The impermeability mechanism of water-proof self-compacting concrete (WPSCC )w as studied. The mechanism and influential factors, such as water-cement ratio(w /c), dosage of powder, superplasticizer, sand content, agg...The impermeability mechanism of water-proof self-compacting concrete (WPSCC )w as studied. The mechanism and influential factors, such as water-cement ratio(w /c), dosage of powder, superplasticizer, sand content, aggregate conte nt, fly ash, UEA, PP fiber, on compactibility and crack resistance of WPSCC were analyzed. A type of WPSCC successfully applied in tunnel liner with its validit ies, conveniences and economies by mockup test was developed and optimized. Expe rimental results show that the WPSCC has good workability, mechanical properties and impermeability when reasonable requirements are fulfilled.展开更多
We aimed to reuse the propylene oxide sludge(POS).Propylene oxide sludge shell-aggregate(POSS-A)and propylene oxide sludge gradient shell-aggregate(POSGS-A)whose main hydrated phase is tobermorite were successfully ma...We aimed to reuse the propylene oxide sludge(POS).Propylene oxide sludge shell-aggregate(POSS-A)and propylene oxide sludge gradient shell-aggregate(POSGS-A)whose main hydrated phase is tobermorite were successfully manufactured by the hydrothermal synthesis of POS and silica materials under the condition of autoclaved(180℃,1.0 MPa)curing.Influences of pre-wetting time of coarse aggregate and pressure application mode on the different concretes were investigated.The experimental results show that the concrete with POSS-A as coarse aggregate(POSS-A concrete),the concrete with POS gradient shell-aggregate as coarse aggregate(POSGS-A concrete),sintered aggregate concrete and common concrete,all have excellent impermeability performance whatever the pre-wetting time of coarse aggregate is 0.5 h or 24 h,and the pre-wetting time of coarse aggregate has a negligible influence on the concrete.The influence degree of pressure application mode on the impermeability performance of the sintered aggregate concrete is the greatest among three kinds of concrete,which has a negligible influence on impermeability performance of the other concretes.POSGS-A can be used as a green building light aggregate in hydraulic concrete.展开更多
The relationship of unstable osmosis coefficient to time and osmosis deep is derived from the osmosis equation in this paper. Mercury porosimeter is used to study the pore structure of cement mortar. The method of vol...The relationship of unstable osmosis coefficient to time and osmosis deep is derived from the osmosis equation in this paper. Mercury porosimeter is used to study the pore structure of cement mortar. The method of volume density is used to determine the changes of specific pore volume, and therelation between pore structure and impermeability is analyzed. Although the drythermal curing method has many advantages over other curing method, the directional pore along the direction of evaporization of water is formed inside concrete. The harmful pore above 2000(?) is increased and the average diameter of pore rises. As a result, the mortar impermeability loses seriously.展开更多
Impermeability of tunnel structural material after exposure to high temperature determines residual service life and security. The present study explores impermeability deterioration and water absorption change (expre...Impermeability of tunnel structural material after exposure to high temperature determines residual service life and security. The present study explores impermeability deterioration and water absorption change (expressed as w(T, t)) of tunnel structural material after exposure to 200℃, 300℃, 400℃, 500℃, and 600℃respectively. Structural cementitious material was devised according to the requirements of segment used in Yangtze River tunnel of Wuhan which has been in constructing. Effect of high temperature on impermeability is evaluated by impermeability deterioration factor (abbr. IDF) and w(T, t).Testing results indicate that impermeability of concrete decreases with the increase of temperature up to 600℃, and serious impermeability deterioration occurs at temperature above 300℃. Furthermore, concrete with higher impermeability is more sensitive to high temperature above 400℃.展开更多
The impermeability of concrete of the exterior wall of the underground tunnel in water-rich stratum is a key concern of engineers.Taking the Aixihu highway tunnel in Nanchang city as an example,the impermeability of t...The impermeability of concrete of the exterior wall of the underground tunnel in water-rich stratum is a key concern of engineers.Taking the Aixihu highway tunnel in Nanchang city as an example,the impermeability of the concrete in the side wall of the highway tunnel is tested,through multiple tests,such as the embedded steel pipe,water injection,and field observation.The results show that,under the action of 2mpa of water pressure,no water flow permeates from the side wall of the concrete tunnel,indicating that the impermeable performance of concrete tunnel in this section meets the engineering requirements,and hoping that this research can be used as a reference for other similar projects.展开更多
The migration of nitroglycerin(NG) has always been the critical issue that harmfully impacts the structural integrity and operational reliability of the solid rocket motor, which is mainly composed by Nitrate Ester Pl...The migration of nitroglycerin(NG) has always been the critical issue that harmfully impacts the structural integrity and operational reliability of the solid rocket motor, which is mainly composed by Nitrate Ester Plasticized Polyether(NEPE) propellant/Hydroxyl-terminated Polybutadiene(HTPB) liner/Ethylene Propylene Diene Monomer(EPDM) insulation bonding system. This paper proposes an innovative surface modification method attempting to modify the EPDM insulation layer coated with reduced graphene oxide(RGO), which exhibits ability to weaken the NG absorption by EPDM insulation layer,blocking the pathway of NG migration into EPDM insulation materials. The microstructure of RGO-coated layer was analyzed and the formation mechanism was investigated. The RGO-coated layer is well bonded to the HTPB liner, and its anti-migration performance to NG at different temperatures has been evaluated. Comparing with blank samples under the same storage conditions, the RGO-coated layers can reduce the diffusion coefficient of NG by up to 87.3% and increase the diffusion activation energy of NG by14.8 kJ,mol^(-1). This research provides a new strategy to effectively inhibit NG migration in NEPE propellant/HTPB liner/EPDM insulation bonding system.展开更多
Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater cont...Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater contaminant remediation project?This study evaluates the necessity of impermeable curtains for groundwater contaminant remediation projects.Specifically,it considers remediation efforts based on the Pump and Treat(PAT)technique under various hydrogeological conditions and contaminant properties,comparing the total remediation cost and effectiveness.To further investigate,a multi-objective simulation and optimization model,utilizing the Multi-Objective Fast Harmony Search(MOFHS)algorithm,was employed to identify optimal groundwater remediation system designs that without impermeable curtains.Both a two-dimensional(2-D)hypothetical example and a three-dimensional(3-D)field example were used to assess the necessity of constructing impermeable curtains.The 2-D hypothetical example demonstrated that the installation of impermeable curtain is justified only when the dispersivity(αL)of the contaminant reaches 100 meters.In most cases,particularly at sites with porosity(n)under 0.3,alternative,more cost-effective,and efficient remediation strategies may be available,making impermeable barriers unnecessary.The optimization results of the 3-D field example further corroborate the conclusions derived from the 2-D hypothetical example.These findings provide valuable guidance for more scientifically informed,reasonable,and cost-effective groundwater contaminant remediation projects.展开更多
The transient flow mathematical model of arbitrary shaped heterogeneous reservoirs with impermeability barrier is proposed in this paper. In order to establish this model, the perturbation method is employed and the s...The transient flow mathematical model of arbitrary shaped heterogeneous reservoirs with impermeability barrier is proposed in this paper. In order to establish this model, the perturbation method is employed and the solution of model is expanded into a series in powers of perturbation parameter. By using the Boundary Element Method (BEM) and Duhamel principle, wellbore pressure with effects of skins and wellbore storage is obtained. The type curves are plotted and analyzed considering effects of heterogeneity, arbitrary shape and impermeable barriers. Finally, the results obtained by perturbation boundary element method is compared with the analytical solution and is available for the transient pressure analysis of arbitrary shaped reservoirs.展开更多
The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and morta...The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and mortar mixtures was implemented to improve their strength and waterproofing, respectively, using compression and water absorption tests according to their corresponding standards (ASTM C1231, ASTM D2938, and ASTM C1585). The samples were evaluated at different concentrations and curing ages. In addition, different sand/cement ratios were considered for the mortar. The results revealed that there was a 9.4% increase in compressive strength in concrete and a 23.7% reduction in water absorption in mortar for the 5:1 ratio. These changes would be the result of the interaction of the nanoporous additive in the atomic crystal structure of the material demonstrating the nanotechnological nature of allophane.展开更多
Cementitious capillary crystalline waterproof materials(CCCW for short)offer durability and excellent waterproofing properties,making them a popular option for building waterproofing.Some scholars have studied the pro...Cementitious capillary crystalline waterproof materials(CCCW for short)offer durability and excellent waterproofing properties,making them a popular option for building waterproofing.Some scholars have studied the proportioning of such materials.However,these studies lack the relationship between the impermeability pressure of mortar and the components,and the mechanism of action is somewhat debatable.Therefore,we adopted a two-step method in our experiments.Firstly,we screened out the components that significantly impact impermeability from a variety of active components by orthogonal test.We then optimized the design of the active group ratio using the simplex lattice method.Lastly,we conducted a performance test of the optimal ratio and explored the waterproofing mechanism of homemade CCCW.展开更多
This study aimed to devise strategies for alleviating the detrimental impacts of floods in the vicinity of a dike. Experiments were conducted in an open rectangular channel to investigate the flow dynamics under varyi...This study aimed to devise strategies for alleviating the detrimental impacts of floods in the vicinity of a dike. Experiments were conducted in an open rectangular channel to investigate the flow dynamics under varying dike conditions. To address concerns related to intense whirls and concentrated flow around the dike head, comparative analysis was performed in terms of flow structures and energy reduction around I-shaped and T-shaped dikes with two ratios of wing length (lw) to dike length (ld) (lw/ld = 1.41 and 2.43). The T-shaped dike wings were equipped with diverse designs: angled footing, delta vane, and streamlined tapered, resulting in elevated backwater in front of the dike, reduced velocity, and enhanced energy reduction. The findings indicated that elongating the wing reciprocally affected the depth-averaged velocity (at the dike head and near the adjacent dike bank), concurrently impacting flow deflection, backwater rise, and energy reduction rate. The T-shaped dike, specifically with an angled footing (lw/ld = 2.43), yielded optimal outcomes. These included significant reductions in maximum energy (46%), tip velocity (98%), and dike adjacent bank velocity (90%), as well as significant flow deflection towards the mainstream, outperforming the I-shaped impermeable dike. The proposed solutions exhibit efficacy in mitigating rapid deterioration during floods, securing both the dike head and the neighboring bank to avert failures in high-energy flow.展开更多
