Numerical Simulation and Prediction of Mine Water A Case Study in Dangtu County of Anhui Province

Du Fuhui Jiang Ying

（College o f Hydroe lectricity，Hebei University of Engineering，Handan，056038，China）

Numerical Simulation and Prediction of Mine Water A Case Study in Dangtu County of Anhui Province

Du Fuhui Jiang Ying

（College o f Hydroe lectricity，Hebei University of Engineering，Handan，056038，China）

In this paper，the regional groundwater flow system in Zhong Jiu iron ore was generalized into three-dimensional unsteady groundwater flow systems w ith homogeneous，isotropic and no boundary lim its.The software of Visual MODFLOW was used to simulate and predict the gushing process.the conclusion was that the calibrated parameters were reasonable and the predicted value can satisfy the demand of the consumption of mining.

Zhong Jiu iron ore；Hydrogeological conditions；Visual MODFLOW；Numerical simulation；Water inflow predicting.

Numerical method includes four steps：hydrogeological model conceptualization，building mathematical model，model calibration，m ine w ater inflow p redicting ect.

1　The Estab lishm ent of the Hydrogeo log ica l Conceptua l Mode l

The mine area w as in water-bearing medium that has no obvious w ater boundary，there are m any clear differences among different w ater-bearing rock groups or even the same ones，but there are still some hydraulic connections.So，the anisotropy aquifer medium that above-370meters in m ining area w as identified as the flow field，w hich is isotropic and has no confined boundary.

In order to reflect the geologic feature，the aquifers w ere generalized into10layers.The simulated range was143km2around the m ine.The boundary w as generalized as general head boundary and the simu lation area w as regarded as heterogeneous isotropic.The ground water flow was defined as transient flow that obey the Darcy's law.

2　The Determ ination of Initial Conditions

The initial flow field was draw n based on the date of the w ater level in december2009，The ten aquifer groups had different initial flow fields because of the minor differences among them and the m inor groundw ater exp loitation quantities.

3　Mathem atical Model of Groundw ater Flow

3.1Discretization

In space，according to geological structure characteristics，hydrau lic characteristics，flow field characteristics，simulation accuracy and the boundary condition，tw o groups of orthogonal grid by11km x13km w hich are parallel to x axis and y ax is divided the study area into14300active cells w hich represent the actual p lanar area.

In time，the simulation time was7th december2009to 7th december2010.and the starting value was regarded as the？initial flow field，while the forecast period was35years.

3.2Mathematical M odel

The mathematical model as follow ing：

Where，His the groundw ater level；K is hyd rau lic conductivity；μis storage coefficient；x，y，z is coordinate variab les；H 1is the level of the border；H 0is the initial groundw ater level；D is the scope of the simulation zone；W is the unit volume flow，Mis the the thickness of the confined aquifer；n is the ex ternal norm al direction of the second boundary； Γ1 is the first boundary； Γ2is the second boundary.

4　Ca lcu lation and Ana lysis o f M ode l

4.1Model Calibration

In the model，the calibration period w as12months，the hydrogeological parameters，initial conditions of w ater head and the boundary conditions w ere regarded as the initial value of m odel ad justab le param eters，the w ater level of pum ping w ells in p ractical pum ping test and the dynam ic data of draw dow n w ere regarded as the observed value in actual measurement.A fter running，the calculated and measured w ater level w ill be fitting analysed.If the calcu lated w as not consistent with the measured and the deviation w as also very big，then the model needed to be given a set of parameters once again that including the storage，conductivity，porosity and yield of bedrock confined aquifer and continued to calcu late until the fitting w as perfect.

4.2Water Fitting Process

In the fitting process，the SDK 304pumping w ell w as used for pumping experiment and the water output is1172m3/d.A t the time of recognition，when the calculated and the measured level matched w ell，the predictive value w as1200m3/d which almost the same as the actual.then，compared with the change of the level data of several observation w ells such as SK 305，ZK 1101，SK 101，ZK701，and adjusted the parameters of the model to make the flow field around the pumping w ells match perfectly with the actual.

By observing the chart of flow field compared with the actual，the conclusion w as that this hydrogeology model w as con form to the actual and can be used for the subsequent forecast process.

4.3Water Inflow Predicting

For this part，formulate a drainage w ater“Q”，calculate the drainage time“t”for a certain drainage level first，then make the Q=f（t）curve by different drainage water and the corresponding drainage time，w hen the drainage model reached a steady state in the end，according to the levels of different m ining，it will solve the steady flow field and calculate the stable flow that entered the mining tunnels，it is the m ine water inflow.

The p lentiful rainfall period is regarded as the calculated stress period，and it converted the rising water level to source sink term，and solved the d rainage model of steady flow，it

············is the largest w ater inflow.

4.4Predicting Results and Analysis

The curve of the changing process for the prediction of m ine w ater inflow over time show ed that the w ater inflow at the initial period of stab le production w as about28000m3/ d.As deposit m ining，the m ine w ater in flow decreased gradually，the decreasing extent also decreased gradually and the m ine w ater situation tended to be stable.the stable w ater inflow w as about18000m3/d.it can satisfy the amount of w ater for m ining.the result of the forecast w as reliable.

5　Conc lusion

Th is study have a h igh degree of sim u lation，sim p le operation，pow erful function.it can fully reflect the specific boundary conditions and w ater dynam ic characteristics of w ater-bearing media.Not only can this study results provide reasonable gists for planning of w ater resources in the project，but also the evaluation m ethod had ex tensive app lication prospects and im portant p rom otional value.

References:

［1］Prediction and numerical simulation of groundwater f low field of Liguanpu wells.Cao Guangzhu.Faculty of Land Resource，Kunming University of Science and Technology，Kunming65009，China；

［2］Research and Application of Groundwater Numerical Simulation. Song Yanxun.

［3］Review of the uncertainty analysis of groundwater numerical simulation.Wu Jichun；Zeng Xiankui；Nanjing University，Nanjing 210093，China.