Underground Measurements Research Articles

The Ongoing Deep Underground Measurement of 22Ne(α,n)25Mg at the Ion Beam Facility of the INFN-LNGS

The Ongoing Deep Underground Measurement of 22Ne(α,n)25Mg at the Ion Beam Facility of the INFN-LNGS

Determination of strength of UG2 chromitite pillars at Impala Platinum from laboratory tests and FLAC3D

The results of FLAC3D modelling on chromitite Upper Group 2 Reef pillars from the Bushveld Complex of South Africa are described. The model input parameters were determined from laboratory triaxial tests with post-failure measurements. These geomechanical tests were performed on rock materials within the pillars and the immediate pillar foundations. In the models, post-failure behaviour was simulated using the concept of cohesion softening. Models were built to determine the strength and behaviour of pillars with a width-to-height ratio of approximately two. The original research aimed to find a suitable depth below the surface where Impala Platinum Ltd could safely introduce crush pillars; however, the paper only describes the model results: the ideal depth of the crush pillar introduction is not discussed. The results of the modelling are compared with the PlatMine formula for peak pillar strength and with an underground instrumented pillar located elsewhere on the same reef. Some insight into the effects of grid size on strength is also provided. Further underground measurements are recommended to verify the model results.

Deep-underground dark matter search with a COSINUS detector prototype

Sodium iodide (NaI)-based cryogenic scintillating calorimeters using quantum sensors for signal readout have shown promising first results toward a model-independent test of the annually modulating signal detected by the DAMA/LIBRA dark matter experiment. The COSINUS Collaboration has previously reported on the first above-ground measurements using a dual-channel readout of phonons and light based on transition edge sensors (TESs) that allows for particle discrimination on an event-by-event basis. In this article, we outline the first underground measurement of a NaI cryogenic calorimeter readout via the novel remoTES scheme. A 3.67 g NaI absorber with an improved silicon light detector design was operated at the Laboratori Nazionali del Gran Sasso, Italy. A significant improvement in the discrimination power of e−/γ events to nuclear recoils was observed with a fivefold improvement in the nuclear recoil baseline resolution, achieving σ=441 eV. Furthermore, we present a limit on the spin-independent dark matter nucleon elastic scattering cross section, achieving a sensitivity of O(pb) with an exposure of only 11.6 g d. Published by the American Physical Society 2024

Omnidirectional borehole detector for muography: Design and performance evaluation

Muography using cosmic ray muons is a non-invasive and environmentally friendly imaging technique with comprehensive applicability across various fields such as mineral exploration, archaeology, and engineering, etc. Given characteristics of high penetration and broad energy spectrum of cosmic ray muons, three-dimensional density distribution of objects up to hundreds of meters can be well reconstructed. In mineral exploration and archaeology applications, conventional planar detectors are too large and usually deployed in spacious rooms like tunnels or outdoors, which seriously limits the deeper and broader applications of muography. A type of borehole muon detector is highly desired to address this. In the work, we introduce a novel borehole-type muography detector comprising annular and prismatic plastic scintillators, allowing for its deployment in boreholes. In the paper, the structural design of the detector is described in details and its performance is evaluated numerically and experimentally. Comprehensive investigation on components and on the system as a whole were conducted. According to our commissioning tests, the detector we propose has an omnidirectional field of view without blind spots, with an angular uncertainty of 27.4 mrad and a position uncertainty of 2.29 mm in the azimuthal direction, an angular uncertainty of 20.6 mrad and a position uncertainty of 10.31 mm in the zenithal direction. Detection efficiencies for both annular and prismatic scintillators were measured as 90.3 ± 0.53% and 92.27 ± 0.82%. In addition, an underground location was investigated, survival rate distributions being calculated from above-ground and underground measurements. The results indicate its capability to successfully address muography applications This novel borehole-type detector has the potential to address industry demand for lower-cost, more flexible muography solutions.