The self-healing action of a permeable crystalline coating on the po rous mortar was investigated by two times impermeability test. Moreover, the sel f-healing mechanism of cement-based materials with the permeable cr...The self-healing action of a permeable crystalline coating on the po rous mortar was investigated by two times impermeability test. Moreover, the sel f-healing mechanism of cement-based materials with the permeable crystalline c oating was studied by SEM. The results indicate that the permeable crystalline c oating not only seals the pores and cracks in mortar during its curing process, but also heals the permeable pathway caused by first impermeability test or crac ks produced by freeze-thaw cycles. Therefore, cement-based materials can be im proved by the permeable crystalline coating for the self-healing function. SEM images prove that the self-healing function is realized by generating a great q uantity of non-soluble dendritic crystalline within the pores and cracks, which prevents the penetration of water and other liquids.展开更多
With the gradual depletion of shallow coal resources,the Yanzhou mine in China will enter the lower coal seam mining phase.However,as mining depth increases,lower coal seam mining in Yanzhou is threatened by water inr...With the gradual depletion of shallow coal resources,the Yanzhou mine in China will enter the lower coal seam mining phase.However,as mining depth increases,lower coal seam mining in Yanzhou is threatened by water inrush in the Benxi Formation limestone and Ordovician limestone.The existing prediction models for the water burst at the bottom of the coal seam are less accurate than expected owing to various controlling factors and their intrinsic links.By analyzing the hydrogeological exploration data of the Baodian lower seam and combining the results of the water inrush coefficient method and the Yanzhou mine pressure seepage test,an evaluation model of the seepage barrier capacity of the fault was established.The evaluation results show the water of the underlying limestone aquifer in the Baodian mine area mainly threatens the lower coal mining through the fault fracture zone.The security of mining above confined aquifer in the Baodian mine area gradually decreases from southwest to northeast.By comparing the water inrush coefficient method and the evaluation model of fault impermeability,the results show the evaluation model based on seepage barrier conditions is closer to the actual situation when analyzing the water breakout situation at the working face.展开更多
The impermeability of isentropic surfaces by the potential vorticity substance （PVS） has often been used to help understand the generation of potential vorticity in the presence of diabatic heating and friction. In ...The impermeability of isentropic surfaces by the potential vorticity substance （PVS） has often been used to help understand the generation of potential vorticity in the presence of diabatic heating and friction. In this study, we examined singularities of isentropic surfaces that may develop in the presence of diabatic heating and the fictitious movements of the isentropic surfaces that are involved in deriving the PVS impermeability theorem. Our results show that such singularities could occur in the upper troposphere as a result of intense convective-scale motion, at the cloud top due to radiative cooling, or within the well-mixed boundary layer. These locally ill-defined conditions allow PVS to penetrate across an isentropic surface. We conclude that the PVS impermeability theorem is generally valid for the stably stratified atmosphere in the absence of diabatic heating.展开更多
Microbiologically⁃induced calcite⁃precipitation(MICP)has been increasingly studied in structural repair including self⁃healing and external applications.Among various MICP pathways,enzymatic urea hydrolysis is suggest...Microbiologically⁃induced calcite⁃precipitation(MICP)has been increasingly studied in structural repair including self⁃healing and external applications.Among various MICP pathways,enzymatic urea hydrolysis is suggested to be applied as external repair instead of self⁃healing.This study comprehensively characterised the enzymatic urea hydrolysis pathway in physical,impermeable,and mechanical rejuvenation of concrete cracks.The visual quality of repaired structures was presented,and the importance of humidity in the remediation of cracks was demonstrated.Moreover,this study investigated the differences in the effectiveness of repair between premixing bacteria with urea and without any premixing.With premixing,there was a concern that the accelerated reactions would precipitate calcite in the shallow spaces of the cracks and impede deeper healing.However,the observed results indicated that neither physical nor impermeable rejuvenation of concrete cracks repair would be detrimentally affected.The results obtained from this study will allow further development in commercialisation since the effectiveness of repair has been confirmed with an improvement in its efficiency.展开更多
