Dam Safety Instrumentation with Case Study

Transcription

1 Dam Safety Instrumentation with Case Study Dr. Rajbal Singh Joint Director Rock Mechanics Discipline Central Soil and Materials Research Station (CSMRS), New Delhi

2 Dam Instrumentation Safety of Dam Construction First Filling Operation Refinement of Design Back Analysis

3 Status of Dam Instrumentation in India 4800 Dams under construction 200 Instrumented Dam (< 5 %) About 50 years ago, instruments were not usually specified in Water Resources ProjectProposalsandinstruments were installed only when problems were encountered during construction and operation of the project. Instrumentation is generally specified in each Project Proposal: Tala, Tehri, NJP, SSP, Indira Sagar.

4 Tala Hydroelectric Project, Bhutan 89 O 40' 89 O 40' TO THIMPHU DAM ROAD TO DAM SITE & ADIT NO. 1 C1 ADIT NO.1 C2 ADIT NO.2 ROAD TO GEDUCHU ADIT NO. 3 ROAD TO PADECHU ADIT NO. 2 KM 7.5 ROAD TO POWER HOUSE C4 ROAD TO KALIKHOLA ADIT NO. 5 C5 POWER HOUSE TAIL RACE TUNNEL ROAD TO MIRICHINGCHU ADIT NO. 4 KM 80 P.T. ROAD C3 HEAD RACE TUNNEL ADIT NO.5 MONITAR ADIT NO.3 ADIT NO.4 KM 45 TO PHUENTSHOLING

5 Layout of Head Race Tunnel Dam Complex RD 0 RD 3456 Takctchu D/s 2244m Thiyomachu D/s m U/s m Thiyomachu (101m) Padechu (268m) RD 9399 D/s m U/s m Geduchu (963m) RD D/s m U/s m AGO Reach Kalikhola (520m) Mirchingchu (320m) RD Mirchingchu D/s m U/s m RD Kalikhola Powerhouse Complex RD By Pass of HRT D/s m U/s m C1 C2 C3 C4 C5 HRT km HRT km HRT km HRT km Excavation of HRT from 11 Faces

6 PROJECT FEATURES Dam on River Wangchu Concrete Dam - 92 m height 130 m length (Located 3 km d/s of Chukha Power House) Diversion Tunnel m diameter 356 m length

7 U/S View of Dam Intake Structures Coffer Dam Diversion Tunnel

8 Dam D/S with Sluices Glacis (HPC) During Construction During Operation

9 Dam U/S & D/S during Operation

10 Instrumentation Programme at THEP Planning Technical Specifications Contractual Arrangement Calibration of Instruments Supply Installation Monitoring

11 Instrumentation Programme at THEP Accuracy of Data Analysis Documentation/Report DAS Attitude/Interest of Project Management Instrumentation Responsibility Cost of Instrumentation [3%]

12 Cost and Power Generation Cost to Completion Rs million Project Fully financed by the Govt. of India Indian Technology Instrumentation Cost Annual Generation million units Cost per unit - Rs per unit (India) - Rs per unit (Bhutan)

13 Instrumentation at Tala Project Quality Control and Instrumentation Contractual Arrangements EnCardio Rite Electronics Ltd., Lucknow Calibration of Instruments Supply Installation Monitoring Reporting of Monitoring Documentation

14 Instruments Installed in Dam S. No Name of Instrument Temperature Meter Pore Pressure Meter Joint Meter/ Crack Meter MPBX Normal Plumb Line Total No. of Instruments Proposed Installed Remarks Monitoring Monitoring Monitoring 9 7 Monitoring 2 2 Monitoring 6 Inverted Plumb Line 1 1 Monitoring Concrete Pressure Cell Vibrating Wire Strain Meter Up Lift Pressure Pipe Strong Motion Accelerograph Sets Sets 20 4 Monitoring Monitoring Monitoring Monitoring 11 Automatic Water Level Recorder 2 2 Monitoring

15 Instruments Installed in Dam Instruments Installed = 282 Nos. Instruments Working = 277 Nos. Instruments Not Working = 5 NOs.

