Water-rock interaction and groundwater mixing are important phenomena in understanding hydrogeological systems and the stability of rock slopes especially those consisting largely of moderately watersoluble minerals l...Water-rock interaction and groundwater mixing are important phenomena in understanding hydrogeological systems and the stability of rock slopes especially those consisting largely of moderately watersoluble minerals like calcite. In this study, the hydrogeological and geochemical evolutions of groundwater in a limestone quarry composed of three strata: limestone layer(covering), interbedded layer under the covering layer, and slaty greenstone layer(basement) were investigated. Water-rock interaction in the open-pit limestone quarry was evaluated using PHREEQC, while hierarchical cluster analysis(HCA)and principal component analysis(PCA) were used to classify and identify water sources responsible for possible groundwater mixing within rock layers. In addition, Geochemist's Workbench was applied to estimate the mixing fractions to clarify sensitive zones that may affect rock slope stability. The results showed that the changes in Ca2+and HCO3àconcentrations of several groundwater samples along the interbedded layer could be attributed to mixing groundwater from the limestone layer and that from slaty greenstone layer. Based on the HCA and PCA results, groundwaters were classified into several types depending on their origin:(1) groundwater from the limestone layer(LO),(2) mixed groundwater flowing along the interbedded layer(e.g., groundwater samples L-7, L-11, S-3 and S-4), and(3) groundwater originating from the slaty greenstone layer(SO). The mixing fractions of 41% LO: 59% SO, 64% LO: 36% SO, 43%LO: 57% SOand 25% LO: 75% SOon the normal days corresponded to groundwaters L-7, L-11, S-3 and S-4,respectively, while the mixing fractions of groundwaters L-7 and L-11(61% LO: 39% SOand 93% LO: 7% SO,respectively) on rainy days became the majority of groundwater originating from the limestone layer.These indicate that groundwater along the interbedded layer significantly affected the stability of rock slopes by enlarging multi-breaking zones in the layer through calcite dissolution and inducing high water pressure, tension cracks and potential sliding plane along this layer particularly during intense rainfall episodes.展开更多
Wave-current interaction and its effects on the hydrodynamic environment in the Beibu Gulf(BG) have been investigated via employing the Coupled Ocean–Atmosphere–Wave–Sediment Transport(COAWST) modeling system. The ...Wave-current interaction and its effects on the hydrodynamic environment in the Beibu Gulf(BG) have been investigated via employing the Coupled Ocean–Atmosphere–Wave–Sediment Transport(COAWST) modeling system. The model could simulate reasonable hydrodynamics in the BG when validated by various observations.Vigorous tidal currents refract the waves efficiently and make the seas off the west coast of Hainan Island be the hot spot where currents modulate the significant wave height dramatically. During summer, wave-enhanced bottom stress could weaken the near-shore component of the gulf-scale cyclonic-circulation in the BG remarkably, inducing two major corresponding adjustments: Model results reveal that the deep-layer cold water from the southern BG makes critical contribution to maintaining the cold-water mass in the northern BG Basin.However, the weakened background circulation leads to less cold water transported from the southern gulf to the northern gulf, which finally triggers a 0.2℃ warming in the cold-water mass area;In the top areas of the BG, the suppressed background circulation reduces the transport of the diluted water to the central gulf. Therefore, more freshwater could be trapped locally, which then triggers lower sea surface salinity(SSS) in the near-field and higher SSS in the far-field.展开更多
This study of the gneiss-fractured-rock aquifer in Yaoundé capital of Cameroon determines: the aquifer setting-flow systems, the aquifer type, seasonal variations in rock-water interactions, evolution of the hydr...This study of the gneiss-fractured-rock aquifer in Yaoundé capital of Cameroon determines: the aquifer setting-flow systems, the aquifer type, seasonal variations in rock-water interactions, evolution of the hydrogeochemical processes, physicochemical parameters and the suitability for domestic-agro-industrial use of the groundwater. Physicochemical field tests were carried out on 445 wells during four seasons for EC, pH, TDS, Temperature and static water level from July 2016 to May 2017. 90 well samples were analyzed 45 samples per season: wet/dry. 38 borewell logs were used together with structural data to determine the aquifer setting. The field physico-chemical and laboratory analysis data of well samples were mounted unto various GIS software platforms: Global mapper, AqQa, Aquachem, Rockworks, Logplot7, Surfer and ArcGIS, to get indices/parameters/figures, by use of Durov’s, Piper’s and Gibbs diagrams, Water quality index WQI, USSL ratio, Sodium Absorption ratio SAR, Percent sodium %Na, Kelly Ratio KR, Magnesium Absorption Ratio MAR, Total Hardness TH, Residual Sodium Carbonate RSC and Permeability Index PI that were determined. The process of groundwater ions acquisition is three-fold: by recharge through atmospheric precipitation, by ion exchange/simple dissolution between the rock-groundwater and by groundwater mixing in its flow path. Water types are Ca-HCO3, Mg-HCO3 and Mg-Cl while hydrogeochemical facies are Ca-Mg-HCO3 and Ca-Mg-Cl-SO4. Most water samples are fresh, potable and soft all seasons. The hydrogeological conceptual model is that of a three-layered single phreatic fractured-rock-aquifer while other researchers postulated a two-aquifer, phreatic and semi-confined, two-layered model.展开更多
