Project vinh phuc flood risk and water resource management

Project: Vinh Phuc Flood risk and Water resource Management TABLE OF CONTENTS CHAPTER OVERVIEW .3 1.1 INTRODUCTION 1.2 BASIS FOR RDS PREPARATION 1.3 PROJECT INTRODUCTION 1.4 PROCESS OF REPAIRING, UPGRADING 3 CHAPTER NATURAL, PEOPLE’S LIVING, ECONOMIC CONDITIONS OF THE PROJECT AREA .8 2.1 GEOGRAPHICAL LOCATION 2.2 TOPOGRAPHICAL, GEOMORPHOLOGIC CHARACTERISTICS 2.3 GEOLOGICAL CHARACTERISTICS 2.4 METEOROLOGICAL, HYDROLOGICAL CONDITIONS 2.5 SOCIO-ECONOMIC CURRENT SITUATION 8 11 13 CHAPTER ASSESSING STATUS OF CLUSTER WORK .15 3.1 EARTH DAM 15 3.1.1Main dame 15 a.Dam-crest 15 a.Upstream dam slope 16 b.Downstream dam slope 16 3.1.2Auxiliary dam 20 a.Dam crest 20 b.Upstream dam slope 21 c.Downstream dam slope 21 3.1.3Auxiliary dam 22 c.Upstream slope 23 d.Downstream dam slope 23 3.2 SPILLWAY 24 3.3 INCIDENT SPILLWAY 26 3.4 INTAKE CULVERT 27 3.5 MANAEGEMENT ROAD 29 3.6 MANAGEMENT HOUSE 30 3.7 MONITORING EQUIPMENTS 30 3.8 RESERVOIR MANAGEMENT & OPERATION WORK 31 3.9 PLANS FOR FLOOD AND STORM PREVENTION AND DAM RESCUE 31 CHAPTER ASSESSMENT OF THE DAM SAFETY .33 4.1 HYDROLOGICAL CALCULATION AND FLOOD REGULATION 33 4.2 CALCULATION OF DAM REST ELEVATION 33 4.2.1Calculation sequence 33 4.2.2Calculation results 36 4.3 CALCULATION OF CHECKING SEEPAGE 37 4.3.1Calculation purpose 37 4.3.2Applied calculation method and programme .37 Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management 4.3.3Calculation documents .37 4.3.4Calculation results 40 4.4 CALCULATION OF DAM STABILITY CHECK 40 4.4.1Calculation method and programme 40 4.4.2Calculation documents .40 4.4.3Calculation result of stability .41 4.5 OPERATION AND MAINTENANCE PLAN FOR THE WORK 42 6.1 CONCLUSION 43 6.2 RECOMMENDATION 44 Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management CHAPTER OVERVIEW 1.1 INTRODUCTION 1.1.1 Name of project, package - Project: Vinh Phuc Flood Risk and Water Resource Management Project (VPFRWMP) - Package: Consultancy on Preparation of Report on Dam Safety (RDS) for Thanh Lanh reservoir 1.1.2 The Owner - The Owner: Vinh Phuc ODA Management Board 1.1.3 Organizations, individuals preparing Report on Dam Safety - Organizations in charge of RDS preparation: Development Research and Consultancy Centre (DRCC) - Officers involved in RDS preparation Project Manager: Assoc Pr – Ph.D Nguyen Canh Thai Hydraulic Experts: Msc Dương Van Vien Msc Le Hong Phuong Eng Truong Ba Thin Eng Trinh Duy Thanh Msc Tran Duy Quan Technical Experts: Assoc Pr – Ph.D Hoang Thanh Tung Dr Ngo Le An Dr Tran Kim Chau 1.1.4 - Location of Project area Location: Trung My commune, Binh Xuyen District, Vinh Phuc province 1.2 BASIS FOR RDS PREPARATION 1.2.1 Legal basis - Construction Law No 50/2014/QH13 dated 18th June, 2014 - Decree No 143/2003/ND-CP dated 28th November, 2003 regulating in detail the implementation of a number of articles of the Ordinance on exploitation and protection of hydraulic works - Decree No 67/2012 / ND-CP dated 10 September, 2012 on amending and supplementing some articles of Decree No 143/2003/ND-CP dated 28 November, 2003 of the Government on detailing the implementation of the some articles of the Ordinance on exploitation and protection of irrigation works Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management - Decree No 112/2008/ND-CP dated 20th October, 2008 on the general management and exploitation of natural resources and environment of hydroelectric, hydraulic reservoirs - Decree No 72/ND-CP dated 07th February 2007 on the dam safety management - Directions of the Government in Document No 21/CT-TTg dated 14th October 2013 on strengthening the reservoir safety management and assurance - Circular No 33/2008/TT-BNN dated 04th February 2008 on guiding a number of articles of Decree No 72/ND-CP - Operational policy on dam safety OP/BP 4.37 of the World Bank 1.2.2 - Other relevant current technical regulations, standards Regulations, standards applied to Report on dam sfaety preparation National Technical Regulation QCVN 04-01:2010/BNNPTNT on the composition and contents of preparing investment report, investment project, and economic and technical report of hydraulic works - National Technical Regulations QCVN 04-05: 2012 /BNNPTNT – Main provisions on designing for irrigation works - National standard TCVN 8216: 2009 – Design of compacted earth dam; - National