The zone 1 embankment contained 876, 700 cubic yards of which 10, 150 cubic yards were power tamped or puddled. In those areas where tests indicated low densities, the material was removed and replaced, and another regular test was made. A special effort was made to hold the rock content of the fill material below 40 percent and the minus 200 screen size above 20 percent. This required careful control and testing. Twenty-five samples (record tests) were given a complete testing program: density, gradation, specific gravity, settlement, and permeability. A 15-pound sample of minus No. 4 material from each test was saved for shipment to the laboratory in Denver. As determined from the 25 record tests, optimum moistures ranged from 14. 5 to 20.6 percent, and laboratory maximum dry densities ranged from 103.3 to 118. 8 pounds per cubic foot. The average percolation rate was 0.61 foot per year with an average settlement of 3.02 percent. Except for 10. 36 feet per year for one sample, percolation rates ranged from 1.59 to 0.01 feet per year. Settlement ranged from 0.8 to 6. 23 percent. All testing was performed in accordance with the Earth Manual. 1/ The material in zone 1 contained considerable rock, so a steel plate with a 10-inch-diameter hole was used as a collar to obtain test material. The holes were approximately 8 inches deep. A cone that fit the hole in the plate was used to pour the calibrated sand. All density tests were taken to the laboratory, screened, moisture samples taken, and then the rapid compaction control method as described in the Earth Manual was followed. A report of the test results was given to the fill inspector within approximately 1-1/2 hours. From this he was able to ascertain the moisture, density, and percentage of rocks in the particular location where the test sample was obtained. It was found that the best densities could be obtained at approximately 2 percent below optimum moisture content with approximately 35 percent rock larger than the No. 4 screen. Control tests indicated that the average fill dry densities were 101.1 percent greater than laboratory maximum dry densities, that the fill was placed with an average of 0.3 percent less than the optimum water content, and that the fill contained an average of 35.5 percent material retained on the No. 4 screen. C. Grouting 58. General. Boyles Bros. Drilling Co. had the subcontract from Mountain States Construction Co. to do all the drilling and grouting. The basic grout plan was to pressure grout the rock foundation under the cutoff walls of the spillway crest and under the inlet channel walls, the rock surrounding the outlet works tunnel, and the joints between the first- and second-stage concrete. The designs for the dam did not include a grouting program for the foundation or the abutments. After the excavation and cleanup were nearly completed, a layer of columnar basalt which was exposed on both abutments between approximate elevations 3160 and 3208 appeared to be more weathered and pervious than previously anticipated, so grouting of these areas was performed under order for changes No. 1. (See sec. 34.) 17"Earth Manual," first edition, Bureau of Reclamation, 1960. More detailed information on grouting at Prineville Dam was reported as follows: (1) Final Grout Report of the Outlet Works Tunnel, February 1960 (see bibliography). (2) Right and Left Abutment Grout Report, February 1960 (see bibliography). (4) Two letter reports on backfill grout in the diversion tunnel, July 31 and October 29, 1959. 59. Tunnel. (a) Low-Pressure Backfill Grouting. --Outlet tunnel backfill grouting in the upstream tunnel section between stations 2+38 and 7+50 was started on July 13, 1959, and completed 5 days later. There were 44 supply holes and 32 vent holes drilled through the concrete arch. Because of the difficulty in placing concrete in the arch, several cold joints developed as well as two large cavities. These cavities were thoroughly cleaned and reformed and a sand-grout mixture was pumped into them before backfill grouting began. All vents and supply nipples were valved 75 feet ahead of backfill operations. Mixtures of cement and sand with water-cement ratios ranging from 0.70 to 0.73 were used in proportions of 1:1, 1:1-1/2, and 1:2 depending on the size of the cavities being filled. Grouting started from station 2+38 and progressed to station 7+50. Pressures of 30 pounds per square inch were used and some refusals reached 40 pounds per square inch. For the 512 linear feet of 11-foot-diameter tunnel which was grouted, 442 sacks of cement and 523 sacks of sand were used. This included the two cavities mentioned above which took 186 cubic feet of grout. This amounted to 2.64 cubic feet per running foot of tunnel. Backfill grouting operations in the downstream portion of the tunnel between stations 7+50 and 11+75 began on August 20, 1959, and were completed 7 days later with the exception of the gate chamber and adit which were drilled and grouted on October 21 and 22. There were 23 supply holes and 10 vent holes drilled in the tunnel arch. With the exception of holes at stations 9+47 and 10+54 where some sand-cement grout was used, all the holes were grouted with a neat cement grout using a water-cement ratio of 1:1. Grouting started from the outlet end and progressed upstream. Supply