Q. Then unless I misunderstand you, what you are suggesting is that that person sitting down at that desk must say, "Don't show me any arithmetic calculations or any books to do with geotextile issues. I can tell you here and now immediately in 10 minutes that nothing like that can work. You will need an impermeable wall"?
A. Exactly. It's a common-sense approach, exactly what I'm saying, yes."
667 The difficulty which this causes for the Court in accepting Professor Ingold's opinion that the designers had chosen the wrong formula/geotextile in their design, is that it appears to suggest that no matter what textbook or authority the designers could have consulted, they would have fallen into error. This is because, "common sense" would have told them that all these geotextile selection formulae are irrelevant and that an impermeable material ought be selected. I do not take Professor Ingold to be suggesting that this "common sense" conclusion is somehow wrapped up in engineering minutiae. Rather, it appears that Professor Ingold's proposition was that such a conclusion would have been obvious to the designers. Again, Professor Ingold's opinion suffers from a lack of transparency of reasoning processes.
668 Professor Ingold moves away from his position that "common sense" would have shown that these formulae could not be relied upon in the extant situation by pointing to a diagram which preceded these four formulae in his book, and which shows a sloping bank (not a vertical wall as in the present case).
669 The text accompanying this diagram states "This section considers design aspects of geotextile filters beneath revetments". Mr Robb put to Professor Ingold that there is no real difference in theory between a sloping revetment (as shown in the diagram) and a vertical revetment (such as the walls). Professor Ingold stated that there is a big difference, that being that the vertical revetment will be subject to more severe wave slam as, in effect, it is stopped by the wall immediately (as opposed to running up the sloping revetment) [transcript 901.51-902.6]. What this appears to suggest is that the greater force imposed on the vertical wall will mean that the four formula will not, therefore, be applicable to the current situation.
670 What, it is to be noted, is that none of the four formulae have a variable which changes according to the hydraulic gradient. In both the case of the sloping bank and the vertical wall, Professor Ingold states that the hydraulic gradient will be high and alternating [transcript 902.22-29]. Further, hydraulic gradient, in both cases, is measured according to its application at right angles to the slope/wall. It is a variable that can be measured, no matter what the angle at which the slope or wall may be sitting. And although this hydraulic gradient value might be higher in the case of vertical walls, all other things being equal, it does not, on a reading of the text, to which the Court was directed, remove it from being able to be applied under any of the four formulae. In other words, the text and the discussions of the precise formulae do not reveal any point at which they are rendered inappropriate or useless because the hydraulic gradient is too high.
671 Professor Ingold's answers in response to this line of questioning leads to a rejection of his propositions that:
· on a common sense approach, the formula adopted (and the formulae which Mr Robb took Professor Ingold to in his own text) were inappropriate in the current circumstance; and
· the formulae listed in his own text were inappropriate as they were based on variables which were inapplicable to the current circumstance.
The second development: The size of the cavities
672 On the last morning of cross-examination by Mr Smith, Professor Ingold stated that it was his opinion that under the extant wave and tide conditions, the cavity would not be able to grow from the joint to the edge of the geotextile [transcript 801.47-53]
673 Up until this point Professor Ingold's opinion had involved the cavity extending from the joint to the edge of the geotextile. This new proposition was a departure from what had originally been perceived to have been his opinion. It is only on a most equivocal reading of his reports and prior statements that it could be said that Professor Ingold was excluding from his theory the possibility that the cavity would extend from the joint to the edge of the geotextile.
674 The manner in which this clarification by Professor Ingold changes his theory, as set out above, is that, in his later expressed proposition, the geotextile will come apart from the wall, even though it is still pressed up against the wall by sand. The oscillation of the geotextile at the joint is of a sufficient force that it can overcome the pressure exerted by the sand against the geotextile at its edge.
675 What becomes the focus of the factual investigation is no longer, the issue whether the cavity will grow to extend to the edge of the geotextile, but rather, whether the geotextile oscillates to a sufficient degree that it can pull the geotextile away from the wall.
676 Evidence that the geotextile would, in fact, oscillate is in the form of a test carried out by Water Research Laboratory of the University of New South Wales ["WRL"] [PX Vol 37]. The WRL tests are examined in more detail below. Of present relevance of the five tests carried out by WRL, it was the second test in which flapping of the geotextile was recorded as having been observed [PX Vol 37 p94]. The issue that arises is that in some of the other tests, significant sand loss was observed, yet no oscillation was recorded. This would suggest that the oscillation mechanism by which sand loss occurs, as posited by Professor Ingold, does not sufficiently explain why sand loss is occurring. That is, under the WRL tests, sand loss is occurring where oscillation was not recorded.
677 Further, the reasons why Professor Ingold apparently relies upon the WRL tests to justify his theory appear to be out of step with reason. What Professor Ingold says is that the WRL tests showed that sand loss occurred in situations where the 80% density index was achieved; and therefore his theory is sound. This is a logical fallacy. The WRL tests are examined below and found to be too unsafe to base a conclusion on Professor Ingold's oscillation theory. In any event what those tests would need to show (assuming that they are reliable), to support Professor Ingold's theory, would be that the sand losses recorded and observed in those tests took place by a mechanism which accords with his theory. The WRL tests did not achieve this.
678 The simple fact is that there is a serious lack of evidence to support Professor Ingold's theory regarding the oscillation of geotextiles.
WRL Testing Regime
679 In December 1998, a report was published by the Water Research Laboratory of the University of New South Wales ["WRL"] which presented the results from various tests conducted in relation to a physical model of the Millstream wall.