The article describes the somatic polymorphism in Crotalaria retusa L. seeds. Each individual may produce yellow dormant seeds, brown quiescent seeds and unviable dark brown ones. Therefore, regarding physiology it is...The article describes the somatic polymorphism in Crotalaria retusa L. seeds. Each individual may produce yellow dormant seeds, brown quiescent seeds and unviable dark brown ones. Therefore, regarding physiology it is a dimorphism. We show that autogamy reduces dimorphism, favoring the formation of dormant seeds. However, the significant variation in dimorphism is seasonal as consequence of increased viability of dormant seeds under drier weather conditions. The variation is a phenotypic response to changes of humidity in the environment during plant reproduction, a mechanism inducing the prevalence of dormant seeds in the dry season and quiescent seeds during the rainy season. The seasonal alternation between dormancy and quiescence in seasonally dry environments has an apparent adaptive value. The chromatic polymorphism increases on the more humid coast and during the rainy season, due to increased mortality of dormant seeds under wetter weather conditions. Unviable seeds accumulate oxidized phenols in their seed coat that possibly act as induced chemical defenses. Its proportion increases with humidity, accentuating polymorphism, also in response to the increase in the predation rate by larvae of U. ornatrix during the rainy season.展开更多
Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a maj...Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.展开更多
The increased application of chemical fertilizers in citrus orchards and the non-point source nitrogen(N) and phosphorus(P)diffusion threaten the fresh water quality of the Three Gorges Reservoir area of China. A 10-y...The increased application of chemical fertilizers in citrus orchards and the non-point source nitrogen(N) and phosphorus(P)diffusion threaten the fresh water quality of the Three Gorges Reservoir area of China. A 10-year field trial on sloping citrus lands was conducted to evaluate five protection methods for reducing N and P losses: 1) intercropping with perennial white clover(CW); 2) straw mulching of the soil surface(CS); 3) intercropping with yellow daylily contour hedgerows(CH); 4) an impermeable membrane buried in the soil along the contour lines(CM); and 5) intercropping with a rotation of wheat and peanut(CWP). An area of conventional citrus management was also maintained as the control(CK). The results showed that CM and CH were the most effective methods for reducing surface runoff. The sediment yield were reduced at the highest rate by CW and CH and was also significantly reduced by CS. Reduced runoff volume and sediment yield were the crucial mechanism for the reductions in N and P losses. Compared with the control, CW, CS, CH, and CM reduced annual runoff by 9%, 13%, 25%, and 30%, sediment yield by 77%, 55%, 71%, and 28%,N loss by 10%, 23% 36%, and 37%, and P loss by 39%, 31%, 27%, and 25%, respectively. CW, CS, CH, and CM were effective in reducing N and P losses from the sloping citrus land. However, over the long-term, surface soil nutrient accumulation in CW, CS, and CH diminished the benefit of those methods in reducing N and P losses. In addition, CWP increased soil erosion and nutrient loss,which showed that citrus intercropping with other crops was an unsuitable method for citrus sloping land in the Three Gorges area.展开更多
Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled ...Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled discrete element method(DEM)and computational fluid dynamics(CFD)approach is adopted to model suffusion in multi-layered soils with different fines contents,and soils with one or more impermeable zones.The parameters of the CFD-DEM model are first calibrated with the classic Ergun test and a good match with experiment is obtained.Then suffusion in multi-layered soils with different fines contents and impermeable zones is simulated and discussed.The simulation results show that,for soils with multiple layers,the cumulative eroded mass is mainly determined by the fines content of the bottom layer.In general,the higher the fines content of the bottom soil layer,the higher the cumulative eroded mass.In addition,suffusion is more severe if the fines content of the layer above is decreased.Impermeable zones inside soil specimens can increase the flow velocity around those zones,facilitating the migration of fine particles and intensifying suffusion.展开更多
A kind of high impermeable and crack-resistance chemical admixture ( HICRCA) was prepared , which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreb...A kind of high impermeable and crack-resistance chemical admixture ( HICRCA) was prepared , which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances: (1) perfect workability: slump is more than 22cm, theslump afar 3h is about 16cm; (2) high impermeability:for the mortar, the pervious height under a water pressure of 1.5MPa is 1.5cm,for the concrete, the pervious height under a water pressure of 5.0MPa is 2. 2cm;(3) high crack-resistance: there is a micro-expansion at the age of 90d; (4) high compressivestrength: compared with the controlled concrete, the compressive strengths at the age of 3d and 2Sd are improved by 66.4% and 62.0% , respectively. At the same time, the effects of different curing condition on mortar and concrete expansive andshrinkage performance were studied. In addition, the impermeable and crack-resistance mechanism, was investigatedin the present paper.展开更多
基金Funded By the Wuhan Natural Science Foundation for Distin guished Young Scholars(No.20035002016 13)
文摘The impermeability mechanism of water-proof self-compacting concrete (WPSCC )w as studied. The mechanism and influential factors, such as water-cement ratio(w /c), dosage of powder, superplasticizer, sand content, aggregate conte nt, fly ash, UEA, PP fiber, on compactibility and crack resistance of WPSCC were analyzed. A type of WPSCC successfully applied in tunnel liner with its validit ies, conveniences and economies by mockup test was developed and optimized. Expe rimental results show that the WPSCC has good workability, mechanical properties and impermeability when reasonable requirements are fulfilled.
