Compacting granular soils such as sand and gravel is a difficult task. Due to the composition of sand and gravel, water can enter or leave the voids relatively easily. If the voids in the sand are filled with water or completely dry, there is no force to hold the sand particles together.
Vibration applied to these particles tends to produce a dense arrangement. The amount of water in the voids of the granular soil will affect the cohesion of the particles. Pouring sand or gravel from the lathe of a truck or scraper will leave the granular material in a relatively loose state, especially if the sand contains only a small amount of surface moisture. This material must be compacted to provide the required strength. If the material is not compacted, it will cause future settlement.
Vibratory roller
Vibratory rollers are designed to consolidate granular soil to a high density and compact to shallow depths very effectively. These rollers have different sizes and different ton capacity. This type of equipment can work effectively when the soil is placed in a narrow space.
Plate vibrator
Some excellent plate vibrators mount a gasoline engine to a unit that causes the plate to vibrate. These are very effective on sand and small gravel, compacted to a depth or lifting thickness of about 6 inches. Plate vibrators are usually used in small grooves and small diameter pipe installations. Due to its limited power and impact, when the thickness of the lift exceeds 6 inches, it is not recommended to use a flat plate vibrator.
Vibrating hammer
When using a vibratory hammer, the vertical vibration in the pile will disturb or "liquefy" the soil, causing the soil particles to lose friction against the pile. The pile moves downward under its weight plus the weight of the vibrating hammer. Usually an amplitude of at least one inch is required to cause enough soil disturbance to achieve the purpose of piling. The effect of vibratory compaction is very good, because the disturbance of the soil caused by the vibration causes the soil particles to move to a denser configuration. Large amplitude leads to high soil strain level, large influence radius and high compaction degree.
Vibration flotation
Vibration flotation is another very effective method for compacting clean, free-draining sand and gravel. It is similar to a standard internal concrete vibrator, but much larger and more powerful. The probe provides a large-volume water jet, which acts downward and laterally to submerge the soil and destroy the surface tension. This effect allows sand particles to have a greater degree of freedom when the particles vibrate and settle into a compact configuration.
Advances in soil compaction technology
In terms of compacting granular soil, technology is constantly improving. Compaction equipment can use monitoring systems and sensors to measure the stiffness of the soil, and generate numerical values related to the compaction progress to indicate the quality of the compaction process. This technology can reduce the time wasted to compact the area that has already been completed, thereby providing real-time values. This tool allows users to know when the design value is obtained, and prevents excessive use of resources due to excessive compaction of granular soil.
Other important factors
When compacting the soil, measures must be taken to protect the health of employees. Among workers who operate or manage compaction equipment, a disease called Raynaud's syndrome is very common. Transmission of vibrations to the hands and arms throughout the day can cause this disease, which can cause your employees to feel a kind of numbness and tingling of the fingers. If this condition worsens, it can cause loss of sensation in the hand and finger muscles. Some manufacturers have designed devices to reduce vibration. Some jurisdictions have laws restricting working hours during daily exposure to vibration because of the possibility of this disease.
