How to succeed with soil

Good compaction is the foundation of any construction project. It increases bearing capacity and durability, and prevents soil settlement and damage through swelling, frost or water. To be able to choose the right equipment and the right technique, you have to know which type of soil, and how many layers, you are dealing with.

Different soils and materials

CLAY - STICKS TOGETHER

Clay particles stick together and you need high impact force to get the air out. Proper moisture is important when compacting. Wet clay can be molded while dry clay becomes very hard and may crack under pressure. Husqvarna LT rammers are able to transmit the high pressures and shear forces necessary to compact clay at or below optimum water content.

SILT - NEEDS FORCE

Silt is not as cohesive as clay, but still needs proper water content for good compacting. The cohesive soils have the smallest particles of all soils. Silt particles are larger than in clay but they are still small enough to require high energy for deep compacting. A tamper is the best choice for compacting silt.

ROCKFILL - PUT ON THE PRESSURE
Cobbles and boulders need high compaction energy to achieve the necessary density and stability. It is especially important if the material is imbedded in clay or silt that may liquefy when wet. Layer thickness should be at least three times thicker than maximum particle size. Husqvarna LH 700 and LH 804 reversible plate compactors are ideal for large construction projects. The lighter Husqvarna LG 504 works well for smaller ones.

SAND AND GRAVEL - TAKE IT GENTLE
For sand and gravel you can achieve high-density compaction in either a dry or saturated state. The level of compaction depends more on grading than moisture. Too much compaction of sand and gravel is like beating a concrete wall with a sledgehammer. It can crush the material and reduce the load bearing capacity. Depending on the thickness of the layer, a lighter forward plate or heavier reversible plate compactor is recommended.

ASPHALT - LEAVE NO MARKS
Compaction has a profound influence on asphalt performance. Compaction transforms the asphalt mix from a loose state to a compact surface that carries heavy loads. Efficiency of compaction depends heavily on the internal resistance of asphalt. Machines must be able to compact without leaving marks and water helps to create a smooth surface. Here, an asphalt plate compactor or a duplex roller is a safe choice.

What are the different compaction techniques?

IMPACT COMPACTION

In impact compaction, the large stroke height of the tamper creates a powerful downward force to achieve good compaction depth.

VIBRATORY COMPACTION

Vibratory compaction combines static pressure and dynamic force.

STATIC COMPACTION

In static compaction, the underlying surface is exposed to pressure only.

Which compaction technique and equipment suits which soil or material?

Fractions with particle size < 0.075 mm

Use IMPACT FORCE on cohesive soils.

Fractions with particle size > 0.075 mm

Use VIBRATORY FORCE on granular soils and asphalt.

Fractions with particle size < 0.075 mm

Use STATIC FORCE on cohesive soils and asphalt.

Some tips to help you succeed with soil

Check the material and area you need to compact and choose your equipment accordingly. Consider height, e.g. under bridges.
Always compact one layer of soil at a time. See table below for maximum depth. Every layer contributes to the overall bearing capacity of the soil.

Do not over-compact.
Use the Husqvarna compaction indicator to identify when the soil is ideally compacted (available as option on Husqvarna LG 400 and LG 504).