International Journal of Engineering Science Invention Research & Development; Vol. IV, Issue V, NOVEMBER 2017 www.ijesird.com, E-ISSN: 2349-6185 CONTROL OF SEEPAGE IN MASONRY GRAVITY DAM THROUGH SUITABLE CEMENTITIOUS GROUTING Gaurav Banwat1, Surbhi Jain2, Jayesh Balchandani3, Deep Bajoria4, Kumar Shivam5 Department of Civil Engineering, MITCOE, Kothrud, Pune, Maharashtra, India, 411038. Email- gauravbanwat523@gmail.com Abstract— The purpose of this thesis is to present an overview of the state of the art in dam rehabilitation to highlight the major innovations. This paper covers a detailed study of the seepage problem in the dam, its control measures and design provisions for the seepage control in the dam. Exploring these topics include looking at the various causes in the failures of the dam such as hydraulic failure of the dam, seepage failure and the structural failure of the dam. Also explaining the various grouting techniques which are the integral part of the new dam construction as well as control of seepage in old dams and also have a considerable importance as a remedial tool. In recent years however, there have been highly significant advances in the materials, methods and techniques which have increased remarkably the scope and power of grouting in the remedial applications. Keywords— Conventional and Finite Element Analysis of distressed gravity dam, grouting and repairing of dam prototype, Conventional and Finite Element Analysis of the prototypes after grouting. I. INTRODUCTION A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by primarily utilizing the weight of the material alone to resist the horizontal pressure of water pushing against it. A gravity dam is a massive sized dam fabricated from concrete and designed to hold back large volume of water. By using concrete, the weight of the dam is actually able to resist the horizontal thrust of water pushing against it. This is why it is called a gravity dam. Since gravity dams rely on their own weight to hold back water, it is key that they are built on strong foundation of bedrock. If a gravity dam is straight in plane it is known as Straight gravity dam, while if it is curved in plane it is known as Curved gravity dam. A curved gravity dam (or Arch-gravity dam) however, resist forces exerted upon it both by gravity action and arch action. Further a gravity dam is also classified as Solid gravity dam and Hollow gravity dam. A solid gravity dam has its entire body consisting of a solid mass of masonry or concrete. On the other hand, a Hollow gravity dam has a hollow space left within the body of dam. The reason for which the gravity dams need rehabilitation are mainly the time damage and the destructive effects of flash floods and earthquake effects. In our case the dam is heavily distressed and is facing seepage problem. Never the less the lifetime can be extended if they are regularly maintained. II. METHODOLOGY The problem statement of this thesis is as under. A masonry gravity dam is having seepage problem .The top width of the dam is 13.33m, height of the dam is 80.32m and base width of the dam is 73.23m . Suggest a suitable remedy for control of seepage through grouting and analyse the dam for safety. Gaurav Banwat, Surbhi Jain, Jayesh Balchandani, Deep Bajoria and Kumar Shivam Fig.1 Section of the dam ijesird, Vol. IV, Issue V, November 2017/182 International Journal of Engineering Science Invention Research & Development; Vol. IV, Issue V, NOVEMBER 2017 www.ijesird.com, E-ISSN: 2349-6185 The methodology adopted for this thesis consisted of three steps: Step I: Analysis of the distressed gravity dam by conventional gravity method performed manually and by Finite Element Method performed using software LUSAS. Step II: Grouting of the dam prototypes using two different grout mixtures. Step III: Analysis of the dam prototype by conventional gravity method performed manually and by Finite Element Method performed using software LUSAS. Step I: Analysis of the distressed gravity dam by conventional gravity method performed manually and by Finite Element Method performed on software LUSAS: Suitable NDT tests were carried out on the distressed gravity dam to calculate the density of the distressed dam which came out to be 2050 kg/m3. After the density of the distressed dam was calculated the conventional analysis of the dam was done for Load Combination A (Completed reservoir but no tail water and back water or reservoir at empty condition) and Load Combination B (Full reservoir elevation normal dry weather tailwater, normal uplift, ice and silt (if applicable)) and the safety of the dam was checked against overturning sliding and shear which gave out the following results. Load