DRAFT <br />mats may be on the order of one third to one half the total settlement, depending on the <br />actual loading and relative stiffness of the mats. Due to the large size of the foundations <br />and deeper stress influence relative to the spread footings, a significant portion of the <br />estimated settlement is anticipated to occur in the silt and clay soils present beneath the <br />gravel and cobbles. Settlement of these soils generally occurs over a longer period; <br />therefore, some of the mat foundation settlement may occur as post-construction <br />settlement. <br />Mat foundations are typically analyzed as plates on elastic foundations. However, some <br />time-dependent settlement due to consolidation of the underlying soils will result from <br />placing sustained loads on the mat foundations. To account for short-term loading <br />conditions (undrained conditions) such as the initial placement of new loads on the <br />foundations, or future transient loading conditions such as wind or seismic forces, we <br />recommend assuming a coefficient of subgrade reaction, k, of 400 pounds per cubic inch <br />(pci) to evaluate isolated point loading on mat foundations designed and constructed <br />following the recommendations provided in this report. To account for long-term loading <br />conditions and the resulting consolidation settlement of the underlying soils (drained <br />conditions), a significantly lower coefficient of subgrade reaction is generally appropriate <br />for modeling the flexural behavior of the mats. The choice of an appropriate long-term <br />value depends on the distribution of loading on the mats and estimated settlements. For <br />preliminary design purposes, we recommend assuming a long-term coefficient of <br />subgrade reaction value on the order of 50 pci. However, the actual values can vary <br />significantly with location and loading beneath the mats and should be reviewed during <br />final design. It should be understood that this recommended long-term value is intended <br />for evaluating the flexural behavior and reinforcement requirements for the mats and <br />should not be used for estimating foundation settlements. <br />5.4.4 Lateral Resistance <br />Horizontal shear forces can be resisted partially or completely by frictional forces <br />developed between the base of the foundations and the underlying material. The total <br />frictional resistance can be estimated as the normal force (dead load plus real live load) <br />multiplied by the coefficient of friction between the foundation and the underlying <br />material. We recommend using an ultimate value of 0.45 for the coefficient of friction for <br />foundations cast directly on compacted crushed rock as recommended. If additional lateral <br />resistance is required, passive earth pressures against embedded portions of the <br />foundations can be estimated based on an equivalent fluid having a unit weight of 300 <br />pounds per cubic foot (pcf), assuming the foundations are backfilled with structural fill or <br />neat-formed in excavations. This value has been reduced from an ultimate value to limit <br />lateral deformations and assumes the ground surface in front of the foundations is level <br />and does not slope downward away from the foundations. The use of passive earth <br />GRI #6497-A - 2.MO Indoor Football Practice Facility Page 15 <br />August 26, 2021 <br />