This paper presents a microdevice developed to measure the electrical conductivity of a liquid or a saturated porous medium using Wenner method.It is developed in the context of biocementation as soil improvement tech...This paper presents a microdevice developed to measure the electrical conductivity of a liquid or a saturated porous medium using Wenner method.It is developed in the context of biocementation as soil improvement technique,which is used in Civil Engineering applications to produce calcium carbonate through bacterial or enzymatic activity,replacing the use of other binder materials such as cement or resins,and therefore reducing carbon footprint.The microdevice was used to measure urease activity in the soil interstitial fluid,to investigate if bacterial activity could be affected by the presence of the particles and tortuosity from pore geometry.Such analysis is important to understand biocementation mechanism inside the soil and helps to improve the design of such treatment solutions.The device is basically a squared reservoir printed in polypropylene using a 3D printing machine,incorporating stainless steel electrodes in its base.The electrical resistivity was computed adopting Wenner method,by connecting 4 PCB electrodes to a signal generator and an oscilloscope for measuring the voltage when a AC current of 1 mA was applied.Both square and sinusoidal waves with 5 kHz frequency were selected among other frequencies.The measurements were adjusted during the calibration of the microdevice,done using standard salt solutions with known electrical conductivity measured using an electrical conductivity probe.For the bacterial activity measurements,the bacterial and urea solutions were added to a uniform-graded size quarzitic sand(average diameter 0.3 mm)placed inside the microdevice and covering completely the electrodes.Bacterial activity was not affected by the presence of the sand,which confirms that this treatment is effective for this type of soils.展开更多
To estimate the mean value of surface soil water content rapidly,accurately,and nonintrusively,field investigations on soil electrical resistivity(SER)with the Yokogawa 324400 earth resistivity meter and the surface(0...To estimate the mean value of surface soil water content rapidly,accurately,and nonintrusively,field investigations on soil electrical resistivity(SER)with the Yokogawa 324400 earth resistivity meter and the surface(0-150 cm)soil water content(SWC)with time domain reflectometry(TDR),together with the abiotic factors including soil texture,structure. and salinity concentrations were conducted in the Mongolian pine(Pinus sylvestris var.mongolica)plantations on a sandy land.The measurement of SER was based on the 4-probe Wenner configuration method.Relationships between the values of SWC and SER were obtained based on analysis of the abiotic factors of the research site,which play a key role in affecting the soil electrical resistivity.Results indicate that the SER meter could be used to estimate the mean value of SWC in the Mongolian pine plantations on the sandy land during the growing seasons.The bulky nature of the equipment simplified the cumbersome measurements of soil water content with the general methods.It must be noted that the Wenner configuration method could only provide the mean values of the SWC,and the soil texture,structure, temperature,and solute concentrations influenced the SER and further affected the estimation of the SWC by the SER meter.Therefore,the results of this study could be applied on a sandy land during the growing seasons only.However, the SWC of other soil types also may be obtained according to the individual soil types using the procedures of this study.展开更多
An electrical resistivity sounding investigation was carried out within the vicinity of some hand dug wells at Temidire Quarters in Akure, Ondo State, Nigeria. The aim of this study was to compare depth and thickness ...An electrical resistivity sounding investigation was carried out within the vicinity of some hand dug wells at Temidire Quarters in Akure, Ondo State, Nigeria. The aim of this study was to compare depth and thickness resolution power of Schlumberger and Wenner arrays. The investigation involved twenty-four vertical electrical soundings (VES) which consisted of twelve Schlumberger array VES and twelve Wenner array VES. The VES results delineated geoelectric layers beneath each VES locations, their layer resistivities, layer thicknesses and depth to aquifer layer(s). Depth to aquifer layer was also determined from static water level measurement and this aided the aquifer layer delineation from VES results. The geoelectric sounding results showed that the study area is dominated by a KH-curve type which consists of top soil, clay/weathered layer, fractured basement and fresh basement. Results from both Schlumberger and Wenner array data were correlated with the static water level measurement;Schlumberger array was found to have higher correlation value than Wenner array.展开更多
Evaluation of backfilling effectiveness plays a crucial role in the geological environment management and restoration of abandoned open-pit quarries,providing a scientific basis for subsequent greening efforts.Backfil...Evaluation of backfilling effectiveness plays a crucial role in the geological environment management and restoration of abandoned open-pit quarries,providing a scientific basis for subsequent greening efforts.Backfill soil,predominantly composed of silty clay,demonstrates high water retention capacity and elevated moisture content,leading to a pronounced resistivity contrast with the bedrock exposed by quarrying activities.To investigate the distribution of backfill soil subsurface and assess backfilling effectiveness in the study area,this study conducted a comprehensive geophysical investigation utilizing the high-density electrical resistivity tomography(ERT).A total of 19 ERT survey lines were deployed across three distinct areas in Liuyao Village,Huaibei City,Anhui Province,China.The inversion results,derived from both two-dimensional(2D)and three-dimensional(3D),reveal distinct electrical properties of the subsurface materials:the backfill soil layer shows low resistivity features,the fill stone layer exhibits medium to high resistivity,and the bedrock shows the highest resistivity.The 2D inversion results,from the data measured using the Wenner array effectively capture the spatial distribution and structural features of the backfill soil layer.The findings indicate a gradual east-west thinning of the clay layer within the quarry.Furthermore,the northern pit area exhibits a uniform distribution of backfill soil layer,indicative of effective backfilling operations.In contrast,the southern pit area lacks a well-defined clay layer,suggesting suboptimal backfilling effectiveness.展开更多
基金FCT I.P,for the funding through CALCITE Project(ref.PTDC/ECI-EGC/1086/2021).
