DRAFT <br />pressures should be reviewed by GRI on a case-by-case basis during design, as the <br />magnitude of lateral displacement required to mobilize passive resistance depends on the <br />embedment depth of the foundation. <br />5.4.5 Ground Anchors for Uplift Resistance <br />We understand ground anchors may be used in conjunction with the mat foundations to <br />resist uplift loading for the new practice facility. The specific design, installation, and <br />testing procedures for ground anchors are typically developed by a specialty foundation <br />contractor based on subsurface information and performance criteria provided by the <br />owner's geotechnical and structural engineers. Ground anchors consist of small-diameter <br />(commonly 4 inches to 8 inches), drilled-and-grouted, steel-reinforced elements. Ground <br />anchors are typically constructed by drilling a cased hole to the desired depth into a <br />bearing layer, placing a steel reinforcing bar or strands in the cased hole, and pumping <br />grout from the bottom of the hole using tremie methods to form a bond zone as the <br />casing is withdrawn. Provisions for secondary grouting should be incorporated into the <br />design of the anchors to enhance the capacity of the bond zone, and it should be <br />anticipated that at least one episode of secondary grouting will be required to achieve the <br />desired bond-zone capacity. <br />Our experience indicates ground anchors installed into the underlying gravel and cobbles <br />can develop an allowable capacity of at least 150 kips with bond zone lengths on the order <br />of 15 feet to 25 feet, depending on the actual anchor diameter and installation procedures. <br />It should be noted, however, that the subsurface explorations completed for this project <br />and our experience in the project area indicate the gravel and cobbles contain open-work <br />zones that are generally capable of accepting large volumes of grout. The gravel and <br />cobbles may also contain boulders. The presence of open-work zones and boulders can <br />create challenging conditions for the installation of ground anchors and should be <br />addressed in the contract documents and reviewed by the specialty foundation contractor. <br />GRI should review all project submittals related to ground anchors and the specialty <br />foundation contractor should have a contingency plan for mitigating potential issues and <br />successfully installing the anchors. <br />We recommend ground anchors be designed, installed, and tested in accordance with the <br />current Post-Tensioning Institute (PTI) publication PTI DC-35, Recommendations for <br />Prestressed Rock and Soil Anchors and the Federal Highway Administration (FHWA) <br />publication FHWA-IF-99-015, Geotechnical Engineering Circular No. 4, Ground Anchors and <br />Anchored Systems. In accordance with these documents, we recommend the anchors be <br />designed with a minimum free-stressing length of at least 10 feet for bar anchors and 15 <br />feet for strand anchors. However, this should be reviewed during design, as longer free <br />lengths may be required to achieve the desired anchor capacities. Anchors should be <br />GRI #6497-A - 2.MO Indoor Football Practice Facility Page 16 <br />August 26, 2021 <br />