Many inflatable rubber dams develop surface cracks after only two to three years of operation, yet a select few have remained in stable service for 20 years without any significant cracking. This is not merely a matter of luck; it is the result of meeting a comprehensive set of requirements -- including material formulation, fabric structure, production processes, engineering design, and operational management and maintenance.

I. Rubber Compound Formulation (The Core Internal Factor)

Selection of Base Rubber: For environments with high levels of sand, gravel, or exposed riverbeds, chloroprene rubber (CR) is preferred; for environments with intense sunlight, modified EPDM with high weather resistance should be used. These base rubbers inherently possess strong resistance to ozone and photo-oxidative aging. 
Additive System: Incorporate sufficient quantities of high-quality antioxidants, antiozonants, UV-resistant carbon black (e.g., N330), and plasticizers to delay the scission of rubber molecular chains and inhibit ozone-induced cracking. The proportions of these additives must be carefully balanced to prevent significant "blooming" (migration of ingredients to the surface). 
Rubber Layer Thickness: Ensure an adequate thickness for the outer rubber cover, accounting for potential wear and aging; the layer should not be thinned merely to reduce costs.

II. Fabric Reinforcement and Calendering Process

Utilize high-strength polyester fabric as the reinforcement skeleton. During the calendering process, ensure uniform tension to achieve strong adhesion between the fabric and the rubber, preventing delamination. If the fabric and rubber separate, the outer layer will quickly develop stress-induced cracks. 
Precise Control of the Vulcanization Process: Maintain stable vulcanization temperature, duration, and pressure to ensure thorough and uniform cross-linking of the rubber. Under-vulcanized rubber is prone to aging and becoming tacky, while over-vulcanized rubber becomes brittle and highly susceptible to cracking. 
Proper Pattern Design: The dam bag must be designed so that, upon inflation, stress is distributed evenly, avoiding long-term localized stress concentrations.

III. Engineering Design and Anchoring System

Ensure sound structural design for the dam floor and abutment walls, along with a robust anchoring system. The dam bag should be free from constant, excessive pulling or sharp-angle folding, which helps minimize fatigue cracks caused by repeated bending. 
Protection Against Bed Load: Implement measures such as bed protection and anti-scour trenches to reduce the continuous impact and abrasion of the dam bag surface by sand, gravel, and pebbles. Once the outer layer is worn thin, UV radiation and ozone can rapidly penetrate, triggering cracks. 
Optimized Overflow Design: Ensure proper overflow design to avoid persistent localized pounding or resonance, preventing fatigue cracking caused by cyclic stress.

IV. Operational Management and Control

Prohibit long-term operation under excessive pressure or water levels to minimize sustained high stress on the dam bag. Regulate the frequency of inflation and deflation cycles to prevent fatigue damage caused by repeated deformation.
In cold winter conditions, avoid forced inflation; low temperatures reduce the toughness of the rubber, making it prone to brittleness and cracking.

V. Routine Inspection and Maintenance

Regularly clear accumulated silt, sediment, and sharp debris from the dam surface to prevent cuts or abrasions. Even minor nicks can serve as starting points for cracks.
Promptly repair small areas of damage to prevent aging agents or environmental elements from penetrating the material through these openings.
Periodically monitor the appearance, thickness, and elasticity of the dam bags to address early signs of aging before they escalate.

Conclusion

Achieving a service life of over 20 years without cracking relies on several key factors: a weather-resistant material formulation, robust bonding of the rubberized fabric, the elimination of stress concentrations, protection against erosion from sand and gravel, and scientific operation and maintenance. The absence of any one of these elements will significantly shorten the dam's lifespan.