Comparison of permeability test methods to characterize on-site rainwater infiltration

Transcription

1 Comparison of permeability test methods to characterize on-site rainwater infiltration July Jooho Chung, Miyajawa Hiroshi, Mooyoung Han 1

2 Contents 1. Introduction 2. Materials & Methods 3. Results & Discussion 4. Conclusion 2

3 1. Introduction (1) Background (2) Low Impact Development (LID) Facilities (3) Infiltration Facility Installation Procedure (4) Necessity of proper Hydraulic conductivity (5) Objectives 3

4 1) Introduction (1) Background Drought Heat island phenomena Urban flooding Low Impact Development Heavy Rain Heavy Rain Infiltration Retention Infiltration facility Retention Retention Rain-Harvesting facility Runoff reduction Reservoir Retention River runoff Reduction 4

5 (2) Low Impact Development (LID) Facilities [LID- Sponge city] Sponge city concept 吸 infiltration 净 cleaning 滞 saving 蓄 harvesting A project to solve the country's flooding problems. To overcome urban floods and droughts and encourage the securing of water resources. 排 discharging 用 using 5

6 1) Introduction (3) Infiltration Facility Installation Procedure 1. Soil characteristic measurement 2. Infiltration facility design 3. Infiltration facility construction Hydraulic conductivity, K

7 (4) Necessity of proper Hydraulic conductivity Hydraulic conductivity, K Overestimated A lack of facility installation Possibility of Flood Underestimated Excessive installation of facilities Economic waste Efficiency & Affordability 7

8 1) Introduction (4) Objectives Identification of rainwater infiltration characteristics Determination of applicable permeability test for infiltration of rainwater 9

9 2. Materials and methods (1) On-site Infiltration characteristics of rainwater (2) Hydraulic Conductivity methods 10

10 2) Materials and methods (1) On-site Infiltration characteristics of rainwater 1. Unsaturated Soil Surface zone of soil is unsaturated zone and remain as unsaturated soil even in the event of rainfall. 2. Vertical Infiltration Rainwater infiltration during rainfall is due to gravity and infiltrates vertically. INFILTRATION from saturated pond RUN OFF Soil zone UNSATURATED Capillary PERCOLATION fringe Ground water zone SATURATED 3. Different flow velocity and direction Evaporation Run off, Percolation, Infiltration, Storage Three phase 1Air 2Soil Particle 3Water 5. Influence of Previous rainfall Monthly Precification(mm) 11

11 2) Materials and methods (2) Hydraulic Conductivity methods [ Typical methods used to measure the permeability of soil ] TSB Disc Permeameter K Ring Infiltrometer ETC (based on Darcy s law) Comparison of permeability tests with rainwater characteristics. 12

12 (2) Hydraulic Conductivity methods 1.TSB Method 2. Ring infiltrometer 3. ETC (Darcy s Law) scale casing standpipe seal surface H Borehole extension L H Smear zone Auger hole TBM step1 TBM step2 Filter(gravel) Filter (sand) Diameter 20cm Fully saturated soil K v, K h Measure the water level based on falling head method. Fully saturated soil K v, K h Measure the constant water level changing in Inner ring Fully saturated soil, horizontal flow K h 13

13 (2) Hydraulic Conductivity methods 4. Disk Permeameter Unsaturated permeability Measures decreasing water level in mariotte bottle occurred by small negative pressure at ponding on soil surface. Tube A Relatively low-permeability soil Z 1 Mariotte bottle Tube B Bubble tower Z 2 Disk with membrane Relatively high-permeability soil 14

14 3. Results and discussion (1) Hydraulic Conductivity comparison (2) Hydraulic Conductivity Test Methods Comparison 15

15 3) Results and Discussion (1) Hydraulic Conductivity comparison 1. Two Stage Borehole test / Double-ring Infiltrometer Soil Site Type Depth In-situ Clay (USCS) 40m Condition Steady water flow Same water ponding Hydraulic Conductivity (K) [ E-10 cm/s] TSB test Double-ring Infiltrometer 2.1 < % In TSB method, Hydraulic conductivity is underestimated by excavation surface disturbance. Comparison of four methods to assess Hydraulic conductivity 16 C.Benson et al. (1997)

