Characteristics of groundwater and urban emergency water sources optimazation in Luoyang,China

The construction of emergency water sources is the material basis for ensuring urban water safety,and it is also an inherent requirement for maintaining social stability and development.The hydrogeological characteristics of groundwater in Luoyang City from the aspects of the division of groundwater aquifer groups,water yield property and groundwater dynamics were described in this paper.Two emergency water sources were selected on basis of comprehensively considering groundwater resources and ecological environmental effects,groundwater quality and exploitation technology,etc.Then it further analysed the aquifer types,water yield properties and groundwater recharge,runoff and discharge conditions of the two emergency water sources,and evaluate the groundwater resources quantity of the water sources.The results are that the shallow underground aquifer in Luoyang City is thick,coarse,and stable in lithology and thickness.The two water sources enjoy good exploitation potential and can be used as backup water sources to supply water in the event of a water source crisis.

Ground water hydrochemical characteristics: seawater intruded area in eastern and southern coast of Laizhou Bay

Eastern and southern coastal zones of Laizhou Bay are the most representative seawater intruded areas in the world, with two intrusion sources of contemporary seawater and paleobrine. In order to reveal the complicated hydrochemical changing process and the mechanism of fresh groundwater being polluted by saltwater, we conducted long-term observation and hydrochemical analysis at four observing sections of typical salt-fresh water transitional zone. The study indicates that seawater and brine intrusion processes have different hydrochemical features, and that ion exchange and adsorption actions between water and aquifer produce great influence on the intrusion.

Bearing capacity analysis using the method of characteristics

Using the method of characteristics,the bearing capacity for a strip footing is analyzed.The method of characteristics leads to an exact true limit load when the calculations of the three terms in the bearing capacity formula are consistent with one collapse mechanism and the soil satisfies the associated flow rule.At the same time,the method of characteristics avoids the assumption of arbitrary slip surfaces,and produces zones within which equilibrium and plastic yield are simultaneously satisfied for given boundary stresses.The exact solution without superposition approximation can still be expressed by Terzaghi＇s equation of bearing capacity,in which the bearing capacity factor N γλ is dependent on the dimensionless parameter λ and the friction angle φ.The influence of groundwater on the bearing capacity of the shallow strip footing is considered,which indicates that when the groundwater effect is taken into account,the error induced by the superposition approximation can be reduced as compared with dry soil condition.The results are presented in the form of charts which give the modified value（Nwγλc /Nγλc） of bearing capacity factor.Finally,an approximated analytical expression,which provides results in close agreement with those obtained by numerical analysis in this paper,has been suggested for practical application purposes.

Distribution of the Ordovician Fluid in the Tahe Oilfield and Dynamic Response of Cave System S48 to Exploitation

The Tahe Oilfield is a complex petroleum reservoir of Ordovician carbonate formation and made up of spatially overlapping fracture-cavity units. The oilfield is controlled by a cave system resulting from structure-karst cyclic sedimentation. Due to significant heterogeneity of the reservoir, the distribution of oil and water is complicated. Horizontally, a fresh water zone due to meteoric water can be found in the north part of the Akekule uplift. A marginal freshening zone caused by water released from mudstone compaction is found at the bottom of the southern slope. Located in a crossformational flow discharge zone caused by centripetal and the centrifugal flows, the main part of the Tahe Oilfield, featuring high salinity and concentrations of CI^- and K^＋＋Na^＋, is favorable for accumulation of hydrocarbon. Three types of formation water in the Tahe Ordovician reservoir are identified： （1） residual water at the bottom of the cave after oil and gas displacement, （2） residual water in fractures/pores around the cave after oil and gas displacement, and （3） interlayer water below reservoirs. The cave system is the main reservoir space, which consists of the main cave, branch caves and depressions between caves. Taking Cave System S48 in the Ordovician reservoir as an example, the paper analyzes the fluid distribution and exploitation performance in the cave system. Owing to evaporation of groundwater during cross-formational flow, the central part of the main cave, where oil layers are thick and there is a high degree of displacement, is characterized by high salinity and Br^- concentration. With high potential and a long stable production period, most wells in the central part of the main cave have a long water-free oil production period. Even after water breakthrough, the water content has a slow or stepwise increase and the hydrochemistral characteristics of the produced water in the central part of the main cave are uniform. From the center to the edge of the main cave, displacement and enrichment of oil/gas become weaker, residual water increases, and the salinity and concentration of Br^- decrease. At the edge of the main cave, although the wells have a high deliverability at the beginning with a short stable production period and water-free production period. After water breakthrough, the pressure and deliverability drop quickly, and the water content rises quickly. The hydrochemistral characteristics of the produced water are relatively uniform. Wells in the branch caves have a relatively low deliverability at the beginning, with a short stable production period. Water breakthrough appears quickly and then the pressure and deliverability drop quickly. The salinity and concentrations of CI^-and K^＋＋Na^＋ are usually fluctuant or descend slowly in the produced water. Wells in low areas of ancient karst have a low deliverability and a short stable production period. The yield drops quickly and the water content is high, while the characteristics of the produced water may vary significantly well to well. The salinity and concentrations of CI^-and K^＋＋Na^＋ in the produced water are usually fluctuant with a precipitous decline.

Compilation of hydrogeological map of China

Hydrogeological map is one of the important carriers of groundwater related information.It directly reflects the hydrogeological conditions and previous investigation and research results of a mapping area.The hydrogeological map of China is a map reflecting the characteristics of hydrogeology and groundwater dynamics on a national scale.On the basis of the hydrogeological map of China(1:4000000)compiled in 1988,this map compilation attempted to update and enhance the existing map,with the latest survey results from the project of National Investigation and Evaluation of Groundwater Resources and Environmental Problems led by China Geological Survey.Task of the mapping program included redefining groundwater types,quantifying the classification standard of the groundwater and adding the pore-fissure water in laterite layer of hilly basin.The multilayer structures for porous,karst and porous-fractured groundwater and their water-rich grades are reflected on the map.Based on the comprehensive summary of the latest hydrogeological data of China,this research conducts an in-depth analysis of the regional distribution characteristics of groundwater in China,utilizes a digital mapping process and establishes a cartographic database for the purpose of further use.With the enrichment of the content and the continuous improvement of cognitive level,mapping content can be updated quickly,which has practical significance for the concept of surveying and mapping and scientific popularization.