Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Publication
- Publication Type
Articles 31 - 58 of 58
Full-Text Articles in Engineering
Research On The Evolution Law Of Roadway Surrounding Rock Fissure Based On Fractal Dimension, Ding Wanqi, Ma Zhenqian, Zu Ziyin, Xie Hongfei, Yang Wei, Chen Chuan
Research On The Evolution Law Of Roadway Surrounding Rock Fissure Based On Fractal Dimension, Ding Wanqi, Ma Zhenqian, Zu Ziyin, Xie Hongfei, Yang Wei, Chen Chuan
Coal Geology & Exploration
To explore the evolution law of surrounding rock fissures under the influence of horizontal stress and dynamic disturbance in argillaceous roadways, the deformation and failure characteristics of argillaceous roadways, the evolution law of surrounding rock fissures and the fractal evolution characteristics of surrounding rock fissures under dynamic disturbance are studied by such methods as field investigation, numerical simulation and fractal theory analysis, with the 226 track gate of Shanjiaoshu Mine in Panzhou City as the engineering background. The results show that before dynamic disturbance, the expansion range of fracture zone and plastic zone of roadways gradually increases with the increase …
Mining Subsidence Analysis Of Gently Inclined Coal Seams Based On Flac3d And Dem Data, Gan Zhihui, Shang Hui, Du Rongjun, Zhan Huizhu
Mining Subsidence Analysis Of Gently Inclined Coal Seams Based On Flac3d And Dem Data, Gan Zhihui, Shang Hui, Du Rongjun, Zhan Huizhu
Coal Geology & Exploration
Shizuishan Mining Area in Ningxia Province is located in the western Yellow River. The subsidence of the mined-out area causes frequent surface ecological and environmental problems. The analysis of coal mining subsidence will play a positive role in environmental remediation the Yellow River Basin. Taking Shizuishan Coal Mine as an object to study the evolution characteristics of surrounding rock stress and displacement field of gently inclined coal seam, a three-dimensional numerical model of the gently inclined coal seam based on the numerical simulation software FLAC3D was established. The variation of stress, plastic zone, and displacement in the surrounding rocks …
Rock Breaking Mechanism Of Composite Impact Of Full-Size Pdc Bit Based On Finite Element Analysis, Peng Xu, Hao Shijun
Rock Breaking Mechanism Of Composite Impact Of Full-Size Pdc Bit Based On Finite Element Analysis, Peng Xu, Hao Shijun
Coal Geology & Exploration
In order to solve the problems of low rock breaking efficiency in hard formation and the decrease of bit life caused by stick-slip vibration of drilling tools, the full-size bit composite impact rock breaking mechanism was studied by finite element method(ANSYS). The effects of impact frequency, WOB(weight on bit) and rotational speed on the efficiency of rock breaking were analyzed. It was found that both tensile and compressive stresses existed in rock during bit rock breaking, and rock failure was manifested in comprehensive failure of “tensile & compressive shear”. It is concluded that under the condition of torsional impact frequency …
Numerical Simulation Of The Influence Of No-Flow Recharge Aquifer On Cbm Drainage, Liu Bing, Zhang Songhang, Tang Shuheng, Wang Pengfei, Zhai Jiayu, Ji Chaoqi
Numerical Simulation Of The Influence Of No-Flow Recharge Aquifer On Cbm Drainage, Liu Bing, Zhang Songhang, Tang Shuheng, Wang Pengfei, Zhai Jiayu, Ji Chaoqi
Coal Geology & Exploration
Coalbed methane wells in southern Qinshui Basin have the characteristics of high water yield and low gas yield, while some wells present high water yield and high gas yield characteristics. Generally speaking, the high water yield of coalbed methane wells is mostly related to the aquifer with recharge. In this case, based on the coal reservoir geological condition of Shizhuangnan Block and the actual situation of coalbed methane vertical well production, the influence of non-flow recharge aquifer on reservoir pressure variation and CBM outflow rule was simulated by using a three-dimensional coal reservoir simulation software (SIMEDWin) with gas and water …
Numerical Simulation Of Safe Distance Through Roadway Drilling Under Dynamic Load Of Large Diameter Rescue Well, Li Bizhi, Hao Shijun, Liu Mingjun, Zhang Qiang, Bai Gang, Mo Haitao
Numerical Simulation Of Safe Distance Through Roadway Drilling Under Dynamic Load Of Large Diameter Rescue Well, Li Bizhi, Hao Shijun, Liu Mingjun, Zhang Qiang, Bai Gang, Mo Haitao
Coal Geology & Exploration