文摘This paper presents a microdevice developed to measure the electrical conductivity of a liquid or a saturated porous medium using Wenner method.It is developed in the context of biocementation as soil improvement technique,which is used in Civil Engineering applications to produce calcium carbonate through bacterial or enzymatic activity,replacing the use of other binder materials such as cement or resins,and therefore reducing carbon footprint.The microdevice was used to measure urease activity in the soil interstitial fluid,to investigate if bacterial activity could be affected by the presence of the particles and tortuosity from pore geometry.Such analysis is important to understand biocementation mechanism inside the soil and helps to improve the design of such treatment solutions.The device is basically a squared reservoir printed in polypropylene using a 3D printing machine,incorporating stainless steel electrodes in its base.The electrical resistivity was computed adopting Wenner method,by connecting 4 PCB electrodes to a signal generator and an oscilloscope for measuring the voltage when a AC current of 1 mA was applied.Both square and sinusoidal waves with 5 kHz frequency were selected among other frequencies.The measurements were adjusted during the calibration of the microdevice,done using standard salt solutions with known electrical conductivity measured using an electrical conductivity probe.For the bacterial activity measurements,the bacterial and urea solutions were added to a uniform-graded size quarzitic sand(average diameter 0.3 mm)placed inside the microdevice and covering completely the electrodes.Bacterial activity was not affected by the presence of the sand,which confirms that this treatment is effective for this type of soils.
基金Project supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(No.KZCX3-SW-418)the 100 Talents Program of the Chinese Academy of Sciences,China.
文摘To estimate the mean value of surface soil water content rapidly,accurately,and nonintrusively,field investigations on soil electrical resistivity(SER)with the Yokogawa 324400 earth resistivity meter and the surface(0-150 cm)soil water content(SWC)with time domain reflectometry(TDR),together with the abiotic factors including soil texture,structure. and salinity concentrations were conducted in the Mongolian pine(Pinus sylvestris var.mongolica)plantations on a sandy land.The measurement of SER was based on the 4-probe Wenner configuration method.Relationships between the values of SWC and SER were obtained based on analysis of the abiotic factors of the research site,which play a key role in affecting the soil electrical resistivity.Results indicate that the SER meter could be used to estimate the mean value of SWC in the Mongolian pine plantations on the sandy land during the growing seasons.The bulky nature of the equipment simplified the cumbersome measurements of soil water content with the general methods.It must be noted that the Wenner configuration method could only provide the mean values of the SWC,and the soil texture,structure, temperature,and solute concentrations influenced the SER and further affected the estimation of the SWC by the SER meter.Therefore,the results of this study could be applied on a sandy land during the growing seasons only.However, the SWC of other soil types also may be obtained according to the individual soil types using the procedures of this study.
文摘An electrical resistivity sounding investigation was carried out within the vicinity of some hand dug wells at Temidire Quarters in Akure, Ondo State, Nigeria. The aim of this study was to compare depth and thickness resolution power of Schlumberger and Wenner arrays. The investigation involved twenty-four vertical electrical soundings (VES) which consisted of twelve Schlumberger array VES and twelve Wenner array VES. The VES results delineated geoelectric layers beneath each VES locations, their layer resistivities, layer thicknesses and depth to aquifer layer(s). Depth to aquifer layer was also determined from static water level measurement and this aided the aquifer layer delineation from VES results. The geoelectric sounding results showed that the study area is dominated by a KH-curve type which consists of top soil, clay/weathered layer, fractured basement and fresh basement. Results from both Schlumberger and Wenner array data were correlated with the static water level measurement;Schlumberger array was found to have higher correlation value than Wenner array.
基金Supported by National Key Research and Development Program of China(No.2023YFC3707901)。
文摘Evaluation of backfilling effectiveness plays a crucial role in the geological environment management and restoration of abandoned open-pit quarries,providing a scientific basis for subsequent greening efforts.Backfill soil,predominantly composed of silty clay,demonstrates high water retention capacity and elevated moisture content,leading to a pronounced resistivity contrast with the bedrock exposed by quarrying activities.To investigate the distribution of backfill soil subsurface and assess backfilling effectiveness in the study area,this study conducted a comprehensive geophysical investigation utilizing the high-density electrical resistivity tomography(ERT).A total of 19 ERT survey lines were deployed across three distinct areas in Liuyao Village,Huaibei City,Anhui Province,China.The inversion results,derived from both two-dimensional(2D)and three-dimensional(3D),reveal distinct electrical properties of the subsurface materials:the backfill soil layer shows low resistivity features,the fill stone layer exhibits medium to high resistivity,and the bedrock shows the highest resistivity.The 2D inversion results,from the data measured using the Wenner array effectively capture the spatial distribution and structural features of the backfill soil layer.The findings indicate a gradual east-west thinning of the clay layer within the quarry.Furthermore,the northern pit area exhibits a uniform distribution of backfill soil layer,indicative of effective backfilling operations.In contrast,the southern pit area lacks a well-defined clay layer,suggesting suboptimal backfilling effectiveness.