16 (1) Hydraulic Conductivity comparison 2. Double-ring Infiltrometer / Disk Permeameter Site Type Soil Depth Condition Dummerstorf. Germany Sandy loam ( WRB classifications) 50mm Annual precipitation: 65mm Annual temperature: 8.2 C Steady water flow Same water ponding Hydraulic Conductivity (K) [ E-4 cm/s] Double ring Infiltrometer Disk Permeameter 2.3 > % Pressure losses across thin sand layer is the reason. Double-ring and tension infiltrometer measurements Of hydraulic conductivity and mobile soil regions John M. Köhne 17 et al.(2011)

17 (1) Hydraulic Conductivity comparison 3. Two stage borehole method/ Disk Permeameter Site Type Soil Depth Condition Chiba.Japan Sandy soil mixed with clay( USCS) 30mm Annual precipitation: 139mm Annual temperature: 17.5 C Same water ponding Hydraulic Conductivity (K) [ E-3 cm/s] Two Stage Borehole Disk Permeameter 1.17 < % In TSB method, Hydraulic conductivity is underestimated by excavation surface disturbance. Report of on-site infiltration methods in Chiba ken Miyajaki takeshi.(2005) 18

18 [Hydraulic conductivity Comparison] Methods Ring infiltrometer Clay (a) Benson, et al (1997) Hydraulic conductivity(cm/s) Sandy loam (b) Rostock (2005) Sandy soil mixed with clay (c) 宮澤博 (2012) 3.3E E-02 - Difference 1571% 1352% 714% TSB 2.1E E-03 Disk permeameter Remarks TSB Risk of soil disturbance Underestimated hydraulic conductivity - 1.7E E-03 Ring Infiltrometer Difficulty to apply a wide range of soil characteristics Overestimated hydraulic conductivity TSB Risk of soil disturbance Underestimated hydraulic conductivity 19

19 2) Materials and methods (1) On-site Infiltration characteristics of rainwater 1. Unsaturated Soil RUN OFF 2. Vertical Infiltration INFILTRATION from saturated pond Soil zone UNSATURATED Capillary PERCOLATION fringe Ground water zone SATURATED 4. Three phase 5. Influence of Previous rainfall 3. Different flow velocity and direction 6. on-site infiltration 20

20 (2) Hydraulic Conductivity Test Methods Comparison Vertical infiltration Unsaturated soil Different flow velocity and direction Three phase Influence of Precious rainfall Remarks ETC (Darcy s law) X X X X X Cam measure only horizontal flow In-situ experiments fail to detect site characteristics TSB X X X X Assuming saturated soil Possible disturbance during construction. Ring infiltrometer X X X Assuming saturated soil Disk permeameter The most reliable measurement method in the on-site hydraulic conductivity evaluation is the disk permeameter 21

21 [ Disk Permeameter s reliable data ] Infiltration rate Runoff rate Comparison of rainfall infiltration to Creek in eastern. P.Nyman, et al. (2014) Infiltration velocity measurement using Disk Permeameter gives approximately similar result compare to the modeling data (P.Nyman,2014) 22

22 4. Conclusion 23

23 4) Conclusion Rainwater infiltration is gaining much attention to improve the water circulation status in LID or Spongy city projects around the world. However, Rainwater infiltration into the soil is unique area, unlike general infiltration. 1. vertical infiltration 2. Unsaturated soil 3. characteristic of on-site soil The proper determination of rainwater permeability in soil is essential in the design. Until now, the permeability test was either an in-site test or did not take into account the infiltration characteristics of rainwater during the on-site test. Among several existing permeability test methods, the most accurate method is found to be Disk permeameter method. 24

24 What about your country? what do you think? 25

25 Thank you 26

26 [ Future study ] 1. Determination of proper hydraulic conductivity with soil characteristics of the Korea and China 2. Suggestion of the standards of infiltration facility design Infiltarion Storage 3. Prediction of infiltration facility performance Maximize the facility performance & Reduction of Flood effect StorageInfiltarion 27