Services
TerraSystems provides specialized ground improvement services designed to enhance soil performance and support structural integrity.
Sectors We Serve
We support foundation stability and site preparation for a broad range of commercial and infrastructure developments.
Dynamic Compaction
A cost-effective method that densifies loose soils and uncontrolled fill by dropping heavy weights from height, improving load-bearing capacity, and reducing settlement.
What is Dynamic Compaction
Dynamic compaction is a specialized ground improvement technique utilized for compacting old fills as well as soft or loose natural soils. This method has consistently proven to be an effective and economical alternative to preloading, deep foundations, deep vibratory compaction, and undercutting and replacement.
The Process
These dynamic stresses are generated by the impacts of heavy steel weights or tampers, which are dropped from heights of up to 70 feet on a predetermined grid pattern.
Crater Formation
The impact forms a crater at the drop point that may be up to 7 feet deep.
Backfilling
The craters are then backfilled by pushing or dumping either on-site or imported fill material into them.
Multiple Passes
Depending upon the level of improvement required, several phases or passes of high-energy tamping may be needed.
The "Ironing" Pass
Following the completion of high-energy tamping, a closely-spaced low-energy (or "ironing") pass is generally performed to compact the crater backfill material.
How Much Improvement is Possible?
The results of dynamic compaction are highly customizable based on the project parameters:
- The overall degree of improvement is dependent on the total energy applied to the ground.
- We use various correlations to select the appropriate applied energy to achieve the desired end product.
- The depth of improvement is strictly proportional to the energy per drop and the configuration of the tamper.
- Outstanding results are possible; allowable foundation bearing pressures of up to 6,000 psf are achievable with dynamic compaction.
Densified Aggregate Piers (TerraPiers)
TerraSystems utilizes various techniques for installing aggregate piers, including our DHT Terrapier™ using down- hole tampers, our Vibro Terrapier™ using powerful vibrators, and our IDP Terrapier™ using high-energy deep impacts.
IDP Terrapier™
TerraSystems utilizes various techniques for installing aggregate piers, including our IDP Terrapier™ using high-energy deep impacts. The Impact Densification Pier (IDP) technology was developed to combine the benefits of aggregate pier technology and dynamic compaction technology.
The IDP Terrapier™ Difference
It is the only system that uses large energy impacts to densify and prestrain the subsurface layers below the depth of the piers.
With this unique technique settlement below the base elevation of the aggregate piers can be greatly reduced or eliminated.
It can be used in any soil type where a hole can be augered, including silts, clays, organic deposits and most sands.
The energy levels that are generated by the high-energy impacts are approximately a hundred times higher than with conventional aggregate pier construction techniques.
Although limited soil densification occurs with other aggregate pier installation techniques, IDP ramming technology is a soil densification process that also produces an aggregate pier.
The aggregate pier-soil matrix is much stronger than with any other aggregate pier installation method, resulting in superior settlement control and higher bearing pressures.
The IDP technique has been used on projects with column loads varying from 50 Kips up to 5,000 Kips.
The IDP Terrapier™ Technique
The technique involves first augering a 30 to 36 inch-diameter hole to depths of 5 to over 25 feet.
The augering process provides a direct observation of the subsurface layers, allowing rapid field modifications to the design, if required.
Aggregate is then added to the hole and densified with a 5 to 6 ton circular steel tamper, using multiple drops from heights of up to about 40 feet, depending on design requirements.
This ramming action results in a very dense expanded base bulb as well as a significant zone of compacted soil beneath the base bulb.
Thin lifts of aggregate are then added and vertically compacted with the tamper until the design bearing elevation is reached.
IDP Advantages
Combines two proven technologies.
Extremely strong piers, verified with modulus testing.
Superior settlement control.
Rapid installation rates with up to 50 piers per day being common.
Visual observation of soil types through auger cuttings.
Green technology, assisting in LEED certification.
Low cost.
Bearing pressures of up to 10,000 psf, with 6,000 psf being common.
Vibro Terrapier™
TerraSystems utilizes various techniques for installing aggregate piers, including our Vibro Terrapier™ using powerful vibrators. Vibro Terrapiers™ provide a cost-effective alternative to typical deep foundation support.
The Vibro Terrapier™ Difference
Vibro Terrapiers™ are vertical columns of densely-compacted aggregate, installed using powerful down-hole vibrators.
The technique is used primarily to increase the bearing capacity and reduce settlement of building foundations, support floor slabs, and increase the stability of retaining walls and slopes.
Vibro Terrapiers™ can be constructed above and below the groundwater table and in any soil type.
The technique is applicable for light to heavy foundation loads, for small to large projects, and for treatment depths of 5 to over 30 feet.
The Vibro Terrapier™ technique results in aggregate piers with very high modulus values in the compacted aggregate, often in the range of 2,000 to 4,000 TSF.
Significant lateral prestraining of the surrounding soil matrix occurs due to the large lateral forces generated by powerful horizontal mode vibrators.
The Vibro Terrapier™ Technique
Terrapiers™ are constructed by removing or displacing soil to create a cavity in the ground, penetrating soft zones, and then backfilling with aggregate from the bottom up using vibratory and displacement techniques.
Very high lateral stresses are generated by the compaction action in the aggregate, resulting in a high-modulus aggregate pier surrounded by pre-strained soil.
The primary technique uses a special rig with a down-hole vibrator.
Our smallest vibrator is capable of 45,000 pounds of lateral force and nearly 50,000 pounds of vertical force, insuring a tightly compacted layer of aggregate.
The typical installation of a Vibro Terrapier™ begins with pre-drilling a hole to the design depth.
After the cavity has been created, a layer of aggregate is placed at the bottom and compacted with the vibrator.
