Measuring rock moisture using different techniques in the sandstone area of Saxony

2021 ◽  
Author(s):  
Oliver Sass
Keyword(s):  
Electrical Resistivity ◽  
Sensor Data ◽  
Schmidt Hammer ◽  
Good Reliability ◽  
Traffic Lights ◽  
Weathering Processes ◽  
Rock Stability ◽  
Microwave Sensor ◽  
Weakness Zones ◽  
Measurement Principle

<p>Rock moisture is an understudied factor governing weathering and rockfall. Many weathering processes like hydration, thermal and frost cracking are governed by moisture availability. However, weathering studies have primarily focussed on temperatures. The role of moisture supply has not been given the same attention, also because there is no humidity sensor that meets all requirements for application in rock.</p><p>In the sandstone area of Saxony in eastern Germany ("Saxonian Switzerland"), climbing on wet rock poses a safety problem as the sandstone loses stability when saturated. Visitor guidance measures ('rock traffic lights') were implemented to temporarily stop climbing at rocks that are too wet. To accompany this measure, we carried out a pilot study at the Gohrisch sandstone massif, involving moisture measurements in the four cardinal directions at the rockwall base and near the summit of the massif. We used a combination of (a) electrical resistivity electrodes, combined with wind-driven rain collectors; (b) 2D-electrical resistivity (ERT); (c) microwave sensors (MW) with four sensor heads for different penetration depth and (d) Schmidt Hammer (SH) measurements to assess rock stability. All techniques were accompanied by laboratory measurements at rock samples.</p><p>Electrical resistivity, MW readings and SH rebound all showed very good correlations with rock moisture in laboratory samples. However, the range of values measured in the field strongly differed from laboratory values so that the calibration curves could not be applied to field data. Presumeably this is due to lithological differences between the fresh quarry samples and the pre-weathered rock faces.  </p><p>ERT profiles using adhesive electrodes showed good reliability (RMS error 5-14%). Most sites were slightly wet at the surface, drier at 5-15 cm depth and moderately wet at 20-30 cm depth (1000 – 8000 Ohmm). The site Bottom North was much wetter than all others, and the two top positions were dried out at the surface probably due to wind. This distribution was roughly confirmed by microwave sensor data. Direct correlation between MW and ERT measurements was poor as measurement principle and geometry are very different.</p><p>Schmidt Hammer data was very consistent with microwave moisture in the lab (lower rebound at wetter surfaces); however not in the field, where the wetter Bottom North site showed highest rebound values. The summit positions showed significantly lower rebound which we attribute to stronger weathering (more dry-wet cycles). Lab results show that the sandstone loses stability (SH rebound) mainly between 60% and 100% pore saturation. Currently we cannot reliably determine if this saturation was actually reached in the field.</p><p>The combined interpretation of all measurements, even if imperfectly calibrated, points to surface-parallel weakness zones that have developed at all sites except of Bottom North which is almost never hit by sunlight. Water supply by rainfall is weak at the almost vertical sites; water rather seems to infiltrate in flat areas and to seep out at the base of the massif. The results help to understand the distribution of dampness in the rock and will be supplemented by continuous monitoring and numerical simulations.</p>

Measuring rock moisture using different techniques in the sandstone area of Saxony

2020 ◽  
Author(s):  
Oliver Sass
Keyword(s):  
Electrical Resistivity ◽  
Sensor Data ◽  
Degree Of Saturation ◽  
Microwave Range ◽  
Schmidt Hammer ◽  
Good Reliability ◽  
Traffic Lights ◽  
Weathering Processes ◽  
The North ◽  
Rock Stability

