Projects Using US Grout to Stabilize Weak Soils
Cementitious grouts are clean, economical solution for improving the soil profile for many geotechnical challenges. Once injected into the soil, the grout works for centuries...stabilizing weak soil structure, imparting load-bearing compressive strength, and sealing against leachate within almost any soil type—even the fine-grained soils that defeat effective penetration by other grouts.
The construction of a new, nine-story tower over the existing courtyard area and low-rise portion of the Radisson Plaza Hotel in Kalamazoo called for the new spread footings to overlap the existing foundations—an arrangement that would cause excessive settlement of existing columns. The native soil consisted of fine to coarse sand with less than 10% silt. The hydraulic conductivity varied with depth, with much of the soil stabilization needing to be down below the water table.
Desired long-term strength and the ability to permeate variations in soil structure led to the selection of Ultrafine Cementitious Grout by the contractor. The Ultrafine Grout thoroughly permeated the soil across the soil variation spectrum, resulting in a grouted soil that extended 10 feet below the bottom of both new and existing footings and extending 5 feet beyond the edges of the existing footings. This design provided support for 12,000 pounds per square inch and less than one-half an inch of settlement.
Selection Factors. The grouting contractor, Spartan Specialties, selected U.S. Grout Ultrafine Cementitious Grout for the following reasons: High compressive strength; extreme longevity; low internal cohesion; ability of the grout to permeate the soil in a manner similar to sodium silicate; immediate and personal attention by U.S. Grout and a willingness to tailor the grout to the needs of the job; competitive price; excellent technical advice; and a long list of satisfied users.
Process and Result. Using sleeve pipe, grouting was performed from the bottom up. 50 gallons of grout per vertical foot, at a water/cement ratio of 2/1, were injected under a pressure of 100 psi. A cylindrical mass of grouted soil approximately 5 feet in diameter centered on each injection hole was achieved. Post-grout cores were taken and tests indicated compressive strengths approximating 800 psi, well in excess of the 250 psi required.
A major renovation to Hill Auditorium on the University of Michigan campus included establishing additional loads to existing foundations for structural revisions and new HVAC equipment. The additional loads would cause settlement, cracking the exterior facade or interior elements.
The soil below the existing foundations consists of coarse sand and gravel with occasional cobbles. The design engineer specified permeation grouting below the existing footings to increase elastic modulus, thereby reducing settlement of the existing foundation when additional load was applied.
Selection Factors. U.S. Grout Ultrafine Cementitious grout was selected because of its non-hazardous nature, extremely low hydraulic conductivity, exceptional longevity, low coefficient of pressure filtration, low internal cohesion, and high compressive strength. Additionally, the grout permeates in a manner similar to sodium silicate, completely filling all voids in the soil.
Process and Result. A triangular injection hole pattern over the footing area was selected. Grouting was performed through a multi-port sleeve pipe, commencing at the bottom and proceeding upwards. Each port was injected a second time after two hours. The perimeter was injected first to contain the grout from the interior injections. Water/dry grout ratio was 2/1 by weight. Unconfined uniaxial compressive strength of cores tested at about 1300 psi. A supplemental in-situ pressuremeter test in one hole was also performed with no indication of failure.
As the world-wide distributor for US Grout products, Avanti International (www.avantigrout.com • 800-877-2570) provides the customer service, objective professional advice, material estimates, and the caliber of world-class technical support that comes only from 35 years of geotechnical experience.
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