standard TCVN 8421: 2010: Hydraulic works – Waves and ships-induced load and force on the works; 1.2.3 Current regulations, standards Materials and softwares used in the report a Used documents: To conduct the Dam safety report, the consultants made a number of main contents and volume as follows: - Collection of design documents of Thanh Lanh reservoir relating to RDS preparation: + Documents of investment project of Thanh Lanh reservoir prepared in 1999 by Hydraulic construction consulting company No.1 - Survey, gathering of documents and studied about the livelihood, socioeconomy in the project area: + The population and society: Surveying and assessing the status of population and society in the project area + The situation of economic development, the development direction + The situation of flood, flooding and drought in the project area Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management - Documents of natural conditions of the project area: + Documents of meteorology: rain, wind, temperature, sunlight, air humidity + Documents of hydrology: inflow, flooding flows - Documents of topography, geology: + Documents of terrain, geology, surveying work at technical design phase, prepared in 1999 by Hydraulic construction consulting company No.1 b Used softwares: - GeoStudio 2007 (Canada) : seepage calculation, stability of earth dam - DTL2002 (Water resource University): calculate the flood regulation - Other related solfwares 1.3 PROJECT INTRODUCTION 1.3.1 Project objectives The objective of the project is to enhance the flood and inundation prevention capability, mitigate the impact of disasters on the living of residents in the project area, and enhance the efficiency of agriculture and non-agriculture production, contributing to poverty reduction at the local Besides, the project contributes to controlling flood risk, reducing and regulating flood for the basin of Phan river, Ca Lo river; improving the capacity of flood drainage, water storage and regulating for Phan River, Ca Lo river; establishing infrastructures for the development of industrial parks and attracting investment; improving ecological environment and forming regulating reservoirs, matching the general plan for construction of Vinh Phuc urban, Vinh Phuc province to 2030, with a vision to 2050 1.3.2 Objective of the dam safety consultancy services Objective of the consultancy services is to assess Thanh Lanh reservoir dam safety and auxiliary works to ensure that the investor could apply the necessary measures to ensure dam safety This objective will be achieved by visual inspection for the dam and auxiliary works, and assessing the safety conditions of the reservoir and dam, including process of management, operation and maintenance at the present The assessment shall comply with the procedures and regulations of Vietnam and the standards of the World Bank 1.3.3 Overview of the work Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management Thanh Lanh reservoir was built in Trung My commune, Binh Xuyen district, Vinh Phuc province The Reservoir was started the construction in 2001 and put into use in 2006 Headworks cluster includes main dam, intake culvert placed left abutment of the main dam, auxiliary dams and spillway located in the middle of the Auxiliary Dam No line Thanh Lanh reservoir which is the work of grade II (Under QCVN 0405:2012/BNNPTNT) was built with the tasks to irrigate agricultural land of 1200ha of four Communes of Trung My, Thien Ke, Ba Hien and Son Loi In addition, it has also used to prevent flooding for communes in the lowland area of Binh Xuyen district, supplying the living water for residents in the beneficial area in the dry season… Current parameters of the works: No Parameter I Reservoir Whole area of basin Total storage Effective storage Dead storage NWL Hi-rising WL II Dead level Earth Dam Value Km2 106m3 106m3 106m3 m m m 23.0 10,621 9,892 0.729 +76.60 +77.50 +62.20 Main dam Structure Elevation of dam crest Elevation of parapet wall crest Width of dam crest Length of dam crest Max height of dam Upstream slope coefficient Elevation of upstream berm Width of upstream berm Downstream slope coefficient Elevation of downstream berm Width of downstream berm Unit Homogeneous earth dam m m m m m +78.10 +79.10 5.0 362.0 29.0 2.75 - 4.5 +68.10 3.5 2.75 – 3.0 +60.10 3.5 m m m m Auxiliary