<p>Rock moisture is an understudied factor governing weathering and rockfall. Many weathering processes like hydration, shrinking/swelling and thermal cracking are governed by moisture availability, and a high degree of saturation is a precondition for frost cracking. However, weathering studies have primarily focussed on temperatures. The role of moisture supply has not been given the same attention, also because there is no humidity sensor that meets all requirements for application in rock.</p><p>In the sandstone area of Saxony in eastern Germany ('Saxonian Switzerland'), climbing on wet rock poses a safety problem as the sandstone loses stability when saturated. Voluntary visitor guidance measures ('rock traffic lights') were implemented to temporarily stop climbing at rocks that are too wet. To accompany this measure scientifically, we carried out a pilot study at the approx. 70 m high Gohrisch sandstone massif, involving moisture measurements in the four cardinal directions (N, E, S, W) at the rockwall base, and at N and S near the summit of the massif. We used a combination of (a) electrical resistivity electrode pairs, combined with wind-driven rain (WDR) collectors; (b) 2D-electrical resistivity (ERT); (c) handheld microwave sensors with four sensor heads for different penetration depth; (d) numerical simulations and (e) Schmidt Hammer measurements to assess rock stability. All techniques were accompanied by laboratory measurements at rock samples.</p><p>WDR was registered at two of six sites, the distribution being due to micro-topography rather than wind direction. At these sites a clear response of (decreasing) resistivity on driving rain was registered. ERT profiles using adhesive electrodes showed good reliability (RMS error 5-14%). Most sites were slightly wet at the surface, drier at 5-15 cm depth (which might be due to surface-parallel zones of weakness) and moderately wet at 20-30 cm depth (1000 – 8000 Ohmm). The site Bottom North was much wetter than all others, and the two top positions were dried out at the surface probably due to wind.</p><p>This distribution was confirmed by microwave sensor data: Moisture contents show little differences between the sites except of the North site which was wetter at all depths. Schmidt Hammer data was very consistent with microwave moisture in the lab (lower rebound at wetter surfaces); however not in the field, where the wetter Bottom North site showed highest rebound values. The summit positions showed significantly lower rebound which we attribute to stronger weathering (more dry-wet cycles).</p><p>Lab results show that the sandstone loses stability (SH rebound) mainly between 60% and 100% pore saturation. Currently we cannot reliably determine if this saturation was actually reached in the field. According to ERT calibration, saturation >60% was only reached near the surface at North Bottom, while at some decimetres depth, saturation rarely exceeded 50%. Calibration from electrical resistivity to moisture and microwave reflectance to moisture was successful in the lab; however, the measured resistivity and microwave range did not match the values measured in the field. Calibration needs to be achieved directly at the field site which remains an open task.</p>

scholarly journals Experimental Study on Electric Resistivity Characteristics of Compacted Loess under Different Loads and Drying-Wetting Cycles

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yu Zhou ◽  
Guoyu Li ◽  
Wei Ma ◽  
Dun Chen ◽  
Fei Wang ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electric Resistivity ◽  
Engineering Properties ◽  
Dissipated Energy ◽  
Compression Tests ◽  
Large Area ◽  
Compression Process ◽  
Weathering Processes ◽  
Resistivity Method ◽  
Compacted Loess

Densely compacted loess foundations of many man-made infrastructures are often exposed to various loads and extreme weathering processes (e.g., drying-wetting cycles), which significantly deteriorate their mechanical properties. Traditional methods applied to characterize soil engineering properties are primarily based on visual inspections, point sensors, or destructive approaches, the results of which often have relatively high costs and cannot provide large-area coverage. The electrical resistivity method is a reasonable alternative that provides a nondestructive, sensitive, and continuous evaluation of the soil physical properties. Thus, the relationships between electrical resistivity and soil strength should be understood, particularly for scenarios in which soils undergo significant loads and cycles of drying and wetting. In this study, a suite of laboratory tests simulating loads (consolidation tests, unconfined compression tests, and uniaxial cyclic unloading-reloading tests) and seasonal field conditions (drying-wetting cycle tests) were conducted to quantitatively assess their deterioration effects on the geophysical and geotechnical properties of compacted loess. The experimental results indicated that electric resistivity decreases with the increase in stress and then approaches a stable value after the stress becomes 200 kPa. During the uniaxial compression process, the electric resistivity corresponds to both the stress and strain of loess in real-time. The electrical resistivity of loess reflects plastic damage under uniaxial unloading-reloading tests, but it is deficient in representing the dissipated energy of loess. The electrical resistivity of loess samples increases as the number of drying-wetting cycles increases but decreases with increasing cycle numbers after stabilization under consolidation load. The electrical resistivity can effectively characterize the mechanical and deformation characteristics of loess samples under loads and drying-wetting cycles, exhibiting a certain potential for long-term monitoring of soil engineering properties.