Practical Aspects of Using Modern Laser Scanning Techniques for Measuring Mine Excavations

Abstract For more than a dozen or so years now, there has been growing interest in the use of modern laser scanning measurement methods in numerous mining operations engaged in underground excavation. However, the simple possession of a scanner does not guarantee satisfactory measurement results. This study sets out the results of scanning mine excavations in an active mine and describes the current guidelines on various aspects of the measurement process. These guidelines were developed on the basis of several hundred measurements carried out over the last dozen or so years. This study also outlines the typical measurements errors observed over the course of many years. These errors, resulting partly from hardware limitations and partly from human error when planning or actually performing measurements, were an important factor behind the introduction of standards regulating underground measurements. This study discusses in detail not only scanning that utilises traditional stationary laser scanners but also scanning based on mobile scanners. It also presents possible areas of future technological development in line with global trends.

Flexible Resource Allocation-Efficient Water Use Strategies Facilitate Invasion of Invasive Vine Sicyos angulatus L.

The invasive vine Sicyos angulatus L. destroys the natural ecosystem of invaded areas. Understanding the differences in growth and development between S. angulatus and other plants is necessary to explore the invasion mechanisms of S. angulatus and implement appropriate prevention and control measures. Thus, this study compared the growth, photosynthesis, and root characteristics of invasive liana S. angulatus and other three vine plants, Ipomoea nil (L.) Roth, Ipomoea purpurea (L.), and Thladiantha dubia Bunge, at different growth stages: seedling, flowering, and fruiting. The results showed that the total biomass of S. angulatus in the fruiting stage was 3-6 times that of the other three plants, and the root biomass ratio and root-shoot ratio decreased throughout the growth stage. Throughout the growth stage, the total leaf area of S. angulatus was significantly higher than that of the other three plant types, and the specific leaf area of S. angulatus at the seedling and flowering stages was 2.5-3 and 1.4-3 times that of the other three plants, respectively. The photosynthetic rate, stomatal conductance, and transpiration rate of S. angulatus at the fruiting stage were significantly higher than those of the other three plants, and its water use efficiency was higher than that of the other three plants at the three growth stages, indicating its strong photosynthetic capacity. The root activity and root pressure of S. angulatus were also significantly higher than those of the other three plants at the seedling and flowering stages. These results show that S. angulatus flexibly allocates resources to its aboveground parts during the growth stage to ensure that the plant obtains the space necessary for its growth and development and that with the help of higher root pressure and root activity, S. angulatus can maintain higher photosynthesis and water use efficiency with fewer resources. Therefore, the prevention and control of S. angulatus requires a combination of aboveground and underground measures. Spraying conventional weedicide/herbicide and manually removing aboveground plants may lead to its resurgence.

Research and application of small-diameter hydraulic fracturing in situ stress measurement system

Abstract. Observation and estimation of the stress state in the deep crust is a crucial challenge in in situ stress measurement work. The hydraulic fracturing method is an important borehole-based technique for absolute in situ stress measurement. The small-diameter hydraulic fracturing in situ stress measurement system described in this article consists mainly of underground measurement components (serial small-diameter packers and dual-circuit connecting installation rods) and surface control components (hydraulic fluid control system, data acquisition system, and high-pressure oil pump with controllable flow). It enables series measurement of small-sized boreholes for in situ stress and provides a maximum measurement range of 30–45 MPa. The subsequent calculation of in situ stress data adopts a uniform design method to discuss the influence of various external factors on rock fracturing values. The small-diameter hydraulic fracturing in situ stress measurement system has the advantages of simple and lightweight structure, short testing time, high success rate, and low requirements for rock integrity and pressurization equipment. It has formed a series of small-diameter in situ stress measurement equipment which has been innovatively promoted to the field of underground tunnel safety assessment in coal mines and metal mining areas. It has an important practical value and economic significance in accurately determining the in situ stress state of deep development areas.

Application of the most frequent value method for ^{39}Ar half-life determination

An evaluation method supported by robust statistical analysis was applied to historical measurements of ^{39}Ar half-life. The method, based on the most frequent value (MFV) approach combined with bootstrap analysis, provides a more robust way to estimate ^{39}Ar half-life, and results in T_{1/2}(MFV) = 268.2^{+3.1}_{-2.9} years with uncertainty corresponding to the 68% confidence level. The uncertainty is a factor of 3 smaller than that of the most precise re-calculated ^{39}Ar half-life measurements by Stoenner et al. and a factor of 2.7 smaller than that of the adopted half-life value in nuclear data sheets. Recently, the specific activity of the beta decay of ^{39}Ar in atmospheric argon was measured in several underground facilities. Applying the MFV method to a specific activity of ^{39}Ar from underground measurements results in SA_{{^{39}text {Ar}}/text {Ar}}(text {MFV}) = 0.966^{+0.010}_{-0.018} , , text {Bq/kg}_{text {atmAr}} with uncertainty corresponding to the 68% confidence level. In this paper the method to determine the half-life of ^{39}Ar using the specific activity of ^{39}Ar in atmospheric argon is also discussed.