Water–rock interaction(WRI)is a topic of interest in geology and geotechnical engineering.Many geological hazards and engineering safety problems are severe under the WRI.This study focuses on the water weakening of ...Water–rock interaction(WRI)is a topic of interest in geology and geotechnical engineering.Many geological hazards and engineering safety problems are severe under the WRI.This study focuses on the water weakening of rock strength and its infuencing factors(water content,immersion time,and wetting–drying cycles).The strength of the rock mass decreases to varying degrees with water content,immersion time,and wetting–drying cycles depending on the rock mass type and mineral composition.The corresponding acoustic emission count and intensity and infrared radiation intensity also weaken accordingly.WRI enhances the plasticity of rock mass and reduces its brittleness.Various microscopic methods for studying the pore characterization and weakening mechanism of the WRI were compared and analyzed.Various methods should be adopted to study the pore evolution of WRI comprehensively.Microscopic methods are used to study the weakening mechanism of WRI.In future work,the mechanical parameters of rocks weakened under long-term water immersion(over years)should be considered,and more attention should be paid to how the laboratory scale is applied to the engineering scale.展开更多
The interactions on gold active and migratory quantities and rates between tuffaceous slate and solu tions with different compositions were experimentally studied at 200 ℃, 20 MPa, in a high pressure apparatus. After...The interactions on gold active and migratory quantities and rates between tuffaceous slate and solu tions with different compositions were experimentally studied at 200 ℃, 20 MPa, in a high pressure apparatus. After reaction, tuffaceous slate became light colored and soft, and its mass density reduced. The amount of gold extracted from tuffaceous slate ranges widely, from 0 027 to 0 234 μg/g. Chlorine solution may activate appreciable amount of gold, and the gold migratory rate is high enough, from 50 70% to 92 30%, which reveals that sulphur and chlorine work together in solutions to accelerate gold activation and migration, and to realize gold mineralization in favorable places.展开更多
To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test(HPPT),including measuring sensors of pore water pressure and displ...To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test(HPPT),including measuring sensors of pore water pressure and displacement of the rock mass,was designed according to the hydrogeological condition of Heimifeng pumped storage power station.With the assumption of radial water flow pattern in the rock mass during the HPPT,a theoretical formula was presented to estimate the coefficient of permeability of the rock mass using water pressures in injection and measuring boreholes.The variation in permeability of the rock mass with the injected water pressure was studied according to the suggested formula.By fitting the relationship between the coefficient of permeability and the injected water pressure,a mathematical expression was obtained and used in the numerical simulations.For a better understanding of the relationship between the pore water pressure and the displacement of the rock mass,a 3D numerical method based on a coupled hydro-mechanical theory was employed to simulate the response of the rock mass during the test.By comparison of the calculated and measured data of pore water pressure and displacement,the deformation behaviors of the rock mass were analyzed.It is shown that the variation of displacement in the fractured rock mass is caused by water flow passing through it under high water pressure,and the rock deformation during the test could be calculated by using the coupled hydro-mechanical model.展开更多
Hydrogeochemical simulation is an effective method to study water-rock interaction. In this paper, PHREEQM was used for the simulation of water-rock interaction under water flooding in the Renqiu Oilfield. Calculated ...Hydrogeochemical simulation is an effective method to study water-rock interaction. In this paper, PHREEQM was used for the simulation of water-rock interaction under water flooding in the Renqiu Oilfield. Calculated results revealed that when fresh water was injected into the reservoir, Cl\+- and Na\++ would decrease without involvement in water-rock interaction. Erosion to dolomite will lead to an increase in Ca\+\{2+\}, Mg\+\{2+\} and CaHCO\++\-3. Saturation index of calcite and aragonite decreased first and then increased. With fresh water accounting for up to 70%, mixed water has the strongest erosion ability. Deoiled water has erosion ability under high temperature and high partial pressure of CO\-2. Pyrite and gypsum were sensitive to deoiled water, which can cause the dissolution of pyrite and the precipitation of gypsum. Micrographs revealed a great deal of information about water-rock interaction.展开更多
In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of ...In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of different slope angles. By exerting static and dynamic loads on the specimens, the mechanical characteristics of rock mass with fissure water under these loads can be analyzed. Our experimental results indicate that the static compressive strength of saturated fractured rock mass is related to the slope angle. The lowest compressive strength of fractured rock mass occurs when the slope angle is 45°, while the highest strength occurs when the specimen has no fractures. Fissure water can weaken the strength of rock mass. The softening coefficient does not vary with the slope angle and type of load. The hydrodynamic pressure of fractured rock mass gradually increases with an increase in dynamic load. For a 0° slope angle, the hydrodynamic pressure reaches its highest level. When the slope angle is 90°, the hydro-dynamic pressure is the lowest.展开更多
