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Marine and Riverine Projects:
Yarra Bank Improvements.

Landing stage and promenade near Princes Bridge

Fig.1. The completed landing stage / 'wharf' / 'promenade', with steamer alongside. University of Melbourne Archives, Reinforced Concrete & Monier Pipe Co Collection, GPNB-1135. (For photos of construction work, see Figs. 7 and 8 below.)

Summary.

In 1907, Melbourne City Council awarded a contract to the Reinforced Concrete & Monier Pipe Construction Co for approximately 200 feet (61m) of low-level wharf on the north bank of the Yarra River, extending east from Princes Bridge. It provided a promenade, with a vertical face to allow motor launches and rowing boats to come alongside. Monash's first rough design dates from September 1906. Construction commenced on 16 September 1907 and was completed on 14 October, just in time for the Henley-on-Yarra Regatta. The front of the platform was supported by a row of reinforced concrete piles, and the back by a ground beam. Precast fascia panels attached to the piles retained earth and provided a vertical face reaching down to Low Water Mark. The deck was of in-situ reinforced concrete, with cross-beams spanning from the piles to the ground-beam. The work was supervised for the City Council by H E Morton and A C Mountain.

Detailed story

Negotiations and design.

The first intimation of the scheme in the RCMPC records is a drawing in pencil, on the back of a wages sheet, dated 9 September 1906, with a notation: "approx 35/- per ft run". It is likely that Monash, on learning that such a facility was contemplated, had suggested that it be built in reinforced concrete and had commenced negotiations on its nature and price. This first drawing shows the wharf with a concrete deck 9 feet (2.74m) wide and a parapet wall whose river face is relieved by large recessed panels. The front of the platform is supported on a row of reinforced concrete piles, spaced at 30 feet intervals (9.14m). The wall acts as a stiff beam, spanning from pile to pile to support the front edge of the deck. A somewhat peculiar feature is that the piles are cut off where they emerge from the earth, and are extended by a sort of rectangular blade having the same thickness as the pile, and a width (parallel to the river) of 3 feet (914mm). The entire construction appears to be monolithic. The river bank is shown with a slope of 27 degrees, and protected by existing stone pitchers. (Fig.2)

Fig.2. Cross-section of Monash's first proposal, 9 September 1906.

By 22 September, the pile spacing has been reduced to 10 feet and the piles reach much higher, being cut off just below deck level. However, shortened 'blades' form a feature on each third pile. The wall has been simplified, and a downward projection has been added to form a fascia panel reaching down to Low Water Level. (Fig.3).

Fig.3. Cross-section with fascia panel below parapet, 22 September 1906.

There was no further development until July 1907. On 21st, Monash prepared calculations headed "Final Design". A new drawing of the same date shows a considerably revised scheme (Fig.4). The parapet has been omitted and replaced by a kerb. The fascia below deck level is formed from reinforced concrete panels measuring 12 feet (3.66m) longitudinally and 4 feet (1.22m) vertically, to be precast on site, and then placed in position. Each panel, strengthened by edge beams and cross-ribs, spans as a simply-supported beam between piles now 12 feet apart. The panels present a smooth face to the river, flush with the face of the piles. This configuration was to become Alternative C in the formal tender.

Fig.4. Cross-section with precast fascia panel, 21 July 1907.

Technical Note. At this stage, Monash used the Brix formula (as given in Beton und Eisen 1904, p.69.) to calculate the degree to which a pile should be hammered into the ground to ensure a load-carrying capacity of 10,000 pounds force (44.5kN). Taking a cross-section 12" × 12" (305 × 305 mm), he assumed the pile to be 16 feet (4.88m) long, with a mass of 2400 lb (1089kg). He calculated that it should be driven to the point where a weight (or 'monkey') of one ton (1.02t), falling through 2 feet (610mm), would drive it only a further 5/8" (15.9mm) into the ground.