基金Funded by the National Nature Science Foundation of China(Nos.51468053,51772153,11662015,and 51769026)。
文摘We aimed to reuse the propylene oxide sludge(POS).Propylene oxide sludge shell-aggregate(POSS-A)and propylene oxide sludge gradient shell-aggregate(POSGS-A)whose main hydrated phase is tobermorite were successfully manufactured by the hydrothermal synthesis of POS and silica materials under the condition of autoclaved(180℃,1.0 MPa)curing.Influences of pre-wetting time of coarse aggregate and pressure application mode on the different concretes were investigated.The experimental results show that the concrete with POSS-A as coarse aggregate(POSS-A concrete),the concrete with POS gradient shell-aggregate as coarse aggregate(POSGS-A concrete),sintered aggregate concrete and common concrete,all have excellent impermeability performance whatever the pre-wetting time of coarse aggregate is 0.5 h or 24 h,and the pre-wetting time of coarse aggregate has a negligible influence on the concrete.The influence degree of pressure application mode on the impermeability performance of the sintered aggregate concrete is the greatest among three kinds of concrete,which has a negligible influence on impermeability performance of the other concretes.POSGS-A can be used as a green building light aggregate in hydraulic concrete.
文摘The relationship of unstable osmosis coefficient to time and osmosis deep is derived from the osmosis equation in this paper. Mercury porosimeter is used to study the pore structure of cement mortar. The method of volume density is used to determine the changes of specific pore volume, and therelation between pore structure and impermeability is analyzed. Although the drythermal curing method has many advantages over other curing method, the directional pore along the direction of evaporization of water is formed inside concrete. The harmful pore above 2000(?) is increased and the average diameter of pore rises. As a result, the mortar impermeability loses seriously.
基金Funded by National High-Tech Research and Development Program of China(No.2005AA332010)
文摘Impermeability of tunnel structural material after exposure to high temperature determines residual service life and security. The present study explores impermeability deterioration and water absorption change (expressed as w(T, t)) of tunnel structural material after exposure to 200℃, 300℃, 400℃, 500℃, and 600℃respectively. Structural cementitious material was devised according to the requirements of segment used in Yangtze River tunnel of Wuhan which has been in constructing. Effect of high temperature on impermeability is evaluated by impermeability deterioration factor (abbr. IDF) and w(T, t).Testing results indicate that impermeability of concrete decreases with the increase of temperature up to 600℃, and serious impermeability deterioration occurs at temperature above 300℃. Furthermore, concrete with higher impermeability is more sensitive to high temperature above 400℃.
基金the Applied Research Project of National Outstanding Young Scientists Fund Grant(51725802)National Natural Science Foundation of China-High Speed Rail Joint Fund(U1934208)Jiangxi Provincial Natural Science Foundation Key Project(20192ACB20001).
文摘The impermeability of concrete of the exterior wall of the underground tunnel in water-rich stratum is a key concern of engineers.Taking the Aixihu highway tunnel in Nanchang city as an example,the impermeability of the concrete in the side wall of the highway tunnel is tested,through multiple tests,such as the embedded steel pipe,water injection,and field observation.The results show that,under the action of 2mpa of water pressure,no water flow permeates from the side wall of the concrete tunnel,indicating that the impermeable performance of concrete tunnel in this section meets the engineering requirements,and hoping that this research can be used as a reference for other similar projects.
基金National Natural Science Foundation of China(Grant No.22175059)to provide fund for conducting experiments.
