Factors affecting health of Ash Dyke and Preventive Measures. Kukreti RC Chowdhury Ujjwal Naresh D N

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1 Factors affecting health of Ash Dyke and Preventive Measures Kukreti RC Chowdhury Ujjwal Naresh D N 1 1

2 ENVIRONMENTAL REGULATIONS Before any construction activity - MOEF clearance is a must MOEF stipulation Minimum land Safe design of dyke No breach/failure No leachates- liner Effluent discharge TSS less than 100ppm Control of Fugitive dust 2

3 ASH DISPOSAL To dispose off ash, dyke is required It s a kind of tailing dam: made of earth or ash

4 INVESTIGATIONS Sub soil exploration & Geo Hydrological studies Access suitability & availability of soil Type of section Sub soil characteristics TYPE OF SECTION and METHOD of CONSTRUCTION 4

5 CRITERIA FOR SAFE DESIGN. MATERIAL PROPERTIES for deciding type of DYKE and method of CONSTRUCTION FOUNDATION FILL NO OVERTOPPING ADEQUATE FREE BOARD --- min 1.5m as per IS SETTLEMENT OF DYKE/FOUNDATION FOUNDATION STABILITY SHEAR STRESSES should be less than SHEAR STRENGTH SEEPAGE LINE WITHIN d/s FACE of DYKE SEEPAGE ANALYSIS TO PREVENT PIPING ACTION IN FOUNDATION & EMBANKMENT SLOUGHING & TOE SOFTENING INTERNAL DRAINAGE like (SAND CHIMNEY, SAND BLANKET, ROCK TOE,TOE DRAIN) is provided ---as per IS:9429 SLOPES TO be PROTECTED AGAINST WAVE ACTION,WIND ACTION,RAIN WASH,VELOCITY OF FLOW ---as per IS 8237 STABILITY OF SLOPES STABILITY ANALYSIS ALLOWABLE FACTORS OF SAFETY (FOS) --- as per IS 7894 STATIC >= 1.5, DYNAMIC >= 1.0 5

6 Design Stable slopes Internal drainage

7 CONSTRUCTION SEQUENCE Surface Treatment of Dyke Foundation Transportation of Lagoon ash Spreading and Compaction Benching& Soil cover Compaction of Slopes Final face of the ash Dyke

9 Signs of healthy dyke 9

10 Sign of Healthy dyke Dyke raisings Starter dyke Slurry pipe lines Rock toe No Sign of distress d/s is dry 10

FACTORS affecting HEALTH OF DYKE during OPERATION Overtopping/ Breach Piping/ sand boil/ quick sand Erosion of U/s & D/s Slope Seepage from body of Dyke Water logging on D/s of dyke Mismatch between

11 FACTORS affecting HEALTH OF DYKE during OPERATION Overtopping/ Breach Piping/ sand boil/ quick sand Erosion of U/s & D/s Slope Seepage from body of Dyke Water logging on D/s of dyke Mismatch between availability and dyke planning. Neglecting signs of distress Leakage from pipes on dyke. Cracks, Wet spots, Settlement/ subsidence etc Siltation/ vegetation in toe drains Rat Holes Fugitive Dust emissions 11

12 Overfilling Overfilling leads to overtopping Overtopping leads to breach Pheratic line is disturbed 12 12

13 Over fill 13

14 Signs of Distress :Water Stagnation, & Piping Seepage from body of dyke Water logging

15 Rock Toe - Dry Maintain Free- board Uniform Disposal 15

16 S No. Factor Affects Function Preventive Measure 1. Overfill a) Leads to overtopping & breach b) Longitudinal & Lateral cracks are developed causing distress to dyke c) Damages internal drainage causing causing piping due to which Phreatic line gets disturbed, which gets aggravated due to wind & surface run-off d) Impairs the intersection of the appurtenant structures making repairs very difficult. e) Fugitive dust emission f) Spillage impacting environment 2 Piping/ Seepage/ sandboil 3 Erosion of slopes, rain cut /gullies a) Will cause material loss, which weaken the dyke section. b) Triggers subsidence c) Triggers breach a) Will reduce resisting strength of Dyke b) Phreatic line may cut the body of dyke leading to piping c) Slope failure a) Maintain mandatory minimum freeboard of 1.5 m as per IS : a) Internal drainage arrangement is provided to maintain the phreatic line in a predetermined path. b) The filter material meets the filter criteria to avoid blockage of filter & maintain exit gradient. The minimum thickness is ensured & maintained. c) To dissipate pore pressure filter size from finer to coarser size particle is provided in rock toe. d) To maintain the continuity of the drainage from the body of dyke upto exit filter is connected to toe drain & rock toe. e) Maintain dry conditions on d/s. a) Stable slopes required from design to be maintained and during construction required degree of compaction is achieved. b) Before taking the dyke into service, the slope protection measures are completed. c) Slopes shall be protected like turfing on d/s slope & rip-rap if required upto HFL. 16

17 S No. Factor Affects Function Preventive Measure 4 Water Stagnation Inundation on d/s. 5 Non-uniform Slurry disposal/ discharge close to the dyke / leakage of slurry pipes. a) Will weaken the foundation of dyke. b) Will trigger sliding failure c) Will cause piping/sand boil a) Will erode the slopes & heel of the dyke and weaken the dyke section & weaken the dyke base, which will result in unstable condition. a) Rock toe & toe drain are provided & connected to nearest natural Nallah. b) Ensure no blockage/ siltation/ vegetation in toe drain/ pheripheral drain. c) The surface run-off from the top of dyke is to be trained towards d/s slope through slope drain guided by kerb wall. The slope drain are to be brought to toe drain. a) The exit of discharge shall be atleast 5H away from heel of dyke. (where H = height of dyke). b) To avoid leakage/ bursting of slurry pipes, plan and implement for rotation of pipes/replacement. 6. Fugitive Dust Emission a) negative impact on the environment a) Operating Dyke : i) Maintain sheet of water over the ash bed. ii) Ensure uniform discharge by garland & shifting the discharge points iii) Vegetation : Elephanta Grass/ beshram shrubs etc are grown b) Non Operating Dyke : i) Provide Sprinkling System ii) Earth/any suitable material as cover. 17

18 Control of Fugitive dust Operating Non operating Abandoned 18 18

Monitoring and Inspection Monitoring dykes and

to danger signals is a continuing critical

Instrumentation data will fore tell of any

19 Monitoring and Inspection Monitoring dykes and reacting quickly to inadequate performance or to danger signals is a continuing critical aspect for dyke safety. Instrumentation data will fore tell of any abnormal behavior Inspection will reveal condition of dyke which threaten safety/stability Prepare check list Operating guide lines Annual audit help operate safe disposal 19

Emergency Action Plan and Response Preparedness In

20 Emergency Action Plan and Response Preparedness In order to mitigate the failure, preventive measures shall be accorded top priority. However, measures shall be initiated to minimize the effects of failures. A emergency plan and response preparedness shall be in place. Mock drills Training Increase awareness towards dyke safety 20

21 Management Initiatives CCTV Online Monitoring Lighting Mast Drag light

22 SAPLINGS TO CONTROL FUGITIVE DUST VEGETATION TO AVOID EROSION

23 In Harmony with Nature Birds flocking to Ash Ponds COMMITED TO PROTECT ENVOIRNMENT TO SAVE PLANET EARTH SARVE JHANA SUKHINAV BHAVANTHU

Chapter 4. Main problems in a canal network 4.1 INTRODUCTION

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