The proposals were then evidently shown to the City Surveyor and his Assistant who demanded a check on the ability of the panels to resist hydrostatic pressure. They also informed Monash that for much of the length of the wharf, the slope of the bank was not 1 in 2 (27 degrees) as previously advised; but 1 in 3 (18 degrees). This required that the ground beam be deeper (Fig.5).

Fig.5. Cross-section with revised slope of bank.

On 26th, Monash offered to build not less than 200 feet (61m) of platform for £2-7-6 per foot run. This included reinforced concrete piles 12 feet apart, of 12" × 12" cross-section, driven to a test yield indicating 4.5 tons capacity (4.57 tonnes); a ribbed plate face wall, and a deck designed to carry 120 pounds per square foot (5.75 kPa).

Public tenders. Threat of a timber alternative.

Monash must have been disconcerted when, on 3 August, the Council called public tenders suggesting that it would accept a simple timber retaining wall back-filled with earth to form a promenade, instead of the scheme he had negotiated. No mention was made of any need to provide a deck, or to present a flush face to the river. The timber piles of such a wall would have stood in front of the sheeting, and offered obstructions to boats coming alongside. The Specification was framed in performance terms. The face of the wharf had to be able to withstand impact from the mooring of motor boats, plus any outward pressure due to retained earth. Tenderers were required to "submit their designs together with all particulars as to materials and statical calculations". However, minimum dimensions were specified for the piles and sheeting of a timber wall, with a list of acceptable timber species.

Finding himself in danger of being undercut by a competitor from the timber industry, Monash hurriedly prepared reinforced concrete versions of an equivalent scheme. The tops of the piles were to be joined by a capping beam. Below this, a thin concrete wall would span behind the piles. Monash recommended that the heads of the piles be tied back to a concrete 'sleeper' buried in the bank and reinforced with a railway rail (Fig.6); but also offered a wall without ties in case the Council engineers considered it acceptable.

Fig.6. Proposal for a piled r.c. retaining wall tied back to a sleeper beam. Alternative B of the formal tender.

RCMPC's formal tender of 12 August 1907 thus included three alternatives:

The prices per foot run were:

Two days later, Mountain advised that the Council would accept Alternative C, provided that completion was guaranteed by the end of the following month, September 1907.

Construction.

Realising that manufacture of the piles was on the 'critical path' for speedy construction, Monash issued urgent instructions to the RCMPC factory. Nineteen piles 20 feet (6.10m) long were required. They should be poured within 6 to 8 days and be strong enough to resist driving within 4 to 5 weeks. To avoid delay, Works Manager Alex Lynch was given drawings of the piles that had been used at the Hindmarsh Bridge, with written instructions relevant to the present project. A special drawing was required for the 18 precast fascia panels, but there was less urgency in this case.

Technical Note. Pile reinforcement consisted of 4 bars 1" in diameter, with ties of 3/16" diameter. The head was to have extra reinforcement of 4 short bars of 5/8", 3/4", or 7/8" diameter bars and a spiral of No. 8 gauge wire of about 1½ " to 2" pitch for 3'-0" down the pile. Monash gave Lynch advice on pile driving. He was to use much smaller blows than for timber piles. He was to start with a hammer drop not greater than 12", until the penetration per blow came down to ½ " or less. Then he could increase the drop to 18" until the yield was again down to ½ ". The process should then be repeated with a drop of 24". After that, the pile should carry the desired load with an adequate factor of safety, but just to be sure, Lynch should give it an extra 10 blows. The total yield should be 4" or less. Monash noted that these instructions assumed a soil of typical stiffness.