Systematic analysis and comparative study of the chemical compositions of rocks and ores from the main types of zeolite deposits in the surroundings of the Songliao Basin have shown that the process of formation of ze...Systematic analysis and comparative study of the chemical compositions of rocks and ores from the main types of zeolite deposits in the surroundings of the Songliao Basin have shown that the process of formation of zeolite from volcanic and pyroclastic rocks is generally characterized by the relative purification of SiO\-2, i.e., SiO\-2/Al\-2O\-3 ratios tend to increase, alkali earth elements (CaO+MgO) and H\-2O are relatively enriched, and the alkali metals (K\-2O+Na\-2O) are depleted in their total amount. The alkali metals K and Na follow different rules of migration and enrichment during the formation of mordenite and clinoptilolite. In the process of formation of mordenite more Na\++ will be imported and K\++ will be lost remarkably. On the contrary, in the process of formation clinoptilolite more K\++ will be incorporated and Na\++ will become obviously depleted.展开更多
Based on the theoretical modelling of water-rock δD-δ18O isotopic exchange process,the evolution and sources of ore-forming fluid in four metallogenic epochs of the Jinduicheng su-perlarge-scale porphyry-type molybd...Based on the theoretical modelling of water-rock δD-δ18O isotopic exchange process,the evolution and sources of ore-forming fluid in four metallogenic epochs of the Jinduicheng su-perlarge-scale porphyry-type molybdenum deposit were investigated. It was revealed that in thepre-metallogenic and early-metallogenic epehs, the ore-forming fluid was a residual fluid derived from magmatic water-wall rock interaction at middle to high temperatures (T = 250 -500℃) and lower W/R ratios (0. 1 > = W/R >0.001 ), while in the metallogenic and Post-metallogenic epochs, the ore-forming nuid was a residual fluid derived from meteoric water-wallrock interaction at midd1e to lower temperatures (T = 150 - 310℃ ) and relatively high W/Rratios (0. 5 >W/R≥0.1 ). The meteoric water played an important role in molybdenum min-eralization, and at the main metallogenic epoch the W/R ratio reached its maximum value.展开更多
Based on analyses of experimental results of water jet drilling, the fluid motion law in rock pores and the tendency of energy distribution, the rock-breaking process under high pressure water jet drilling has been s...Based on analyses of experimental results of water jet drilling, the fluid motion law in rock pores and the tendency of energy distribution, the rock-breaking process under high pressure water jet drilling has been studied systematically. The research indicates that the main interaction between the rock and water jet is interface coupling, that the impacting load and the static pressure of the water jet act together to make the rock break, and that the stress wave is the main factor. Water jet drilling can be divided into two stages: At the initial stage, the stress wave plays the main role and most of the rock breaking takes place; at the later stage, the existing rock defects, for instance, micro-holes and micro-cracks, are propagated and merged to make macroscopic damage, and then the diameter of the jet-drilled hole is expanded.展开更多
Size and quantity of fractured zone and non-fractured zone are controlled by cracks contained in deep rock masses. Zonal disintegration mechanism is strongly dependent on the interaction among cracks. The strong inter...Size and quantity of fractured zone and non-fractured zone are controlled by cracks contained in deep rock masses. Zonal disintegration mechanism is strongly dependent on the interaction among cracks. The strong interaction among cracks is investigated using stress superposition principle and the Chebyshev polynomials expansion of the pseudo-traction. It is found from numerical results that crack nucleation, growth and coalescence lead to failure of deep crack- weakened rock masses. The stress redistribution around the surrounding rock mass induced by unloading excavation is studied. The effect of the excavation time on nucleation, growth, interaction and coalescence of cracks was analyzed. Moreover, the influence of the excavation time on the size and quantity of fractured zone and non-fractured zone was given. When the excavation time is short, zonal disintegration phenomenon may occur in deep rock masses. It is shown from numerical results that the size and quantity of fractured zone increase with decreasing excavation time, and the size and quantity of fractured zone increase with the increasing value of in-situ geostress.展开更多
The effect of water compressibility on the seismic responses of arch dams is not well understood.In this paper,a numerical model is developed with rigorous representation of the dynamic interaction between arch dam-wa...The effect of water compressibility on the seismic responses of arch dams is not well understood.In this paper,a numerical model is developed with rigorous representation of the dynamic interaction between arch dam-water- rock foundation.The model is applied to the seismic response analysis of an arch dam with a height of 292m designed to a seismic intensity of IX.It is shown that consideration of the water compressibility clearly decreases the stress responses at key positions of the dam,while the added mass model gives a conservative estimate.展开更多
An accurate and efficient numerical method for solving the crack-crack interaction problem is presented. The method is mainly by means of the dislocation model, stress superposition principle and Chebyshev polynomial ...An accurate and efficient numerical method for solving the crack-crack interaction problem is presented. The method is mainly by means of the dislocation model, stress superposition principle and Chebyshev polynomial expansion of the pseudo-traction. This method can be applied to compute the stress intensity factors of multiple kinked cracks and multiple rows of periodic cracks as well as the overall strains of rock masses containing multiple kinked cracks under complex loads. Many complex computational examples are given. The dependence of the crack-crack interaction on the crack configuration, the geometrical and physical parameters, and loads pattern, is investigated. By comparison with numerical results under confining pressure unloading, it is shown that the crack-crack interaction under axial-dimensional unloading is weaker than those under confining pressure unloading. Numerical results for single faults and crossed faults show that the single faults are more unstable than the crossed faults. It is found from numerical results for different crack lengths and different crack spacing that the interaction among kinked cracks decreases with an increase in length of the kinked cracks and the crack spacing under axial-dimensional unloading.展开更多