Aiming at the sudden inburst of formation water and drilling fluid into a roadway along the borehole during through roadway drilling operation, which results in the secondary injury of the trapped personnel, ABAQUS geotechnical numerical simulation method was adopted, the model was established with the surface rescue well of the roadway of No.3 coal seam in Pingshang Coal Mine as an example, the plastic deformation characteristics of the surrounding rock of the roadway roof and the optimization of safe through roadway distance under drilling dynamic disturbance were studied. The results show that the dynamic disturbance caused displacement deformation and plastic …
Numerical Simulation And Test Of Gas Drainage With Water Jet Layered Pressure Relief And Permeability Enhancement In Soft Coal Seam, Liu Xiao, Li Yong, Xuan Dequan, Hu Shixiong, Jing Tianxiang, Xu Sen
Numerical Simulation And Test Of Gas Drainage With Water Jet Layered Pressure Relief And Permeability Enhancement In Soft Coal Seam, Liu Xiao, Li Yong, Xuan Dequan, Hu Shixiong, Jing Tianxiang, Xu Sen
Coal Geology & Exploration
Hydraulic punching is the main technical measure to enhance permeability and drainage of coal seam gas. The pressure relief effect is mainly evaluated by the coal output. However, there are some problems such as large coal output, uneven pressure relief and easy stress concentration. Therefore, this paper puts forward the soft coal interlayer water jet layered pressure relief and permeability increasing gas drainage technology. Considering the influence of gas pressure compression and coal matrix adsorption gas expansion on the coal mass deformation, a multiphysics theoretical model under the coupling condition of stress field, fracture field and seepage field was established. …
Development Of Deep Geothermal Energy And Its Influence On Geothermal Water Flow Field: Taking The Development Of Deep Geothermal Energy In Lankao County For An Example, Song Qianjin, Wang Gang, Xu Yichuan, Cheng Lei
Development Of Deep Geothermal Energy And Its Influence On Geothermal Water Flow Field: Taking The Development Of Deep Geothermal Energy In Lankao County For An Example, Song Qianjin, Wang Gang, Xu Yichuan, Cheng Lei
Coal Geology & Exploration
In order to study the influence of deep geothermal energy development on the flow field of thermal reservoir, deep geothermal energy development in Lankao County is selected as the research object. The geological structure and regional structure of the study area since Cenozoic are analyzed, and the of geothermal exploitation and existing problems in the area are investigated. According to the types of geothermal energy, the characteristics of the Quaternary(Q), Neogene Minghuazhen Formation(N2) and Neogene Guantao Formation(N1) are analyzed. The conditions of fault distribution, thermal reservoir development and water-resisting boundary in the area are found out …
Investigation And Simutation On The Model And Prevention Technology Of Water Inrush From Roof Bed Separation, Zhang Wenquan, Wang Zaiyong, Wu Xintao, Shao Jianli, Lei Yu, Wu Xunan
Investigation And Simutation On The Model And Prevention Technology Of Water Inrush From Roof Bed Separation, Zhang Wenquan, Wang Zaiyong, Wu Xintao, Shao Jianli, Lei Yu, Wu Xunan
Coal Geology & Exploration
In order to prevent water inrush from roof separation, a partial backfill scheme is proposed for simulation study. First of all, based on the existing data, many kinds of separation water inrush accidents occurred in China were summarized and analyzed, and the disaster model of separation water accumulation was studied deeply. Then, taking the separation water accident of 1307 working face in the first mining area of a mine in Shaanxi Province as an example, the hydrogeological conditions and the relationship between upper aquifer and separation water inrush were analyzed, and the development characteristics of roof separation space of working …
Numerical Analysis On Csw Fracturing Behavior Of Coal Seam Under Constraint Of Geological And Engineering Conditions, Qin Yong, Li Hengle, Zhang Yongmin, Zhao Youzhi, Zhao Jincheng, Qiu Aici
Numerical Analysis On Csw Fracturing Behavior Of Coal Seam Under Constraint Of Geological And Engineering Conditions, Qin Yong, Li Hengle, Zhang Yongmin, Zhao Youzhi, Zhao Jincheng, Qiu Aici
Coal Geology & Exploration