Ultra low background Micromegas detectors for BabyIAXO solar axion search

The International AXion Observatory (IAXO) is a large scale axion helioscope that will look for axions and axion-like particles produced in the Sun with unprecedented sensitivity. BabyIAXO is an intermediate experimental stage that will be hosted at DESY (Germany) and that will test all IAXO subsystems serving as a prototype for IAXO but at the same time as a fully-fledged helioscope with potential for discovery.One of the crucial components of the project is the ultra-low background X-ray detectors that will image the X-ray photons produced by axion conversion in the experiment. The baseline detection technology for this purpose are Micromegas (Microbulk) detectors. We will show the quest and the strategy to attain the very challenging levels of background targeted for BabyIAXO that need a multi-approach strategy coming from ground measurements, screening campaigns of components of the detector, underground measurements, background models, in-situ background measurements as well as powerful rejection algorithms. First results from the commissioning of the BabyIAXO prototype will be shown.

Improved S factor of the C12(p,γ)N13 reaction at E=320–620 keV and the 422 keV resonance

The 12C(p,{\gamma})13N reaction is the onset process of both the CNO and Hot CNO cycles that drive massive star, Red and Asymptotic Giant Branch star and novae nucleosynthesis. The 12C(p,{\gamma})13N rate affects the final abundances of the stable 12,13C nuclides, with ramifications for meteoritic carbon isotopic abundances and the s-process neutron source strength. Here, a new underground measurement of the 12C(p,{\gamma})13N cross-section is reported. The present data, obtained at the Felsenkeller shallow-underground laboratory in Dresden (Germany), encompass the 320-620 keV center of mass energy range to include the wide and poorly constrained E = 422 keV resonance that dominates the rate at high temperatures. This work S-factor results, lower than literature by 25%, are included in a new comprehensive R-matrix fit, and the energy of the 1+ first excited state of 13N is found to be 2369.6(4) keV, with radiative and proton width of 0.49(3) eV and 34.9(2) keV respectively. A new reaction rate, based on present R-matrix fit and extrapolation, is suggested.

Comprehensive use of the Gutenberg–Richter law and geotomography for improving seismic hazard evaluation in hard coal mines

Mining-induced seismicity occurs in numerous underground mines worldwide where extraction is conducted at great depths or in areas characterised by complex tectonic structure. It is accompanied by rock bursts, which result in the loss of working functionality and the possibility of accidents among personnel. The issue of a constant and reliable seismic hazard evaluation is of key significance for both the safety of miners and the stability of production. Research on its improvement is directed at developing new interpretive solutions and methods. The nature of the presented solution is the complex interpretation of seismological data that characterise rock mass seismicity and of underground measurement results in the form of a map presenting the longitudinal wave propagation velocity distribution in the rock surrounding the mined coal seam. The solution was tested in hard coal mines located in the Upper Silesian Coal Basin. The mines are equipped with a modern seismological system enabling the constant monitoring of seismicity together with hazard level evaluation as well as with seismic apparatus for conducting periodic measurements of the seismic wave propagation velocity before the mining face. Comprehensive seismic hazard evaluation criteria were determined based on the obtained results, involving the anomaly of the Gutenberg–Richter law “b” value and the maximum longitudinal seismic wave propagation velocity in the roof rock. The obtained experience and the result validation of this new comprehensive hazard evaluation method confirm its practical usefulness and indicate the directions of improvement for the solution in question.