ELECTRICAL RESISTIVITY APPLIED TO OPTIMIZATION OF BLASTING DESIGN AT PRODUCTION BENCHES: A CASE STUDY AT ABÓBORAS MINE, QUADRILÁTERO FERRÍFERO, MINAS GERAIS – BRAZIL

2018 ◽  
Vol 36 (4) ◽  
pp. 1
Author(s):  
Andre Luiz Vieira ◽  
Marco Antonio Braga ◽  
Jair Carlos Koppe ◽  
Lorena Andrade Oliveira ◽  
Maria Filipa Perez da Gama
Keyword(s):  
Electrical Resistivity ◽  
Iron Ore ◽  
Friable Material ◽  
Daily Production ◽  
Usual Model ◽  
Weathering Processes ◽  
Resistivity Method ◽  
Geophysical Model ◽  
Quadrilátero Ferrífero ◽  
Compact Rock

ABSTRACT. Quadrilátero Ferrífero is one of the main regions of iron ore production in the world. The action of the weathering processes promotes the conformation of compact rock immersed in friable material. The usual model of blasting applied in production benches, with blast drillholes distributed homogeneously, produces boulders of compact rock, which are impracticable to extract and grind, causing impacts on daily production of iron ore. Therefore, this work proposes a methodology capable of overcoming this problem caused by weathering, using the electrical resistivity method. The application of it was carried out at the Abóboras mine (VALE S.A.), and was able to differentiate two types of materials, interpreted as compact and friable itabirite. With the use of the electrical data, it was possible to generate a geophysical model that allowed to determine the position of the compact itabirite boulders. From this model, it was possible to optimize the blasting design, with higher concentration of detonation drillholes where the model indicated the compact rock. With the appropriate tests, it was observed a 75% decrease in the amount of boulders present in the fragmented material as compared to the usual model. Consequently, there was a significant increase in ore loading effectiveness, thus optimizing iron ore production.Keywords: Applied geophysics, iron ore, mining. RESUMO. Quadrilátero Ferrífero é uma das principais regiões de produção de minério de ferro no mundo. A ação dos processos intempéricos promovem a conformação de rochas compactas imersas em material friável. O modelo usual de detonação e desmonte aplicado em frentes de lavra, com furos de detonação distribuídos de modo homogêneo, gera matacões de rocha compacta, o que inviabiliza sua extração e moagem e impacta na produção diária de minério de ferro. Desse modo, este trabalho propõe uma metodologia capaz de suplantar esse problema causado pelo intemperismo, através da utilização do método de eletrorresistividade. A aplicação do método foi realizada nas dependências da mina de Abóboras (VALE S.A.), e foi capaz de diferenciar dois tipos de materiais, interpretados como itabirito compacto e friável. Com o uso dos dados elétricos, foi possível gerar um modelo geofísico que possibilitou determinar a posição dos blocos de itabirito compacto. A partir desse modelo, houve uma otimização da malha de desmonte, com maior concentração de furos de detonação onde o modelo indicou rocha compacta. Com os devidos testes de detonação, foi observado diminuição dos matacões em 75% em relação à malha de desmonte usual. Como resultado, houve significativo aumento da efetividade do carregamento de minério, e consequente otimização da produção de minério de ferro.Palavras-chave: Geofísica aplicada, minério de ferro, mineração.

scholarly journals Hybrid Traffic Forecasting Model With Fusion of Multiple Spatial Toll Collection Data and Remote Microwave Sensor Data