16 U/S View of Dam, Intake Structures Coffer Dam, Diversion Tunnel TYPE: CONCRETE GRAVITY HEIGHT: 92 M NO. OF BLOCKS: 7 UNDERSLUICES: 5 OVER SPILLWAY:

17 LOCATIONS OF INSTRUMENTS IN DAM BLOCK 2

18 Concrete Placement in Tala Dam Concrete Completed- March 2006 EL EL ELEVATOR SHAFT 2500X2400 1NO. OVERFLOW SPILLWAY 1000 PARAPET EL EL EL EL EL NOS. 2 SLUICE CROSS GALLERY SPILLWAY (6500 X 13150) EL EL EL EL EL EL EL EL SUMP WELL EL EL FOUNDATION GALLERY

19 LOCATIONS OF INSTRUMENTS IN DAM BLOCK 5

20 OBSERVATION OF TEMPERATURE METERS 35 B2T2 B2T3 B5T3 B5T7 B5T C 22 0 C 15 1/3/2001 1/4/2001 5/5/ /11/01 1/1/2002 1/2/2002 7/3/2002 2/4/ /11/02 7/1/2003 9/2/2003 9/3/ /4/2003 9/5/2003 Temperature ( o C) Date

21 OBSERVATION OF TEMPERATURE METERS TEMPERATURE METER BLOCK B5T16 B5T17 B5T18 B5T19 B5T20 B5T21 B5T DATE Figure 6A: Observation of Temperature meters B5T16 to B5T22

22 OBSERVATION OF TEMPERATURE METERS New Temperature M eters Of Block B2T19 B2T20 B2T21 B2T22 B2T23 B2T24 DATE Figure 5B : Observat ion of Temperat ure Met ers B2T19 t o B2T24

23 Temperature Meters in Block B2T1 B2T2 B2T3 B2T4 B2T5 B2T6 B2T7 B2T8 B2T9 B2T10 B2T11 B2T12 B2T13 B2T19 B2T14 B2T20 B2T15 B2T21 B2T16 B2T22 B2T17 B2T23 B2T18 B2T24 B2T25 B2T26 B2T27 B2T28 B2T /01/ /04/ /05/ /12/ /01/ /03/ /04/ /01/ /02/ /03/ /04/ /01/ /02/ /04/ /05/ /09/ /10/ /12/ /01/ /02/ /04/ /05/ /06/ /08/ /09/ /11/ /12/ /01/2006 Monitoring Time (Date) Temprature (degree c)

24 Cement Content & Concrete Temperature Cement Content kg/m 3 Temperature of Mass Concrete Remarks ( ) Cracking ( ) Cracking ( ) Cracking ( ) No Cracking ( ) No Cracking ( ) No Cracking ( ) No Cracking

25 60 50 Strength of In-situ Cores with Age and Cement Content Compressive Strength, MPa Compressive Strength Testing Age Cement Content, Kg/m Testing Age, days

26 35 Compressive S trength (MPa) Cube Compressive Strength at Different Testing Age Testing Age (Days) Cement Content = 200 kg/m3 Cement Content = 190 kg/m3 Cement Content = 180 kg/m3 Cement Content = 170 kg/m3 Cement Content = 160 kg/m3 Comp. Strength = 15 MPa after 365 days Comp. Strength = 12.5 MPa after 28 days 31.46

27 Pore Pressure Meters in Block B5P1 B5P2 B5P3 B5P4 B5P5 B5P6 B5P7 B5P8 B5P9 B5P10 B5P11 B5P12 B5P13 B5P14 B5P15 B5P /03/ /04/ /11/ /09/ /02/ /03/ /11/ /01/ /02/ /04/ /09/ /10/ /01/ /02/ /06/ /12/ /11/ /10/ /04/ /11/ /02/ /03/ /05/ /06/ /08/ /09/ /10/ /12/ /01/2006 Monitoring Time (Date) Pore Pressure (kg/cm2)

28 Stress Meters in Block /01/ /04/ /12/ /02/ /04/ /01/ /02/ /04/ /06/ /07/ /08/ /10/ /12/ /01/ /03/ /05/ /09/ /11/ /01/ /05/ /04/ /6/ /09/ /10/ /12/2005 B2S1 B2S2 B2S3 B2S4 B2S5 B2S6 B2S7 B2S8 B2S9 B2S10 Monitoring Time (Date) Stress (kg/cm2)

