Engineered Fill

Ground improvement techniques are increasingly used for new projects on sites previously considered as economically unjustifiable or technically not feasible. These sites can now be developed by removing the unsuitable soils and replacing them with engineered fill. Successful placement of engineered fill requires proper equipment and techniques, suitable materials, and testing to verify proper compaction.

By understanding the principles of soil mechanics, SME’s CMS experts evaluate not only the engineered fill itself, but subsurface conditions at project sites to determine proper placement, as well as layer thickness and compaction levels. In addition, we provide laboratory testing and settlement monitoring of engineered fill or the underlying soils; recommendations for soil stabilization in areas to support buildings, pavements, and engineered fill; observation of proof-rolling of the exposed soils after the topsoil is removed to locate areas which may require additional excavation or rework; and monitoring of excavating operations to determine when specified materials have been exposed.

SME performs additional engineered fill services including:

  • Soil type identification
  • Compaction level specification
  • Field density testing
  • Surcharge/preload monitoring
  • Moisture/density relationship (Proctor)
  • Proof-roll evaluations
  • Excavation and subgrade preparation
  • Fill placement observation
  • Foundation material verification
  • Dewatering
  • Quality control construction monitoring and testing
  • Instrumentation and settlement monitoring

Field Density Testing

Field density tests are used to measure the moisture content and the percent compaction of the engineered fill material placed during backfill or grading operations. Density tests are obtained to confirm that the soil is adequately moisture conditioned and compacted in compliance with the project recommendations. Poorly compacted material below footing or slab areas can lead to settlement and building distress issues including wall and ceiling cracks, differential settlement of floors; or windows or doors not opening or sliding properly.


Construction projects are using sites which were considered unsuitable in the past. Soft soils have a low bearing capacity and/or are susceptible to consolidation resulting in large settlements when subjected to building loads. One method to successfully build on soft soil deposits is to use surcharge/preloading to pre-treat the soil prior to building construction to prevent large or differential settlements and potential damage to structures.

SME’s Geotechnical engineers use surcharge/preloading to improve weak, compressible soil by subjecting the site to a load (generally in the form of added fill or surcharge) that exceeds the loading to be applied by the finished construction. We monitor the rate and magnitude of the settlement using settlement plates to determine the amount of time the surcharge needs to remain in place to achieve the required level of settlement. Once the desired settlement is achieved, the surcharge is removed and construction can begin. The duration of the loading depends on the amount of surcharge/preloading, soil compressibility, layer thickness and drainage characteristics of the subsurface soils. Sometimes a system of vertical sand or wick drains is employed in conjunction with the preloading to reduce the consolidation time and allow for earlier use of the site.

SME has experience with the following services:

  • Surcharge plans and specifications
  • Surcharge/preload monitoring
  • Embankment preloading
  • Vertical drains
  • Oversee removal and disposal of surcharge material


Proof-rolling is used in earthwork and pavement construction to verify uniform behavior and stability of the subgrade before placement of fill. If fill is placed over unsuitable soil, the subgrade may not provide proper support and may hinder proper compaction of the fill.  Additionally, a poor subgrade may consolidate under the weight of the earth fill, causing settlement and cracks in structures supported by the fill. To determine if the subgrade is adequate, SME proof-rolls the soil using heavy construction equipment to roll across the ground surface while monitoring the reaction of the surface, watching for deflections (development of rutting, pumping, or ground weaving).

SME has considerable experience with proof-roll investigation, testing, and monitoring. Our services include:

  • Proof-roll monitoring and testing    
  • Subgrade investigation
  • Material verification
  • Electric cone penetrometer testing
  • Flat plate dilatometer testing
  • Pressuremeter testing

Material Verification

Both natural and manmade fill materials are used for a variety of construction purposes. Because fill material may come from different or multiple sources, it is important to verify  that any material brought onto a site meets engineering specifications for its particular use.

SME provides a wide range material verification services including determining soil characteristics and verifying the materials will be acceptable for use as fill; investigating the proposed borrow source; verifying that materials below footings are adequate to achieve desired bearing capacity; verifying excavations are extended to proper depth and have reached proper material level; classifying and testing controlled fill materials; verifying use of proper materials, proper compaction, and lift thicknesses during placement and compaction; observing subgrade and verifying that the site has been prepared properly prior to placement of controlled fill; and providing solutions to treat, modify, or stabilize materials to permit their re-use within a development.

Other SME material verification services include:

  • Subgrade material verification
  • Native-fill material verification
  • Imported material verification
  • Site soil classification and characterization
  • Additive material verification (lime, cement, sand, pozzolan, etc.)
  • In-house laboratory testing
  • In-field sampling and testing

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Louis J. Northouse, PE

Vice President/Regional Office Manager

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