249 Drilled shafts were the chosen foundation type. However, the lateral load resistance of the drilled shafts in the weathered rock was not known with reasonable engineering certainty. Lateral load testing was therefore proposed.
C.2 LATERAL LOAD TEST SETUP Drilled shafts for lateral load testing were constructed at the site, each embedded entirely within the shale inter-bedded with limestone. The embedment length in rock for each shaft was 18 feet. The shafts were 6
feet in diameter, and each was reinforced with a cage comprising 36 #11 longitudinal steel bars. A spiral consisting of #6 bar with a pitch of 2 to 3 inches provided the shear reinforcement. The shafts had a center to center spacing of 18 feet (i.e., 3 diameters) and each was instrumented with an inclinometer casing and an array of strain gauge pairs, spaced at 2 to 3
feet vertical intervals, per Figure C. The drilled shafts were pushed apart in the test using a hydraulic jack and steel strut between the shafts. A load cell was installed to measure the applied lateral load (Figure C. Lateral loads were applied in increments of 50 or 100 kips, up to a maximum load of 1126 kips. Each load was held until the rate of deflection at the top of the shaft was less than 0.04 inches per minute. Inclinometer readings were taken just prior to the application of each load increment.
Figure C Drilled shaft lateral load test setup and instrumentation, Dayton, Ohio. 250
C.3 LATERAL LOAD TEST RESULTS The lateral load test results obtained from simultaneously pushing the two shafts apart include load- deflection curves for the tops of the two shafts, profiles of deflection versus depth from the inclinometers
at each increment of load, and the strain gauge readings at each load increment. Figure C presents the load-deflection measured at the top of each shaft during each increment of load application. The deflections plotted are averaged from three dial gauge readings at the head of Shaft #4 and two dial gauge readings at the head of Shaft #3. The response in both shafts is similar, indicative of a consistent response of the rock mass at the two locations spaced 18 feet apart. It is also apparent
that the response is nonlinear, even at small deflections. A permanent deflection of 0.05 inches was measured at the top of the shafts on unloading from the maximum test loads. Figure C and Figure C show the lateral deflection versus depth profiles for drilled shafts #3 and #4 respectively, that were derived from the inclinometer data. These plots illustrate that deflections occurred
along the entire shaft lengths, even in the early stages of the test.
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