combination A: The overturning factor , sliding factor and the shear friction factor all came out to give the values as infinity which inculcated that the dam was safe for Load Combination A. Load Combination B: For this combination the dam actually falied in all three checks giving values as: FoS against overturning =0.55(<1.5) ; FoS against sliding = 0.9(<1.2) ,FoS against shear = -0.98(<1). Similar results were calculated from the stressdiagrams got after FEM analysis . The stress diagrams are as under: Load Combination A: Fig.2Stresses in X-direction Fig.3 Stresses in Y-direction Fig.4 Shear Stresses Load Combination B: Fig.5 Stresses in X-direction Fig.6 Stresses in Y-direction Fig.7 Shear Stresses Gaurav Banwat, Surbhi Jain, Jayesh Balchandani, Deep Bajoria and Kumar Shivam ijesird, Vol. IV, Issue V, November 2017/183 International Journal of Engineering Science Invention Research & Development; Vol. IV, Issue V, NOVEMBER 2017 www.ijesird.com, E-ISSN: 2349-6185 Step II: Grouting of the dam prototypes using two different grout mixtures: After the analysis was done for the distressed gravity dam then suitable blocks of sizes 1Mx1Mx1M were prepared using stone masonry which had voids and seepage which resembled the condition of distressed gravity dam. NDT tests were performed on the blocks. The ultrasonic pulse velocity meter was used and the readings were noted as under : Later on after the grouting was completed the blocks were allowed for curing for a period of 90 days. They then were again checked for improvement in density by the NDT test performed using ultrasonic pulse-velocity meter. The lesser the time required by the wave to cover the distance the more was the degree of the improvement in the density. The readings after grouting were as under: Sr. No. Time in microseconds U1 U2 U3 M1 M2 M3 L1 L2 L3 U4 U5 U6 M4 M5 M6 L4 L5 L6 263, 285 394, 389 277, 286 374, 290 331, 320 289, 299 340, 325 331, 276 255, 267 392, 402 313, 334 282, 264 372, 311 261, 304 291, 306 323, 307 336, 347 316, 313 Table NDT on Blocks Sr. No. Time in microseconds U1 U2 U3 M1 M2 M3 L1 L2 L3 U4 U5 U6 M4 M5 M6 L4 L5 L6 511, 741 483, 634 506, 519 530, 504 539, 570 516, 527 595, 567 528, 513 551, 517 555, 688 695, 525 536, 576 585, 526 565, 570 516, 553 505, 536 533, 744 527, 529 Seeing the readings of the NDT after grouting it is clear that the density of the blocks have increased to a great extent. After this cores of sizes 30 cm in diameter and 60cm in length were taken out from the blocks using a core cutter machine. This cores were then tested for their compression strength under a compression testing machine for the improvement in the strength. The remaining scrap was then collected for calculating the density of the block after grouting. The density of two blocks with different grouts were calculated as under: Block grouted with flyash and cement: Total mass = 86.2 kg havg = 55.3 cm ravg = 14.55 cm Volume = 36779.09 cm3 As the time is known , distance travelled by the wave is known ( 1M), velocity of the wave can be calculated. This was done just to check the improvement in the density of the block after grouting. Two types of grout mix were used during the grouting process. One was a mixture of cement(60%), flyash(40%) and water and another contained bentonite(2%), cement(70%) and fly ash(28%). Plasticizers were also used . The mixtrures were then compared for their efficiencies and economy. Before grouting both mixtures were tested under different tests as consistency test, initial and final setting time, compression test, flowability test by marsh cone, settlement test, and Density = pH value to check their consistency and workability. Gaurav Banwat, Surbhi Jain, Jayesh Balchandani, Deep Bajoria and Kumar Shivam = 2.34x 103 kg/cm3 ijesird, Vol. IV, Issue V, November 2017/184 International Journal of Engineering Science Invention Research & Development; Vol. IV, Issue V, NOVEMBER 2017 www.ijesird.com, E-ISSN: 2349-6185 Failure load = 217 KN Wt of dry stones = 42.95 kg % wt of dry stones = = 49.82% 65% of 86.2 kg = = 56.03 kg volume of dry stones = 7.3 x 10-3 m3 volume of 65% of stones (V )= = x 7.3 x10-3m3 V= Volume of motor = volume of core - volume of 65% stones = (36.779x10-3 - 9.5x210-3) = 27.259x10-3 m3 Weight of dry mortar = 86.2 - 42.95 = 43.25 kg Weight of 35%mortar = = = W =39.99kg Total weight of modified core = 39.99 + 56.03 = 96.02 kg Density of modified core = = 2610.72 kg/m3 ’ Assuming that we have achieved the designed density as 2350 kg/m3. Block grouted with flyash , cement and bentonite: Total Mass = 80.85 kg Havg = 52.4 cm Ravg = 14.525 cm Volume=36779.09 cm3 = 52.55 kg 65%of 86.2 kg = volume of dry stones = 8.25 x 10-3 m3 volume