After this layer has been sufficiently compacted, more aggregate is added in roughly one foot layers.
The compaction and filling process continues to the required height of the pier.
In situations where the water table is too shallow to allow drilling, a bottom-feed technique can be used to place stone to the tip of the vibrator.
Advantages
High Bearing Pressure
Superior Settlement Control
Low Cost
Rapid Installation
Environmentally Friendly
Proven Experience
Rammed Aggregate Pier - DHT Terrapier™
TerraSystems utilizes various techniques for installing aggregate piers, including our DHT Terrapier™ using down-hole tampers. This technique has been used for thousands of projects throughout the United States and abroad.
The DHT Terrapier™ Difference
The DHT Terrapier™ system offers a highly engineered approach to ground improvement:
DHT Terrapiers™ are vertical columns of highly-compacted aggregate using vertical tamping with a down-hole hammer and a specially-designed circular foot for compaction of the aggregate.
The technique is used primarily to increase the bearing capacity and reduce settlement of building foundations, support floor slabs, and increase the stability of retaining walls and slopes.
The DHT Terrapier™ system is an ideal technique for installation of aggregate piers above the groundwater table and is particularly effective in allowing the use of high bearing pressures in old fill soils.
It is applicable for light to heavy foundation loads, but is most economical for light to medium loads where the depth of treatment can be maintained below about 20 feet.
The DHT Terrapier™ technique results in aggregate piers with very high modulus values in the compacted aggregate.
Lateral prestraining of the surrounding soil matrix occurs due to the lateral bulging that occurs during the tamping process.
The DHT Terrapier™ Technique
The DHT technique involves first augering a 30 to 36 inch-diameter hole to depths of 5 to over 25 feet.
The augering process provides a direct observation of the subsurface layers, allowing rapid field modifications to the design, if required, to fit the actual subsurface conditions.
Aggregate is then added to the base of the hole and densified with a down-hole impact hammer with a specially-designed circular foot.
This ramming action results in a very dense base bulb of aggregate surrounded by soil.
Thin lifts of aggregate are then added and vertically compacted with the tamper until the design bearing elevation is reached.
The ramming action densifies the aggregate as well as compacting and prestraining the surrounding soil matrix.
DHT Advantages
Proven technology, with thousands of successful projects.
Extremely strong piers, verified with modulus testing.
Superior settlement control.
Rapid installation rates with up to 50 piers per day being common.
Visual observation of soil types through auger cuttings.
Green technology, assisting in LEED certification.
Low cost.
High bearing pressures, with up to 6,000 psf being common.
Frequently Asked Questions
Dynamic Compaction
I've heard a lot about Rammed Aggregate Columns, shouldn't I use them instead of dynamic compaction?
Rammed Aggregate Columns, which we install under the trade name Terrapiers, can also be an excellent solution when ground improvement is needed. However, Terrapiers commonly cost 2 to 10 times the cost of dynamic compaction, and we would never advise the more costly option unless it was necessary. As the only contractor who uses both methods, we are uniquely qualified to assist your design team in determining the most appropriate ground improvement solution for your project.
Isn't Dynamic Compaction the same as Rapid Impact Compaction (RIC)?
It’s similar, in that both processes use impact to improve the soils. However, RIC uses a relatively light weight (7 tons) falling a very small distance (3 to 4 feet), so its effect is very limited. Its manufacturer suggests a maximum depth of compaction of 3 meters in very clean sands, decreasing rapidly with increasing fines content. Dynamic compaction, on the other hand, uses weights of 6 to 20 tons falling from heights of up to 80 feet, and can achieve a significantly greater depth and degree of improvement.
How do you know it has been successful?
The geotechnical consultant may specify a variety of subsurface testing techniques to verify that the improvement has been achieved. Unfortunately, experience has shown that in many cases, the testing does not accurately indicate the amount of improvement, unless it is done weeks or even months after the compaction is done. The simplest, and perhaps the most reliable indication of improvement is through elevation surveys of the compaction. Area. If the surface has been lowered, significant improvement has occurred.
Will it work on my site?
Dynamic compaction can work in most soil types, but the suitability depends on many factors, including soil type, groundwater conditions, proposed construction type, and type and location of other nearby buildings. We routinely assist owners, general contractors, and design consultants in deciding just what type of ground improvement is the most suitable for a specific project.
Can I do it myself?
You can certainly buy a crane and build yourself a weight and try it. On the other hand, we’ve invested a lot of years in learning both the technical and practical aspects of the process, and made plenty of mistakes along the way. Do you really want to go through that learning process on your own for just one project?
What about vibrations?
Vibrations are not as high as most people would expect. We have worked within 50 feet of existing buildings, and withing 15 feet of underground utilities without causing damage. A much bigger concern in most cases is public perception, because you can feel the vibration long before its strong enough to cause damage. IT is often very important to document conditions of surrounding buildings before dynamic compaction, and to monitor vibrations throughout the construction process.
I have to compact below the groundwater table, it can't work there, right?
We have done hundreds of projects in which the soils below the groundwater were improved. However, when planning a project where the groundwater is near the surface, it becomes important to conduct the compaction in a series of phases. After each phase of compaction, we wait until the piezometric pressure returns to normal before applying additional compaction effort.
How do you know when to stop?
We plan our compaction program using a combination of published guidelines and corporate experience, but we continually monitor the tamper penetration, ground heave, and other visible indications to verify that the ground is reacting as we anticipated. Based on those visual observations, we may decide to do additional compaction in some or all of the compaction area.
Who designs the program, and who is responsible for the results?
In many cases, a geotechnical consultant designs the details of the compaction program. In those cases, the consultant should take responsibility for the resulting performance. On the other hand, we offer complete design services, and can provide engineering evaluations of the completed compaction operations.