As a revolutionary technology for rock stratum reformation, the controllable shock wave(CSW) fracturing technology has achieved remarkable effect in coal seam reconstruction, and application exploration in the field of coal safety mining has been carried out. However, the previous understanding of the basic CWS fracturing rules under the constraints of geological engineering factors is insufficient due to the limitation of experimental and field monitoring conditions, which restricts the exploration of the fracturing mechanism and the optimization of the field operation parameters. In view of this, based on the description of CSW coal seam reformation and its engineering scientific problems, the …
Numerical Simulation Of Pore Structure Stress Characteristics Of Coal And Rock Mass, Wang Gang, Jiang Chenghao, Chen Xuechang
Numerical Simulation Of Pore Structure Stress Characteristics Of Coal And Rock Mass, Wang Gang, Jiang Chenghao, Chen Xuechang
Coal Geology & Exploration
In order to explore the stress distribution around the pores of coal and rock mass under different loading modes, the skeleton model of coal and rock mass with different pore shapes was constructed through CT three-dimensional reconstruction technology, and uniaxial and triaxial compression experiment simulations were conducted using ABAQUS software. The results showed that under uniaxial compression, the upper and lower regions of spherical pores showed tensile stress concentration, while the left and right regions showed compressive stress concentration. The stress concentration types in the long and short axis of elliptic pores were distinct with different dip angles. Under uniaxial …
Freezing Temperature Field Characteristics Of Multi-Loop Pipers Under Different Working Conditions At The Interface Of Deep Thick Sand And Clay, Yang Qing, Rong Chuanxin, Li Mingjing, Yang Guobing
Freezing Temperature Field Characteristics Of Multi-Loop Pipers Under Different Working Conditions At The Interface Of Deep Thick Sand And Clay, Yang Qing, Rong Chuanxin, Li Mingjing, Yang Guobing
Coal Geology & Exploration
When drilling in a complex heterogeneous formation, due to the limitation of bit crown shape, the cutters of each part of the bit are subjected to non-uniform force, and the cutters at the local location are subjected to large impact load, which lead to the occurrence of bit vortex. In order to solve the problem, a “multi-level force balance” cutter circumferential arrangement scheme is proposed. By establishing the rock breaking finite element simulation model of the bit, the mechanical characteristics of the cutter and the bit under three circumferential cutter distribution modes(clockwise, counterclockwise and “multi-level force balance”) are analyzed. Simulation …
Simulation Of The Cutter Arrangement Pattern Of The Arc Pdc Drill Bit, Ju Pei, Wang Chuanliu
Simulation Of The Cutter Arrangement Pattern Of The Arc Pdc Drill Bit, Ju Pei, Wang Chuanliu
Coal Geology & Exploration
When drilling in a complex heterogeneous formation, due to the limitation of bit crown shape, the cutters of each part of the bit are subjected to non-uniform force, and the cutters at the local location are subjected to large impact load, which lead to the occurrence of bit vortex. In order to solve the problem, a “multi-level force balance” cutter circumferential arrangement scheme is proposed. By establishing the rock breaking finite element simulation model of the bit, the mechanical characteristics of the cutter and the bit under three circumferential cutter distribution modes(clockwise, counterclockwise and “multi-level force balance”) are analyzed. Simulation …
Development Characteristics Of Freezing Temperature Field Of Coastal Soft Soil Strata, Chen Junhao, Zhuang Yan, Chen Bijian, Zhao Zhenwei, Wang Qiyun
Development Characteristics Of Freezing Temperature Field Of Coastal Soft Soil Strata, Chen Junhao, Zhuang Yan, Chen Bijian, Zhao Zhenwei, Wang Qiyun
Coal Geology & Exploration
In order to research the temperature fields and development law of freezing in the construction of connected aisle in coastal soft soil stratum, based on connected aisle between Luoxiu road station and Baise road station of Shanghai subway Line 15, the thickness and average temperature of frozen curtain, and the freezing process were analyzed. The temperature fields and development law of freezing were predicted by the three-dimensional numerical model of the connected aisle and the temperature data which were analyzed. The results show that the inherent pressure in soft soil causes initial pressure in the pressure relief hole. A lot …
Overburden Failure Simulation Under Double Coal Seams Mining In A Coal Mine In North Shaanxi Province, Sun Xueyang, Zhang Qi, Li Cheng, Zhang Lei