文摘The migration of nitroglycerin(NG) has always been the critical issue that harmfully impacts the structural integrity and operational reliability of the solid rocket motor, which is mainly composed by Nitrate Ester Plasticized Polyether(NEPE) propellant/Hydroxyl-terminated Polybutadiene(HTPB) liner/Ethylene Propylene Diene Monomer(EPDM) insulation bonding system. This paper proposes an innovative surface modification method attempting to modify the EPDM insulation layer coated with reduced graphene oxide(RGO), which exhibits ability to weaken the NG absorption by EPDM insulation layer,blocking the pathway of NG migration into EPDM insulation materials. The microstructure of RGO-coated layer was analyzed and the formation mechanism was investigated. The RGO-coated layer is well bonded to the HTPB liner, and its anti-migration performance to NG at different temperatures has been evaluated. Comparing with blank samples under the same storage conditions, the RGO-coated layers can reduce the diffusion coefficient of NG by up to 87.3% and increase the diffusion activation energy of NG by14.8 kJ,mol^(-1). This research provides a new strategy to effectively inhibit NG migration in NEPE propellant/HTPB liner/EPDM insulation bonding system.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3702200)the National Natural Science Foundation of China(Grant Nos.42372279 and U2267218)the Natural Science Foundation of Anhui Province(Grant No.JZ2022AKZR0451).
文摘Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater contaminant remediation project?This study evaluates the necessity of impermeable curtains for groundwater contaminant remediation projects.Specifically,it considers remediation efforts based on the Pump and Treat(PAT)technique under various hydrogeological conditions and contaminant properties,comparing the total remediation cost and effectiveness.To further investigate,a multi-objective simulation and optimization model,utilizing the Multi-Objective Fast Harmony Search(MOFHS)algorithm,was employed to identify optimal groundwater remediation system designs that without impermeable curtains.Both a two-dimensional(2-D)hypothetical example and a three-dimensional(3-D)field example were used to assess the necessity of constructing impermeable curtains.The 2-D hypothetical example demonstrated that the installation of impermeable curtain is justified only when the dispersivity(αL)of the contaminant reaches 100 meters.In most cases,particularly at sites with porosity(n)under 0.3,alternative,more cost-effective,and efficient remediation strategies may be available,making impermeable barriers unnecessary.The optimization results of the 3-D field example further corroborate the conclusions derived from the 2-D hypothetical example.These findings provide valuable guidance for more scientifically informed,reasonable,and cost-effective groundwater contaminant remediation projects.
基金Project supported by the National Natural Science Foundation of China (Grant Nos: 50174011 10172028) the Science Tech. Research Program of Heilongjiang Provincial Education Department (Grant No: 10531032).
文摘The transient flow mathematical model of arbitrary shaped heterogeneous reservoirs with impermeability barrier is proposed in this paper. In order to establish this model, the perturbation method is employed and the solution of model is expanded into a series in powers of perturbation parameter. By using the Boundary Element Method (BEM) and Duhamel principle, wellbore pressure with effects of skins and wellbore storage is obtained. The type curves are plotted and analyzed considering effects of heterogeneity, arbitrary shape and impermeable barriers. Finally, the results obtained by perturbation boundary element method is compared with the analytical solution and is available for the transient pressure analysis of arbitrary shaped reservoirs.
文摘The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and mortar mixtures was implemented to improve their strength and waterproofing, respectively, using compression and water absorption tests according to their corresponding standards (ASTM C1231, ASTM D2938, and ASTM C1585). The samples were evaluated at different concentrations and curing ages. In addition, different sand/cement ratios were considered for the mortar. The results revealed that there was a 9.4% increase in compressive strength in concrete and a 23.7% reduction in water absorption in mortar for the 5:1 ratio. These changes would be the result of the interaction of the nanoporous additive in the atomic crystal structure of the material demonstrating the nanotechnological nature of allophane.
文摘Cementitious capillary crystalline waterproof materials(CCCW for short)offer durability and excellent waterproofing properties,making them a popular option for building waterproofing.Some scholars have studied the proportioning of such materials.However,these studies lack the relationship between the impermeability pressure of mortar and the components,and the mechanism of action is somewhat debatable.Therefore,we adopted a two-step method in our experiments.Firstly,we screened out the components that significantly impact impermeability from a variety of active components by orthogonal test.We then optimized the design of the active group ratio using the simplex lattice method.Lastly,we conducted a performance test of the optimal ratio and explored the waterproofing mechanism of homemade CCCW.