IEEE Access ◽  
2018 ◽  
Vol 6 ◽  
pp. 79211-79221 ◽  
Author(s):  
Yinli Jin ◽  
Erlong Tan ◽  
Li Li ◽  
Guiping Wang ◽  
Jun Wang ◽  
...  
Keyword(s):  
Sensor Data ◽  
Forecasting Model ◽  
Traffic Forecasting ◽  
Microwave Sensor ◽  
Collection Data ◽  
Toll Collection

scholarly journals An improved traffic lights recognition algorithm for autonomous driving in complex scenarios

2021 ◽  
Vol 17 (5) ◽  
pp. 155014772110183
Author(s):  
Ziyue Li ◽  
Qinghua Zeng ◽  
Yuchao Liu ◽  
Jianye Liu ◽  
Lin Li
Keyword(s):  
Data Fusion ◽  
Autonomous Driving ◽  
Recognition Algorithm ◽  
Sensor Data ◽  
Optimal Size ◽  
Data Set ◽  
Traffic Lights ◽  
Sensor Data Fusion ◽  
Multi Sensor Data Fusion ◽  
Public Data

Image recognition is susceptible to interference from the external environment. It is challenging to accurately and reliably recognize traffic lights in all-time and all-weather conditions. This article proposed an improved vision-based traffic lights recognition algorithm for autonomous driving, integrating deep learning and multi-sensor data fusion assist (MSDA). We introduce a method to obtain the best size of the region of interest (ROI) dynamically, including four aspects. First, based on multi-sensor data (RTK BDS/GPS, IMU, camera, and LiDAR) acquired in a normal environment, we generated a prior map that contained sufficient traffic lights information. And then, by analyzing the relationship between the error of the sensors and the optimal size of ROI, the adaptively dynamic adjustment (ADA) model was built. Furthermore, according to the multi-sensor data fusion positioning and ADA model, the optimal ROI can be obtained to predict the location of traffic lights. Finally, YOLOv4 is employed to extract and identify the image features. We evaluated our algorithm using a public data set and actual city road test at night. The experimental results demonstrate that the proposed algorithm has a relatively high accuracy rate in complex scenarios and can promote the engineering application of autonomous driving technology.

scholarly journals Joint Use of Spaceborne Microwave Sensor Data and CYGNSS Data to Observe Tropical Cyclones

2020 ◽  
Vol 12 (19) ◽  
pp. 3124
Author(s):  
Shiwei Wang ◽  
Shuzhu Shi ◽  
Binbin Ni
Keyword(s):  
Wind Speed ◽  
Tropical Cyclones ◽  
Inner Core ◽  
Mean Absolute Error ◽  
Absolute Error ◽  
Maximum Wind Speed ◽  
Sensor Data ◽  
Maximum Wind ◽  
Microwave Sensor ◽  
The Mean

The joint use of spaceborne microwave sensor data and Cyclone Global Navigation Satellite System (CYGNSS) data to observe tropical cyclones (TCs) is presented in this paper. The Soil Moisture Active and Passive (SMAP) radiometer was taken as an example of a spaceborne microwave sensor, and its data and the CYGNSS data were fused to fix the center of a TC and to measure the maximum wind speed around the TC inner core. This process included data preprocessing, image fusion, determination of the TC center position, and the estimation of the TC’s intensity. For all of the observed hurricanes, the experimental results demonstrated that the proposed method obtains a more complete structure of the TC and can measure the surface wind speed around the TC inner core at more frequent intervals compared to the case where the SMAP radiometer data or the CYGNSS data are employed alone. Furthermore, when comparing the TC tracks obtained by the proposed method with the best tracks provided by the National Hurricane Center (NHC), we found that the mean absolute error values ranged between 18.4 and 46 km, the standard deviation varied between 15.1 and 28.2 km, and both of these were smaller than the values obtained by only using the CYGNSS data. In addition, when comparing the maximum wind speed around the TC inner core obtained by the proposed method with the best track peak winds estimated by the NHC, we found that the mean absolute error values ranged between 7.7 and 15.7 m/s, the root-mean-square difference values varied between 8.6 and 18 m/s, the correlation coefficients varied between 0.1782 and 0.9877, the bias values varied between −8.5 and 4.5 m/s, and all of these values were smaller in most cases, than those obtained by only using the CYGNSS data.

