Stachiw 



14-inch internal diameter concrete spherical hull models with pene- 

 trations (Figure 4) closed by inserts (Figure 5) of different ridi- 

 gities. Only two sizes of inserts, and three kinds of insert ma- 

 terials were experimentally evaluated. All of the models were 

 waterproofed prior to implosion testing in simulated hydrospace 

 facility. 



PHASE III - Investigation concerned itself with the design, 

 fabrication, and testing of two concrete habitat models (Figure 6) 

 with 16-inch external and 14-inch internal diameters. The models 

 were equipped with operational windows and wire feed-throughs 

 located inside penetrations of the concrete sphere (Figure 4) 

 reinforced by annular penetration flanges (Figure 7). 



OBJECTIVES AND PROCEDURES OF THE INVESTIGATION 



PHASE I - The objective of the tests was to touch upon as 

 many facets of concrete hull's behavior under hydrostatic pressure 

 as possible, rather than research any one of them exhaustively. 

 Thus the hydrostatic tests on the simple concrete spheres were 

 employed to explore ultimate compressive strength of concrete 

 under short-term and long-term loading, the latter at hydrostatic 

 pressures approaching the critical pressure. Experiments were 

 also conducted to investigate the leakage of water through unpro- 

 tected concrete at different hydrostatic pressure levels. Because 

 of the exploratory nature of these tests, only one to three spheres 

 were tested in each type of experiment. Experimental data from 

 such a small number of test samples are considered to be indicators 

 of the general level of magnitude of the parameters studied, but 

 not conclusive and final evidence of these parameters. Once the 

 general magnitude of the parameters investigated is known, an 

 accurate plan can be drawn up for future experiments to more 

 thoroughly evaluate and define the physical and mechanical pro- 

 perties of concrete under the external hydrostatic pressure of 

 seawater . 



PHASE II - The testing to destruction of the spherical hull 

 models had as its objective a quantitative evaluation of the 

 relationship between the size and rigidity of the penetration 

 insert, and the critical pressure of the whole concrete hull as- 

 sembly under hydrostatic pressure. The concrete spherical hull 

 models with solid penetration inserts of different rigidity had 

 the same dimensions and were cast from the same mix as the models 

 without penetrations. Since it is known that the stress concen- 

 tration around a penetration in the hull is to a large degree 

 dependent on the size and on the mismatch between the rigidity of 

 the penetration insert and that of the hull material, two sizes 

 of penetrations and three types of insert materials were selected 

 that represented a wide range of rigidity properties. The two 

 selected sizes of model penetration inserts were considered to 

 be representative of penetration inserts required for full size 

 spherical structure. The 32°30' size insert simulated a penetra- 



224 