Overburden Failure Simulation Under Double Coal Seams Mining In A Coal Mine In North Shaanxi Province, Sun Xueyang, Zhang Qi, Li Cheng, Zhang Lei
Coal Geology & Exploration
Under the conditions of multi-seam mining, the overburden failure of coal seams has unique characteristics, which affects the mine production arrangement. Taking a mine in northern Shaanxi Province as an example, based on the geological and mining conditions of the mine, the influence of double-seam mining on overburden rock damage was analyzed by using the method of similar material simulation experiment and numerical simulation. The results show that the height of the caving zone and the height of the fractured zone in the overburden of coal seam obtained by using similar material simulation and numerical simulation with different widths of …
Surface Efficient Gas Extraction Mode Based On Full Coverage Of Working Face, Fang Jiawei, Han Baoshan, Zhou Jiajia, Wang Zhengxi, Zhang Dingliang, Liu Jia, Xu Jianjun
Surface Efficient Gas Extraction Mode Based On Full Coverage Of Working Face, Fang Jiawei, Han Baoshan, Zhou Jiajia, Wang Zhengxi, Zhang Dingliang, Liu Jia, Xu Jianjun
Coal Geology & Exploration
Aiming at the problems of soft and broken coal seam, low permeability, difficulty in gas extraction and low drainage efficiency in working face, a full-coverage mode for gas extraction in working face through the horizontal well group with staged fracturing roof at both ends is proposed. Taking a mine in Suxian mining area of Huaibei coalfield as an example, based on the characteristics of in-situ stress and working face distribution, combined with the analysis of gas geological conditions and coal seam mechanical properties in the area, the cross section dipole sonic logging method was used to optimize the orientation of …
Development Characteristics Of Water Conducted Fracture Zone Based On Overburden Structural Effect, Cao Zubao, Wang Qingtao
Development Characteristics Of Water Conducted Fracture Zone Based On Overburden Structural Effect, Cao Zubao, Wang Qingtao
Coal Geology & Exploration
In order to study the roof water disaster caused by coal mining in Huanglong coalfield, taking mining failure of layered overburden as research object, four typical composite structural models for coal-soft rock-hard rock-soft rock-hard rock(combination I), coal-soft rock-soft rock-hard rock-hard rock(combination Ⅱ), coal-hard rock-soft rock-hard rock-soft rock(combination Ⅲ) and coal-hard rock-hard rock-soft rock-soft rock(combination IV) were generalized. Numerical simulation and theoretical calculation were used to analyze the mining failure characteristics of different overburden combinations and correlation between water conducting fissures and lithologic combination structure of overburden. The law of the effect of overburden structure on the development height of water …
Influence Factors And Formation Properties Of Temperature Field In The Frozen Wall Of Double Ring Pipes, Li Huaixin, Lin Bin, Wang Peng
Influence Factors And Formation Properties Of Temperature Field In The Frozen Wall Of Double Ring Pipes, Li Huaixin, Lin Bin, Wang Peng
Coal Geology & Exploration
In order to research the change law of the temperature field of the frozen wall of double-circle pipes, an auxiliary shaft in Huainan coalmine was taken as the research object, the FLAC3D software was used to numerically simulate the formation process of the temperature field of the frozen wall of double-circle pipes and the influence of different factors on average temperature of frozen wall based on the relevant geological parameters. The research results show that temperature of the soil in the double-circle pipes is the lowest, and temperature on both sides increases gradually, the interval between frozen holes is …
Design And Numerical Simulation Of Multi-Layer Bit With Extra-High Matrix, Sun Qibin, Shen Lina, Yang Gansheng, Tian Guoliang, Ruan Hailong, Chen Xi
Design And Numerical Simulation Of Multi-Layer Bit With Extra-High Matrix, Sun Qibin, Shen Lina, Yang Gansheng, Tian Guoliang, Ruan Hailong, Chen Xi
Coal Geology & Exploration
Aiming at the problem that the life of the diamond bit is limited by the height of the bit matrix, an optimized design scheme of an impregnated diamond bit with extra-high multi-layer matrix was proposed. In the design of the bit, eccentric staggered cutting teeth, alternate waterways and water baffles were introduced to ensure the cooling and effective drilling of the bit. Through strength and hydraulic flow field simulation, the strength of the drill bit was checked, the rationality of the waterway structure was verified, and the finished product of the drill bit was further realized. The drill bit breaks …