Early in September, a punt was hired from a Mr J Schwarz of Footscray, and work commenced with Alex Lynch as foreman. Operations on site continued from 16 September to 16 October. The routine of construction was enlivened by the usual quibbles between client and contractor. Mountain seems to have been so concerned that Monash might be setting the scene for claims for extras; that he refused to consider even reasonable appeals for consideration. A few days after work commenced, Monash told him that sewerage works on the north bank of the river were restricting access to the site, and asked if he could help. Mountain's reply was unsympathetic. The sewerage was the responsibility of the Melbourne & Metropolitan Board of Works, so the problem was not his. RCMPC had given no indication that they wanted to use the north bank, and had delivered all their materials to the south bank without notification. Monash replied that he was not trying to blame Mountain, but felt it should have been obvious that RCMPC would want to use the north bank. They had dropped the materials at the south bank because there was no alternative.

Fig.7. Barge-mounted pile-driver at work (foreground). Three driven piles can be seen, projecting well above water. Work has commenced on cutting down the nearest pile to required length, exposing the reinforcement for integration into the longitudinal beam that will support the deck. University of Melbourne Archives, Reinforced Concrete & Monier Pipe Co Collection GPNB-1136.

Next, Morton demanded that the 'monkey' be dropped through four feet (1.22m), rather than two. Monash was in Adelaide at the time, and asked John Gibson to point out that RCMPC was using a 34 cwt (1.73t) monkey rather than the customary 20 cwt (1.02t). However, he told Gibson: "We have not got sufficient length of pile to work down to anything like the resistance [Morton] wants." He declared a willingness to drive the piles down as far as their length would permit, and took full responsibility for the quality of the work.

Fig.8. Work at a more advanced stage. In the foreground (beyond the steps) are precast fascia panels awaiting installation. The tops of cut-down piles, with reinforcement exposed, can be seen along the water's edge. In the background is Princes Bridge. (Monash worked as a site engineer on its foundations in the mid-1880's.) University of Melbourne Archives, Reinforced Concrete & Monier Pipe Co Collection GPNB-1137.

On 28th September, Mountain complained about the slow rate at which piles were being installed. The MMBW had now finished its work on the north bank. There was only a week to go if the deck was to set by the end of September and be ready for the Henley-on-Yarra Regatta. Monash countered with a claim that changes in requirements had caused delay, due to extra and awkward work. The actual water level had been 16" higher than the High Water Level shown on the drawings, and had always been 20" above the Low Water Level shown. Work had been held up and complicated because the wharf deck was only 15" above normal High Water Level, and the greater part of the face plates was submerged in silt instead of hanging free as planned. Mountain claimed that the abnormal water levels were due to the long stretch of westerly winds, blowing up river. He hoped RCMPC would have more favourable weather in future.

The concrete structure was completed on 14 October, a fortnight past the target date; leaving only a fortnight for it to gain strength before it had to support a crowd for the Regatta. It was agreed that the timber props used in construction should be left under the deck until the event had occurred.

RCMPC's final account for the wharf was presented on 13 November, for £522-4-0. This included a claim for extras, amongst which was sub-aqueous excavation (including lifting of stone pitchers) to permit placement of the fascia panels.

Additional contract.

In January 1908, Monash wrote to Mountain to say that if the wharf were ever extended, it would be good to make a firm decision on the exact location and length, and survey the slope of the bank accurately, before work started. He noted that, as the previous contract had now been settled, his present suggestions could not be interpreted as setting the scene for a claim for extras. (His letter implies that RCMPC had not been properly recompensed for their work, but it does not mention an actual figure for the loss.) Mountain's reply was as courteous as Monash's, though still guarded. "I have read your reasoning carefully: and much of it is evidently a reasonable and fair statement of facts. Before anything is settled for future work, I will be glad to have a chat with you, as suggested: and see if I can frame conditions which will be mutually satisfactory, without causing extravagant expenditure."

Late in June 1908, Monash submitted a tender for a further 204 feet of wharf, 13 feet wide, at £542-18-0, offering a reduction of £15-6-0 in the price if the width were reduced to 11'-6". The Council drawing this time shows much more detail. There are frequent cross-sections of the river bank, with precise levels, and two typical cross-sections for the wharf, depending on whether a deep or shallow ground-beam was appropriate. Mountain rang Monash on 7 July to say that the option for the narrower deck had been accepted. There would be 17 bays of 12 feet span.

