Canadian Dam Association Bulletin - Summer 2016 - 23

to the USACE Prof. Casagrande wrote "Professor Terzaghi developed a method for determining the grain size composition of filters so that they will protect the underlying soil from erosion and at the same time be sufficiently pervious than the soil to be effective as a filter. Although this method was patented by Prof. Terzaghi in 1932... he has informed the writer... that he has no objections to the general use of this method" (USACE 1938). Permeability criterion: D15F ≥ 4 · D15B Filtration criterion: D15F ≤ 4 · D85B Filters for the foundation material were designed using these criteria. A two-layer filter and a single layer filter were considered. The gradations of the filters and the foundation materials are presented in Figure 3. To verify the efficacy of the filters, nine laboratory tests were conducted on compacted filter/base soil specimens. The two-layer filter was subjected to a hydraulic gradient, i, of 50 for 10 days continuously and the single layer filter was subjected to a gradient of 7 or 11 for up to 16 hours. There was no loss of fines from the base soil during the testing. For practical reasons, the two-layer filter was used in the dam (Brown 1940). 3.6 Compaction of the Embankment For the most part, the dam was to be constructed of the locally available alluvium of silt and sand. It was recommended by a board of consultants chaired by Prof. Casagrande that these materials be compacted to a degree above the "critical density" and that a program of test fills be conducted to determine the best means of compaction. Two material types were designated for test fills: Material "A" composed of 60% fine sand and 40% nonplastic silt and Material "B" composed of fine to medium-grained sand. As previously noted, there were no compaction standards and it was not known how best to compact specific types of soils. Accordingly, the test fill program consisted of 34 test embankments using every feasible type of compaction method while varying the water content, number of passes and layer thicknesses. The test embankments for rolling equipment were 12-m-long, 4-m-wide and of various heights while those for tamping, vibrating or jetting equipment were 1.5 to 6-m-square and 1.2-m-high. The minimum and maximum void ratios of Materials "A" and "B" were obtained by laboratory testing. After compaction, void ratio profiles of the test fills were developed by manual excavation of the fills, taking "constant volume" samples using thin-walled brass tubes, and measurement of the density and water content in the laboratory. It was recommended that the embankment be constructed using 30-cm-thick layers and that each layer be compacted with 6 passes of a rolling compactor such as a tractor-drawn disc roller or a tractor-drawn smallfoot sheep's foot roller such as was used in the testing program, and that a minimum degree of compaction of 80 % be attained. It should be noted that a pass was defined as complete coverage of the surface by the tractor treads, resulting in at least two coverages by the roller (USACE 1938). The test fill program is summarized in Table 2. 3.7 Preventing Flow Failure of the Embankment Foundation Liquefaction of silt and sand under the static loading of the dam leading TABLE 2: SUMMARY OF TEST FIELD PROGRAM Compaction Method (Material) Results Rolling Equipment: Smooth roller (A) Disc roller (A, B) Large-foot sheep's foot roller (A) Small-foot sheep's foot roller (A, B) Modified sheep's foot roller (A) (A) All equipment achieved >90% R.C. depending on layer thickness and number of passes. The large-foot sheep's foot roller gave the most favorable results. The small-foot sheep's foot roller gave the least favorable results. Tamping Equipment: Drop-weight tamper (A) ... Air hammer tamper (A) ... Pneumatic hand tamper (A) ... Average R.C. of 64 to 80% ... 75-cm-thick layers, 8 passes: R.C.=85% ... 45-cm-thick layers, 1 pass: R.C.=64% ... 15-cm-thick layers, 2 passes: R.C.=80% Vibratory Equipment: External vibrator (A) External vibrator with 1-ton-weight (A) Internal vibrator (A) Average R.C. of 80 to 100% Higher degree of compaction when saturated. Honeycomb structure with voids to 25 mm in size. Jetting Equipment (A) Very little compaction effect due to relatively low permeability. Combined Methods (A) Improved compaction (up to 115%), probably due to increased number of passes. Canadian Dam Association * Summer 2016 (B) Average R.C. of 70 to 75% 23

Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Summer 2016

BOARD OF DIRECTORS
NEW WEBSITE LEADS CDA RECENT NON-TECHNICAL INNOVATIONS
ICOLD NEWS
THE FRANKLIN FALLS DAM: DESIGN, CONSTRUCTION AND RESPONSE TO THE 1982 GAZA (NEW HAMPSHIRE) EARTHQUAKE
CDA CONFERENCE 2016
CDA OFFERS ASSISTANCE AFTER BRAZIL DAM DISASTER
DAM SAFETY REVIEWS TECHNICAL BULLETIN
TIME TO RENEW YOUR MEMBERSHIP
NOTICE OF AGM
BUYERS’ GUIDE AND TRADE LIST
CALL FOR PAPERS
Canadian Dam Association Bulletin - Summer 2016 - cover1
Canadian Dam Association Bulletin - Summer 2016 - cover2
Canadian Dam Association Bulletin - Summer 2016 - 3
Canadian Dam Association Bulletin - Summer 2016 - 4
Canadian Dam Association Bulletin - Summer 2016 - 5
Canadian Dam Association Bulletin - Summer 2016 - 6
Canadian Dam Association Bulletin - Summer 2016 - BOARD OF DIRECTORS
Canadian Dam Association Bulletin - Summer 2016 - 8
Canadian Dam Association Bulletin - Summer 2016 - NEW WEBSITE LEADS CDA RECENT NON-TECHNICAL INNOVATIONS
Canadian Dam Association Bulletin - Summer 2016 - 10
Canadian Dam Association Bulletin - Summer 2016 - 11
Canadian Dam Association Bulletin - Summer 2016 - ICOLD NEWS
Canadian Dam Association Bulletin - Summer 2016 - 13
Canadian Dam Association Bulletin - Summer 2016 - THE FRANKLIN FALLS DAM: DESIGN, CONSTRUCTION AND RESPONSE TO THE 1982 GAZA (NEW HAMPSHIRE) EARTHQUAKE
Canadian Dam Association Bulletin - Summer 2016 - 15
Canadian Dam Association Bulletin - Summer 2016 - 16
Canadian Dam Association Bulletin - Summer 2016 - 17
Canadian Dam Association Bulletin - Summer 2016 - 18
Canadian Dam Association Bulletin - Summer 2016 - 19
Canadian Dam Association Bulletin - Summer 2016 - 20
Canadian Dam Association Bulletin - Summer 2016 - 21
Canadian Dam Association Bulletin - Summer 2016 - 22
Canadian Dam Association Bulletin - Summer 2016 - 23
Canadian Dam Association Bulletin - Summer 2016 - 24
Canadian Dam Association Bulletin - Summer 2016 - 25
Canadian Dam Association Bulletin - Summer 2016 - 26
Canadian Dam Association Bulletin - Summer 2016 - 27
Canadian Dam Association Bulletin - Summer 2016 - 28
Canadian Dam Association Bulletin - Summer 2016 - 29
Canadian Dam Association Bulletin - Summer 2016 - 30
Canadian Dam Association Bulletin - Summer 2016 - 31
Canadian Dam Association Bulletin - Summer 2016 - 32
Canadian Dam Association Bulletin - Summer 2016 - 33
Canadian Dam Association Bulletin - Summer 2016 - CDA CONFERENCE 2016
Canadian Dam Association Bulletin - Summer 2016 - 35
Canadian Dam Association Bulletin - Summer 2016 - 36
Canadian Dam Association Bulletin - Summer 2016 - 37
Canadian Dam Association Bulletin - Summer 2016 - 38
Canadian Dam Association Bulletin - Summer 2016 - 39
Canadian Dam Association Bulletin - Summer 2016 - 40
Canadian Dam Association Bulletin - Summer 2016 - 41
Canadian Dam Association Bulletin - Summer 2016 - 42
Canadian Dam Association Bulletin - Summer 2016 - 43
Canadian Dam Association Bulletin - Summer 2016 - 44
Canadian Dam Association Bulletin - Summer 2016 - 45
Canadian Dam Association Bulletin - Summer 2016 - 46
Canadian Dam Association Bulletin - Summer 2016 - CDA OFFERS ASSISTANCE AFTER BRAZIL DAM DISASTER
Canadian Dam Association Bulletin - Summer 2016 - 48
Canadian Dam Association Bulletin - Summer 2016 - 49
Canadian Dam Association Bulletin - Summer 2016 - 50
Canadian Dam Association Bulletin - Summer 2016 - DAM SAFETY REVIEWS TECHNICAL BULLETIN
Canadian Dam Association Bulletin - Summer 2016 - 52
Canadian Dam Association Bulletin - Summer 2016 - NOTICE OF AGM
Canadian Dam Association Bulletin - Summer 2016 - BUYERS’ GUIDE AND TRADE LIST
Canadian Dam Association Bulletin - Summer 2016 - 55
Canadian Dam Association Bulletin - Summer 2016 - CALL FOR PAPERS
Canadian Dam Association Bulletin - Summer 2016 - 57
Canadian Dam Association Bulletin - Summer 2016 - 58
Canadian Dam Association Bulletin - Summer 2016 - cover3
Canadian Dam Association Bulletin - Summer 2016 - cover4
Canadian Dam Association Bulletin - Summer 2016 - outsert1
Canadian Dam Association Bulletin - Summer 2016 - outsert2
Canadian Dam Association Bulletin - Summer 2016 - outsert3
Canadian Dam Association Bulletin - Summer 2016 - outsert4
Canadian Dam Association Bulletin - Summer 2016 - outsert5
Canadian Dam Association Bulletin - Summer 2016 - outsert6
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