文摘This study aimed to devise strategies for alleviating the detrimental impacts of floods in the vicinity of a dike. Experiments were conducted in an open rectangular channel to investigate the flow dynamics under varying dike conditions. To address concerns related to intense whirls and concentrated flow around the dike head, comparative analysis was performed in terms of flow structures and energy reduction around I-shaped and T-shaped dikes with two ratios of wing length (lw) to dike length (ld) (lw/ld = 1.41 and 2.43). The T-shaped dike wings were equipped with diverse designs: angled footing, delta vane, and streamlined tapered, resulting in elevated backwater in front of the dike, reduced velocity, and enhanced energy reduction. The findings indicated that elongating the wing reciprocally affected the depth-averaged velocity (at the dike head and near the adjacent dike bank), concurrently impacting flow deflection, backwater rise, and energy reduction rate. The T-shaped dike, specifically with an angled footing (lw/ld = 2.43), yielded optimal outcomes. These included significant reductions in maximum energy (46%), tip velocity (98%), and dike adjacent bank velocity (90%), as well as significant flow deflection towards the mainstream, outperforming the I-shaped impermeable dike. The proposed solutions exhibit efficacy in mitigating rapid deterioration during floods, securing both the dike head and the neighboring bank to avert failures in high-energy flow.
基金Funded by the Scientific and Technological Project of Hubei Province(2004BCS005)
文摘The self-healing action of a permeable crystalline coating on the po rous mortar was investigated by two times impermeability test. Moreover, the sel f-healing mechanism of cement-based materials with the permeable crystalline c oating was studied by SEM. The results indicate that the permeable crystalline c oating not only seals the pores and cracks in mortar during its curing process, but also heals the permeable pathway caused by first impermeability test or crac ks produced by freeze-thaw cycles. Therefore, cement-based materials can be im proved by the permeable crystalline coating for the self-healing function. SEM images prove that the self-healing function is realized by generating a great q uantity of non-soluble dendritic crystalline within the pores and cracks, which prevents the penetration of water and other liquids.
基金financial support from the National Natural Science Foundation of China(No.41702326)the Jiangxi Provincial Natural Science Foundation(No.20202ACB214006)+2 种基金the Innovative Experts,Long-term Program of Jiangxi Province(No.jxsq2018106049)the Supported by Program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technologythe Innovation Fund Designated for Graduate Students of Jiangxi Province(No.YC2020-S451)。
文摘With the gradual depletion of shallow coal resources,the Yanzhou mine in China will enter the lower coal seam mining phase.However,as mining depth increases,lower coal seam mining in Yanzhou is threatened by water inrush in the Benxi Formation limestone and Ordovician limestone.The existing prediction models for the water burst at the bottom of the coal seam are less accurate than expected owing to various controlling factors and their intrinsic links.By analyzing the hydrogeological exploration data of the Baodian lower seam and combining the results of the water inrush coefficient method and the Yanzhou mine pressure seepage test,an evaluation model of the seepage barrier capacity of the fault was established.The evaluation results show the water of the underlying limestone aquifer in the Baodian mine area mainly threatens the lower coal mining through the fault fracture zone.The security of mining above confined aquifer in the Baodian mine area gradually decreases from southwest to northeast.By comparing the water inrush coefficient method and the evaluation model of fault impermeability,the results show the evaluation model based on seepage barrier conditions is closer to the actual situation when analyzing the water breakout situation at the working face.
基金supported bythe National Science Foundation (USAGrant No. ATM-0758609)+1 种基金the National Aeronautics and Space Administration (USAGrant No. NNG05GR32G)
文摘The impermeability of isentropic surfaces by the potential vorticity substance （PVS） has often been used to help understand the generation of potential vorticity in the presence of diabatic heating and friction. In this study, we examined singularities of isentropic surfaces that may develop in the presence of diabatic heating and the fictitious movements of the isentropic surfaces that are involved in deriving the PVS impermeability theorem. Our results show that such singularities could occur in the upper troposphere as a result of intense convective-scale motion, at the cloud top due to radiative cooling, or within the well-mixed boundary layer. These locally ill-defined conditions allow PVS to penetrate across an isentropic surface. We conclude that the PVS impermeability theorem is generally valid for the stably stratified atmosphere in the absence of diabatic heating.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51278157).
文摘Microbiologically⁃induced calcite⁃precipitation(MICP)has been increasingly studied in structural repair including self⁃healing and external applications.Among various MICP pathways,enzymatic urea hydrolysis is suggested to be applied as external repair instead of self⁃healing.This study comprehensively characterised the enzymatic urea hydrolysis pathway in physical,impermeable,and mechanical rejuvenation of concrete cracks.The visual quality of repaired structures was presented,and the importance of humidity in the remediation of cracks was demonstrated.Moreover,this study investigated the differences in the effectiveness of repair between premixing bacteria with urea and without any premixing.With premixing,there was a concern that the accelerated reactions would precipitate calcite in the shallow spaces of the cracks and impede deeper healing.However,the observed results indicated that neither physical nor impermeable rejuvenation of concrete cracks repair would be detrimentally affected.The results obtained from this study will allow further development in commercialisation since the effectiveness of repair has been confirmed with an improvement in its efficiency.