Water sealing performance is important for underground water-sealed oil storage(UWSOS).The key issues concerning water sealing performance mainly include the permeability of fractured rock mass(FRM),water-sealed safet...Water sealing performance is important for underground water-sealed oil storage(UWSOS).The key issues concerning water sealing performance mainly include the permeability of fractured rock mass(FRM),water-sealed safety(WSS),water curtain performance,and prediction and control of water inflow.This paper reviews the progress of above four key issues on water sealing performances.First,the permeability of an FRM is the basis of water sealing performance,and several commonly used permeability test methods and spatial variation characteristics of permeability are outlined.Second,the current water sealing criteria are compared,and the evaluation methods of WSS are summarized.Third,the design parameters and efficiency evaluation of water curtain systems(WCSs)are introduced.The water inflow of oil storage caverns(OSCs)can reflect the water sealing effect,and the prediction methods and control measures of water inflow are also summarized.Finally,the advantages and disadvantages of the current research are discussed,and the potential research directions are pointed out,such as optimization of water sealing criteria and FRM model,quantitative evaluation of WCS efficiency,accurate prediction of water inflow,and improvement of grouting technology.展开更多
In order to elucidate the origin and migration of basinal brines in the Bachu Bulge, Tarim Basin, we have carried out analyses on chemical composition, and boron, hydrogen and oxygen isotopes of formation waters toget...In order to elucidate the origin and migration of basinal brines in the Bachu Bulge, Tarim Basin, we have carried out analyses on chemical composition, and boron, hydrogen and oxygen isotopes of formation waters together with the XRD of clay minerals from the Paleozoic strata. The waters show Ca, B, Li and Sr enrichment and SO4 depletion in the Carboniferous and Ordovician and K enrichment in part of the Ordovician relative to seawater. The relationship between δD and δ^18O shows that all the data of the waters decline towards the Global Meteoric Water Line with the intersection of them close to the present-day local meteoric water, suggesting that modern meteoric water has mixed with evaporated seawater. The ^87Sr/^86Sr ratios range from 0.7090 to 0.7011, significantly higher than those of the contemporary seawater. The δ^11B values range from +19.7 to +32.3‰, showing a decrease with the depth and B concentrations. The results suggest that isotopically distinct B and Sr were derived from external sources. However, since the percentages of illite are shown to increase with depth among clay minerals in the study area, i.e., illite is due to precipitation rather than leaching during deeper burial, it is unlikely for illite to have contributed a significant amount of B to the waters. Thus, B with low δ^11B values is interpreted to have been added mainly from thermal degradation of kerogen or the basalts in the Cambrian and Lower Ordovician.展开更多
To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom...To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.展开更多
Oilfield waters from Cenozoic and Mesozoic terrestrial and Paleozoic marine environments in the Tarim Basin show no obvious difference in water chemistry except Br and isotopic compositions. The Paleozoic marine strat...Oilfield waters from Cenozoic and Mesozoic terrestrial and Paleozoic marine environments in the Tarim Basin show no obvious difference in water chemistry except Br and isotopic compositions. The Paleozoic marine strata have higher Br concentrations than the terrestrial sediments, and the lack of obvious relationship between Br and Ⅰ suggests that Br is not, for the most part, derived from the degradation of organic matter. The oilfield waters are characterized by high TDS (total dissolved solids), ranging from 120000mg/L to 320000mg/L,relatively low Mg, high Ca, Sr, and CF relative to Br of evaporating seawater, suggestive of enhanced water-rock interaction. (Al (organic acid anions) concentrations are generally lower than 1500 mg/L with high values occurring over the temperature range from 95℃ to 140℃ ,in the Cambrian to Jurassic systems, and nearby unconformities. Organic acids are considered to be generated mainly from thermal maturation of kerogens during progressive burial of the Jurassic-Triassic and Cambrian-Ordovician systems, biodegradation of crude oils nearby unconformities, and thermochemical sulfate reduction in part of the Cambrian and Ordovician strata.High Al concentrations up to 3 mg/L to 5. 5 mg/L tend to occur in the waters of high OAA or petroleum- bearing intervals, suggesting the presence of organic complexing agents. Calculation by SOLMINEQ. 88 with updated database shows that AlAc2+ may account for more than 30%of the total Al. IsotoPic measurements (δD, δ18O) provide evidence for the following types of waters: diagenetically- modified connate meteoric water from the Jurassic and Triassic strata;diagenetically-modified connate marine water from the Cambrian and Ordovician strata; subaerially-evaporated water from the Cenozoic and Cretaceous strata; and mixed meteoric-evaporated or/and diagenetically modified connate water from the Carboniferous strata and reservoirs adjacent to the J/C and T/C unconformities. Those waters with very negativeδD values from -51. 30‰. to - 53. 80‰ (SMOW) and positive δ18 O values from 2. 99‰ to 4. 99‰(SMOW) in the continuous burial of the Cambrian-Ordovician system are explained to have resulted from hydrocarbon-water and water-rock interactions.展开更多