Study on the influence of the tectonic evolution of Shuangyashan Basin on gas occurrence and extraction in mines

The formation and later evolution of coal-bearing basins in eastern Heilongjiang are controlled by multi-phase tectonic movements, and the Shuangyashan Basin is tectonically located at the southern end of the Sanjiang Basin in the northeast. The paper focuses on the regional geological and tectonic evolution of the Shuangyashan Basin and its influence on the gas occurrence law and extraction difficulty of the Jixian Coal Mine. The study determined that the gas occurrence of the mine in the Suibin-Jixian depression basin has regional aggregation and caprock sealing characteristics. The gas pressure and content of the 9# Coal Seam were measured in the underground test, and the results showed that the 9# coal seam is a hard-to-extract coal seam with low permeability. Aiming at the issue of hard-to-extract gas in 904 Working Face of 9# Coal Seam which is affected by depression basin and derived secondary tectonic conditions, numerical calculation and analysis of gas extraction effect of working face with different extraction parameters were carried out by COMSOL software, the results showed that: negative extraction pressure has less influence on gas extraction effect under basin conditions; when 113 mm diameter borehole is used for gas extraction, gas pressure decreases to 0.72 MPa; when the spacing of extraction borehole is 2 m, the gas pressure is reduced by 20%; when the coal seam permeability is increased by 10 times to more than 0.015 mD, the gas pressure is reduced by more than 50%. The optimized gas extraction scheme with 113 m diameter, 2 m borehole spacing, and 15 kPa negative pressure was proposed for the test working face, and combined with supercritical CO2 fracturing and permeability enhancement technology. Under underground measurement, the coal seam gas content was reduced by 39.7% compared to the original gas extraction scheme. It can be seen that the reasonable gas extraction scheme and coal seam pressure relief and permeability enhancement technology can significantly improve the gas extraction rate, and the extraction effect is remarkable.

S-process Nuclear Reaction Rates

In stars the 13C(α, n)16O and 22Ne(α, n)25Mg reactions are the two main sources of neutrons for the so-called slow neutron capture process (s-process), which is one of the main mechanisms for the stellar synthesis of heavy elements. About 13C(α, n)16O, in despite of many efforts in measuring its cross section at the lower energies, only high uncertainty data above the s-process Gamow window (150 keV < Ecm < 230 keV) were available, due mostly to the difficulties on suppress the natural background. Indeed, only recently the LUNA collaboration performed high precision underground measurements of the reaction cross section inside the Gamow window, improving the accuracy of its extrapolation at the lower energies. Again due to natural background, only upper limits for the 22Ne(α, n)25Mg reaction cross section are currently known in the s-process Gamow window (450 keV < Ecm < 750 keV). For this, the ERC founded project SHADES (Unina/INFN) aims to perform high precision and high sensitivity measurements of the 22Ne(α, n)25Mg reaction cross section down to the neutron threshold. A sensitivity improvement of at least two orders of magnitude over the state of the art is expected thanks to the low natural background environment of the INFN-LNGS laboratory in Italy, the high beam current of the new LUNAMV accelerator and the Beam Induced Background events suppression performed by SHADES hybrid detectors array. In this paper I will present the LUNA efforts to estimate nuclear reaction rates for 13C(α, n)16O, with a focus on the R-Matrix analysis performed with the code AZURE2 to extrapolate nuclear reaction rates at stellar energies and the estimate of their uncertainty through Monte Carlo methods. I will also present an overview of the SHADES project to measure 22Ne(α, n)25Mg in the Gamow window and the first results on the setup commissioning.

Determining the reasonable volume required to inject liquid CO2 into a single hole and displace CH4 within the coal seam in bedding boreholes: case study of SangShuPing coal mine

