Ground Improvement Uses Diverse and Innovative Techniques to Change the Engineering Properties of Soils for More Efficient and Cost-Effective Design Options
Why Ground Improvement?
Rapid growth across Canada, specifically in recent decades, has seen high-quality land become scarce or unusable. Weak and highly compressible or collapsible soils often create serious negative consequences for a project if they are not significantly improved. Modification or improvement of soils plays an important role in terms of foundation stability, particularly in situations relating to load-bearing soils under new or existing structures. Ground improvement has distinct advantages when compared to over-excavation or ground replacement.
What is Ground Improvement?
Ground improvement is the stabilization of soils to increase their bearing capacity, provide stability, control seepage, and provide liquefaction resistance. GeoSolv’s Geo-Structural Engineering Team provides sound recommendations for ground improvement that include rigorous analyses of site soils and applied structural loads, along with the use of specialized equipment and construction procedures for modifying the ground’s character, with or without the addition of engineered material. Technologies to do so include: GP3® System, Impact® System, Rampact® System, X1® System, Densipact® System and Rapid Impact Compaction.
How is Ground Improvement Achieved?
The feasibility of a ground improvement approach for your project can be assessed based on the available geotechnical information and an understanding of the proposed structure and site works. Having a complete picture of the geology and geotechnical conditions of the site, a clear understanding of the planned structure, loading conditions, planned structure elevations and site grades−along with the clear identification of compressible or other weak soils prior to completing a detailed design is critical to project success.
Ground Improvement Applications
- Building Foundations and Floor Slabs
- Retaining Walls, Slopes and Embankments
- Tanks and Power Plants
- Transportation (Rail, Roads, Airports)
- Geotechnical/Geological Hazards
- Seismic Risk and Liquefaction
- Underground Infrastructure
Ground Improvement Delivery by GeoSolv
GeoSolv’s specialized teams of ground technicians and technical experts work in partnership with their clients. In early stages or due-diligence exercises, GeoSolv can provide free advice to owners and their consulting team to help them understand if there are more cost-effective options for dealing with their difficult soil conditions. If GeoSolv does not have the right solution for the project, this will be clearly identified early in the process, and other options outside the GeoSolv suite of solutions will be suggested to assist the owner in finding the right solution, not just the GeoSolv solution.
Ground Improvement Systems Comparison
|Ground Improvement Systems Comparison||Rammed Aggregate Pier Systems||Rapid Impact Compaction||Stone Columns||Vibro Compaction||Dynamic Compaction|
|Suitable for Misc. Fill Soils?|
|Suitable for Sand?|
|Suitable for Silt/Clay?||*|
|Suitable for Peat/Organics?|
|Massive Lateral Stress Increase?|
|Vertical Ramming Energy?|
|Clean & Dry Construction?|
|High Shear Strength for Global Stability?|
*The horizontal vibration used to install stone columns can negatively impact the existing silt and clay soils. Care should be taken when considering stone columns in these soils, and reduced capacities are likely.
Geopier® Rammed Aggregate Pier System
The precision Rammed Aggregate Pier (RAP) System called “Geopier®” was developed by the Geopier Foundation Company early in the 1990s to provide an efficient and cost-effective foundation solution for the support of settlement sensitive structures in very difficult soil conditions. This innovative system was developed to avoid massive over-excavation and replacement in more cohesive soils. Due to its unique construction method, Geopier RAP elements provide greater capacity than traditional stone columns – particularly in non-sand soil conditions (clay, silt, organic-containing and fill soils).
The Unique Advantages of Geopier RAP’s Versus Stone Columns
How can you do more with the Rammed Aggregate Pier system compared to the traditional stone column process? Here are a few of the unique features of RAP systems that outperform stone columns and other systems.
Thin lifts of aggregate are rammed to form a pier with undulating sides. Thin lifts allow for better compaction of the aggregate and results in high shear strength and stiffness. The tamper forces aggregate into the RAP element sidewalls – providing excellent pier-soil coupling.
Direct Crowd Force
Rather than being lowered off a crane, the vertical ramming energy is augmented by direct machine downward crowd pressure of 15 to 30 tonnes on each lift. Direct crowd combined with the vertical ramming energy (not horizontal) massively densifies the stone and drives up lateral stress in the enclosing soil, resulting in higher performance.
The Rammed Aggregate Pier® (RAP) construction method is easily adaptable to use recycled concrete or cement treated aggregate. Alternative aggregates provide flexibility to achieve more in various soil types.
Geopier RAP elements can be installed in almost all soil conditions. The vertical ramming process contributes to increasing the lateral stresses in the matrix soils, which is especially important for soils with silt or clay content that do not respond well to horizontal vibrations.
The ramming process produces the superior strength of a Geopier Rammed Aggregate Pier (RAP) and develops constructed aggregate friction angles greater than 48 degrees – almost 40% greater than those reported for stone columns. Higher friction angles provide greater pier capacity, which means fewer Geopier elements are required.
Higher Bearing Pressure
Higher friction angles allow for higher bearing capacities, which results in smaller footings and lower foundation costs. Be aware that you may find your stone column or generic “aggregate pier” supplier looking to dial back bearing capacity as a result of a lower capacity pier on your next project. Insist on a Rammed Aggregate Pier for maximum bearing performance.
Better Settlement Control
The unique ramming process creates piers that are two to nine times stiffer than stone columns. Versatile Geopier RAPs can be used for light to heavily loaded structures in most soil conditions.
The orientation of installation forces is an important distinction when considering ground improvement methods in Ontario. While some geologic regions in the province are known for their deposits of sand, non-sand soil such as silt and clay are more commonly encountered in Ontario and project teams must carefully consider the performance of stone column (aggregate pier) elements in these soils. Fill is also a common occurrence – particularly in the Greater Toronto Area. No ground improvement system performs better than Geopier in undocumented fill.
Want to learn more about Geopier RAPS?
Contact us today for your complimentary In-House Educational Session at your place of business. Simply email us at firstname.lastname@example.org, or call us at (905) 266-2599
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