Hydrological process simulation in the earth dam and dike by the Program PCSiWaPro

Transcription

1 Fakultät Umweltwissenschaften, Fachrichtung Hydrowissenschaften. Hydrological process simulation in the earth dam and dike by the Program PCSiWaPro Jinxing Guo, Peter-Wolfgang Graeber

2 Table of contents Introduction Hydrological regime analysis Description of simulation Program PCSiWaPro Simulation results Conclusions Literature 2

3 1. Introduction Earth dam and dikes as an effective flood protection systems about km of dike length in Germany (Müller, 1999) Coastal Dike in Holland(Reference: Boskalis and Van Oord) 3

4 1. Introduction Earth slope brings various serious problems to the nearby areas (like the landslide). Constantly appearing causes have a great weight on the issue of slope stability, like the heavy rainfall event and the change of the ground water level. Simulation is necessary, especially in forecasting the hydrological process and landslide in the earth slope. (Photo: Reuters) (Photo: André Künzelmann/UFZ) 4

5 2. Hydrological regime analysis Hydrological process in the earth dam and dike is influenced by various factors, such as structures (e.g. cores), soil materials, atmospheric conditions (e.g. precipitation) and vegetation. unsaturated saturated Water balance in the saturated and partially saturated zone (I. Hasan et al., 2012) The effect of precipitation Direct influence on the water content change in the unsaturated slope and seepage line (in an extreme rainfall event) 5

6 2. Hydrological regime analysis The importance of vegetation Influence on the water content in the upper layer of earth slope via the soil-plantatmosphere continuum (Coppin et al., 1990.) Numerical model analysis: Calculation of seepage in a earh slope model (numerical modeling) Water balance (especially in an extrem rainfall event) How fast is the unsaturated area moistened in order to lead to the earth slope instability (landslide)? 6 6

7 2. Hydrological regime analysis Laboratory analysis: Result from a physical model experiment in IWD of TU Dresden Clear hydrological process Landslide in the partially saturated region [Source: Aigner, 2004] 7

8 Theory background: Richard Equation balance θ = t x i K K A ij h x θ- volumetric water content t - time xi (x1=x, x2=z) - coordinates K - hydraulic conductivity h - pressure head S - sources/sinks θ = θ r, w + φ θ 3. Description of Program PCSiWaPro r, w j + K θ A iz [ ( ) n ] 1 1 n 1+ α h c r, l flux and water S VAN-GENUCHTEN-LUCKNER equation (Water retention curve) Ф - porosity θr,w - residual water content θr,l - residual air content α - scaling factor n - slope factor hc - capillary pressure head 8

9 3. Description of Program PCSiWaPro Advantages: Based on Richard s equation and van Genuchten-Luckner model Exact calculation of seepage line in dams Consideration of atmospheric boundary conditions, root water uptake and soil evaporation Consideration of hysteresis in unsaturated zone Application of pedotransfer function implemented parameter identification algorithm integrated weather generator for arbitrary time series in high resolution Calibration system for all points 9

10 3. Description of Program PCSiWaPro Advantages: 1) Installation of the weather generator transient infiltration fronts with a temporal resolution up until 30 minutes application for the unknown location by the method of the spatial interpolation with the geographic coordinate of the surrounding climate stations 10

11 3. Description of Program PCSiWaPro Advantages: 2) Calibration system for all points Output data available for all points in the model system easy calibration of the simulation results with the observation data 11

12 3. Description of Program PCSiWaPro Advantages: 3) Application of the pedotransfer functions four types of functions (Vereecken et al., 1989; Weynants et al., 2009; Teepe et al., 2002; Woesten et al., 2001) an example: Vereecken et al., 1989; to estimate the VAN GENUCHTEN-LUCKNER parameters α and n) easy to be operated 12

13 3. Description of Program PCSiWaPro Model setup Boundary conditions Transient flooding level, rainfall (an example) Analysis of function of rubber wall (an example) 13

14 3. Description of Program PCSiWaPro Material parameters 14

15 4. Simulation results 1) Simulation for the laboratory experiment Simulation of the physical dam model with atmospheric BC also a test of rubber wall efficiency cm Pressure head Water content 15

16 4. Simulation results 2) Simulation for a case study in a Chinese earth dam daily precipitation (m/d) water level in the reservior above the see level (m) 0.00 Jan Feb Mar Apr May Jun Jul Aug Sep 77.0 date Precipitation (m/d) water level(m) Precipitation and water level change in a Chinese earth dam in

17 4. Simulation results Change of water content during the simulation time ( ) Clear movement of the seepage line slight sandy clay- θr=0.01; θs= 0.52, α=0.084 (1/cm), n=1.08, k=9*10-7 m/s silty sand- θr=0.01, θs=0.38, α=0.204 (1/cm), n= 1.23, k=4*10-5 m/s Clay core 17

18 4. Simulation results Change of water saturation during the simulation time ( ) 18

19 4. Simulation results Water level in the clay core Water level (above the sea level) (m) caculated by PCSiWaPro measured by pore water pressure measurer 242 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Time (2012) 19

20 4. Simulation results Water level (above the sea level) (m) Water level in the dam slope 231 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Time (2012) caculated by PCSiWaPro measured by pore water pressure measurer The agreement between the measured values and the computed ones using the program PCSiWaPro was good for both cases. Deviations could be caused by poorly estimated hydraulic soil parameters which are based on the given DIN 4220 values and not on actual measurements from China. 20

21 4. Simulation results 3) A study case of a dump slope in the mining pit in Germany locating between Leipzig and Bitterfeld with the City of Delitzsch in the center which has been shaped by the lignite mining activities for more than one century existing of the high groundwater level in the slope Location of this study area (Brueckner et al., 2013) 21

22 4. Simulation results A simplified structure of a dump site laopo# 22

23 4. Simulation results Simulation for a dump slope without precipitation Water saturation on June 30 th, 2004(the white lines are the borders of different soil layers with different hydraulic conductivity) focusing mainly on the position of the seepage line 23

24 4. Simulation results Simulation for a dump slope without precipitation Water content simulation results on June 30 th, 2004 Due to the larger porosity of the clay layer (dark blue zone), it exhibits the higher saturated water content (0.52) than that of the sandy layer (light blue zone) (0.4). Due to the constant groundwater table, the water level in the observation well was found to be also stable; There was a nice fitness between the simulated and measured data, and only a little deviation (0.3 m) has been detected. 24

25 5. Conclusion The program PCSiWaPro has been proved to be applicable for our stady cases in Germany and China; however the little deviation between the simulated result and the measured data was mainly caused by the poorly estimated soil parameters data. In order to get a higher resolution of the simulation results, more local investigation of soil parameters is in great need. 25

26 Too much water causes instability! leeyankun.blogspot.com 26