The piling was sub-contracted to Messrs. Ross, Fraser and Patience at a price of £47, and a punt was hired this time from the Melbourne Harbor Trust. Monash reported to Mountain on 28 August 1908 that the work was substantially complete, but he would again leave the timber supports under the deck to cope with crowds expected for the visit of the "Great White Fleet" of the US Navy to Melbourne (29 August - 5 September 1908).

On 17 October, Mountain complained that the steps provided in two of the bays were not complete, yet the Henley Regatta was to take place on 24th. (Three attempts had been made to render the lower treads, but the mortar had been washed off each time by the rapid rise of the tide.) He withheld final payment until 13 January 1909, but finally gave in, with the rendering still not achieved.

Yarra South Bank Retaining Wall

Fig.9. Work on the south bank retaining wall. Along the water's edge can be seen the tops of Monier pipes, sunk into the river bed to be filled with concrete, to form the foundations of the wall. At left middle are precast wall units awaiting placement on the foundations. (They are lying on their sides.) In the distance is a section of completed wall ready to be back-filled with earth to form the promenade. University of Melbourne Archives, Reinforced Concrete & Monier Pipe Co Collection NN718. A print from this negative is dated 31 May 1911. UMA holds three more images of work on this project: NN719, NN720 and NN721.

Planning, Design, and Tender

During the annual Henley-on-Yarra Regatta, 'house boats' were moored along the river bank to provide sheltered vantage points for viewing the rowing events. The 1911 annual report of the Melbourne Amateur Regatta Association lists a number of Melbourne clubs as having houseboats: the Alexandra, Athenaeum, Australian, Bohemian, Commercial Travellers', University, and Wallaby clubs. The Savage Club and the Mercantile Rowing Club had pavilions on the adjoining lawn. However, socialising was hindered by "the uneven nature of the bank" which made it difficult to pass from one houseboat to another. The Regatta Association approached the State Minister for Public Works, W L Baillieu, who in December 1910 agreed to help finance a 600-foot length of retaining wall behind which earth could be filled, to establish a level promenade. The estimated cost of £450 would be shared equally between the Government and the Association.

Announcements in the Melbourne Age and Argus on 23 December are filed in RCMPC's archives. The government's involvement meant that the work came under the direction of the Chief Engineer of the Public Works Department, Carlo Catani. The supervising engineer was George Kermode. Both of these men were well known to Monash from previous projects.

The Department's proposal was summarised by Monash on 2 March 1911. The wall was to be founded on miniature caissons sunk in the river's edge at intervals of 10 feet. These would be like a box without bottom or top, three feet (914mm) square in plan, and 2'-9" (838mm) deep, with a wall thickness of six inches (152mm). The bottom edges of the walls would be chamfered to allow the caisson to be forced into the bank until only 6 inches of wall projected above Low Water Level. The earth would then be excavated from within the box and the interior filled with concrete. On this foundation would be placed precast concrete beams, 15" (381mm) deep and about two feet (610mm) wide, reinforced with railway rails. These would span from caisson to caisson. The upper part of the wall would be formed by in-situ concrete 2'-5" (737mm) deep, placed on top of the beams. The whole would be finished off by a coping of partially dressed capping stones (Fig.10).

Fig.10. Cross-section of the PWD's gravity wall design.

As was his custom, Monash decided to offer an alternative and cheaper solution, which would beat competition from less inventive tenderers. The custom-made caissons would be replaced with off-the-shelf Monier pipes from RCMPC's factory. The mass concrete gravity retaining wall of the PWD design would be replaced by a more economical precast wall unit (Fig 11) made close to the site. The pipes were to be two feet in diameter and forced three feet into the soil, deeper than in the PWD proposal.

Fig.11. Cross-section of Monash's alternative, with Monier pipe foundations and precast wall units.

In his letter of tender, Monash noted that the thrust line due to pressure from backfill would pass well within the middle third of the base of the wall unit, but that if Catani wished, the units could be set back from the front face of the cylinders to increase stability.

