Laserfiche WebLink
Project No. D-3885-06 <br />Christ Our Savior Catholic Parish <br />Dynamic Compaction of Dry Soils <br />Relatively dry soils (e.g., soils above the groundwater table) with low density or softer <br />consistency tend to undergo a certain degree of compaction during a seismic event. <br />Earthquake shaking often induces significant cyclic shear strain in a soil mass that <br />responds to the vibration by undergoing volumetric changes. Volumetric changes in dry <br />soils take place primarily through changes in the void ratio (usually contraction in loose <br />or nonnally consolidated, soft soils, and dilation in dense or overconsolidated, stiff soils) <br />and secondarily through particle reorientation. Such volumetric changes are generally <br />non-recoverable. The potential for such settlement is minor in comparison to earthquake <br />induced liquefaction settlement because the thickness of dry soils is relatively less. Any <br />such additional settlement in addition to liquefaction settlement would further justi$ the <br />need for deep foundations or other suitable foundation treatment methods. <br />The following table shows the settlement due to liquefaction: <br />SETTLEMENT DUE TO LIOUEFACTION <br />Based on Mw 6.6 and PGA of 0.59 (USGS Desien Maps. Fieure 22-7) <br />Cone <br />Penetration/ <br />Boring <br />Groundwater @ 5 ft Historical High Groundwater @ l+ feetatSite <br />Settlement (inch) <br />Saturated Dry Total Saturated Dry Total <br />CPT.I 0.51 I 0.005 0.52t 0.66 0.02 0.68 <br />CPT.2 t.207 0.005 1.212 1.40 0.01 1.41 <br />CPT.3 0.888 0.004 0.892 l.l6 0.01 1.1'7 <br />CPT.4 0.s39 0.005 0.544 0.66 0.02 0.68 <br />I8 <br />I <br />I <br />T <br />I <br />I <br />t <br />I <br />I <br />T <br />I <br />I <br />I <br />t <br />I <br />I <br />I <br />t <br />I <br />I <br />I <br />I <br />I