1. BUET 1 B ANGLADESH U NIVERSITY OF E NGINEERING AND T ECHNOLOGY (BUET) Dept. of Civil Engineering Comparison of soil slope erosion of bare soil & soil covered with jute geo-textile (JGT) B ANGLADESH U NIVERSITY OF E NGINEERING AND T ECHNOLOGY (BUET) Dept. of Civil Engineering Comparison of soil slope erosion of bare soil & soil covered with jute geo-textile (JGT)

2. BUET 2 3 components:  container for preparing soil slope.  container for collecting eroded soil and runoff.  rainfall distribution system. APPARATUS

3. BUET 3 3 components:  container for preparing soil slope.  container for collecting eroded soil and runoff.  rainfall distribution system. APPARATUS Opening at toe of slope Fig.: container for preparing soil slope container for preparing soil slope

4. BUET 4 3 components:  container for preparing soil slope.  container for collecting eroded soil and runoff.  rainfall distribution system. APPARATUS

5. BUET 5 3 components:  container for preparing soil slope.  container for collecting eroded soil and runoff.  rainfall distribution system. APPARATUS 2 mm dia 1.27mm c/c drilling 30 º angle between two line of drill Fig.5: Pipe network system. orifice meter With pipe network.

6. BUET 6 APPARATUS 3 components:  container for preparing soil slope.  container for collecting eroded soil and runoff.  rainfall distribution system. Fig.: Perforated steel tray system. Pipe network shower system Perforated steel tray system. Fig.: Perforated steel tray system with orifice meter.

7. BUET 7 TEST SPECIFICATION  FM of soil = 0.86 Fig. : Schematic diagram of soil slope. Rainfall characteristic:  Average rainfall intensity of Bangladesh : 50-100 mm/hr. TThe rainfall intensity used in model : 100- 125 mm/hr.

8. BUET 8 TEST PROCEDURE  Test for bare soil: Fig.: Failure surface of bare soil at beginning of rainfall.

9. BUET 9 TEST PROCEDURE  Test for bare soil: Video of rainfall on bare soil Click to play

10. BUET 10 TEST PROCEDURE  Test for bare soil: Fig.: failure surface after 1 hr.

11. BU ET 11 TESTPROCEDURETESTPROCEDURE  Test for bare soil: Fi g. : fa il ur e s ur fa ce af te r 1 hr. What may happen if water accumulates at bottom ? Accumulation of water at bottom Soil liquefaction may occur if we allow water to accumulate at bottom

12. BU ET 12 TESTPROCEDURETESTPROCEDURE  Test for bare soil: Fi g. : fa il ur e s ur fa ce af te r 1 hr. What may happen if water accumulates at bottom ? Click to play

13. BUET 13 TEST PROCEDURE  Test for JGT covered soil: Fig.: Slope surface after 1 hr. Fig.: Slope surface of JGT protected soil at the beginning. Fig.: Slope surface of JGT protected soil after 4hr 30min of rainfall.

14. BUET 14 TEST PROCEDURE  Test for JGT covered soil: land slide after 4 hr Click to play

15. BUET 15 TEST PROCEDURE For 1 st hour :  mass of soil eroded is measured in every 10 minutes using synthetic geo-textile.  Volume of runoff water is measured in every 10 minutes Fig.: Amount of soil eroded at different times when geojute is used 50-60 min 40-50 min 30-40 min 20-30 min 10-20 min

16. BUET 16 TEST PROCEDURE  Test for soil slope covered with vegetation: Fig.: Slope surface after 1 hr. rainfall Fig.: Surface of slope of soil covered with vegetation at the beginning Fig.: Surface of slope of soil covered with vegetation after 4hr 30min of rainfall.

17. Percent soil erosion – time graph 17 BUET

18. Cumulative Percent soil erosion – time graph 18 BUET

19. Cumulative Percent soil erosion – time graph 19 BUET

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21. Cumulative runoff – time graph 21 BUET

22. Water supply- runoff graph 22 BUET

23. 23 Bared soilJGT covered soil Vegetation covered soil Rainfall1 hr Intensity117.33 mm/hr122.6 mm/hr127.27mm/hr Erosion 15.74 % of total mass of soil 1.64 % of total mass of soil 15.74 % of total mass of soil Runoff 0.0779 m3 for 0.133 m3 water supply 0.0651 m3 for 0.139 m3 water supply 0.0779 m3 for 0.133 m3 water supply

24. TEST RESULT  Total reduction in erosion compared to bare soil Geojute  In case of Geojute : 89.6%. (15.74 – 1.64)/15.74*100%. = 89.6%. vegetation  In case of vegetation: 93.5%. (15.74 – 1.03)/15.74*100%. = 93.5%. 24 BUET