dam Structure Elevation of dam crest Width of dam crest Length of dam crest Max dam height Hmax Upstream slope coefficient Homogeneous earth dam m m m m Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province +79.10 5.0 76.0 12.0 3.0 Project: Vinh Phuc Flood risk and Water resource Management No Parameter Unit Value 2.75 Downstream slope coefficient III IV Auxiliary dam Structure Elevation of dam crest Width of dam crest Length of dam crest Max dam height Hmax Upstream slope coefficient Downstream slope coefficient Intake culvert Type of culvert Elevation of intake-culvert sill Dimension Length of culvert Slope of culvert bottom ic Flow regime Spillway Form of spillway Width of water spill Number of valve gates Form of valve-gate Elevation of spillway sill Continuous form Form of dissipation Homogeneous earth dam m m m m +79.10 5.0 159.0 9.1 3.0 2.75 RC box culvert m m m +60.0 100 112.0 0.01 Unpressurized Spill of pragmatic ophixerop with valve gate 10.0 m unit Arch-shaped valve-gate m +71.6 Chute Dissipation tank 1.4 PROCESS OF REPAIRING, UPGRADING Thanh Lanh resevoir was built and put into use in 2007, the work has been in operation for years, the process of repairing, upgrading is as follows: - In 2009, spouting-drilling to handle the waterproofing for auxiliary dam No - In 2013, constructing the rivetment to protect the management road from the main Dam to Spillway - In March 2015, repairing the opening and closing machine of the downstream cone valve of the intake culvert; replacing high-pressure pump and oil-feeding hydraulic pipe system Repairing the management house, replacing all windows and doors, making the metal-sheet roofing for purposes of heat-resistance and leakage Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management CHAPTER NATURAL, PEOPLE’S LIVING, ECONOMIC CONDITIONS OF THE PROJECT AREA 2.1 GEOGRAPHICAL LOCATION Thanh Lanh reservoir has the location of Work construction in Trung My commune, Binh Xuyen district, Vinh Phuc province, and is far from the center of Vinh Yen city of 12km in the direction of Northwest - The North: is bordered by Tam Dao mountain range, and Thai Nguyen province - The East : is bordered by Ngoc Thanh commune, Phuc Yen town - The West: is bordered by Minh Quang commune, Tam Dao district - The South: is bordered by Ngoc Thanh commune, Phuc Yen town Project area Figure 2.1 Location of Work 2.2 TOPOGRAPHICAL, GEOMORPHOLOGIC CHARACTERISTICS In the North of Vinh Phuc is Tam Dao mountain range stretching from Dao Tru commune (Tam Dao) - the northernmost point of the province to Ngoc Thanh commune (Phuc Yen) - the easternmost point of the province with a length of 30 km, Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management the Southwest is surrounded by the Red River and Lo River forming topographical type gradually lowering from the Northeast to the Southwest and dividing the province into three areas with specialized topography: plains, hills, low and medium mountains - Plain topography: includes 76 communes, wards and towns, with a natural area of 46,800ha The plain areas consists of old and new alluvial areas The old alluvial area is mainly formed by alluvial of large river systems such as the Red River, Lo River, Day River, the area of this region is relatively wide, including the North of Me Linh1, Yen Lac and Vinh Tuong districts and the South of Tam Duong, Binh Xuyen districts, which were formed in the same period of the Red River delta formation (Quaternary – Pleistocene Era) The new alluvial area along the rivers in the districts of Song Lo, Lap Thach, Vinh Tuong, Yen Lac, Me Linh, the south of Binh Xuyen, which were formed in the Quaternary period – Holocene Era The land in plain area is enriched by alluvial of the Red River, so it is very fertile, and the ideal condition to develop intensive agriculture economy - Hill topography: includes 33 communes, wards and towns, with an natural area of 24,900ha This is favorable area for the development of industrial crops, fruit trees and crops, combining with raising cattle, creating favorable conditions for the restructuring of crops and raising by increasing the production of food goods - Lower and middle mountain topography: has a natural area of 56,300ha, accounting for 46.3% of the natural area of the province The topography of mountainous areas is complex and separated, with many