Canadian Dam Association Bulletin - Summer 2016 - 25

Figure 4: Schematic and photo of the first modern triaxial testing device (USACE 1938). to flow failure was another primary concern of the designers. However, how to evaluate the potential for static liquefaction was unknown. Prof. Casagrande wrote to the USACE "I had concluded the existence of a 'critical density' (also called 'critical porosity' or 'critical void ratio') from the fact that loose sands reduced their volume during shear and that dense sands expanded, but that this value had never been determined experimentally", furthermore "I still had the mistaken idea that the critical porosity was independent of the normal stress" (USACE 1938). Two series of direct Canadian Dam Association * Summer 2016 shear tests were then conducted on soils from the Franklin Falls Dam site. However, the results proved inconclusive with respect to volumetric behavior. A "simple" prototype triaxial compression testing apparatus had been developed by Prof. Casagrande at MIT in 1930. The Franklin Falls Dam project provided the impetus for the improvement of this device, such as the addition of a loading apparatus to allow stress or strain-controlled testing (USACE 1938). Specimens from the Franklin Falls Dam site were possibly the first ever subject to triaxial testing as we know it today. A schematic and photograph of the triaxial device are shown in Figure 4. The triaxial testing results confirmed the existence of a critical density and that it is dependent on the confining stress, the angle of internal friction of the soils was found to vary from 32° to 44° with decreasing void ratio and a minimum relative compaction of 80% was recommended for the embankment and foundation soils. There was a difference of opinion with respect to the need to treat the foundation soils (USACE 1938): Prof. Casagrande wrote "...the loose fine sand underlies only two relatively narrow sections of the dam... Thus, if the loose fine sand is liquefied, the shearing stresses which this part of the foundation are carried are automatically transferred to the adjacent sections... until consolidation, which would occur in a very short time" (USACE 1938). Brown (1940) wrote "It is known that a dense, cohesionless soil in a saturated state has a tendency to increase its void spaces u nder deformation, which results in a temporary deficiency of pore water and consequent increased shearing resistance... Opposite effects are caused when a loose, cohesionless soil is deformed. The pore spaces decrease, excess pore water is formed, and the shearing strength of the mass is reduced.... If of general extent and not relieved, the latter condition is capable of causing flow failure." Ultimately, it was decided that the foundation soils should be treated and at least 6 field tests were conducted to determine the potential for densification of the foundation soils using explosives. One such test (Field Test No. 6) consisted of a 12-m-square area where holes were drilled at 3-m-spacing and explosives placed at a depth of 4.5 m. The explosives were detonated 25

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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