scholarly journals Fracture network characterisation of a landslide by electrical resistivity tomography

2014 ◽  
Vol 2 (6) ◽  
pp. 3965-4010 ◽  
Author(s):  
S. Szalai ◽  
K. Szokoli ◽  
A. Novák ◽  
Á. Tóth ◽  
M. Metwaly ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Fracture Network ◽  
Physical Parameters ◽  
Good Tool ◽  
Loess Landslide ◽  
Resistivity Tomography ◽  
Rock Stability ◽  
Fracture Systems ◽  
Landslide Evolution

Abstract. In contrary to most of the landslide studies which concentrate to the sliding surface in this paper the fracture system of a loess landslide is investigated. The continuity and geometry, orientation and dip of the major fractures are crucial parameters for assessing rock stability and landslide evolution. Rain infiltrating moreover easily into the rock mass through fractures providing lubrication for the material to slide, and increases the self-mass of the material increasing the slumping rate. Fracture maps enable beside of the characterisation of the fractured area the delineation of the endangered area of slow-moving landslides in due time and getting information about its inner structure. For constructing such maps Electrical Resistivity Tomography (ERT) measurements have been carried out using different geoelectric configurations. In spite of the high density of the fractures and their changing physical parameters in function of their water content – which make the interpretation rather difficult – a number of fractures have been detected and more or less well localised. On the basis of the present research the application of the Schlumberger and the Pole-Dipole arrays is recommended to fulfil the aim of the study. The optimised Stummer array is at the same time the only array which presents conductive anomalies (supposedly water filled fractures), as well, and indicates that fractures elongate deep downwards. Because these features seem to be realistic based on field observations or theoretical considerations the Stummer array may be a very good tool for completing e.g. P-Dp measurements. The study area could have been divided by all arrays into differently fractured zones, which assists a lot in understanding the landslide structure and evolution. It was shown, moreover, that in the still passive area there are thick fractures, too, verifying its dangerousness, as well. The ERT results enabled localising the rupture surfaces of future slumps which proved to be distributed uniformly with about 10 m distance between them and predicting mass movements which may prevent the slump along the visible fracture. Similar unidirectional fracture systems could be investigated by the ERT method for any hydrogeological or engineering geological aim.

scholarly journals Interannual changes in sea-ice conditions on the Arctic Sea Route obtained by satellite microwave data

2011 ◽  
Vol 52 (58) ◽  
pp. 237-247 ◽  
Author(s):  
Hiroki Shibata ◽  
Kazutaka Tateyama ◽  
Hiroyuki Enomoto ◽  
Shuuhei Takahashi
Keyword(s):  
Sea Ice ◽  
Arctic Sea Ice ◽  
Sensor Data ◽  
The Arctic ◽  
North Coast ◽  
Sea Ice Extent ◽  
Microwave Sensor ◽  
Arctic Sea ◽  
Microwave Data

AbstarctWith decreases in Arctic sea-ice extent in recent years, the Northern Sea Route (NSR) and Northwest Passage (NWP), which we collectively term the Arctic Sea Route (ASR), have become open for navigation more frequently. The ASR connects the Pacific and Atlantic Oceans, with the NSR following the Siberian coast, and the NWP following the north coast of North America. This study evaluated long-term ice concentrations along both routes using microwave data from the SMMR and SSM/I sensors, and analyzed details using data from the AMSR-E passive microwave sensor. The data were used to determine the number of navigable days according to various sea-ice concentrations. Analysis of SMMR and SSM/I data showed a remarkably large number of navigable days on the NSR since 1995. For the NWP, the low resolution of the SMMR and SSM/I data for the Canadian Arctic Archipelago made analysis difficult, but long-term change in the sea-ice distribution on the ASR was indicated. Analysis of the AMSR-E microwave sensor data revealed navigable days along the NSR in 2002 and from 2005 to 2009 (except 2007). For navigation purposes, the sea-ice decrease in specific regions is important, as well as the decrease across the Arctic Ocean as a whole. For the NWP, numerous navigable days were identified in the period 2006–08.

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