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
China is rich in geothermal resources,especially in Fujian Province,where 207 exposed hot springs have been discovered.The maximum temperature recorded in geothermal wells is above 121℃ in this province,indicating a ...China is rich in geothermal resources,especially in Fujian Province,where 207 exposed hot springs have been discovered.The maximum temperature recorded in geothermal wells is above 121℃ in this province,indicating a high geothermal resource potential.However,large-scale breakthroughs in geothermal exploration are hindered by a lack of clear geothermal genetic models.In this study,the genetic model of a faultcontrolled mediumelow-temperature convection geothermal zone in the Fujian coastal area was determined by considering the tectonic characteristics of the area and the hydrochemical characteristics of the geothermal fluid(recharge,runoff and discharge characteristics,geothermal reservoir temperature,geothermal fluid circulation depth and renewability).The results showed that the exposed hot springs and high-temperature geothermal boreholes were concentrated in the Fu'aneNanjing and ChangleeZhao'an fault zones.At the intersection or faultbend of these two fault zones,there was strong stress release and activity,as demonstrated in the exposed parts of the high-temperature geothermal resources.The ChangleeZhao'an fault zone had a greater circulation depth,with an average heat storage temperature of 140℃,reflecting high geothermal resource potential.Considering the current temperature of the hot springs,Xiamen Bay and NanjingeJiulong River were identified as the next geothermal development zones.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supported by China Huaneng Group science and technology projects(No.HNKJ21-HF310,and HNKJ22-H10)China Huaneng Group science and technology project(Research and Application of Thermal Energy Evaluation and Gas Coupling Technology in Fengdong Huaneng Heating Zone,TY-21-HJK09)China Huaneng Group High-Level Talents Programme(Research on Spatial Distribution and Control Technology of Methane in Yunnan Diandong Mining Area).
文摘China is rich in geothermal resources,especially in Fujian Province,where 207 exposed hot springs have been discovered.The maximum temperature recorded in geothermal wells is above 121℃ in this province,indicating a high geothermal resource potential.However,large-scale breakthroughs in geothermal exploration are hindered by a lack of clear geothermal genetic models.In this study,the genetic model of a faultcontrolled mediumelow-temperature convection geothermal zone in the Fujian coastal area was determined by considering the tectonic characteristics of the area and the hydrochemical characteristics of the geothermal fluid(recharge,runoff and discharge characteristics,geothermal reservoir temperature,geothermal fluid circulation depth and renewability).The results showed that the exposed hot springs and high-temperature geothermal boreholes were concentrated in the Fu'aneNanjing and ChangleeZhao'an fault zones.At the intersection or faultbend of these two fault zones,there was strong stress release and activity,as demonstrated in the exposed parts of the high-temperature geothermal resources.The ChangleeZhao'an fault zone had a greater circulation depth,with an average heat storage temperature of 140℃,reflecting high geothermal resource potential.Considering the current temperature of the hot springs,Xiamen Bay and NanjingeJiulong River were identified as the next geothermal development zones.