Previously, determining the injection volume of liquid CO2 used to displace CH4 in coal seam boreholes has lacked scientific input, and has mostly been based on engineering experience and analogy. Here, one scientific method combining theoretical analysis, physical experimentation, and underground measurements was used to determine the reasonable injection volume for a single borehole along a coal seam when injecting liquid CO2 to displace CH4 within the coal seam. Therefore, the amount of CH4, ΔXCH4 , that needs to be displaced by injecting liquid CO2 in a single borehole was obtained by theoretical calculation, and the displacement ratio, β , of CH4 displaced by injecting liquid CO2 under different pressures was analyzed. An in-situ test was designed to obtain the relationship between the injection volume and the distribution of the CO2 content in coal seams located at different distances from the injection hole and the other two key parameters in the equation, such as the influence coefficient, η, of the distribution of the CO2 content in the coal seam and the effective diffusion radius, l0. Based on the relationship between ΔXCH4 , β , η and l0, the empirical equation for the reasonable injection volume of single hole is obtained, and the correction equation is obtained after considering the influence coefficient ξ of CO2 flow non-uniformity. The results showed that to displace CH4, 6.1–7.7 m3 is a reasonable liquid CO2 injection volume range within a single borehole along the bed in 3303 working face when ΔXCH4 is 0.75 m3 t−1, β is 0.0088–0.01, η is 0.275, l0 is 16 m and ξ is 0.155. This method provides a theoretical basis and scientific guidance for applying liquid CO2 injection technology to displace CH4 in coal seams.

Estimating the Attenuation of ELF-Band Radio Waves in the Earth’s Crust by Q-Bursts

Q-bursts are extremely low-frequency (ELF) wave packets spawned by exceptionally powerful lightning strokes. As the Earth’s surface bears finite conductivity, ELF-band radio waves can also be detected under the ground. Q-bursts detected in the magnetic field near the surface and at a depth of 140 m were compared to characterize signal attenuation in the Earth’s crust. The applied analysis incorporates data from permanent ELF measuring sites and the World Wide Lightning Location Network so that simultaneous surface and underground measurements were not needed. The analysis in the 2–140 Hz frequency band yielded <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim \!70 ~\Omega \mathrm{m} $ </tex-math></inline-formula> bulk resistivity. The corresponding skin depths, 1470, 1100, and 920 m for the lowest three Schumann resonance (SR) modes at 7.8, 14.1, and 20.0 Hz, respectively, were found to decrease at a rate proportional to the inverse of the square root of the frequency. A well conductive clay-rich ground layer under the surface can explain the obtained relatively low resistivity compared to known values of local andesitic bedrock. Incorporating independently obtained near-surface ground resistivity values in the evaluation of magnetotelluric (MT) surveys is suggested to improve results for the upper crust layers. The advantages of using Q-bursts in surveying the properties of the Earth’s crust by electromagnetic (EM) methods are pointed out.

Measurement of cosmogenic Li9 and He8 production rates at RENO

We report the measured production rates of unstable isotopes $^9$Li and $^8$He produced by cosmic muon spallation on $^{12}$C using two identical detectors of the RENO experiment. Their beta-decays accompanied by a neutron make a significant contribution to backgrounds of reactor antineutrino events in precise determination of the smallest neutrino mixing angle. The mean muon energy of its near (far) detector with an overburden of 120 (450) m.w.e. is estimated as 33.1 +- 2.3 (73.6 +- 4.4) GeV. Based on roughly 3100 days of data, the cosmogenic production rate of $^9$Li ($^8$He) isotope is measured to be 44.2 +- 3.1 (10.6 +- 7.4) per day at near detector and 10.0 +- 1.1 (2.1 +- 1.5) per day at far detector. This corresponds to yields of $^9$Li ($^8$He), 4.80 +- 0.36 (1.15 +- 0.81) and 9.9 +- 1.1 (2.1 +- 1.5) at near and far detectors, respectively, in a unit of 10$^{-8}$ $\mu^{-1}$ g${^-1}$ cm${^2}$. Combining the measured $^9$Li yields with other available underground measurements, an excellent power-law relationship of the yield with respect to the mean muon energy is found to have an exponent of $\alpha$ = 0.75 +- 0.05.

Modeling of Floor Heave in Underground Roadways in Dry and Waterlogged Conditions

Floor heaving is a phenomenon that occurs in almost all mining roadways and tunnels. It can restrain the advance of the heading face or cause serious problems during roadway use. The highest levels of floor uplifting are observed in coal mines, which can reduce the output or even stop it altogether. The floor heaving intensity depends on the rock type, the stress in the rock mass, and rocks’ mechanical properties. Floor deformation develops when the secondary state of stress is formed around the working, and it is much higher and more dynamic in the case of waterlogged rocks. The presence of water increases the floor’s propensity to heave, especially clay rocks, such as claystones or mudstones, if they include water-absorbed minerals. In this paper, we present a new modeling methodology for roadway floor heave. The modeling covers a dry floor condition in which the parameters of the Hoek-Brown failure criterion are gradually lowered over time, and a waterlogged floor condition, in which the strength and strain parameters of the rocks are gradually reduced in line with their progressive saturation. In the second case, the claystone floor’s geomechanical parameters were investigated, and the rocks were subjected to water for up to 24 h. The results of the numerical simulation were compared with the in situ measurements of convergence and floor heave in the same coal mines from which the rock samples were collected. The consistency between the numerical simulations and the underground measurements reached 90–99%.

