Dry sharing, dam construction should be done?

The dam is a very common structure in water conservancy projects, mainly used for water storage and irrigation. Strengthen the quality control of its construction process, is conducive to its normal operation. This paper combines years of construction experience on dam construction and quality control is described.　　

1 Geological conditions

The reservoir area is a sloping disk, the strata of the mud pan age Yujiang layer sandstone, Donggangling tuff, on the mud pan age Durujiang group of tuff, shale, etc., geologic structure in the sloping south-central, folded and fractured most of the north and south, parallel to the river. Therefore, most of the reservoir area is in the soluble carbonate rocks, reservoir livestock water, there is no regular leakage around the section, plus the reservoir groundwater is not deep, the ground water flow is abundant, for a good reservoir.　　

2 design notes

2.1 orifice design

1) the choice of water discharge method of gravity dams, the main way of water discharge is open overflow and orifice overflow, the former in addition to flood discharge can also be excluded from the ice or other floating objects. When the gate is set, the top elevation of the gate is roughly flush with the normal high water level, and the top elevation of the weir is lower, so that the opening height of the gate can be used to adjust the water level and discharge flow, which is suitable for large and medium-sized projects,, so in order to enable the reservoir to have a larger flood discharge capacity, the design adopts the open type of overflow.　　

2) Determination of the total length of the overflow dam section of the preliminary formulation of the thickness of the gate pier, the pier thickness d = 7m, side pier thickness t = 5.5m, the total length of the overflow dam section B0: B0 = nb + (n-1) d + 2t = 5 × 12 + (5-1) × 7 + 2 × 5.5 = 99m.

3) Determination of the height of the gate gate height = the normal high water level - the weir top elevation + ( 0.1～0.2)=182-176+(0.1～0.2)=6+(0.1～0.2)take 6.5m.

4)Determination of shaped design head Maximum head on the weir Hmax=Calibrated flood level - weir top elevation, i.e., Hmax=184.73-176=8.73m. shaped design head Hs=(75%～95%)Hmax=6.5475-8.2m. 6.5475 ~ 8.2935m, take 7.5m.

5) flow capacity calibration using the weir flow formula Q = σmmξB (2g) 0.5H01.5 sub-case calibration overflow weir flow capacity, the results of the calculations know that | (Q, -Q) / Q | & lt; 5%, indicating that the design of the orifice meets the requirements.　　

2.2 Drainage hole design

The power generation hole in this design is designed as a pressurized hole, the irrigation hole is designed as a non-pressurized hole, using the power generation tail water supply. The design of pressurized drain hole is set up at the inlet of the power generation hole with barrage and accident gate (also used as maintenance gate), the working gate is arranged at the outlet, the hole section is round, and the hole is lined with steel plate. Power generation hole **** set up four, for the unit water supply mode.　　

1) the hole diameter D of the proposed maximum power generation flow 87.687m3 / s, *** there are four units, by the formula D = (4Q / πVp) 0.5 to calculate. Where: Q is a number of power generation holes lead to the flow, m/s; Vp for the hole allowable flow rate, m/s, for power generation holes Vp = 3m/s ~ 3.6m/s; then D = [87.687/3.14 × 3] ~ [87.687/3.14 × 3.6] = 3.05m ~ 2.785m, take D = 3m.

2) Inlet body shape design of the inlet inlet The top is elliptic curve, the equation is x2/a2+y2/b2=1, where: a is the elliptic long half-axis, circular inlet, a is the diameter of the circular hole; rectangular inlet, the top curve a is the height of the hole h, the side curve a is the width of the hole B; b is the short half-axis of the ellipse, circular inlet, b=0.3a; rectangular inlet, the top curve b=(1/3～1/4)a, the side curve b=a/5. Here a=3, b=0.3a=1, then there is x/9+y=1.

3) The gate and the gate slot inlet are set up with a stopper and a plane accident gate, and a plane working gate. The accident gate is arranged close to the upstream dam surface, and the size of the gate slot is 0.8m×0.5m rectangular gate slot.　　

4) gradient section in the inlet gate after the gradient section, gradient section using rounded transition, the length of which is (1.5 ~ 2.0)D, here take 5m.

5) outlet outlet before the use of 1:10 pressure slope section, the exit section, the area of 85% to 95% of the borehole cross-section, due to the borehole cross-section area of A = π (D/2)2 = 7.065m2, so the exit section area is 6.065m2, and the exit section area is 6.065m2, and the exit section area is 6.065m2. Therefore, the area of the exit section is 6.005m2～6.711m2. The exit section is square, its size is 2.5m×2.5m, and the area is Ac=6.25m.

6) Drainage capacity checking and calculating the drainage capacity is calculated according to the pipe flow formula Q=μAc(2gH). Where μ for the flow coefficient; Ac for the outlet section of the relief hole area, m2; H for the reservoir level and the exit of the water surface of the height difference between. Take the flow coefficient μ = 0.85, then Q = 0.85 × 6.25 × (2 × 9.8 × 39) 0.5 = 146.878m3 / s.

7) unpressurized relief hole design irrigation hole working gate is arranged in the inlet, the top of the orifice after the working gate is elevated to form unpressurized flow. Inlet body shape design inlet from the inlet curve section, maintenance gate groove and pressure slope section, the inlet curve is also used 1/4 elliptic curve, followed by a straight line pressure slope section, the slope is 1:5, the length of 6m.

3 Construction

3.1 Dam top structure

1) gate layout working gate layout in the overflow dam section slightly downstream, to prevent When the gate is partially opened, the water tongue is detached from the dam surface and negative pressure is formed. The use of plane steel gate, the size of the door for 5m × 12m, the work of the gate upstream of the maintenance gate, the net distance between the two gates for 2m.

