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Lead wires connecting the gages t o manually operated switch boxes were made up of 120-ft long twisted pairs of s o l i d core 20-gage copper wire. The 120-ft length of lead wires was determined t o be the greatest length required between the most remote gage i n s t a l l a t i o n and the mon- i t o r i n g s t a t i o n . These pairs were twisted, stripped, and marked, and then shipped t o the s i t e ready f o r use. Switch boxes with provisions f o r zero balancing gage readout were used. Gage readout was by a Baldwin l ^ e N portable s t r a i n indicator. Arragnements f o r gate switching and readout are shown i n Fig. 13. EQUIIMENT FOR MEASURING LOAP AND PRESSURE Three devices were used to measure pressure. Mounted d i r e c t l y on each pump was a Bourdon type d i a l gage. These gages were monitored contin- uously during the tests t o maintain pressure at the intended l e v e l . Also connected i n the hydraulic l i n e were Model 28 continuous s t r i p chart pressure recorders manufactiured by B r i s t o l Company. These Bourdon type s t r i p recorders were capable of measuring pressure t o 6000 p s i . An ink stylus marked pressvu-e continually on recording paper th a t moved at the rate of three inches per hour. In these u n i t s , stylus displacement was 0.75 i n . per 1000 p s i . The t h i r d device f o r measxiring pressure was a Baldwin SR-k type pressure transducer. A portable s t r a i n indicator was used t o monitor the pressure c e l l . Calibration was 5 p s i pressure per m i l l i o n t h on the s t r a i n indicator. Six load c e l l s were placed at selected load points i n each t e s t . (2) The c e l l s were di s t r i b u t e d over the t e s t area t o check that load was applied evenly t o the slab. Readout of these load c e l l s was obtained through the same switch box and s t r a i n indicator used t o record read- out of the pressure transducer. A load c e l l i n po s i t i o n i n the load- ing system i s shown i n Fig. ik. The load c e l l was placed between the ram and the anchoring grip on the strand. Plastic bags over the load c e l l s provided protection from weather. Capacity of each load c e l l s was 50 kips. S e n s i t i v i t y of the c e l l s was about 10 l b per m i l l i o n t h indicated s t r a i n . 2-10