Numerical Simulation Of Layer-Crossing Propagation Behavior Of Hydraulic Fractures At Coal-Rock Interface, Li Haozhe, Jiang Zaibing, Shu Jiansheng, Fan Yao, Du Tianlin
Numerical Simulation Of Layer-Crossing Propagation Behavior Of Hydraulic Fractures At Coal-Rock Interface, Li Haozhe, Jiang Zaibing, Shu Jiansheng, Fan Yao, Du Tianlin
Coal Geology & Exploration
Based on the analysis of coal-rock interface, the vertical propagation behavior of hydraulic fractures at coal-roof interface was studied by using finite element method. The influence of some geological and engineering factors on fracture layer-crossing behavior was analyzed. Results have shown that in-situ stress and shear strength of coal-rock interface are the two main factors affecting the fracture propagation at the coal-rock interface. Greater vertical stress difference coefficient and interfacial shear strength make fractures more easier for crossing the interface. Meanwhile, the difference of elastic modulus and tensile strength between coal and rock has less effect on the fracture vertical …
Numerical Simulation Of Propagation Law Of Pore-Fracture Under Uniaxial Stress, Guo Xiucheng
Numerical Simulation Of Propagation Law Of Pore-Fracture Under Uniaxial Stress, Guo Xiucheng
Coal Geology & Exploration
in order to study the law of crack propagation under different pore-fracture conditions, the crack propagation process, acoustic emission law and stress-strain curve under different crack inclination angle and different heterogeneous coefficient were numerically simulated by using RFPA software. At the same time, the results are compared with the experimental results. The results show that the cracks of the intact specimen are produced along the shear direction, while the cracks of the specimens with pores occur along the side of the crack tip and the orifice. The secondary cracks in horizontal direction and bifurcation at the prefabricated crack tip or …
Influencing Factors Of Azimuth Electromagnetic Wave Roof And Floor Detection While Drilling Along Coal Seam, Chen Gang, Fan Yiren, Li Quanxin
Influencing Factors Of Azimuth Electromagnetic Wave Roof And Floor Detection While Drilling Along Coal Seam, Chen Gang, Fan Yiren, Li Quanxin
Coal Geology & Exploration
Aiming at the problems of poor detection accuracy and low efficiency of roof and floor interface in horizontal well drilling in coal mine, the design idea of explosion-proof azimuth electromagnetic wave logging tool while drilling in coal mine is put forward. In order to suit the working environment of underground coal seam, the influence of instrument parameters such as source distance, transmitting frequency and coil installation angle on signal response was obtained by forward simulation. The results show that the received signal strength of the azimuth electromagnetic wave instrument while drilling increases with the increase of transmitting frequency, coil distance …
Test Of The Influence Of Dynamic Water Grouting Diffusion Radius Of Fractures In Rock, Gu Shuancheng, Sun Guanlin, Su Peili, Li Jinhua
Test Of The Influence Of Dynamic Water Grouting Diffusion Radius Of Fractures In Rock, Gu Shuancheng, Sun Guanlin, Su Peili, Li Jinhua
Coal Geology & Exploration
Water-cement ratio and grouting pressure are the key factors in the design of hydrodynamic grouting. In this paper, based on the self-designed simulated fissure hydrodynamic grouting indoor test platform, the dynamic water grouting test was carried out, the diffusion mode of the slurry in fractures was discussed. The relationship among the diffusion radius of pure cement slurry, the grouting pressure and water-cement ratio was analyzed. The experimental results were verified by computational fluid dynamics software. The results show that the diffusion mode of the slurry is partition diffusion. When the grouting pressure is constant, the diffusion radius is inversely proportional …
Study On Slope Stability And The Effect Of Highfill On The Mechanical Properties Of Red Clay Foundation, Gao Shengxiang, Xu Qiang, Ma Hongyu, Wu Shenglin, Wu Kang, Liu Peng, Wu Zehui
Study On Slope Stability And The Effect Of Highfill On The Mechanical Properties Of Red Clay Foundation, Gao Shengxiang, Xu Qiang, Ma Hongyu, Wu Shenglin, Wu Kang, Liu Peng, Wu Zehui
Coal Geology & Exploration
