19E - SANTA ANA GRADE SEPARATION PROJECT

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Santa Ana Boulevard Grade Separation September 13, 2011 Page 5 Deep Foundation Design: To facilitate fabrication and cost estimate, we recommend using the same pile type as the bridge abutment. However, the axial pile demand should be 45 tons for retaining wall and the corresponding HP pile section is HP 10x42. Using a 45 -ton service demand, a preliminary pile length of 50 feet is recommended. Construction Considerations Groundwater was not encountered in any of the as -built borings down to about elevation +50 feet. Therefore, groundwater is not anticipated to be encountered during pile construction and footing construction at the supports and walls. However, groundwater level can fluctuate due to seasonal rainfall amount, local irrigation and groundwater recharge program, and other man- made conditions. If groundwater is encountered during footing construction, it should be controlled in accordance with Section 19 -3.03D of the Caltrans Standard Specifications (Caltrans, 2010). If groundwater is encountered during CIDH pile construction, contractor should be prepared to use a "wet' method of construction for the CIDH piles. As a standard Caltrans practice for "wet' construction, PVC tubings should be installed within the reinforcement cage for gamma -ray testing. Based on the As -Built LOTB sheets of the nearby structures, the onsite soils are generally loose to very dense coarse grained materials and these materials are susceptible to caving. If caving occurs, a temporary casing can be used. The casing should have an inside diameter larger than or equal to the pile diameter and should be placed tight in the hole. Vibratory hammers or oversized drilling are not allowed for casing installation. In the event that any boring becomes bell- shaped and cannot be advanced due to severe caving, all loose material should be removed from the bottom of the boring and the caved region filled with a low strength sand - cement slurry. Drilling may continue when the slurry has reached its initial set. Based on the As -Built LOTB sheets of the nearby structures, gravel and cobbles were recovered during drilling operations in multiple borings and are expected to be encountered during CIDH pile construction. While there could be a trace amount of cobbles between 6 inches and 1 foot diameter, the largest rocks of significance that will be encountered would likely be small cobbles, in the 3- to 6 -inch diameter range. While the oversized material will likely create difficult drilling conditions, large - diameter augers typically have flights with wide spacing and a shallow pitch allowing rock pieces, cobbles and boulders to be extracted from the drilled hole. Rock augers and clean -out buckets can also be used to extract oversized material where a high concentration of gravel and cobbles are encountered. References Abrahamson, N. A., and Silva, W., 1997, `Empirical Response Spectral Attenuation Relations for Shallow Crustal Earthquakes," Seismological Research Letters, Vol. 68, No. 1, January/February. AREMA, 2009, "Manual for Railway Engineering," American Railway Engineering Association, Chapters 8, 9, 15. =Y tics Inc. -- - G Mee ae�9,1aan�g