STABILITY ANALYSIS OF STABILITY ANALYSIS OF MULA DAMMULA DAM

(EARTHEN DAM) (EARTHEN DAM)

By

Prof.M.PWAGH

IntroductionIntroduction

Dams may be defined as an obstruction or a Dams may be defined as an obstruction or a barrier built across a stream or a river.barrier built across a stream or a river.

Purpose of Dam:Purpose of Dam: 1. Controlling Flood1. Controlling Flood 2. Irrigation2. Irrigation 3. Water Supply3. Water Supply 4. Generation of Electricity (Hydro Power)4. Generation of Electricity (Hydro Power) 5. Used for fish Culture5. Used for fish Culture 6. Diversion of Water6. Diversion of Water 7. 7. 6 MW Hydro- power generation6 MW Hydro- power generation (Under Construction)(Under Construction)

Objective of ProjectObjective of Project

To study the salient features of Mula DamTo study the salient features of Mula Dam To Carry out Stability Analysis of Mula Dam To Carry out Stability Analysis of Mula Dam To Study Hydro Electric Power Plant To Study Hydro Electric Power Plant Design of Spillway Design of Spillway To Study Instrumentation in DamsTo Study Instrumentation in Dams

Types of DamTypes of Dam

Dams are of the following types:Dams are of the following types:

1. Embankment Dam 1. Embankment Dam

2. Gravity Dam2. Gravity Dam

3. Arch Dam3. Arch Dam

Earthen DamEarthen Dam Earthen Dam are classified as:Earthen Dam are classified as: Homogenous Embankment typeHomogenous Embankment type

Zoned Embankment type: It consists Zoned Embankment type: It consists

of more than one type of material i.e. of more than one type of material i.e.

the central impervious core is flanked the central impervious core is flanked

by zones of materials considerably by zones of materials considerably

more pervious.more pervious. Diaphragm typeDiaphragm type

Methods of ConstructionMethods of Construction There are two methods of construction There are two methods of construction

of Earthen dam:of Earthen dam: 1. 1. Hydraulic – fill methodHydraulic – fill method: In this : In this

method excavation & transportation of method excavation & transportation of soils are done by using water. soils are done by using water.

2. 2. Rolled – fill methodRolled – fill method: In this, material : In this, material is transported from the borrow pits to is transported from the borrow pits to dam site by trucks & scrapers and dam site by trucks & scrapers and spread to form layers of 15 to 45 cm spread to form layers of 15 to 45 cm thickness.thickness.

MULA Project - IntroductionMULA Project - Introduction This Project was considered in 1877 for a This Project was considered in 1877 for a

storage project for irrigation for Rahuri & storage project for irrigation for Rahuri & Newasa TahsilsNewasa Tahsils..

The river Mula rises in Western Ghats of The river Mula rises in Western Ghats of Harischandragad in ranges of SahyadriHarischandragad in ranges of Sahyadri

This is one of the major projects constructed on This is one of the major projects constructed on Mula river, a tributary of River Godavari, at Mula river, a tributary of River Godavari, at Baregaon Nandur, Tal: Rahuri, Dist: Baregaon Nandur, Tal: Rahuri, Dist: Ahmednagar.Ahmednagar.

The Catchment area is elongated to leaf shape The Catchment area is elongated to leaf shape and has total area of 2274 sq.kmand has total area of 2274 sq.km

Review of Mula ProjectReview of Mula Project Mula Dam is a Earthen Dam with Gated Mula Dam is a Earthen Dam with Gated

SpillwaySpillway.. The length of dam is 2856 M.The length of dam is 2856 M.

The Maximum Height of Dam is 48.13 M.The Maximum Height of Dam is 48.13 M.

Spillway is Masonry type having total length Spillway is Masonry type having total length 298.70 M.298.70 M.

The gates are Radial type & are 11 nos.The gates are Radial type & are 11 nos. The designed discharge is 5947.20 Cumecs.The designed discharge is 5947.20 Cumecs.

Method of AnalysisMethod of Analysis

The analysis of dam is done by Swedish The analysis of dam is done by Swedish circle Method for upstream and circle Method for upstream and downstream slope.downstream slope.

Phreatic line is decided.Phreatic line is decided. U/S slope is checked for sudden U/S slope is checked for sudden

drawdown condition.drawdown condition. D/S slope is checked for steady seepage D/S slope is checked for steady seepage

condition.condition.

Design Design

Factor of safety = resisting forces / Factor of safety = resisting forces / Actuating forcesActuating forces

Factor of safety for U/S = 1.72 > 1.5Factor of safety for U/S = 1.72 > 1.5

Factor of safety for D/S = 1.8 > 1.5Factor of safety for D/S = 1.8 > 1.5

Spillway Spillway

Spillway is structure constructed at a dam site Spillway is structure constructed at a dam site for effectively dispersing of surplus water from for effectively dispersing of surplus water from upstream to downstream.upstream to downstream.

LocationLocation:- a spillway may be either within the :- a spillway may be either within the body of dam or at one end of it or entirely body of dam or at one end of it or entirely away from it.away from it.

Spillway of Mula dam is located at left saddle.Spillway of Mula dam is located at left saddle. It is Ogee spillway with 11 radial gates.It is Ogee spillway with 11 radial gates.

Types of SpillwayTypes of Spillway Classification based on function:Classification based on function: 1. Main or Service Spillway.1. Main or Service Spillway. 2. Auxillary Spillway2. Auxillary Spillway 3. Emergency Spillway3. Emergency Spillway

Classification based on Flow through Classification based on Flow through Spillway:Spillway:

1. Gated /Controlled Spillway1. Gated /Controlled Spillway 2. Ungated / Uncontrolled Spillway.2. Ungated / Uncontrolled Spillway.

Types of SpillwayTypes of Spillway Classification based on prominent Classification based on prominent

features pertaining:features pertaining: Free overfall / Straight drop Free overfall / Straight drop

SpillwaySpillway Chute / Open / Trough SpillwayChute / Open / Trough Spillway Side Channel SpillwaySide Channel Spillway Shaft / Morning glory SpillwayShaft / Morning glory Spillway Conduct / Tunnel SpillwayConduct / Tunnel Spillway Siphon SpillwaySiphon Spillway Overflow or Ogee Spillway Overflow or Ogee Spillway

Forces acting on SpillwayForces acting on Spillway Water PressureWater Pressure Uplift pressureUplift pressure Pressure due to Earthquake forcesPressure due to Earthquake forces Silt PressureSilt Pressure Wave PressureWave Pressure Ice PressureIce Pressure Self WeightSelf Weight

Failure of SpillwayFailure of Spillway

By Overturning about the toe By Overturning about the toe

By Crushing By Crushing

By development of TensionBy development of Tension

By Shear FailureBy Shear Failure

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