Water Conservancy Project Air Inflatable Rubber River Water Dam/Rubber Dam/Air Shield Dam/Foundation/Dam Bag

Construction of Rubber Dams: Technical Protocol & Best Practices

Rubber dams—flexible, inflatable hydraulic structures fabricated from high-performance synthetic rubber—demand specialized construction workflows to ensure air/water tightness, structural durability, and reliable operation in low-head water management scenarios (e.g., irrigation networks, urban water features, flood mitigation systems). The process is centered on foundation rigidity, precise handling of the dam bag, and seamless integration of the inflation system, addressing the unique challenges posed by working with flexible materials. Below is a comprehensive, phase-by-phase breakdown of rubber dam construction, including technical specifications, quality control benchmarks, and industry-standard procedures.

1. Pre-Construction Phase: Planning & Preparation

1.1 Site Assessment & Design Validation

• Hydrological & Geological Surveys:

• Measure the watercourse’s width, average depth, and flow velocity to confirm dam dimensions (typical height: 1–5m; length: matching channel width to avoid flow bypass).

• Conduct soil bearing capacity tests (minimum requirement: 150 kPa) to identify weak layers (e.g., silt, peat). For soils with low bearing capacity, design reinforcement measures (e.g., gravel backfilling, geotextile stabilization).

• Layout Marking:

• Use GPS or total station equipment to mark the dam’s centerline, foundation boundaries, and anchor bolt positions. For curved channels, adjust the layout to follow the natural contour—sharp bends cause uneven stress on the dam bag and increase leak risks.

• Risk Mitigation Planning:

• Develop contingency plans for weather disruptions (e.g., deploy wind barriers for dam bag installation in winds exceeding 5 m/s) and on-site repairs (stock vulcanization kits for rubber tears, spare gaskets for sealing joints).

1.2 Material Sourcing & Quality Verification

1.3 Equipment & Safety Readiness

• Machinery: Excavators (10–15 ton, for foundation digging), vibratory rollers (compaction force ≥20 kN, for soil compaction), 10–20 ton mobile cranes (equipped with soft nylon slings to avoid dam bag damage), air/water pumps (matched to inflation system requirements).

• Safety Equipment: Non-slip work boots, nitrile gloves (to prevent rubber scratches), life jackets (for near-water operations), temporary fencing (to secure the construction zone), and first-aid kits (stocked for cuts, abrasions, and water-related emergencies).

2. Foundation Construction: Building a Stable Base

2.1 Site Clearing & Excavation

• Debris Removal: Clear rocks, tree roots, and vegetation from the construction area. For riverbed sites, dredge silt and organic matter to expose stable soil or bedrock (minimum depth: 500mm) to eliminate foundation settlement risks.

• Trench Excavation:

• Width = dam bag width + 2× anchor plate width (typically 1.2–2m, depending on dam size).

• Depth = 600–1000mm (adjusted for soil stability; deeper for soft soils).

• Dig a rectangular trench along the dam’s centerline. Dimensions:

• Slope trench walls at 1:1.5 to prevent collapse during construction.

2.2 Foundation Reinforcement

• Soil Stabilization:

• For soils with bearing capacity<150 kPa: Add a 300–500mm layer of graded gravel (particle size 5–30mm) or geotextile-reinforced soil. Compact the layer with a vibratory roller to achieve ≥93% compaction degree (tested via nuclear density gauge).

• Concrete Base Pouring:

• Pour a C30 reinforced concrete base (thickness 200–300mm) into the trench. Embed HRB400 steel reinforcement bars (diameter 12–16mm, spacing 200×200mm) to resist tensile stress and prevent cracking.

• Use a laser level and screed board to ensure the concrete surface is level (flatness ≤3mm/m) and aligned with the dam’s centerline.

2.3 Anchoring System Installation

• Bolt Positioning:

• Use a precision steel template to place anchor bolts in the wet concrete. Ensure bolt spacing matches the dam bag’s edge holes (tolerance: ±2mm) to avoid misalignment during bag installation.

• Extend bolts 100–150mm above the concrete surface (for dam bag clamping) and cover threads with plastic caps to protect against concrete contamination.

• Concrete Curing:

• Cover the concrete base with wet burlap or geotextile and cure for ≥14 days (maintain moisture to prevent shrinkage cracks). For temperatures<5°C, use insulation blankets to avoid freezing.

• Test concrete compressive strength after 28 days (minimum requirement: 30 MPa) using cube samples before proceeding to dam bag installation.

3. Rubber Dam Bag Installation: Precision Handling

3.1 Pre-Installation Preparation

• Protective Layer Placement: Lay a geotextile or rubber pad over the entire concrete base (covers the trench and adjacent areas) to prevent the dam bag from abrasion by concrete aggregates or residual debris. Ensure the pad is flat and free of wrinkles.