of 65% of stones (V) = = V= x 8.25 x10-3m3 =10.20x10-3m3 Volume of motor = volume of core - volume of 65% stones =(3634.713x10-3 - 10.2x10-3) =24.21x10-3 m3 Weight of dry mortar=80.85-45.3=35.55kg Weight of 35%mortar = W =32.92kg Total weight of 32.92+52.55=85.47kg ’ Density of modified core = modified core = = 2462 kg/m3 Assuming that we have achieved the designed density as 2350 kg/m3. After getting the improved density of 2350 kg/m3, the analysis was done for the improved density block and was checked for safety against overturning, sliding and shear. Step III: Analysis of the dam prototype by conventional gravity method performed manually and by Finite Element Method performed using software LUSAS: The calculated density of the blocks after grouting was then used for the conventional as well as Finite Element Analysis and was checked for the stability. The analysis was done for Load Combinations A (empty condition), B (Full reservoir elevation normal dry weather tailwater, normal uplift, ice and silt (if applicable)) and E (Filled dam along with earthquake forces). The results after analysis were as under: Load Combination A: FoS for overturning = Infinity ( >1.5) ; safe Shear friction factor = Infinity ( >1) ; safe Load Combination B: FoS for overturning = 1.59 ( >1.5) ; safe Shear friction factor = 1.39 ( >1) ; safe Load Combination E: FoS for overturning = 1.16 (<1.5) fails Shear Friction Factor = 1.25 (1.0) safe Same results were calculated from the values of the stresses obtained by Finite Element Analysis using LUSAS software. The stresses are as shown under: = Gaurav Banwat, Surbhi Jain, Jayesh Balchandani, Deep Bajoria and Kumar Shivam ijesird, Vol. IV, Issue V, November 2017/185 International Journal of Engineering Science Invention Research & Development; Vol. IV, Issue V, NOVEMBER 2017 www.ijesird.com, E-ISSN: 2349-6185 Fig.8 Stresses in X- direction Fig.9 Stresses in Y- direction Fig.14 Stresses in X- direction Fig.15 Stresses in Y- direction Fig.10 Shear Stresses Load Combination B: Fig.16 Shear Stresses Fig.11 Stresses in X- direction Fig.13 Shear Stresses Load Combination E: Fig.12 Stresses in Y- direction III. CONCLUSIONS After performing analysis by conventional gravity method and finite element method the following are the conclusions we came with: 1. After grouting with both the grout mixtures the design density of 2350 kg/m3 was achieved. 2. The tensile stresses and the compressive stresses have been observed to be lower than the permissible limits, factor of safety against overturning, sliding and shear also were under permissible limits for Load Combinations A, B. 3. The tensile stresses and the compressive stresses have been observed to be higher than the permissible limits, factor of safety against overturning also was beyond the permissible limit for Load Combination E i.e. extreme load condition even for the designed density of dam masonry. 4. To attain stability of dam against the extreme load condition the base width of the dam needs to be increased to a Gaurav Banwat, Surbhi Jain, Jayesh Balchandani, Deep Bajoria and Kumar Shivam ijesird, Vol. IV, Issue V, November 2017/186 International Journal of Engineering Science Invention Research & Development; Vol. IV, Issue V, NOVEMBER 2017 www.ijesird.com, E-ISSN: 2349-6185 suitable value and again the analysis also grateful to our HOD Prof. Dr. Shantini Bokil for mentoring us throughout the project. needs to be performed for the dam section with increased base width. REFERENCES 5. From the analysis performed it is learnt [1] Effect of bentonite on rheological behaviour of cement grout in presence of superplasticizer by K.Benyounes, A.Benmounah. that the grout mixture with the use of [2] Study on permeation grouting using cement grout in sandy soil by bentonite will be economical for treating P.Dayakarl1, K.Venkat Raman2, Dr. K.V.B.Raju3. [3] A study of modelling of sliding failure of concrete gravity dam due to the dam. 1 2 ACKNOWLEDGEMENT We sincerely wish to express our deep sense of gratitude and indebtness to our guide Prof. M.M.KURULEKAR, Department of Civil Engineering, MIT College of Engineering, Pune for her inspiring guidance, constant encouragement and her meticulous efforts carried out for completion of this thesis. We are [4] [5] earthquake force by Susovan Sinhal , Dr. Aloke K. Datta , Dr. Piush Topdar3. Rehabilition technique for severely damaged concrete gravity dams stated the suitability of retrofitting technique. Determination of Strength Parameters of a Masonry dam by Flat Jack method by K.R.Dhawan1, A.V.Patil2 and S.J.Pillai3. Gaurav Banwat, Surbhi Jain, Jayesh Balchandani, Deep Bajoria and Kumar Shivam ijesird, Vol. IV, Issue V, November 2017/187