This paper takes a highfill slope in Anning in Yunnan Province as a case, using investigation, monitoring and other methods, on the basis of the distribution characteristics of red clay, the physical and mechanical properties of red clay before and after filling were analyzed, then the stability of slope was studied by numerical simulation software. The results show that the physical and mechanical indexes of the red clay foundation decrease first and then increase before and after the fill project, the stability of the fill slope shows the trend of decrease first and then increase. The ground fissures in the …
Numerical Simulation On Mechanism Of Thrust Fault Reactivation During Mining, Min Feihu, Xiang Biwei, Liu Hui, Zhu Xiaojun
Numerical Simulation On Mechanism Of Thrust Fault Reactivation During Mining, Min Feihu, Xiang Biwei, Liu Hui, Zhu Xiaojun
Coal Geology & Exploration
It is a hot issue in mine disaster research about the activation of faults during the process of coal mining and excavation. In order to reveal the influence of coal mining on fault activation under different fault dip conditions, Xinji No.2 mine in Huainan coalfield was taken as an example, and numerical simulation with FLAC3D was used to systematically study the dynamic activation law of thrust faults during mining beside the faults, and to clarify the relationship among fault activation position and fault dip angle and excavated distance of working face. The results show that the fault activation is …
Reasonable Length Of Working Face 11-101 During Mining Above Confined Aquifer In Tuanbai Mine, Li Gang, Zhang Kai, Su Junhui, Wang Jinbo
Reasonable Length Of Working Face 11-101 During Mining Above Confined Aquifer In Tuanbai Mine, Li Gang, Zhang Kai, Su Junhui, Wang Jinbo
Coal Geology & Exploration
The working face 11-101 of Tuanbai coal mine in Huozhou, Shanxi Province is exploited above aquifer. In order to prevent floor water inrush accidents during mining, research combination of elasto-plastic theory, on-site measurement and numerical simulation was carried out to analyze the development rule of failure depth of the floor, then the reasonable length of the mining face under this condition was determined. The result shows that with the advancement of working face, the bottom plate of lagging working face is stretched and destroyed at about 6 m behind the lagging working face, and the bottom plate has a wedge …
Numerical Analysis Of Temperature Field Of Underwater Dredging Artificial Frozen Plate, Wu Yuwei, Hu Jun, Wang Zhixin, Zeng Dongling, Wang Shucheng
Numerical Analysis Of Temperature Field Of Underwater Dredging Artificial Frozen Plate, Wu Yuwei, Hu Jun, Wang Zhixin, Zeng Dongling, Wang Shucheng
Coal Geology & Exploration
In order to understand the development of the temperature field of artificial freeze dredging plates and the process of the formation of frozen curtains, the finite element analysis was used to perform numerical analysis using the single factor analysis method for research of the frozen process in different circumstances of geometric size of plate and physical environment of the soil under water. The results show that the correlation between the different geometric dimensions of the frozen plate and the dredging depth is weak, and the geometric dimension of the frozen plate can only change the area of dredging; for the …
Review Of Computer-Aided Numerical Simulation In Wind Energy, Aaron Miller, Byungik Chang, Roy Issa, Gerald Chen
Review Of Computer-Aided Numerical Simulation In Wind Energy, Aaron Miller, Byungik Chang, Roy Issa, Gerald Chen
Civil Engineering Faculty Publications
Many advances have been made during the last decade in the development and application of computational fluid dynamics (CFD), finite element analysis (FEA), numerical weather modeling, and other numerical methods as applied to the wind energy industry. The current information about this area of study may help researchers gage research efforts. Specifically, micro-siting, wind modeling and prediction, blade optimization and modeling, high resolution turbine flow modeling, support structure analysis, and noise prediction have been the main focuses of recent research. The advances in this area of research are enabling better designs and greater efficiencies than were possible previously. The trends …
Conceptualization Of Hydrologic Systems [Outline], Kenneth E. Kolm
Conceptualization Of Hydrologic Systems [Outline], Kenneth E. Kolm
Uncovering the Hidden Resource: Groundwater Law, Hydrology, and Policy in the 1990s (Summer Conference, June 15-17)
4 pages.