文摘Water-rock interaction and groundwater mixing are important phenomena in understanding hydrogeological systems and the stability of rock slopes especially those consisting largely of moderately watersoluble minerals like calcite. In this study, the hydrogeological and geochemical evolutions of groundwater in a limestone quarry composed of three strata: limestone layer(covering), interbedded layer under the covering layer, and slaty greenstone layer(basement) were investigated. Water-rock interaction in the open-pit limestone quarry was evaluated using PHREEQC, while hierarchical cluster analysis(HCA)and principal component analysis(PCA) were used to classify and identify water sources responsible for possible groundwater mixing within rock layers. In addition, Geochemist's Workbench was applied to estimate the mixing fractions to clarify sensitive zones that may affect rock slope stability. The results showed that the changes in Ca2+and HCO3àconcentrations of several groundwater samples along the interbedded layer could be attributed to mixing groundwater from the limestone layer and that from slaty greenstone layer. Based on the HCA and PCA results, groundwaters were classified into several types depending on their origin:(1) groundwater from the limestone layer(LO),(2) mixed groundwater flowing along the interbedded layer(e.g., groundwater samples L-7, L-11, S-3 and S-4), and(3) groundwater originating from the slaty greenstone layer(SO). The mixing fractions of 41% LO: 59% SO, 64% LO: 36% SO, 43%LO: 57% SOand 25% LO: 75% SOon the normal days corresponded to groundwaters L-7, L-11, S-3 and S-4,respectively, while the mixing fractions of groundwaters L-7 and L-11(61% LO: 39% SOand 93% LO: 7% SO,respectively) on rainy days became the majority of groundwater originating from the limestone layer.These indicate that groundwater along the interbedded layer significantly affected the stability of rock slopes by enlarging multi-breaking zones in the layer through calcite dissolution and inducing high water pressure, tension cracks and potential sliding plane along this layer particularly during intense rainfall episodes.
基金The Program for Scientific Research Start-up Funds of Guangdong Ocean University under contract No.101302/R18001the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)under contract No.ZJW-2019-08+1 种基金the National Key Research and Development Program of China under contract No.2016YFC1401403the National Natural Science Foundation of China under contract Nos 41476009 and 41776034
文摘Wave-current interaction and its effects on the hydrodynamic environment in the Beibu Gulf(BG) have been investigated via employing the Coupled Ocean–Atmosphere–Wave–Sediment Transport(COAWST) modeling system. The model could simulate reasonable hydrodynamics in the BG when validated by various observations.Vigorous tidal currents refract the waves efficiently and make the seas off the west coast of Hainan Island be the hot spot where currents modulate the significant wave height dramatically. During summer, wave-enhanced bottom stress could weaken the near-shore component of the gulf-scale cyclonic-circulation in the BG remarkably, inducing two major corresponding adjustments: Model results reveal that the deep-layer cold water from the southern BG makes critical contribution to maintaining the cold-water mass in the northern BG Basin.However, the weakened background circulation leads to less cold water transported from the southern gulf to the northern gulf, which finally triggers a 0.2℃ warming in the cold-water mass area;In the top areas of the BG, the suppressed background circulation reduces the transport of the diluted water to the central gulf. Therefore, more freshwater could be trapped locally, which then triggers lower sea surface salinity(SSS) in the near-field and higher SSS in the far-field.
文摘This study of the gneiss-fractured-rock aquifer in Yaoundé capital of Cameroon determines: the aquifer setting-flow systems, the aquifer type, seasonal variations in rock-water interactions, evolution of the hydrogeochemical processes, physicochemical parameters and the suitability for domestic-agro-industrial use of the groundwater. Physicochemical field tests were carried out on 445 wells during four seasons for EC, pH, TDS, Temperature and static water level from July 2016 to May 2017. 90 well samples were analyzed 45 samples per season: wet/dry. 38 borewell logs were used together with structural data to determine the aquifer setting. The field physico-chemical and laboratory analysis data of well samples were mounted unto various GIS software platforms: Global mapper, AqQa, Aquachem, Rockworks, Logplot7, Surfer and ArcGIS, to get indices/parameters/figures, by use of Durov’s, Piper’s and Gibbs diagrams, Water quality index WQI, USSL ratio, Sodium Absorption ratio SAR, Percent sodium %Na, Kelly Ratio KR, Magnesium Absorption Ratio MAR, Total Hardness TH, Residual Sodium Carbonate RSC and Permeability Index PI that were determined. The process of groundwater ions acquisition is three-fold: by recharge through atmospheric precipitation, by ion exchange/simple dissolution between the rock-groundwater and by groundwater mixing in its flow path. Water types are Ca-HCO3, Mg-HCO3 and Mg-Cl while hydrogeochemical facies are Ca-Mg-HCO3 and Ca-Mg-Cl-SO4. Most water samples are fresh, potable and soft all seasons. The hydrogeological conceptual model is that of a three-layered single phreatic fractured-rock-aquifer while other researchers postulated a two-aquifer, phreatic and semi-confined, two-layered model.
