It's not unusual for a silo, railcar, or other storage container to experience a backup of materials. Certain items might stick to each other or to the walls of the container or get clogged through the chute or hopper at the bottom of the container. There are a few ways you can avoid this happening so that your materials don't get damaged and so that production is not slowed by this blockage; note a few popular options here. 

Mind the humidity

Humidity is a very common culprit for materials sticking together and not flowing properly. The dampness in the air can cause some materials to expand as they absorb this added moisture, so a hopper or chute gets clogged. Humidity and moisture can also react with some materials and cause sticking so that a bridge of materials is created across a storage container. This can also cause the materials to stick to the walls of the container. You need to ensure you're doing everything possible to mind the humidity in the area of your storage container; this can be as simple as adding ventilation so that humidity can escape, lowering the temperature so the air won't hold that humidity, or even adding a commercial dehumidifier to your space. 

Vibrations

Vibrations can help materials flow in any container as they can easily shake items away from the walls of the container and keep them from clinging to each other. Commercial vibration equipment can be hooked to the sides of containers and send those vibrations up each side, or they can concentrate their vibrations along the upper part of the container so bridges don't form. A commercial vibration piece can also shake particles loose around the hopper or chute so there is less blockage. However, this might not be a solution for delicate materials that could break up under vibration or those that might just stick together even more when you vibrate the container.

Air cannons

Air cannons are a good choice for loosening materials in any area of the container; they shoot a blast of air around the materials to loosen them from walls, the chute or hopper, and from each other. The pressure of air from air cannons can usually be adjusted so the air doesn't damage delicate materials, and the direction of air can be changed so you can address bridges, rat holes forming in the middle of your container, or a clogged chute.