Study on the coupling migration law of airflow-respiratory dust of an 8-m high fully-mechanized mining face

8-m super-high fully mechanized mining face has been successfully applied in China, which has brought many difficulties to dust control. The main reason is that the mining height increases and the dust distribution and evolution law are quite different. Targeting the 12,513 fully-mechanized mining face in Bulianta Coal Mine of China in this paper. The spatial evolution of airflow-respiratory dust of an 8-m high fully-mechanized mining face is analyzed using numerical simulation and underground measurement methods. The results reveal that the numerical and measured results are consistent. At the working range from 15 m in front of the shearer to 30 m behind it, the wind speed increases with an average rise of 70% on the coal cutting side. The airflow diffusion at the working face is primarily longitudinal and partly transverse. Along the airflow direction, the respiratory dust concentration in the pedestrian space first increases and decreases, followed by a marginal increase and gradual decrease，and the dust concentration increased with the increase of height, the migration distance of dust particles was directly proportional to time, and the smaller dust particles were prone to transverse diffusion. In the range of 20–30 m from the downwind side of the shearer, the transverse diffusion of coal cutting dust and the dust produced by support coal falling show conversion, leading to the increase of dust concentration. Under the same dust production intensity, compared with ordinary mining height, with the increase of mining height, the influence range of dust diffusion is wider, the floating duration is longer, and the space dust concentration will be reduced, and the support coal falling dust is the main dust pollution source in pedestrian space. The results reveal that the numerical and measured results are consistent, and obtained the relationship of spatial evolutions of respiratory dust

Underground measurement at LUNA found no evidence for a low-energy resonance in the 6Li(p, γ)7Be reaction

The 6Li(p,γ)7Be reaction is involved in all three main nucleosynthesis scenarios: Big Bang Nucleosynthesis, the interaction of cosmic rays with interstellar matter, and stellar nucleosynthesis. Conflicting experimental results have been reported in literature for the 6Li(p,γ)7Be reaction cross section trend at astrophysical energies. A recent direct measurement found a resonance-like structure at Ec.m. = 195 keV, corresponding to an excited state at Ex ~ 5800 keV in 7Be which, however, has not been confirmed by either theoretical calculations or other direct measurements. In order to clarify the existence of this resonance, a new experiment was performed at the Laboratory for Underground Nuclear Astrophysics, located deep underground at Laboratori Nazionali del Gran Sasso (Italy). The 6Li(p,γ)7Be cross section was measured in the energy range Ec.m. = 60-350 keV with unprecedented sensitivity and no evidence for the alleged resonance was found.

Distributed Monitoring With Integrated Probability PCA and mRMR for Drilling Processes

Geological drilling processes involve many variables, and their relationships and dynamic characteristics are highly complicated. In the geological drilling processes, the changes in the operating performance may be invisible under non-optimal conditions, while the data distribution may have significant deviations. The quality of the data collection is difficult to guarantee due to the underground measurement and transmission environment, which increases the uncertainty of the operating condition. Operators have struggled to manage performance monitoring for drilling processes over the decades. To improve the utilization of the instrument measurement data, this paper develops a distributed monitoring method with integrated probability principal component analysis and minimal redundancy maximum relevance. The related process variables are divided into sub-blocks by minimal redundancy maximal relevance algorithm. Then, local detection is gathered integrated probability principal component analysis to formulate global monitoring statistics to realize the whole monitoring scheme. Lastly, real-world production processes are used to verify the feasibility and superiority of the new method. The proposed novelty involves constructing local monitoring models for independent variable sub-blocks taking into account the minimal redundancy maximum relevance of the variable space.