680 The report was commissioned by BHE.
Characteristics of the Model and Tests
681 The models were constructed "life-size". Some parts of the model were made of the same concrete which the real-life walls were made of; other parts were made of strengthened Perspex so that visual observations could be made of the soil and whatever phenomena were occurring [Ex PX.037.0020].
682 Describing the model generally, it consisted of a part of the Millstream wall (where the joint and geotextile was) placed inside a larger box/casing. The wall itself measured 1.5 metres in length and 2.1 metres in height [Ex PX.037.0025]. On one side of the wall, inside the box, was water. On the other side, sand. The distance from the wall to the end of the casing on the marine side was 100mm, and on the landward side 1 metre [Ex PX.037.0025]. A piston operated at the base of the casing on the marine side to simulate the wave conditions [Ex PX.037.0026].
683 The box was made of steel, in which Perspex windows existed.
684 The geotextile applied in the model was the same as was applied in real-life [Ex PX.037.0041].
685 Materials were placed at the points where the walls of the Millstream wall met the walls of the casing, in order that "edge effects" would be minimised or eliminated. The phrase "edge effects" refers to a phenomenon in model testing where, in the present example, water or soil would be able to flow through a gap where the Millstream wall and the casing meet. Such edge effects would decrease the reliability of the test results, and such a phenomenon has been raised by some of the present parties to contest certain findings made by WRL.
686 The WRL report recognises that there are two general types of wave conditions which are extant at the Millstream and Seawalls, and explicitly states that it was only attempting to simulate one of these wave conditions. The wave condition which it did not attempt to simulate was the effect that waves, approaching parallel to the walls, had on the walls. The wave condition which it did attempt to simulate was the effect that waves, approaching at right angles to the walls, had on the walls [Ex PX.037.0023]. This is an important recognition.
687 On 19 June 1997 WRL submitted a proposal to Connell Wagner which detailed a testing regime [PTB.035.0028 and MFI D3(g)]. The model testing brief and scope of works proposal is discussed in paragraph 3. WRL proposed that tests be carried out on models constructed to represent each of the Millstream and Seawalls. Model 1 was to represent the Millstream wall and was to be constructed with perspex walls to facilitate visual observation. Model 2 was to be undertaken if failure was observed in Model 1. Model 2 would involve the construction of concrete panels to replicate reality at the third runway. Models 3 and 4 were proposed to simulate the Seawall panels, and proposed that perspex and concrete panels would be constructed on the same basis as Models 1 and 2 provided for the Millstream walls.
Conclusions on the WRL tests
688 WRL carried out five tests using their model, with variables introduced in the various tests. There are two primary reasons why the WRL tests are highly suspect in terms of providing support one way or the other for any of the expert's theories. The first reason is that there are significant differences between what was modelled in the WRL tests and what is actually present in real life. The second reason is that no single test produces results which are consistent with Professor Ingold's theory; nor do they appear to have replicated results which accord with what has occurred in reality.
689 With regard to the modelling process, the effects of the movement of tide were not replicated: yet tidal movement plays a large role in Professor Ingold's theory insofar as it concerns the creation and breakdown of cavities [transcript 459.50-52]. Secondly, the Seawall was not modelled, the significance in this being that the effects of the no-fines block in the prevention of loss of sand was not tested. Thirdly, certain parts of the modelled wall were made of Perspex (in order that one could see through the wall). The importance of this is that the surface of Perspex is less rough than that of concrete, and as such, it is more likely that geotextile would slip [transcript 1562.51-1563.03].
690 Further, in relying upon the WRL tests, Professor Ingold picks and chooses elements of the individual tests to support different elements of his theory. The problem with this approach is that with care, the reverse may be achieved (that is, the picking and choosing of elements of the individual tests to deny elements of his theory).
691 Only test two reported flapping of the geotextile, yet this is relied upon in support of Professor Ingold's theory [Ex P1 TI-3 [7.11]]. Mr Smith focused part of his cross-examination on the results of test five (this being the test where the 80% density index was achieved). Mr Smith during cross-examination raised the issue that in test five, no sink holes or rat holes were observed, this being inconsistent with Professor Ingold's theory [transcript 463.54-464.07]. Further, this test only resulted in a small loss of sand compared to what is observed at the actual walls, such a sand loss being observed with no accompanying oscillation.
692 What this and the matters referred to below demonstrate is that the WRL tests are simply too unsafe a platform upon which to base a reliable conclusion, one way or the other, upon the acceptability of Professor Ingold's oscillation theory.
693 For reasons which have been left totally unexplained the only WRL model tests that were carried out involved a simulation of the Millstream panels constructed in perspex. No test was carried out on a simulated Seawall model. Notwithstanding that sand loss was found after operation of the perspex Millstream wall model, no test was carried out on a model in which the Millstream wall panels were replicated in concrete.
694 Mr Carley accepted, in answer to a question from the Court, that Model 1 would fail if sand was lost from behind the wall. He also accepted that as the Millstream wall and Seawall panels had different geometries so two separate models would be needed to properly study both of them. Mr Carley said that perspex has lower friction than concrete "so the interface between the geotextile and perspex may be different because of the roughness between the two as well". Mr Carley also accepted that if the test was only carried out with perspex panels, the results may differ from what would be found if concrete panels had been used. According to Mr Carley WRL itself suggested that the perspex was likely to accelerate testing because of the lower friction [T1560-1565].
695 All that Mr Carley could say on the subject of why the full test regime as proposed was not carried out was: