The physicochemical and microbiological assessments of thirteen accessible boreholes in Rumukalagbor in Port Harcourt were ascertained. The studies were carried out in April （onset of the rains） and June （peak of t...The physicochemical and microbiological assessments of thirteen accessible boreholes in Rumukalagbor in Port Harcourt were ascertained. The studies were carried out in April （onset of the rains） and June （peak of the rains） and the results obtained showed that all the water samples tested were acidic （pH 3.12-5.18） with the samples having lower values in June. Eight boreholes （61.5%） had high conductivity values and all boreholes recorded high TDS （total dissolved solids）.These are indications of the presence of dissolved minerals/polluting agents. TH （total hardness） values for all the borehole samples were very low （20 mg/L-60 mg/L）, which are below WHO （World Health Organization） set limit of 200 mg/L. The levels of Ca and Mg ions were determined using AAS （atomic absorption spectroscopy） and these were also observed to be very low. Ca ion concentrations were 0.15 mg/L-20.1 mg/L and Mg ion concentrations were 0.10 mg/L-10.3 mg/L. All the samples but one exceeded the WHO limit for chloride ion concentration for potable water. These high levels can account for the high pH and conductivity values and since water from some boreholes are soft, they are prone to plumbosolvacy. Sulphate and nitrate concentrations in the samples are within the WHO allowable limits. The water samples showed minimal microbial load with 38.5% not having any microbial load.展开更多
The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loo...The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loop anchorage prestressing loss(PL) values of inner lining(IL)in Yellow River-crossing tunnel under two anchorage systems,including twice- tension anchorage system and HM(Chinese transliteration is huanmao)anchorage system,are introduced. The software ANSYS is selected to realize the three-dimensional(3D) finite element modeling to accomplish simulation and calculation works under the two anchorage systems,respectively. Stress processes of IL under the two working conditions,of which one is completed cable tensioning(CCT) and the other is water in the tunnel with the designed water pressure(DWP),are contrasted and analyzed. Impacts of prestressing forces of anchor cables on structural safety under the two anchorage systems are contrasted. The calculation results show that the twice-tension anchorage system can reduce PL effectively and then increase prestresses of wall concrete(WC). Meanwhile,the anchorage system has the advantages of improving security and stability of tunnel structure,reducing project costs and saving steel consumption. The research work is available to related design and construction of anchor cable,and is worthy of promotion and application.展开更多
The karst process acts as carbon sequestration for atmospheric CO_2.The amount of karst carbon sequestration (KCS) depends on the discharge of karst catchment and inorganic carbon concentration of the water body.Based...The karst process acts as carbon sequestration for atmospheric CO_2.The amount of karst carbon sequestration (KCS) depends on the discharge of karst catchment and inorganic carbon concentration of the water body.Based on the data from the monitoring station on Banzhai subterranean stream located in Maolan National Nature Reserve of Guizhou province,the process and influence factors of KCS have been analyzed.It shows that the amount of KCS is about 353 t C per year in the catchment of Banzhai subterranean stream,and there is good linear relationship between the strength of KCS and discharge of the stream at various time scales.Therefore,how to monitor the discharge accurately is the key to the estimation of KCS.And stations with real-time monitoring function are very important for KCS calculation because of strong seasonal variability of the karst water cycle.展开更多
文摘The physicochemical and microbiological assessments of thirteen accessible boreholes in Rumukalagbor in Port Harcourt were ascertained. The studies were carried out in April （onset of the rains） and June （peak of the rains） and the results obtained showed that all the water samples tested were acidic （pH 3.12-5.18） with the samples having lower values in June. Eight boreholes （61.5%） had high conductivity values and all boreholes recorded high TDS （total dissolved solids）.These are indications of the presence of dissolved minerals/polluting agents. TH （total hardness） values for all the borehole samples were very low （20 mg/L-60 mg/L）, which are below WHO （World Health Organization） set limit of 200 mg/L. The levels of Ca and Mg ions were determined using AAS （atomic absorption spectroscopy） and these were also observed to be very low. Ca ion concentrations were 0.15 mg/L-20.1 mg/L and Mg ion concentrations were 0.10 mg/L-10.3 mg/L. All the samples but one exceeded the WHO limit for chloride ion concentration for potable water. These high levels can account for the high pH and conductivity values and since water from some boreholes are soft, they are prone to plumbosolvacy. Sulphate and nitrate concentrations in the samples are within the WHO allowable limits. The water samples showed minimal microbial load with 38.5% not having any microbial load.
基金National Natural Science Foundation of China(No.51079107)Fundamental Research Funds for the Central Universities(No.5082022)
文摘The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loop anchorage prestressing loss(PL) values of inner lining(IL)in Yellow River-crossing tunnel under two anchorage systems,including twice- tension anchorage system and HM(Chinese transliteration is huanmao)anchorage system,are introduced. The software ANSYS is selected to realize the three-dimensional(3D) finite element modeling to accomplish simulation and calculation works under the two anchorage systems,respectively. Stress processes of IL under the two working conditions,of which one is completed cable tensioning(CCT) and the other is water in the tunnel with the designed water pressure(DWP),are contrasted and analyzed. Impacts of prestressing forces of anchor cables on structural safety under the two anchorage systems are contrasted. The calculation results show that the twice-tension anchorage system can reduce PL effectively and then increase prestresses of wall concrete(WC). Meanwhile,the anchorage system has the advantages of improving security and stability of tunnel structure,reducing project costs and saving steel consumption. The research work is available to related design and construction of anchor cable,and is worthy of promotion and application.
基金funded by the project (No.41072192)from National Natural Science Foundation of Chinathe project(No.1212011087122)from China Geological Survey
文摘The karst process acts as carbon sequestration for atmospheric CO_2.The amount of karst carbon sequestration (KCS) depends on the discharge of karst catchment and inorganic carbon concentration of the water body.Based on the data from the monitoring station on Banzhai subterranean stream located in Maolan National Nature Reserve of Guizhou province,the process and influence factors of KCS have been analyzed.It shows that the amount of KCS is about 353 t C per year in the catchment of Banzhai subterranean stream,and there is good linear relationship between the strength of KCS and discharge of the stream at various time scales.Therefore,how to monitor the discharge accurately is the key to the estimation of KCS.And stations with real-time monitoring function are very important for KCS calculation because of strong seasonal variability of the karst water cycle.