rivers and streams This is one of the advantages of Vinh Phuc province compared to the provinces around Hanoi, because there are many favorable conditions for the development of concentrated industrial parks and eco-tourism areas Tam Dao mountain region covers an area of 15,753ha of national forest 2.3 GEOLOGICAL CHARACTERISTICS According to the survey conducted by Hydraulic Consulting Company No.1 (Hec1) in 1999, the geological conditions of the ground are as follows: 2.3.1 Geological conditions of main dam - Layer (1a) is medium - heavy semi-clay, some locations are light semi-clay in brown-yellow and gray-brown color, and in hard and flexible state with tight and Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management moderate structure The layer is mainly distributed in the mudflats of the stream bed, the layer’s thickness is from 0.5÷ 1.0m - Layer (1) is sand and gravel of the stream bed in gray-white, gray-yellow color The gravel content makes up from 50÷ 60%, the rest is gravel, sand and less clay particles The layer is distributed on the surface of the stream bed - Layer (2) is semi-clay containing macadam and pebble in brown-red, browyellow color with the macadam content accounting for 20÷ 45% The earth is in half hard-hard state and tight-medium structure, and distributed mainly in the foothill of the right abutment into small stretch The layer’s thickness is from 1÷ 8m and the layer is derived from eluvial and alluvial (daQ) - Layer (3) is heavy- medium semi-clay containing macadam and laterite in brown-yellow, brown-red color The macadam content accounts for 10-30% of macadam and hard and solid laterite The layer is in hard-half hard state and tightmedium structure and widely distributed on the surface of the hillside Original rock: of the foundation area is located in middle Triassic sediment of grade Ladini of Deo Nhe layer and magma formations of Tam Dao 2.3.2 Geological conditions of flood discharge spillway and auxiliary dam - Layer (3) is heavy-medium semi-clay mixing a great deal of macadam and laterite.It is in gray-brown, gray-yellow color The mechanical and physical properties of this earth are described such as the main dam foundation, the layer is widely distributed on the surface of the spillway line with the thickness from ÷ 3m - Layer (3a) is heavy-medium semi-clay containing macadam in brown-yellow, brown-red color, the macadam content is from ÷ 25%, macadam is soft It is in hardhalf hard state and tight-moderate structure, the layer is distributed in the lenticular form and under layer (3) with the thickness from ÷ 2m - Original rock under the pillway foundation is silty clay stone, sandstone in gray-green, light gray color, stone structure 2.3.3 Auxiliary dam - Layer (3) is medium semi-clay mixing many macadam and laterite in graybrown, gray-yellow color, the mechanical and physical properties of the layer are the same as layer (3) as mentioned the main dam Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 10 Project: Vinh Phuc Flood risk and Water resource Management Comment : With a very crowded number of people living in the downstream of the dam, the people is 7,230 people The downstream includes infrastructure of schools, the Committee, the Health Clinic, the culture house , and to the spiritual Temple, Shrine , The operation & management unit should build flood prevention plan and timely response in case of emergency The local levels and authorities need to pay more attention to in operation & management, invest to repair and have rescue plans in case of emergency Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 32 Project: Vinh Phuc Flood risk and Water resource Management CHAPTER ASSESSMENT OF THE DAM SAFETY With the aim to assess the dam safety in the different working conditions, the dam safety advisory group has carried out calculations for flood regulation, the discharge capacity of the spillway, calculate the stability, seepage of the earth dam under various conditions that may occur during the operation The calculations are based on the applicable design standards and regulations of Vietnam and the World Bank’s regulations 4.1 HYDROLOGICAL CALCULATION AND FLOOD REGULATION Report on hydrological calculations conducted with the frequency of the design and check in accordance with the design standards of Vietnam, with the work of grade II, check