index (GSI) classification for the Trusmadi Formation in Sabah, Malaysia. The GSI classification system is based on the assumption that the rock mass contains a sufficient number of “randomly” oriented discontinuities such that it behaves as a homogeneous isotropic mass. In this study, the GSI relates the properties of the intact rock elements/blocks to those of the overall rock mass. It is based on an assessment of the lithology, structure and condition of discontinuity surfaces in the rock mass and is estimated from visual examination of the rock mass exposed in outcrops or surface excavations. A total of ten (10) locations were selected on the basis of exposures of the lithology and slope condition of the Trusmadi Formation. The Trusmadi Formation regionally experienced of two major structural orientations NW-SE and NE-SW. It consists mostly of dark grey shale with thin bedded sandstones, typical of a turbidite deposit. This unit has been subjected to low grade of metamorphism, producing slates, phyllites and meta-sediments and intense tectonic deformation producing disrupted or brecciated beds. Quartz vein are quite widespread within the joints on sandstone beds. The shale is dark grey when fresh but changes light grey to brownish when weathered. The results are classified as “Poor Rock” to “Fair Rock” in term of GSI. The poor categories (TR2 and TR7) represent slickensided, highly weathered surfaces with compact coatings or fillings or angular fragments. It is also characterized as blocky/ disturbed/seamy, which folded with angular blocks formed by many intersecting discontinuity sets. The fair categories can be divided into two (2) types; type 1 (TR1, TR6 and TR8) which represent as smooth, moderately weathered and have altered surfaces. It is also characterised as very blocky rock, which indicates interlocked, partially disturbed ass with multi-faceted angular blocks formed by 4 or more joint sets. Type 2 (TR3, TR4, TR5, TR9 and TR10) which represent as smooth, moderately weathered and have altered surfaces but characterized as blocky/disturbed/seamy, which folded with angular blocks formed by many intersecting discontinuity sets. It also has persistence of bedding planes or schistosity.

A flexible system for selection of rock mass excavation method

The excavation of rock masses has a crucial importance for the safety and cost of construction of engineering projects. In this study, a flexible excavation assessment (EXCASS) system was developed with two components, the geological strength index (GSI) and the point load strength index (Is50). In order to develop the system, artificial neural network (ANN) analysis were performed using datasets from surface excavations (12 sites in Turkey and 61 sites in Greece reported by Tsiambaos and Saroglou (2010)). The EXCASS system in this study includes two parameters, namely the excavation power index (EPI) and the excavation performance rating (EPR) ranging between the value of 0 and 100. The optimum excavation power index (EPIopt) can be determined theoretically by using ( $$ {\mathrm{GSI}}^2\times \sqrt{{\mathrm{Is}}_{50}} $$ ) as an input when EPR is equal to 0, for the selection of the optimum excavation method. EPR is a rating which provides relative information on the ease or difficulty of the excavation method. Although the value of EPR varies between 0 and ± 100 in the EXCASS system, the use of the excavation method for “normally classes” is recommended in order to achieve costly and efficient excavation. The EXCASS system, on the other hand, has an ability to respond to possible technological developments by associating the excavation method with the EPI rating.

Modified complex variable method for displacement induced by surcharge loads and shallow tunnel excavation

In geo-engineering, mechanical problems of surcharge loads acting on ground surface and shallow tunnel excavation are often encountered. When the complex variable method is applied, such problems turn to non-zero resultant issues and generally result in infinite displacement singularity in geomaterial at infinity, which violates the fact that displacement components at infinity should be zero in field observations. The displacement singularity at infinity caused by non-zero resultants corresponds non-zero coefficients of logarithmic items in complex potentials. To eliminate the singularity at infinity, the symmetrical method is adopted so that the far-field displacement obtained from the modified displacement solution conducted by the complex variable method would be logically identical to the reality. Two fundamental cases of single surcharge load acting on ground surface and single tunnel excavation are presented to verify the modified displacement solution, and good agreements are observed. The main advantage that the proposed solution eliminates displacement singularity at infinity and makes far-field displacement logically accord with field observation is presented by comparing to the original solution. The drawback that the proposed solution is dependent on modified depth is discussed as well.