29 Strain Meters in Dam Block 2 11/02/ /03/ /04/ /05/ /10/ /11/ /12/ /01/ /02/ /06/ /09/ /06/ /08/ /09/ /11/ /12/ /01/2006 B2SN9A B2SN9B B2SN9C B2SN9D B2SN9E B2SN9F Monitoring Time (Date) Strain (micro meter)

30 Report on Instrumentation Monitoring

31 Report on Reprt # 6 Quality Control and Instrumentation for Concrete Gravity Dam of 1020 MW Tala Hydroelectric Project in Bhutan Volume II: Instrumentation Dr. Rajbal Singh Chief Research Officer, Quality Control Engineer-In-Charge, Instrumentation Quality Control Department Tala Hydroelectric Project Authority Gedu, Bhutan October 2006

32 INDEX S. NO. CONTENTS PAGE NO. PREFACE LIST OF TABLES LIST OF FIGURES I v-vi vii-viii 1.0 INTRODUCTION DETAILS OF INSTRUMENTS INSTALLATION OF INSTRUMENTS MONITORING OF INSTRUMENTS CONCLUSIONS 17 ACKNOWLEDGEMENTS 18 REFERENCES 19 TABLES FIGURES ANNEXURES

33 CONCLUSIONS Mass concrete temperature, which was about 10 0 C at the time of placement, has risen up to C and finally settled down between C to C. Due to low ambient temperature (4 0 C) in the month of January, temperature of mass concrete dropped during 3 days from Cto5.2 0 C and increased again up to C. Cement content in mass concrete should be optimized to achieve required strength. High cement content leads to cracking in mass concrete. Temperature readings should be monitored from the time of placement of concrete. Instrument should be calibrated with placement temperature of mass concrete.

34 CONCLUSIONS contd. The pore pressure meters installed have shown pore pressures in the range of 3.2 kg/cm 2 to 4.0 kg/cm 2, in Blocks 2 and 5 respectively. Three joint meters/crack meters installed in blocks 3 and 5 at the cracks, show the increase in crack width in the order of 0.01mm to 0.11 mm. The joint meters installed between two blocks joint have shown insignificant displacement in the range of 0.01mm to 5.40mm.

35 CONCLUSIONS contd. The concrete pressure cells installed in Blocks 2 and 5 have shown pressures in the mass concrete varying from 5.5 kg/cm 2 to 4.4 kg/cm 2 which is 3.8 to 4.76 time lower than theoretically expected stresses of kg/cm 2 and kg/cm 2 based on mass concrete density of 2400 kg/cm 2 and height of blocks 84 m and m above the pressure cells, respectively. However, the pressure cells have shown increasing trend during observations. 9.2 kg/cm 2 & 12.6 kg/cm 2 from FEM The safe design parameters must be made available and may be attached with data acquisition system as alarm for further monitoring the safety of dam.

36 CONCLUSIONS contd. In general, behaviour of all instruments installed in Tala dam was in order with respect to increasing/decreasing trends in observations. A record number of 277 instruments were in working order out of 282. This was possible due to awarding a contract for supply, installation, maintenance and monitoring of instruments before commencement of dam construction.

37 Temperature Meter Instruments Installed Concrete Pressure Cell Pore Pressure Meter Joint Meter/Crack Meter Strain Meter Spider For Strain Rosettes

38 MPBX MULTI POSITION BOREHOLE EXTENSOMETER (MPBX)

39 Instruments Installed READ-OUT UNIT/ DATALOGGER

40 NORMAL & INVERTED PLUMBLINES

41 INSTRUMENTS INSTALLED Uplift pressure Meters Water Level Indicators Surveying Points or Targets

42 INSTRUMENTS INSTALLED SEISMOGRAPH GPS STRONG MOTION ACCELEROMETER SAM

43 INCLINOMETER SYSTEM CASING PROBE CONNECTING CABLE REEL INCLINOMETER DATALOGGER

44 SETTLEMENT MAGNETIC SYST EM DISC/PLATE MAGNET MAGNETIC PROBE SPIDER MAGNET

45 Thank You For your Kind Attention Please