and design flood frequency by Vietnamese Standard TCVN04-05: 2012 is Pdesign=1.0% and Pcheck =0.2%; simultaneously calculating flood level as recommended by the World Bank with frequency P = 0.01% In special cases of the operation, the valve gate blocking can occur, design flood frequency P = 1.0% Calculation results are shown in Table 4.1 Table 4.1 Calculation results of flood regulation Case Bspill = 10m, Bincident spill = 30m P= 1.0% valve gate Calculation cases Zmax (m) Inflow Qmax (m3/s) Discharge flow qmax (m3/s) P= 1.0% 77.12 329.0 233.46 P = 0.2% 77.71 450.0 300.47 P= 0.01% 78.74 705.0 469.88 blocked 79.07 329.0 197.87 Comments : Based on the hydrological calculation results, it showed that the most unfavorable case is the blocked valve gateand, appearing the design flood frequency, the elevation of design flood level in this case is + 79.07m approximately the elevation of parapet wall of +79.10 In order to keep the work safe in any cases, we propose expanding the accidental spillway to lower water level 4.2 CALCULATION OF DAM REST ELEVATION 4.2.1 Calculation sequence Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 33 Project: Vinh Phuc Flood risk and Water resource Management The elevation of dam crest is determined at water levels: Normal water level and design flood water level (NRWL and DFWL) (corresponding to the design flood P=1.0%) and must be higher than CFWL1 (corresponding to the check flood level, P=0.2%), CFWL2 (responding to the check flood level, P=0.01%) Z1 = NWL + ∆h +hsl + a (3.1) Z2 = DFWL + ∆h' + h'sl + a’ (3.2) Z3 = CFWL + a” (3.3) Z4 = CFWL2 (3.4) Z5 = DFWL, valve gate blocked (3.4a) In which: ∆h and ∆h' – wind-induced surge corresponding to the maximum calculation wind, and the maximum average wind hsl and h'sl are the height of wave run-up on slope (reliability of 1%) corresponding to the max calculation wind and the max average wind a, a’, a”- safe freeboard corresponding to NWL, DFWL and CFWL with the work of grade II under Standard TCVN04-05: 2012/BNNPTNT (refers to Table in design standards for compatced soil dam, TCVN 8216-2009, equivalent to the work of grade III), then we have a = 0.7 m; a’ = 0.5 m; a” = 0.2 m Wind frequency calculations is referred to Table in design standards of compacted earth dam TCVN 8216-2009, then the largest and the largest average calculated wind frequencies are 4% and 50%, respectively The dam crest elevation to be selected is the elevation with the max value among the above results - Determine ∆h: V 2D ∆h = kw g ( d + 0,5∆h ) cosαw (3.5) + α: angle between the vertical axis of the water storage area and wind direction + V: calculated velocity of the wind + D: wave momentum + kw: coefficient, referred to Table A2 _TCVN 8421-2010 - Determine hsl : Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 34 Project: Vinh Phuc Flood risk and Water resource Management Under TCVN 8421-2010, the height of wave run-up with the reliability of 1% is determined with the formula as follows: hsl1%=K1 K2 K3 K4.Kα hs1% (3.6) + K1, K2: Coefficients depending on relative roughness and characteristics of dam surface reinforcement materials + K3: coefficient subject to wind velocity and inclined slope coefficient m + K4: Coefficient is determined based on λ ratio and inclined slope coefficient h of the work + Kα: coefficient is determined depending on angle αs + hs1% : Wave height corresponding to the reliability of 1% - Determine hs1%: hs1% is determined according to TCVN 8421-2010 as follows: + Assume that the case in question is deep wave (H > 0.5 λ ) + Calculate with dimensionless index gt gD , , in which t is time of continuous V V2 wind duration: t = (h) + Refer to the graph in Figure A-1_TCVN 8421-2010, determine the dimensionless numbers gh gτ ; v2 v (with two pairs of values corresponding to the values of dimensionless numbers as calculated above) Select the pair of lower values to calculate τ, h , λ + Check conditions of deep wave + Calculate hs1% = K1% .h Refer to the graph in Figure A-2_TCVN 8421-2010 corresponding to gD , we have V2 K1% + K1, K2: coefficient depending on ∆ h1% and character of reinforcement material, refer to Table 6_TCVN 8421-2010 + K3 : with the upstream slope coefficient , refer to table 7_TCVN 8421-2010 Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 35 Project: Vinh Phuc Flood risk and Water resource Management + K4: coefficient depending on λ hs1% and the slope m, refer to the graph in Figure 11_ TCVN 8421-2010 + Kα : With angle αs refer to table 9_TCVN 8421-2010 4.2.2 Calculation results Calculation results of dam-crest elevation with spillway Width Bspillway=10m, Bspillway = 30m No Parameter Unit NWL DFWL (P=1%) CFWL Flood 0.01% Valve gate blocked m 76,60 77,12 77,71 78,74 79,07 m/s 27,00 18,60 78,74 79.07 Water level Wind velocity V Wave momentum D m 1000 1020 Depth H m 22,10 22,62 DH m 0,007 0,003 gD/V2 13,46 28,92 gt/V 7848,00 11392,26 0,0066 0,0105 0,487 0,370 2,16 2,17 1,05 0,80 0,86 1,10 2,353 2,086 m 8,65 6,79 m 0,017 0,017 8,23 8,46 g(hs)tb/V2 hs hs 10 k1% m 11 h1% m 12 gτ / V 13 τ 14 λ Roughness of dam 15 slope 16 l/h1% 17 K1 1 18 K2 0,9 0,9 19 K3 1,475 1,47 20 K4 1,18 1,24 21 hsl m 1,65 1,32 22 a m 0,7 0,5 0.2 23 Zđ m 78,95 78,94 77.91 Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 36 Project: Vinh Phuc Flood risk and Water resource Management Table 4-2 Calculation results of dam crest elevation ∇ dam crest Case Water level NWL DFWL (P=1.0%) CFWL1(P=0.2%) CFWL2(P=0.01%) DFWL blocked CV Unit m m m m m Z 76.6 77.12 77.71 78.74 79.07 ∇ dam crest (calculated) (Current) 78,95 78,94 79.1 77,91 78.74 79.07 Safety level Assured Assured Assured Assured Assured Comments: As per a calculation result of the dam crest elevation, it is shown that the current dam crest elevation +79.10, assured in all circumstances height 4.3 CALCULATION OF CHECKING SEEPAGE 4.3.1 Calculation purpose Seepage through the dam body not only causes water loss in the reservoir but also affects the seepage strength, affects the stability of dam slope and foundations Calculating the seepage through the earth dam requires sufficient data on shape of cross-section, structure and formation of strata of the dam foundation and body as well as data on physio-mechanical parameters of materials of dam body and foundation This following section will present the content and calculation results of the main dam seepage and stability of Thanh Lanh reservoir 4.3.2 Applied calculation method and programme The seepage through the earth dam is calculated in accordance with the finite element method determining the stable saturation line, field of velocity and seepage gradient This method brings out accurate results, particularly in case that the dam contains different complicated materials zones This applied calculation program is GeoStudio 2007 This software is used to model movements and distributions of void pressures in the porous media such as rock and soil – the product developed by GEO - Slope Ternational Ltd., - Canada 4.3.3 Calculation documents h Documents of water level Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 37 Project: Vinh Phuc Flood risk and Water resource Management + Elevation of NWL: ∇ MNDBT = +76.6 m + Elevation of DFWL (P=1.0%): ∇ MNLTK = +77.12 m + Elevation of CFWL (P=0.2%): ∇ MNLKT = +77.71 m + Elevation of CFWL (P=0.01%): ∇ MNLKT = +78.74 m + Elevation of DFWL, valve-gate blocked (P=1.0%, blockedCV): ∇ MNLTK =79.07m + Elevation of dead water level: ∇ MNC = +62.2 m i Geological Documents Based on geological document of Thanh Lanh reservoir, we have the basic data of the soil layer of the dam body and dam bed as follows: Table 4-3 Mechanical and physical indicators of fill soil and dam foundation Soil layer Dam-fill layer Layer 1a Layer Layer 3a Layer γ (KN/m3) C(KG/cm2) ϕ(degree) K(cm/s) 18.2 19.2 17.7 18.5 18.3 21.0 17.0 22.0 25.0 29.0 18012’ 14051’ 16036’ 15049’ 16010’ 1.0× 10-5 1.625× 10-7 4.17× 10-6 9.0× 10-6 6.6× 10-6 j Calculation cross-section - Diagram of Calculation cross-section of the main dam 105 Elevation 95 85 75 65 55 45 35 25 15 -20 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Distance Figure 4-2 Calculation x-section of seepage and stability for main dam slope Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 38 Project: Vinh Phuc Flood risk and Water resource Management - Diagram of Calculation cross-section of auxiliary dam 1: Elevation 90 80 70 60 50 40 -40 -30 -20 -10 10 20 30 40 50 60 70 80 90 100 110 120 130 Distance Figure 4-3a Calculation x-section of seepage and stability check for main dam slope - Diagram of Calculation cross-section of auxiliary dam 2: 95 Elevation 90 85 80 75 70 65 60 55 50 -10 10 20 30 40 50 60 70 80 90 100 110 Distance k Calculation cases - CASE 1: Upstream is NWL +76.6 m, no water at downstream - CASE 2: Upstream is DFWL +77.12 m, water level equivalent at downstream - CASE 3: Upstream is CFWL +78.74 m, water level equivalent at downstream Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 39 Project: Vinh Phuc Flood risk and Water resource Management 4.3.4 Calculation results Table 4-1 Calculation results of checking seepage for main dam of Thanh Lanh reservoir TT Calculation cases Dam TH1 TH2 TH3 TH1 TH2 TH3 TH1 TH2 TH3 Main dam Main dam Main dam Auxiliary dam Auxiliary dam Auxiliary dam Auxiliary dam Auxiliary dam Auxiliary dam Seepage flow Jxymax q(10-6m3/s/m) 3.432 3.851 4.232 1.87 1.976 2.098 1.379 1.488 1.617 3.25 4.12 4.90 0.719 0.746 0.778 0.656 0.659 0.662 Gradient value calculated is high, appearing at the locations such as the cutoff position of dam, stone pile for drainage, at these locations the filter layers were arranged Conclusion: In both cases of calculation, the biggest seepage Gradient value appears at the transitional treated locations, so that the dam assures the safety in terms of seepage 4.4 CALCULATION OF DAM STABILITY CHECK 4.4.1 Calculation method and programme This applied calculation program is SLOPE/W This is a software applied by using the critical equilibrium theory to identify the stability coefficient of rock or soil slopes, that was programmed by GEO - SLOPE International Ltd – Canada This program enables to calculate simultaneously with different methods Calculate the stability of dam slope using Bishop, Jambu methods which are currently popular, produce satisfactory accurate results, and are simple to calculate For the purpose of ensuring the safety in the calculation, the following only present the outcomes of the used method producing the lowest coefficient of safety 4.4.2 Calculation documents l Calculation cross-section Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 40 Project: Vinh Phuc Flood risk and Water resource Management Sections of seepage calculation are used to check the stability of dam slope m.Calculation cases Thanh Lanh reservoir is located in Trung My, Binh Xuyen District, Vinh Phuc province which is the work of Grade II Referring to the Appendix of seismic zoning by administrative place and earthquake-resistance work design standard TCXDVN 375-2006, Binh Xuyen District belongs to the earthquake zone of Level VII under scale of MSK64 Under the provisions of the World Bank, the earthquake of Grade VII and the work of Grade II, it is required to calculate with the cases of earthquake According to TCVN 8216-2009, standards of designing the compacted earth dam and requirements of the World Bank, it is required to conduct stability calculations with cases NWL, DFWL, CFWL and NWL with earthquake event: Table 5-2 Cases of calculating earth dam stability No Case Combination Slope stability Basic Downstream Basic Downstream Special Downstream Special Downstream CASE CASE CASE NWL at Upstream +76.6m; no water at downstream DFWL at Upstream +77.12m; water level is equivalent at downstream DFWL at Upstream +78.74m; water level is equivalent at downstream NWL at Upstream +76.6m; no water at TH4 downstream, with earthquake grade VII 4.4.3 Calculation result of stability Table 5-3 Calculation results of dam stability check Kminmin No Dam Calculation case Combinatio n Main dam Main dam Main dam Main dam Auxiliary dam Auxiliary dam TH1 TH2 TH3 TH4 Basic Basic Special Special 1.329 1.301 1.290 1.208 1.30 1.30 1.10 1.10 TH1 Basic 1.265 1.30 TH2 Basic 1.251 1.30 Downstream slope Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Upstream slope [K] 41 Project: Vinh Phuc Flood risk and Water resource Management No 10 11 12 Dam Auxiliary dam Auxiliary dam Auxiliary dam Auxiliary dam Auxiliary dam Auxiliary dam Kminmin Calculation case Combinatio n Downstream slope TH3 Special 1.234 1.10 TH4 Special 1.175 1.10 TH1 Basic 1.477 1.30 TH2 Basic 1.472 1.30 TH3 Special 1.448 1.10 TH4 Special 1.380 1.10 Upstream slope [K] Conclusion: Based on the calculated results, it is shown that the calculated cases, the stability safety coefficient calculated > allowable coefficient [K], so that the dam ensures the stable conditions 4.5 OPERATION AND MAINTENANCE PLAN FOR THE WORK The operational plans shall comply with the approved operational procedures of the work The maintenance plan shall base on the results annual