基金the National Natural Science Foundation of China(52104155)Natural Science Foundation of Beijing(8212032)Fundamental Research Funds for the Central Universities(2023YQNY).
文摘Water–rock interaction(WRI)is a topic of interest in geology and geotechnical engineering.Many geological hazards and engineering safety problems are severe under the WRI.This study focuses on the water weakening of rock strength and its infuencing factors(water content,immersion time,and wetting–drying cycles).The strength of the rock mass decreases to varying degrees with water content,immersion time,and wetting–drying cycles depending on the rock mass type and mineral composition.The corresponding acoustic emission count and intensity and infrared radiation intensity also weaken accordingly.WRI enhances the plasticity of rock mass and reduces its brittleness.Various microscopic methods for studying the pore characterization and weakening mechanism of the WRI were compared and analyzed.Various methods should be adopted to study the pore evolution of WRI comprehensively.Microscopic methods are used to study the weakening mechanism of WRI.In future work,the mechanical parameters of rocks weakened under long-term water immersion(over years)should be considered,and more attention should be paid to how the laboratory scale is applied to the engineering scale.
文摘The interactions on gold active and migratory quantities and rates between tuffaceous slate and solu tions with different compositions were experimentally studied at 200 ℃, 20 MPa, in a high pressure apparatus. After reaction, tuffaceous slate became light colored and soft, and its mass density reduced. The amount of gold extracted from tuffaceous slate ranges widely, from 0 027 to 0 234 μg/g. Chlorine solution may activate appreciable amount of gold, and the gold migratory rate is high enough, from 50 70% to 92 30%, which reveals that sulphur and chlorine work together in solutions to accelerate gold activation and migration, and to realize gold mineralization in favorable places.
文摘To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test(HPPT),including measuring sensors of pore water pressure and displacement of the rock mass,was designed according to the hydrogeological condition of Heimifeng pumped storage power station.With the assumption of radial water flow pattern in the rock mass during the HPPT,a theoretical formula was presented to estimate the coefficient of permeability of the rock mass using water pressures in injection and measuring boreholes.The variation in permeability of the rock mass with the injected water pressure was studied according to the suggested formula.By fitting the relationship between the coefficient of permeability and the injected water pressure,a mathematical expression was obtained and used in the numerical simulations.For a better understanding of the relationship between the pore water pressure and the displacement of the rock mass,a 3D numerical method based on a coupled hydro-mechanical theory was employed to simulate the response of the rock mass during the test.By comparison of the calculated and measured data of pore water pressure and displacement,the deformation behaviors of the rock mass were analyzed.It is shown that the variation of displacement in the fractured rock mass is caused by water flow passing through it under high water pressure,and the rock deformation during the test could be calculated by using the coupled hydro-mechanical model.
基金TheprojectwasgrantedbytheNationalNaturalScienceFoundationofChina (No .496 72 15 9)
文摘Hydrogeochemical simulation is an effective method to study water-rock interaction. In this paper, PHREEQM was used for the simulation of water-rock interaction under water flooding in the Renqiu Oilfield. Calculated results revealed that when fresh water was injected into the reservoir, Cl\+- and Na\++ would decrease without involvement in water-rock interaction. Erosion to dolomite will lead to an increase in Ca\+\{2+\}, Mg\+\{2+\} and CaHCO\++\-3. Saturation index of calcite and aragonite decreased first and then increased. With fresh water accounting for up to 70%, mixed water has the strongest erosion ability. Deoiled water has erosion ability under high temperature and high partial pressure of CO\-2. Pyrite and gypsum were sensitive to deoiled water, which can cause the dissolution of pyrite and the precipitation of gypsum. Micrographs revealed a great deal of information about water-rock interaction.
基金support for this work, provided by the National Natural Science Foundation of China (No50534040)
文摘In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of different slope angles. By exerting static and dynamic loads on the specimens, the mechanical characteristics of rock mass with fissure water under these loads can be analyzed. Our experimental results indicate that the static compressive strength of saturated fractured rock mass is related to the slope angle. The lowest compressive strength of fractured rock mass occurs when the slope angle is 45°, while the highest strength occurs when the specimen has no fractures. Fissure water can weaken the strength of rock mass. The softening coefficient does not vary with the slope angle and type of load. The hydrodynamic pressure of fractured rock mass gradually increases with an increase in dynamic load. For a 0° slope angle, the hydrodynamic pressure reaches its highest level. When the slope angle is 90°, the hydro-dynamic pressure is the lowest.