The tender price for 600 feet (183m) of wall was £437-10-0. Catani called Monash to a meeting and proposed that the diameter of the pipes be increased to three feet (3'-4" or 1.02m externally). However, the length of the pipes was reduced from three to two feet. (In his notes on the meeting, Monash has "2 feet long (sic)", suggesting that he thought this insufficient.) The price would be unaltered. With these amendments, RCMPC's quote was accepted. Monash issued the necessary requisitions to the factory and prepared a drawing of a more refined wall section, with full reinforcement details. He told Works Foreman Lynch: "We are endeavouring to design them so as to be as light as possible for handling."

Construction

As work progressed the RCMPC team found once again that the slope of the bank was "very much" steeper than shown on the drawings. By 12 May, they were at a point where 4'-0" long cylinders were required.

Towards the end of May it must have been noticed that some sections of the wall were rotating slightly outwards. J A Laing revised the calculations and found a pressure of 3000 psf at the front toe of cylinders 2'-9" deep. (Laing's calculations are rough and arguably conservative.) However, definite forward movement of the top of the wall could be observed, varying along its length with varying resistance of the soil. Monash wrote to Kermode suggesting that the placement of the coping be delayed until the wall had stopped moving, so that the eventual face should be a straight line. He also suggested more careful placement of the backfill, which was being carried out by others.

In July, Monash visited the site and met Kermode who "complained exceedingly re the want of alignment of cylinders, want of bedding of plates and breaks in plates". Monash agreed to fix up whatever was indicated by a PWD officer, and Kermode agreed that two cracked plates could be used for the return ends of the wharf, which were originally to be done in-situ.

On 4 October 1911, Monash submitted a final account for £437-10-0 plus £89-4-0 for mooring rings, giving a total of £526-14-0. After two weeks delay, Kermode wrote "I regret to say that I shall be unable to arrange for a final settlement of accounts at present. The wall is still moving forward and I am afraid that the coping will have to be removed and replaced with a projection before the work can be regarded as satisfactory. I am awaiting with some uneasiness the result of the Henley crowd on the walk immediately at the back of the wall." However, on 9 November, Monash replied that the Henley Regatta was now over, and "the work does not seem to have suffered at all as the result of the heavy strain placed upon it."

Reminders sent to Kermode in November 1911 and January 1912 received no reply, but at a meeting on site on 20 February, Monash undertook to remove and replace the coping, with the cost shared equally between RCMPC and PWD. This seems a reasonable compromise, as the PWD had modified Monash's original design, and seems to have proposed shallower foundations. The repair of the coping was to be done late in the year when it had been ascertained that the wall was sufficiently stable. The cost of replacement was £62-10-0, so PWD's share would be £31-5-0.

RCMPC was thereupon (29 March 1912) awarded a contract for a further 110 feet of wall. In his letter of quote, Monash noted that the original tender had been found to be much below cost. "After making full allowance for possible more favorable circumstances of site and weather, we think that the estimate now furnished amounts to bare cost to ourselves for the additional work." He told Lynch to get the new foundation cylinders in as soon as possible, in case there was a rise in the river level. "I may say that the price we have for the work on this occasion is somewhat better than formerly, but our taking up this fresh work was a condition to our getting anything like a satisfactory settlement for the previous work." The price agreed was £220 which included 20 bays of face wall, an end wall, and mooring rings.

To solve the problem of irregular tilting, an additional reinforced concrete coping was added to the 580 feet of wall so far constructed, and an enlarged r.c. coping was provided to the next 200 foot portion, to bring the top to the same level. Kermode argued that this work was necessitated by "defective design or workmanship of the first section" and added "In my opinion I am meeting you very fairly when I agree to pay half the cost", or £39. Accounts were largely squared in July 1912 when Kermode paid all but £7 of the PWD's contribution, and notified the Regatta Association that its share should now be paid.