assessment, inspection of the works, based on the parameters measured, monitored to propose, and develop appropriate maintenance plans for the work Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 42 Project: Vinh Phuc Flood risk and Water resource Management CHAPTER CONCLUSION AND RECOMMENDATION 6.1 CONCLUSION According to the survey and assessment of current situation by observation, the hydrological calculation results for flood regulation and the calculation results of dam crest elevation, the calculation results of seepage and stability of the dam, we make conclusions on some issues relating to dam safety of Thanh Lanh reservoir as follows: Main dam: - Currently, the dam is stable; the upstream slope is reinforced by concrete, and good quality The downstream is protected by growing grass but the grass is sparse, the earth is eroded, many locations of slope is locally eroded by rain, it is necessary to add drainage ditches on the slope, backfill earth and additionally grow grass to ensure antierosion Dam crest need additional reinforced concrete Auxiliary dam 1: - The dam is stable, the upstream slope using stone riprap is good quality, in the downstream slope, the grass evenly grows, the equipment of additionally covering slope for seepage drainage is good quality The dam crest using macadam is eroded, it needs to be reinforced by using cast-in-situ concrete It is necessary to construct wheel curbs or marker posts, and arrange lights on the dam crest to ensure traffic safety Auxiliary dam 2: - The dam is stable, the upstream slope using stone riprap is good quality, in the downstream slope, the grass evenly grows, the equipment of additionally covering slope for seepage drainage is good quality The seepage discharge through the dam is in the permitted limit It is necessary to arrange lights to create favorable conditions for the operation and management Spillway: The spillway is tructured by reiforced concrete, the spillway has steel arch valve gate, the spillway is good quality Closing and opening valve is normally operated, the spillway is maintained by mechanical equipment periodically in accordance with the operation procedures Water intake culvert: - The water intake culvert is in good quality, the opening and closing is tightly, and its operation is normal Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 43 Project: Vinh Phuc Flood risk and Water resource Management Management road, management house: - The management house is good quality, which ensures the requirements for accommodation, living and working of operational staff The management road is concretied, and good quality which ensures the favorable travel for operation Monitoring equipment: - Currently, the seepage monitoring equipment is broken and needs to be repaired and replaced to ensure the monitoring data during the operation Operation management: - Regarding staffing management framework, it meets the requirements, ensures the conditions for the dam safety The document of Work management is sufficient; the operational staff are trained qualified; has the operation procedures and plans for flood prevention It is necessary to develop a Emergency Preparedness Plan (EPP) due to the crowed population in the downstream of reservoir and many infrastructure of the State; 6.2 RECOMMENDATION In order to promote the efficiency, safety, stability and durability, it is necessary to conduct several following works: - Overcoming some of banging pots exist in reporting by annual maintenance capital of the company, or drilling Waterproof items were approved by the provincial project to accelerate implementation - This is a big dam, so the management of operational needs taken seriously, closely, promptly report the situation to have plans for dealing Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province 44 ... – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management CHAPTER OVERVIEW 1.1 INTRODUCTION 1.1.1 Name of project, package - Project: Vinh Phuc Flood Risk and Water Resource. .. situation of flood, flooding and drought in the project area Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management - Documents... brown-yellow and gray-brown color, and in hard and flexible state with tight and Report on Dam Safety for Thanh Lanh reservoir – Vinh Phuc province Project: Vinh Phuc Flood risk and Water resource Management