基金ThisstudywassupportedjointlybytheNationalNaturalScienceFoundationofChina (No .40 0 72 0 30 )andtheProgramspon soredbytheMinistry
文摘Systematic analysis and comparative study of the chemical compositions of rocks and ores from the main types of zeolite deposits in the surroundings of the Songliao Basin have shown that the process of formation of zeolite from volcanic and pyroclastic rocks is generally characterized by the relative purification of SiO\-2, i.e., SiO\-2/Al\-2O\-3 ratios tend to increase, alkali earth elements (CaO+MgO) and H\-2O are relatively enriched, and the alkali metals (K\-2O+Na\-2O) are depleted in their total amount. The alkali metals K and Na follow different rules of migration and enrichment during the formation of mordenite and clinoptilolite. In the process of formation of mordenite more Na\++ will be imported and K\++ will be lost remarkably. On the contrary, in the process of formation clinoptilolite more K\++ will be incorporated and Na\++ will become obviously depleted.
文摘Based on the theoretical modelling of water-rock δD-δ18O isotopic exchange process,the evolution and sources of ore-forming fluid in four metallogenic epochs of the Jinduicheng su-perlarge-scale porphyry-type molybdenum deposit were investigated. It was revealed that in thepre-metallogenic and early-metallogenic epehs, the ore-forming fluid was a residual fluid derived from magmatic water-wall rock interaction at middle to high temperatures (T = 250 -500℃) and lower W/R ratios (0. 1 > = W/R >0.001 ), while in the metallogenic and Post-metallogenic epochs, the ore-forming nuid was a residual fluid derived from meteoric water-wallrock interaction at midd1e to lower temperatures (T = 150 - 310℃ ) and relatively high W/Rratios (0. 5 >W/R≥0.1 ). The meteoric water played an important role in molybdenum min-eralization, and at the main metallogenic epoch the W/R ratio reached its maximum value.
文摘Based on analyses of experimental results of water jet drilling, the fluid motion law in rock pores and the tendency of energy distribution, the rock-breaking process under high pressure water jet drilling has been studied systematically. The research indicates that the main interaction between the rock and water jet is interface coupling, that the impacting load and the static pressure of the water jet act together to make the rock break, and that the stress wave is the main factor. Water jet drilling can be divided into two stages: At the initial stage, the stress wave plays the main role and most of the rock breaking takes place; at the later stage, the existing rock defects, for instance, micro-holes and micro-cracks, are propagated and merged to make macroscopic damage, and then the diameter of the jet-drilled hole is expanded.
基金supported by the National Natural Science Foundation of China(Nos.50490275 and 50778184)
文摘Size and quantity of fractured zone and non-fractured zone are controlled by cracks contained in deep rock masses. Zonal disintegration mechanism is strongly dependent on the interaction among cracks. The strong interaction among cracks is investigated using stress superposition principle and the Chebyshev polynomials expansion of the pseudo-traction. It is found from numerical results that crack nucleation, growth and coalescence lead to failure of deep crack- weakened rock masses. The stress redistribution around the surrounding rock mass induced by unloading excavation is studied. The effect of the excavation time on nucleation, growth, interaction and coalescence of cracks was analyzed. Moreover, the influence of the excavation time on the size and quantity of fractured zone and non-fractured zone was given. When the excavation time is short, zonal disintegration phenomenon may occur in deep rock masses. It is shown from numerical results that the size and quantity of fractured zone increase with decreasing excavation time, and the size and quantity of fractured zone increase with the increasing value of in-situ geostress.
基金National Natural Science Foundation of China for Distinguished Young Scholar of China Under Grant No.50325826National Natural Science Foundation of China Under Grant No.50309005Science & Technology Development Project of Education Committee of Beijing Under Grant No.KM200310005017
文摘The effect of water compressibility on the seismic responses of arch dams is not well understood.In this paper,a numerical model is developed with rigorous representation of the dynamic interaction between arch dam-water- rock foundation.The model is applied to the seismic response analysis of an arch dam with a height of 292m designed to a seismic intensity of IX.It is shown that consideration of the water compressibility clearly decreases the stress responses at key positions of the dam,while the added mass model gives a conservative estimate.
基金the National Natural Science Foundation of China (Nos. 50679097 and 50778184).
文摘An accurate and efficient numerical method for solving the crack-crack interaction problem is presented. The method is mainly by means of the dislocation model, stress superposition principle and Chebyshev polynomial expansion of the pseudo-traction. This method can be applied to compute the stress intensity factors of multiple kinked cracks and multiple rows of periodic cracks as well as the overall strains of rock masses containing multiple kinked cracks under complex loads. Many complex computational examples are given. The dependence of the crack-crack interaction on the crack configuration, the geometrical and physical parameters, and loads pattern, is investigated. By comparison with numerical results under confining pressure unloading, it is shown that the crack-crack interaction under axial-dimensional unloading is weaker than those under confining pressure unloading. Numerical results for single faults and crossed faults show that the single faults are more unstable than the crossed faults. It is found from numerical results for different crack lengths and different crack spacing that the interaction among kinked cracks decreases with an increase in length of the kinked cracks and the crack spacing under axial-dimensional unloading.