and vent holes were valved 50 feet ahead of the grouting operations. Pressure was held to 30 pounds per square inch. The gate chamber accepted 111 cubic feet of grout through three holes, and the adit connecting the gate chamber and shaft accepted 20 cubic feet of grout. From station 7+50 to station 11+50, excluding the adit and gate chamber, there were 362 cubic feet of cement and 42 cubic feet of sand placed, or 1.01 cubic feet of grout per linear foot of tunnel. After placing the second-stage concrete at the upstream end of the tunnel, the top section was backfilled with a 2:1 sand grout. The area at station 1+90 took 60 cubic feet of grout. There was a large void on the right side between the arch and spring line at station 2+17 which was cleaned out and reformed with supply and vent pipes. This area was grouted with cement-sand grout using the grout pump, and it accepted 13 cubic feet of grout. The top section of the gate chamber at station 7+73 was backfilled with 2:1 sand grout and accepted 38 cubic feet of grout. (b) Pressure Grouting. --A pattern of grout holes 20 feet deep at 20-foot centers staggered as shown on figure 23 was generally followed. A request was made and approved to use 40-foot centers between grout rings in lieu of the 20-foot centers for the portion of the tunnel between stations 3+80 and 6+60. The bottom holes were drilled and grouted first, then the top holes, followed by the side holes after any grout take in the top holes had set. Because of the tight rock and the low grout take, the sequence was not critical. Grouting downstream of the gate chamber was reduced to crown holes 20 feet in depth and on 20-foot centers. A packer was used and placed just beyond the concrete lining and rock contact, and all holes were grouted to refusal using a pressure of 100 to 125 pounds per square inch. A grout mix with a water-cement ratio of 5:1 was generally used. Between stations 2+60 and 7+70, 167 cubic feet of grout was placed in 1, 576 linear feet of drilled hole. Crown holes between stations 8+38 and 10+20 accepted 31 cubic feet of grout in 204 linear feet of drilled hole. (c) Contraction Joint Grouting. --The upstream tunnel elbow section at the contraction joint was grouted on January 19, 1961, 30 days after the second-stage concrete had been placed. All grout systems were washed out for 15 minutes. Neat cement grout mixes with water-cement ratios from 0.5:1 to 1:1 were used. Because some leaks developed through the concrete lining, it was necessary to change the mixes. A maximum pressure of 35 pounds per square inch was used and a total of 48 cubic feet of grout was placed in this area, which indicated a grout take in addition to that required to fill the contraction joint. The gate chamber grouting was done on February 9, 1961, 26 days after secondstage concrete had been placed. This area accepted a very small amount of grout. Neat cement was used and only 2 sacks of cement were placed under a pressure of 50 pounds per square inch which indicated that only the contraction joint accepted grout. 60. Spillway Crest Grouting. Seventeen holes 50 feet in depth and on 10-foot centers across the spillway floor were drilled and grouted. The cutoff trench across the spillway floor served as a partial grout cap for four of the grout holes. All holes were drilled with a 1-1/2-inch-diameter diamond plug bit, through nipples previously set in the rock or concrete. A packer was used to water test and grout at the different stages. In 845 linear feet of drilled hole, 1, 350 cubic feet of sandless grout with a water-cement ratio of 1:1 was used at pressures from 50 to 150 pounds per square inch as needed. This was an average of 1.6 cubic feet of grout per foot of drilled hole. 61. Foundation Grouting. To determine the permeability of the columnar basalt layer between elevations 3160 and 3208, two test holes were drilled at the right abutment at station 1+97.8, elevation 3213. 2, with a dip of 48° to a depth of 61.5 feet and water tested with a packer placed at 41 feet in the hole and using a pressure of 50 pounds per square inch. The hole accepted 15 cubic feet of water in 15 minutes. With the packer raised to 16 feet and using a pumping pressure of 30 pounds per square inch, it accepted 66 cubic feet of water in 15 minutes. A test hole at station 2+14. 1, elevation 3186. 3, with a dip of 48° was drilled to only 30 feet because the columnar block of rock holding the nipple became loose. The hole was water tested and accepted 49 cubic feet of water in 15 minutes with no pumping pressure. Many water leaks were observed through the large seams around the columnar formation. As the left abutment was very similar to the right abutment in geological formation, no testing was believed necessary in that area. A grouting plan was prepared providing for a concrete grout cap on the right abutment (fig. 62) between elevations 3218.4 and 3153.9. Twenty-one grout nipples were placed in the grout cap at 5-foot centers on a dip of 48°. The first eight holes were drilled to a depth of 30 feet with the exception of the second hole which was only 15 feet deep. The remaining holes were drilled 30 and 60 feet deep, alternately. All holes were drilled to their final depths and a packer was used to grout the different stages. Rather than grout each hole in order, the closeout