MDC: Versatility with Dynamic Loading

The Landpac Mini Dynamic Compactor [MDC] was developed to supplement the ground improvement capabilities of the Landpac high energy impact compaction equipment by providing additional flexibility for generating ground improvement in ground strata to a depth of up to 5m.

MDC (attached to a telehandler)

The MDC is essentially a versatile multi-purpose ground improvement tool comprising a compaction mass [ranges from 750kg to 2000kg] that is hydraulically lifted to a height of up to 1.2m and allowed to free fall to generate a high energy dynamic compaction blow. The mass has a square base that contacts with the ground surface and allows for the high compaction energy to be transferred over a relatively large area [750mm x 750mm]. The MDC unit is capable of being cycled at up to 30 blows per minute and can be mounted onto various operating and manipulation platforms including excavators, telescopic handlers etc.

The entire compaction process is electronically controlled and is integrated with a continuous impact response compaction monitoring system similar to that used on the Landpac high energy impact compaction equipment. This allows the MDC to be operated utilising the variables of drop height [variable energy], number of blows [total energy input] and CIR response [ground stiffness/strength] as production and cut-off criteria.

As with the Landpac high energy impact compaction equipment, the compaction energy of the Landpac MDC is transferred in the form of a “dynamic load”. It is possible to generate very high compaction forces when utilising the Landpac MDC equipment and the main features of this high energy MDC process include the following:

1. Compaction Loads.

The high energy and dynamic compaction action of the Landpac MDC equipment leads to typical compaction loads of between 150kN and 350kN being generated depending upon the type and condition of the material being compacted.

2. Material Moisture Condition.

The high energy of the Landpac MDC equipment facilitates compaction of material to a higher maximum dry density than is achievable with conventional roller type of compaction equipment.This high energy also allows for the compaction of material over a wider range of moisture conditions particularly dry of optimum moisture content.

3. Depth of Influence.

The relatively high compaction loads that are generated by the Landpac MDC equipment lead to high surface contact pressure on the soil. This coupled to the relatively large contact area over which the compaction energy transfer takes place, leads to a vastly increased depth of influence of the compaction. Ground improvement is typically measured to effective depths of 2m-3m with depths of up to 5m being recorded in some applications.

4. Compaction Flexibility.

The fact that the MDC unit can be fitted to flexible operating platforms such as excavators and telescopic handlers means that the unit can be easily manipulated and placed in constrained or focussed areas. This allows for deep ground improvement to be carried out in very specific areas and formats and serves as a valuable support tool to the Landpac high energy impact compaction equipment that is better suited to large open areas.

Landpac high energy impact compaction equipment thus provides a process that allows for a wide range of applications from fill works compaction through to deep in-situ ground improvement. In all of the appropriate applications of this equipment it is possible to ensure project cost savings whilst at the same time enhancing the quality assurance of the works relative to the “in service” performance of the materials that have been treated using this equipment.

MDC used in housing developments

 

Typical Applications

The MDC is unique in its ability to perform certain compaction tasks, which up till now have been ignored or done via a very expensive and time-consuming way. The potential applications for this equipment are numerous, with the most obvious listed below:

1. Foundation Compaction

Where structures are to be erected on weak soil, the MDC is ideal in compacting the foundation strip to a much higher load carrying potential. The high energy that is focused on the exact area where the foundations are to be laid ensures a solid and reliable foundation is created, while it saves time, money and effort. Conventional alternatives such as constructing a solid base in thin compacted layers, using raft foundations or constructing much larger strip foundations than is necessary are all aimed at coping with the problem of weak soils, where the MDC will actually address the problem and improve the strength of the soil. Investigations have shown that a cost saving of up to 50% can be achieved, while significant time savings are realized. Typical applications include low-cost housing foundations and industrial foundations.

2. Compaction Adjacent to Structures

The MDC was designed to be able to compact right up against existing structures and right into corners. Compaction against bridge abutments is frequently problematic, with subsequent settlement causing amongst others degradation in the ride quality and an increase in maintenance costs of the road. Due to the ability to vary the energy level, compaction can also be performed over existing structures such as culverts or pipes without risking damage. This makes the MDC ideal to perform remedial compaction on roads where underground pipes are laid or repaired after road construction. Compaction has also been performed up against retaining walls, proving that it can be done very effectively and safely.

3. Trench Compaction

The MDC was designed to be able to compact right up against existing structures and right into corners. Compaction against bridge abutments is frequently problematic, with subsequent settlement causing amongst others degradation in the ride quality and an increase in maintenance costs of the road. Due to the ability to vary the energy level, compaction can also be performed over existing structures such as culverts or pipes without risking damage. This makes the MDC ideal to perform remedial compaction on roads where underground pipes are laid or repaired after road construction. Compaction has also been performed up against retaining walls, proving that it can be done very effectively and safely.

4. Localised Failure Repair

Major costs are incurred annually by authorities and/or agencies in the repair of localized road failure. Many failures re-occur due to the inability of existing small plant to achieve adequate compaction in the repair process. The mobility and ability of the MDC to compact small areas makes it superbly suited to ensure that high quality repairs are performed, and that recurring failures are eliminated. Being vehicle mounted ensures that distant or far removed locations are just as easily reached as any other location.

5. Concrete Breaking

With such high energy available, the MDC can, by fitting a special footplate, break concrete slabs very effectively and rapidly. Where localized repairs are performed in concrete structures such as concrete roads, the section to be removed can be demolished in a fraction of the time it takes conventional equipment.

6. Soil Characterisation

The high mobility and high energy levels obtainable with the MDC provides consulting engineers with the unique opportunity to gather extremely accurate information regarding the response of in-situ soils to compaction before foundation design is undertaken. Knowing the soils load carrying capability, as opposed to estimating it based on very limited laboratory testing, allow engineers to optimize designs and thereby realize huge potential savings. Being inexpensive to operate, the amount of tests can be increased significantly, giving much more accurate information on site characteristics.

7. Other

Other applications include:

o Compaction of Mini Stone Columns

o Compaction of Rock Fills

o Compaction of Railway Line Subgrades

 

Truck mounted MDC