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BATE AND STEWA8T ON adjusted to compensate for any obvious changes in the water present in the new material, if it is to be brought into immediate use.All these points can and should be covered by a skilled " concretor " once the concrete engineer has established his mix on a basis of aggregate supply and site requirement.With adequate planning of formwork, mechanization, and mix design, high-quality concrete is no more expensive to make and place than inferior material, and will certainly last longer.

DiscussionThe Chairman (Mr J. H. Jellett) said that the Paper described some very careful planning of work which had to be carried out under difficult traffic conditions. 106. Had there been any compelling reason for adopting a 13-ft-6-in.-gauge crane track on a SO-ft-wide quay? At Southampton tracks up to 18-ft gauge were used on narrower quays with resultant lower wheel loadings, and benefit to the necessary foundation work. It was possible that the P.L.A. used the 13-ft-6-in. gauge in more restricted sites and had adopted it in the interests of standardization. 107.He felt sceptical about the suggestion that the 200-ft-span shed had cost little more than if it had been constructed in two spans of 100 ft. At Southampton research into the cost of shed construction had shown that whatever might be gained by eliminating columns in sheds was reflected in greater initial cost. Their traffic operators were very keen on having no obstructions in the shed, and the magnificent structure now being discussed offered opportunity for interesting research. Why not cost the cargo operations for a year and then compare them with the cost of operations conducted in the shed after dummy columns had been erected? Such columns ought not to be so slight as to be brushed out of the way by the traffic, and would need to be sufficiently like the real thing to impose the necessary traffic pattern. This would settle once and for all the question whether the cost of eliminating columns in transit sheds was really justified in operation.108. It was stated that mobile cranes would not be permitted to work inside the shed. Why, then, had 20 ft clear minimum head room been provided? Traffic operators were unwilling to stack up to the limit of the headroom and this had an unhappy effect on the capacity of the shed.109. If cranes were not to enter the shed, what necessity was there for the expensive 2o-ft X B-ft doors? How manual would their operation be? Experience had shown that doors of that size, if intended for manual operation, were usually in the end operated with the assistance of electric trucks, the latter exerting pressure in places not intended by the engineer. Were the doors to be operated by a mechanical device of any kind, such as windlassing, to ensure that the manual effort was supplemented?110. At Southampton, also, fibreglass had been used in roofs. Fortunately it had not yet become the subject of fire regulations, and he hoped that such regulations would not be so framed as to prevent the use that had already been made of fibreglass. ~~ ~ ~~ t Proc. Instn civ. Engrs, vol. 15, p. 411 (April 1960). l Downloaded by [] on [11/09/16].

. MILLS M r Page, M r Curtisand M r Mills Regarding the test on the sheet piling, some additional information may be of interest. The loads in four of the tie rods were monitored: two of these rods were instrumented at both quay and anchorage ends and two at the quay ends only.Figs 21 and 22 show that the loads in the quay ends were quite low initially at only 100-200 kN and it was not until the final placing of the 2 m of Thanet sand compacted in 30 cm layers, that the loads increased to 400-500 kN, about two thirds of the 700 kN design load. From Fig. 22 it appears that initially the anchorage loads were dissipated in friction along the rod without any load being transmitted to the anchorage, the rods being under temporary compression at this end.81. A Stothert & Pitt 6 t vibrating roller (developing 96 t impact load) was used to compact the sand and this clearly helped to generate more realistic earth pressures transmitting loads of up to 40 t to the anchorages. If the design had been of the form in which the sheeting was driven entirely through existing soil with the face dredged after completion it is possible that the anchorage loads would have remained low, suggesting an unnaturally high factor of safety.82. Nine piezometer tubes were also installed to monitor movement of groundwater level. Only one of these continued to function throughout the construction period and this happened to be nearest to the instrumented sheet piles. A typical result is given in Fig. 23. This shows groundwater level following the rising tide very closely, which may not be entirely accurate, and could have been distorted by the presence of the piezometer tube itself. With the falling tide, groundwater level is held just below mid-tide and this is probably a true indication of the situation at this section. The design was based on groundwater being at mid-tide level and to that extent appears to be slightly conservative.M r J. N. Black, PLA, Tilbury Docks There were several reasons for choosing a site on the riverside rather than within the dock. The third-generation container ships were just beginning to be built, and we felt it would be advantageous to have a facility which obviated the need for them to go through the lock : the time-saving was important, as most of the large ships using Tilbury have to use the tide for the depth of water. Another reason was