New approach in the application of seismic methods for assessing surface excavatability of sedimentary rocks

In the present study, a new approach on the application of seismic methods for assessing the excavatability of sedimentary rocks for surface excavations is proposed. The excavatability classification system has been developed based on seismic S-waves velocities determined by the multichannel analysis of surface waves. Prior to practical excavations carried out with different excavation methods (blasting, hydraulic breaking, ripping and digging), extensive field and laboratory studies were performed on eight sedimentary rock sites displaying a wide range of weathering and strength conditions in the area of Croatian karst (Dalmatia, Istria, Gorski Kotar). The investigation involved parameters of intact rock, such as compressive strength and point load strength, and parameters of rock mass such as seismic P-waves and S-waves velocities, geological strength index, discontinuity spacing and rock quality designation from borehole core. A new classification was proposed by comparing the measured VS and applied excavation methods on the studied sites. Estimates of several existing classifications were used for comparison and verification. It was found that the estimates of the proposed model are comparable with the estimates of previous research. The proposed method is not applicable to igneous and metamorphic rocks, or for subsurface excavatability assessments.

Depositional Contexts and New Age Controls for Terminal-Pleistocene Megafauna in North-central Chile (31°50′S)

ABSTRACT Sites in north-central Chile have yielded late-Pleistocene megafauna bone remains, occasionally associated with human-made artifacts. However, little is known about the depositional characteristics, the conditions that allow their preservation, and how to identify recurrences facilitating their discovery. This work presents contextual and stratigraphic data, coupled with radiocarbon dates on bone material from surface findings and excavations conducted in Los Vilos (Coquimbo, Chile), which show that this area was rich in Pleistocene terrestrial mammals and that alluvial sequences and dunes have allowed bone preservation and exposure. These results have implications for the search for new evidence and for the interpretation of their historical trajectories. Radiometric age distribution indicates mainly terminal-Pleistocene specimens with the potential of some taxa persisting into the Holocene. These results are used to discuss coexistence and interaction scenarios between extinct faunas and the early record of human beings in the region.

Visual impact evaluation of mines and quarries: the updated Lvi method

The article deals with the evaluation of the visual impact arising from quarrying, mining and civil engineering works that involve extensive surface excavation. An indirect method has been formerly proposed to quantify the level of visual impact (Lvi) based on the two physical variables that define the magnitude of change in a natural landscape: the solid angle subtended by the visible alteration from a given viewpoint (Ωv) and the chromatic contrast between the alteration and the surrounding landscape (ΔEμ). These two objective variables are determined by elaborating the digital images of the landscape under investigation, taken from the most representative viewpoints. The Lvi indicator has proven to be highly correlated with the judgement values expressed by potential observers and thus may represent a valuable operative tool in the environmental impact assessment (EIA) procedures, both for the proponent of new projects and for the governmental authorities in charge of decision-making. This article describes a further development of the Lvi method, which aims at improving the repeatability of the impact evaluation by eliminating some critical issues related to the definition of both the excavation limits and the natural comparison surfaces representing the natural landscape. To that end, the original calculation code has been implemented with two image segmentation algorithms, which objectively designate the areas within the picture to be used for the automatic calculation of the impact level Lvi. The updated code has been validated against the original Lvi method, thus confirming the suitability of the revised methodology to represent the perception of potential observers.

Mapping the extent and methods of small-scale emerald mining in the Panjshir Valley, Afghanistan

Emerald mining in the Panjshir Valley, Afghanistan, has occurred for thousands of years, yet few records exist documenting the detailed spatial extent, techniques, or productivity of small-scale miners. This study proposes new methods to map and monitor the extent and changes in small-scale mining in remote and inaccessible terrain by integrating multispectral remote sensing analysis with archival geologic data and three-dimensional topographic change detection to examine emerald deposit zones and mining activity in the Panjshir Valley. Specifically, previously mapped geologic units known to host emeralds were re-analyzed using Landsat multispectral analysis to investigate the potential distribution of mining activity. Interpretation of very fine-resolution satellite imagery showed that mining activity is becoming more concentrated and transitioning from traditional tunneling methods to mechanized surface excavation. Finally, topographic change analysis of mechanized mine sites was combined with archival grade data to estimate production and consider improved recovery methods by small-scale miners.