文摘The article describes the somatic polymorphism in Crotalaria retusa L. seeds. Each individual may produce yellow dormant seeds, brown quiescent seeds and unviable dark brown ones. Therefore, regarding physiology it is a dimorphism. We show that autogamy reduces dimorphism, favoring the formation of dormant seeds. However, the significant variation in dimorphism is seasonal as consequence of increased viability of dormant seeds under drier weather conditions. The variation is a phenotypic response to changes of humidity in the environment during plant reproduction, a mechanism inducing the prevalence of dormant seeds in the dry season and quiescent seeds during the rainy season. The seasonal alternation between dormancy and quiescence in seasonally dry environments has an apparent adaptive value. The chromatic polymorphism increases on the more humid coast and during the rainy season, due to increased mortality of dormant seeds under wetter weather conditions. Unviable seeds accumulate oxidized phenols in their seed coat that possibly act as induced chemical defenses. Its proportion increases with humidity, accentuating polymorphism, also in response to the increase in the predation rate by larvae of U. ornatrix during the rainy season.
文摘Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.
基金supported by the Eco-environmental Monitoring Network of the Three Gorges Project, Three Gorges Project Construction Committee of the State Council, Chinathe National Natural Science Foundation of China (Nos. 40871147 and 30870410)
文摘The increased application of chemical fertilizers in citrus orchards and the non-point source nitrogen(N) and phosphorus(P)diffusion threaten the fresh water quality of the Three Gorges Reservoir area of China. A 10-year field trial on sloping citrus lands was conducted to evaluate five protection methods for reducing N and P losses: 1) intercropping with perennial white clover(CW); 2) straw mulching of the soil surface(CS); 3) intercropping with yellow daylily contour hedgerows(CH); 4) an impermeable membrane buried in the soil along the contour lines(CM); and 5) intercropping with a rotation of wheat and peanut(CWP). An area of conventional citrus management was also maintained as the control(CK). The results showed that CM and CH were the most effective methods for reducing surface runoff. The sediment yield were reduced at the highest rate by CW and CH and was also significantly reduced by CS. Reduced runoff volume and sediment yield were the crucial mechanism for the reductions in N and P losses. Compared with the control, CW, CS, CH, and CM reduced annual runoff by 9%, 13%, 25%, and 30%, sediment yield by 77%, 55%, 71%, and 28%,N loss by 10%, 23% 36%, and 37%, and P loss by 39%, 31%, 27%, and 25%, respectively. CW, CS, CH, and CM were effective in reducing N and P losses from the sloping citrus land. However, over the long-term, surface soil nutrient accumulation in CW, CS, and CH diminished the benefit of those methods in reducing N and P losses. In addition, CWP increased soil erosion and nutrient loss,which showed that citrus intercropping with other crops was an unsuitable method for citrus sloping land in the Three Gorges area.
基金This work is supported by the Research Grants Council(RGC)of Hong Kong(No.15226322)the National Natu‐ral Science Foundation of China(No.42207210).
文摘Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled discrete element method(DEM)and computational fluid dynamics(CFD)approach is adopted to model suffusion in multi-layered soils with different fines contents,and soils with one or more impermeable zones.The parameters of the CFD-DEM model are first calibrated with the classic Ergun test and a good match with experiment is obtained.Then suffusion in multi-layered soils with different fines contents and impermeable zones is simulated and discussed.The simulation results show that,for soils with multiple layers,the cumulative eroded mass is mainly determined by the fines content of the bottom layer.In general,the higher the fines content of the bottom soil layer,the higher the cumulative eroded mass.In addition,suffusion is more severe if the fines content of the layer above is decreased.Impermeable zones inside soil specimens can increase the flow velocity around those zones,facilitating the migration of fine particles and intensifying suffusion.
基金Funded by Natural Science Foundation of Hubei Province (No.2000J027)
文摘A kind of high impermeable and crack-resistance chemical admixture ( HICRCA) was prepared , which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances: (1) perfect workability: slump is more than 22cm, theslump afar 3h is about 16cm; (2) high impermeability:for the mortar, the pervious height under a water pressure of 1.5MPa is 1.5cm,for the concrete, the pervious height under a water pressure of 5.0MPa is 2. 2cm;(3) high crack-resistance: there is a micro-expansion at the age of 90d; (4) high compressivestrength: compared with the controlled concrete, the compressive strengths at the age of 3d and 2Sd are improved by 66.4% and 62.0% , respectively. At the same time, the effects of different curing condition on mortar and concrete expansive andshrinkage performance were studied. In addition, the impermeable and crack-resistance mechanism, was investigatedin the present paper.