3.2 Dam Bag Unfolding & Alignment

• Unfolding:

• For small dam bags (<20m long): Unroll manually along the protective pad—avoid dragging, as this scratches the rubber surface.

• For large dam bags (>20m long): Use a crane with soft nylon slings (attached to pre-installed lifting lugs on the dam bag) to lift and unroll. Keep the bag taut but not stretched (overstretching damages the fabric reinforcement and reduces lifespan).

• Alignment:

• Adjust the dam bag so its edge holes align with the anchor bolts (tolerance: ±5mm). Use string lines to verify alignment with the dam’s centerline.

• Position the dam bag’s inflation valve near the pump station to minimize pipeline length and pressure loss.

3.3 Anchoring & Sealing

• Edge Clamping:

• Fold the dam bag’s edges over the anchor plates, ensuring EPDM gaskets are placed between the bag and plates to create a water-tight seal.

• Tighten anchor bolts in a diagonal sequence (to distribute pressure evenly) to a torque of 30–50 N·m (use a torque wrench to avoid over-tightening, which tears the rubber).

• Joint Vulcanization (for Multi-Section Bags):

• Temperature: 140–160°C (monitored via thermocouples).

• Pressure: 0.3 MPa (applied via hydraulic clamps).

• Holding time: 15–20 minutes (varies by rubber thickness).

• For dam bags longer than 30m (supplied in sections): Join sections using hot vulcanization:

• After vulcanization, inspect the joint for uniformity and apply a 1–2mm thick layer of EPDM sealant to reinforce the bond.

• Leak Testing:

• Inflate the dam bag to 50% of the design pressure (typically 0.07–0.09 MPa) using the inflation system.

• Spray a soapy water solution on anchor bolts, vulcanized joints, and the inflation valve. Bubbles indicate leaks—tighten loose bolts, reapply sealant, or re-vulcanize joints as needed.

4. Inflation/Deflation System Setup

4.1 Pipeline & Equipment Installation

• Piping Installation:

• Connect the dam bag’s inflation valve to the pump station using PVC or galvanized steel pipes. Use flange joints with rubber gaskets (tightened to manufacturer specifications) to prevent leaks.

• Support pipes with steel brackets (spaced every 2m) to avoid sagging and reduce stress on joints.

• Pump & Valve Integration:

• Mount air/water pumps on a concrete pad (elevated 100mm above ground to prevent water damage) and connect to the pipeline.

• Install pressure gauges (range 0–0.3 MPa, accuracy ±0.01 MPa) and pressure relief valves (set to 1.2× design pressure) to protect the dam bag from over-pressurization.

• For automated systems, integrate solenoid valves with a control panel (programmed for remote operation and pressure monitoring).

4.2 System Testing

• No-Load Test: Operate the pump without pressurizing the dam bag to check for pipe blockages, valve responsiveness, and pump noise (no abnormal vibrations or cavitation).

• Pressure Hold Test:

• Inflate the dam bag to the design pressure (0.12–0.15 MPa) and close the control valve.

• Monitor pressure for 24 hours—no pressure drop indicates a leak-free system. If pressure drops, use a ultrasonic leak detector to locate and repair faults (e.g., tighten flange joints, replace faulty gaskets).

5. Auxiliary Structures Installation

• Trash Racks: Install steel trash racks upstream of the dam (aligned with the channel width) to block debris (e.g., branches, rocks) from contacting the dam bag. Ensure racks are removable for periodic cleaning.

• Downstream Protective Pads: Place rubber pads (5–10mm thick) along the downstream edge of the concrete foundation to reduce abrasion from flowing water or sediment.

• Groundwater Drainage: Install perforated PVC pipes (diameter 100mm) behind the foundation, sloped at 1:100 toward the channel. This drains groundwater and prevents hydrostatic pressure from lifting the foundation.

6. Commissioning & Acceptance

• Full-Scale Performance Testing:

• Uniform inflation (no bulging or sagging).

• Anchor bolt tightness (re-torque if necessary).

• Leaks (no water seepage or pressure drop).

• Inflate the dam bag to the design height and monitor for 72 hours. Check for:

• Deflate the dam bag (ensure it collapses evenly onto the foundation) and repeat the inflation/deflation cycle 3 times to validate system reliability.

• Documentation & Handover:

• Compile construction records: material certificates, test reports (concrete strength, pressure hold, vulcanization quality), and photo documentation of key phases.

• Conduct a joint inspection with the client, supervisor, and design team to verify compliance with specifications. Sign an acceptance certificate once all criteria are met.

Summary