method was used. Pressures of 30 to 80 pounds per square inch were used depending on the location of the packer. Generally a grout with a water-cement ratio of 5:1 was used when starting to grout at the different stages, except where surface leaks or the grout take increased to the extent that thickening of the mix was necessary. To determine the effectiveness of this abutment grouting, a 40-foot test hole was drilled into the abutment between holes P and O at a dip of 34° 30' intersecting holes and N. The first 30 feet were drilled in the flow breccia formation; the remaining 10 feet were drilled in hackly basalt. Numerous grout seams were encountered in this hole throughout its entire depth. After the drilling was completed, the hole was water tested and the following results showed the area was satisfactorily grouted: When water tested at 30 to 40 feet, the hole accepted 1-1/8 cubic feet in 20 minutes at a pressure of 25 pounds per square inch; between 20 and 30 feet it accepted 1-1/4 cubic feet in 20 minutes at 25 pounds per square inch, and between 0 and 20 feet it accepted 2-1/2 cubic feet in 20 minutes at 25 pounds per square inch. The right abutment accepted 324 cubic feet of grout in 714 feet of drilled hole, or an average of 0.45 sack per linear foot. Numerous surface leaks occurred while grouting the top 15 feet and the majority of them were successfully calked. Figure 62. --Right abutment showing part of concrete grout cap and some of the 21 grout nipples. Zone 1 embankment is approximately at elevation 3170. Spillway is under construction at the top of the photograph. P113-129-397, May 2, 1960. The left abutment accepted 435 cubic feet of grout in 875 linear feet of drilled hole or 0.50 sack per linear foot. During 1961 the reservoir was filled to elevation 3220 and no sign of seepage occurred through either abutment. ✓62. Miscellaneous Grouting. When the final cleanup was made in the deep river gorge, there were several seams which did not warrant removing; instead, grout pipe was placed in these seams and later used to grout them. Also, from the two pump sumps at either end of the cutoff trench, grout pipe was extended upward as the fill progressed. There were 17 grout pipes placed including the two 8-inch-diameter pipes used for pumping. When the embankment had been placed to elevation 3080, these pipes were grouted. A neat cement grout was used with a pressure of 40 pounds per square inch. A total of 476 sacks of cement was used for this miscellaneous grouting. 63. Equipment. Drilling of the overall grout program was done with air drills using 1-1/2-inch-diameter diamond plug bits. Air used was supplied by a 600 c.f.m. air compressor. Grouting equipment consisted of a 6- by 4- by 6-inch grout pump and two airmotor mixing tanks (fig. 63). The tanks and pump were mounted on an iron skid frame and were easily moved when necessary. The drill and grout crew of Boyles Bros. Drilling Co. consisted of a foreman, one driller, one helper, and one mixer operator who also operated the grout pump and helped the driller when needed. D. Concrete Materials and Control 64. General. The Keystone Construction Co., Inc., and Associates sublet all concrete work to the subcontractor who performed the tunnel excavation. The subcontractor installed a batching plant with an attached 500-barrel cement silo (fig. 64) approximately three-quarters of a mile downstream from the dam. The aggregate was screened over a vibrating screen into a hopper, which fed a conveyor belt that carried the aggregate into the batch bins. The ingredients for the concrete were weighed into the batch hopper and discharged into transit mixers which were equipped with revolution counters. The water was added through a water meter. 65. Aggregate Investigations. There was little investigation made to find sand and aggregate for this job. The contractor wanted to obtain his aggregate from a deposit in the river channel near the dam; but when a sample from this deposit was sent to Denver to be analized it was rejected because the aggregate was coated and contained soft particles. The basalt outcrops in the area were investigated for coarse aggregate; but in crushing this rock, which contained obsidian, the minus 3/4-inch material was too flaky to be acceptable. The contractor finally decided to procure the sand and aggregate from the Prineville Sand and Gravel Co. in Prineville, 21 miles away. This deposit had been previously approved, but additional samples were sent to Denver for final approval. The specifications required final screening over the batch bins, so all control tests were taken from the material as batched. Numerous tests were taken at the gravel plant near Prineville to assist the supplier in furnishing acceptable material. 66. Cement. Because of alkali-reactive material in the sand and aggregate, type II low-alkali cement was used. The cement was furnished by the Oregon-Portland Cement Co. from Oswego, Oreg. and by the Permanente Cement Co., Portland, Oreg. 67. Laboratory Control. The field laboratory personnel conducted tests to determine the most economical mix consistent with workability, durability, and strength requirements. The maximum water-cement ratios indicated in specifications No. DC-5047 for parts of structures subject to certain conditions are indicated below: |