2) gate pier pier head shape for the upstream semi-circular, downstream using streamlined. The upstream arrangement of the work bridge, the top elevation of the non-overflow dam dam top elevation of 176 m. The thickness of the pier is 7 m, the thickness of the side pier is 5.5 m, the overflow dam is located in the middle of the slit hole, so there is no slit pier. Work gate 0.532 slot depth of 1m, 1m wide, maintenance gate slot depth of 0.5m, 0.8m wide.

3) water guide wall side pier downstream to extend into the water guide wall, the length of which extends to the picking of the end of the flow of the nose can. The height of the side pier should be 0.5m ~ 1.5m above the water depth after gas doping, flat section of the water depth after gas doping estimation formula: hb = h (1 + ξv/100). Where: h, hb for the gas before and after the water depth, m; v for the average flow rate of the calculated section before gas, m / s; ξ for the correction coefficient, generally 1.0 ~ 1.4m / s, v & gt; 20m / s, take the larger value. Then the height of the water guide wall is substituted into the data to get hb=1.8×(1+1.4×22.887/100)=2.377m, 2.377+0.6=2.977m, the water guide wall needs to be divided into seams with a spacing of 17m, and its cross-section is trapezoidal, and the top width is taken as 0.7m.

3.2 Split seams of the dam body and stopping of water

1) The transverse seams are arranged vertically on the axis of the dam. Seam distance is 19m, seam width 2cm, inside the water stop. 2) water stop dam body is equipped with two water-stopping sheet and a seepage control asphalt well. The water stop is made of 1.0mm thick copper, the first water stop is 1.0m away from the upstream dam surface. two water stops are spaced 1m apart, there is a 20cm diameter asphalt well in the middle of the water stop is 30cm deep into the bedrock and embedded with the concrete tightly, and the upper part of the water stop is extended to the top of the dam. 3) Longitudinal joints longitudinal joints are temporary joints with a key groove inside the joints, and the grouting is carried out when the concrete cools down sufficiently and the reservoir is filled with water before storage. Longitudinal seam and dam face orthogonal, seam distance of 20cm. 4) horizontal construction seam concrete pouring block thickness of 4m, longitudinal seam on both sides of the adjacent dam block horizontal seam staggered arrangement, the upper and lower layers of concrete pouring interval for 5d, the upper layer of concrete pouring before the lower concrete chiseling, and rinsing clean, lay 2cm thick cement mortar.　　

3.3 Corridor system

1) Foundation corridor corridor bottom from the dam foundation surface 4m, corridor bottom elevation is 147m, the upstream side (center point) from the upstream dam surface 4m; shape for the shape of the city gate, the bottom width of 2m, 3.5m high, the internal upstream side of the drainage ditch, and at the lowest place set up a catchment well. Parallel to the direction of the dam axis corridor to both sides of the terrain along the gradual increase in slope is not greater than 40.

2) The dam corridor since the foundation corridor along the height of the dam every 18m to set up a layer of corridor, *** set up two layers. The bottom elevation were 161m, 179m, the shape of the city gate hole shape, its upstream side (center point) from the upstream dam surface 4m, the bottom width of 2m, 3m high, the left and right banks each have an exit.　　

3.4 Dam body seepage control and drainage

1) Dam body seepage control in the upstream face of the dam, the overflow face and the downstream face of the dam below the highest water level, using a layer of 2m thick and seepage-proof concrete as the seepage control facilities of the dam body.　　

2) dam drainage from the upstream face of the dam 5m along the direction of the dam axis to set up a row of vertical drainage pipe curtain. The inner diameter of the pipe is 20cm, the spacing is 2.5m, the upper end leads to the top of the dam, the lower end leads to the corridor, vertical arrangement. Drainage pipe adopts sandless concrete pipe.　　

3.5 Strength grade of dam concrete

Dam concrete should meet the requirements of strength, seepage resistance, frost resistance, erosion resistance, scour resistance, low heat, cracking resistance, and volume change when hardening and other properties. In order to rationalize the use of materials, the dam concrete can be used in different parts, different working conditions with different strength levels, the thickness of the upstream face is greater than the downstream face, the thickness of the foundation concrete (Ⅳ area) is 0.1B (B is the bottom width of the dam body), and not less than 3.9m, and there should be a good contact zone between the different strength levels of concrete.　　

3.6 Foundation treatment

1) The seepage control treatment of the dam foundation is drilled in the foundation grouting gallery to set up the seepage control curtain and drainage hole curtain, whose centerline is 3m and 5m respectively from the upstream dam heel. the seepage control curtain adopts expansion cement slurry to do the grouting material, and its location is arranged in the foundation of the dam close to the upstream dam face and both sides of the dam. The depth of the curtain is taken as 10m~30m, the riverbed is deep, and both banks become shallow gradually, the grouting hole diameter is taken as 80mm, the direction is vertical, the hole distance is taken as 2m, and a row is set up.　　

2) Drainage of dam foundationThe drainage hole curtain of the dam foundation is at the downstream of the seepage control curtain, inclined to the downstream, and the angle with the grouting curtain is 10 °, the hole spacing is taken as 3m, the hole diameter is 130mm, and the depth of the hole is 10m～15m, and one row is set along the direction of the dam axis.　　　　

Before the construction, it is necessary to analyze the project carefully and choose the best construction method according to the actual situation of the project. At the same time in the construction, the construction of the management personnel must do a good job of coordination and arrangement, the construction process for strict control, construction personnel to do a good job of quality control and acceptance of key processes to ensure the quality of the project.

It is believed that after the above introduction, we have a certain understanding of the dry sharing, dam construction should be done. Welcome to visit Zhongda Consulting for more information.

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