基金supported by the National Natural Science Foundation of China(Grant Nos.41972300,41572301,and 42107201).
文摘Water sealing performance is important for underground water-sealed oil storage(UWSOS).The key issues concerning water sealing performance mainly include the permeability of fractured rock mass(FRM),water-sealed safety(WSS),water curtain performance,and prediction and control of water inflow.This paper reviews the progress of above four key issues on water sealing performances.First,the permeability of an FRM is the basis of water sealing performance,and several commonly used permeability test methods and spatial variation characteristics of permeability are outlined.Second,the current water sealing criteria are compared,and the evaluation methods of WSS are summarized.Third,the design parameters and efficiency evaluation of water curtain systems(WCSs)are introduced.The water inflow of oil storage caverns(OSCs)can reflect the water sealing effect,and the prediction methods and control measures of water inflow are also summarized.Finally,the advantages and disadvantages of the current research are discussed,and the potential research directions are pointed out,such as optimization of water sealing criteria and FRM model,quantitative evaluation of WCS efficiency,accurate prediction of water inflow,and improvement of grouting technology.
基金supported by the National Natural Science Foundation of China(Grant Nos.40573034 and 40173023)China National Major Basic Development Program"973"(2003CB214605).
文摘In order to elucidate the origin and migration of basinal brines in the Bachu Bulge, Tarim Basin, we have carried out analyses on chemical composition, and boron, hydrogen and oxygen isotopes of formation waters together with the XRD of clay minerals from the Paleozoic strata. The waters show Ca, B, Li and Sr enrichment and SO4 depletion in the Carboniferous and Ordovician and K enrichment in part of the Ordovician relative to seawater. The relationship between δD and δ^18O shows that all the data of the waters decline towards the Global Meteoric Water Line with the intersection of them close to the present-day local meteoric water, suggesting that modern meteoric water has mixed with evaporated seawater. The ^87Sr/^86Sr ratios range from 0.7090 to 0.7011, significantly higher than those of the contemporary seawater. The δ^11B values range from +19.7 to +32.3‰, showing a decrease with the depth and B concentrations. The results suggest that isotopically distinct B and Sr were derived from external sources. However, since the percentages of illite are shown to increase with depth among clay minerals in the study area, i.e., illite is due to precipitation rather than leaching during deeper burial, it is unlikely for illite to have contributed a significant amount of B to the waters. Thus, B with low δ^11B values is interpreted to have been added mainly from thermal degradation of kerogen or the basalts in the Cambrian and Lower Ordovician.
基金support of the National Key Research and Development Program of China(2021YFE0111400)the Shandong provincial natural science foundation(No.ZR2019MEE120)the horizon programme of the EU's funding of the ORCH YD project,EU-H2020(101006752-ORCHYD).
文摘To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.
文摘Oilfield waters from Cenozoic and Mesozoic terrestrial and Paleozoic marine environments in the Tarim Basin show no obvious difference in water chemistry except Br and isotopic compositions. The Paleozoic marine strata have higher Br concentrations than the terrestrial sediments, and the lack of obvious relationship between Br and Ⅰ suggests that Br is not, for the most part, derived from the degradation of organic matter. The oilfield waters are characterized by high TDS (total dissolved solids), ranging from 120000mg/L to 320000mg/L,relatively low Mg, high Ca, Sr, and CF relative to Br of evaporating seawater, suggestive of enhanced water-rock interaction. (Al (organic acid anions) concentrations are generally lower than 1500 mg/L with high values occurring over the temperature range from 95℃ to 140℃ ,in the Cambrian to Jurassic systems, and nearby unconformities. Organic acids are considered to be generated mainly from thermal maturation of kerogens during progressive burial of the Jurassic-Triassic and Cambrian-Ordovician systems, biodegradation of crude oils nearby unconformities, and thermochemical sulfate reduction in part of the Cambrian and Ordovician strata.High Al concentrations up to 3 mg/L to 5. 5 mg/L tend to occur in the waters of high OAA or petroleum- bearing intervals, suggesting the presence of organic complexing agents. Calculation by SOLMINEQ. 88 with updated database shows that AlAc2+ may account for more than 30%of the total Al. IsotoPic measurements (δD, δ18O) provide evidence for the following types of waters: diagenetically- modified connate meteoric water from the Jurassic and Triassic strata;diagenetically-modified connate marine water from the Cambrian and Ordovician strata; subaerially-evaporated water from the Cenozoic and Cretaceous strata; and mixed meteoric-evaporated or/and diagenetically modified connate water from the Carboniferous strata and reservoirs adjacent to the J/C and T/C unconformities. Those waters with very negativeδD values from -51. 30‰. to - 53. 80‰ (SMOW) and positive δ18 O values from 2. 99‰ to 4. 99‰(SMOW) in the continuous burial of the Cambrian-Ordovician system are explained to have resulted from hydrocarbon-water and water-rock interactions.