Drilling , - The wagon drill was successful in drilling the grout 

 holes although, in some locations, loose spalls wasted during the jetty 

 construction in the capstone voids made drilling difficult by jamming the 

 drill. Repeated withdrawals of the drill, before jamming .took place, would 

 finally pulverize or kick aside the spalls, leaving a workable hole. The 

 rock was quite hard and the bits had to be sharpened after about 3 hours of 

 operation. Holes were spaced approximately 8 feet apart, 55 holes being 

 drilled along the center of the jetty in a reach of Iil5 feet. In some 

 places, the holes did not drill true and had small offsets across the voids 

 encountered. In these cases, rubber hose was substituted for the rigid 

 grout nozzle used on true holes. 



Mixing and placing . - The mixer was set up on the beach berm. safely 

 above the high tide about 200 feet south of the jetty (see fig. 2). 

 Ingredients other than sand and water were brought to the mixer in bags 

 and charging was done by hand. The sand was initially piled near the 

 water with a dozer and then measured and put in by wheelbarrows. Mixing 

 water was hauled by tank truck from a temporary f ire-hydrant service 

 provided by the city. From the mixer, the grout was fed into a funnel 

 at the intake of a Simplex grout pump and pumped through a 2-inch pipe 

 line to the holes. A booster pump was required every 250 feet in order 

 to propel grout of the required stiffness through the line. At the end 

 of the line, about 30 feet of 1-1/2-inch hose led to the nozzle which 

 was a 15-foot length of 1-1/2-inch pipe. The nozzle was inserted to the 

 bottom of the hole and withdrawn at such a rate as to form an imagined 

 cone extending from MLLW (top of core) to 10 feet above MLIW wherever 

 possible. The theoretical intersection of the cones between holes was 

 assumed to bring the barrier to +6.0 MLLW elevation. From 6 to 9 cubic 

 yards of grout were intruded into each hole. Where crooked holes did 

 not permit use of the rigid nozzle, the 1-1/2-inch hose, stiffened by a 

 rod inside to prevent veering off into voids, was inserted directly into 

 the hole. An average of 18 cubic yards per working day was placed. 



OBSERVATION, CONTROLS, AND INSPECTION 



The writer was in direct charge of the inspection and administration 

 of the experimental contract and spent about 15 days at the site during 

 the construction period of 57 calendar days. Monitoring the results was 

 difficult and in large part stochastic. The exterior of the jetty did 

 not supply enough "windows" through which to watch the migration and 

 stacking of the intruded grout. Interior conditions before grout place- 

 ment could be partially appraised by probing with a rod. In certain deep 

 surface voids and fissures in the jetty slopes, it was possible to 

 determine the whereabouts of the grout when it migrated to the outside 

 limits of the jetty. Flashlight and probing rod were of assistance here 

 also. In certain deep voids extending to the core, the grout could be seen 

 to congeal and stop flowing in openings as large as a foot or more in 

 diameter - a gratifying sight; more gratifying when the same condition was 

 observed after the tide had dropped and the waves had ceased their attack, 

 leaving the fresh grout surface only pitted and not eroded. 



