The~-y curve is a soil model used in the design of laterally loaded piles. A method is presented to obtain the P-y curve from the pressuremeter curve. This method distinguishes between the friction model and the front resistance model. Using this approach, comparisons are made between the predicted and measured behavior of two laterally loaded piles; one in a soft clay and one in a medium to dense sand. The comparisons show very good agreement and point out that a distinction may have to be made between displacement piles and non displacement piles.

The first part of this article deals with the determination of the critical depth Dc, below which the ground surface has little influence on the soil-structure interaction problem, and with the variation of soil resistance within that critical depth. A new approach is proposed to determine Dc using the relative rigidity of the pile with respect to the soil strength as measured by the pressuremeter limit pressure. The second part of the article summarizes seven pressurementer methods to predict the lateral behavior of piles. Predictions by four of the methods are compared with the results of a full-scale load test. All methods predict the measured behavior with reasonable accuracy suggesting that the pressuremeter provides a sound testing base for the behavior prediction of laterally loaded piles.

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ABSTRACT1. Many populations of sea-ducks, which typically winter at sea but breed on fresh water, are declining. Numbers of common scoters Melanitta nigra (L.) breeding in Scotland halved between 1995 and 2007, despite most breeding sites having special conservation status. To identify potential conservation measures, a 3-year study was conducted, investigating correlates of lake use by scoters.2. At 26 scoter breeding lakes, food abundance (macroinvertebrates) and foraging habitats (substrates, water depth) were measured, and their associations with scoter lake use explored using multi-model inference. Correlates of macroinvertebrate abundance (water quality, fish abundance) were also investigated.3. Averaged over 3 years (2009 -2011), these lakes held 26.7 (SE 6.3) females, around half the Scottish breeding population. Scoters occurred more often at lakes having abundant large-bodied invertebrates and extensive shallow water. Lakes where the average weight of the largest invertebrate in each sample exceeded 4 mg had 9.2 times (females) or 27 times (broods) more scoter records than other lakes. Lakes where water depths (10 m from the shore) averaged less than 1.3 m had 2.5 times (females) or 12 times (broods) more scoter records than other lakes.4. The abundance of large-bodied invertebrates was greater where small fish species (mostly three-spined sticklebacks Gasterosteus aculeatus) were more common and brown trout Salmo trutta were scarcer.5. Results suggest two approaches to scoter conservation. At lakes used for hydro-electricity generation, water level regimes that provide extensive shallow water should be tested to see if these benefit scoters. At lakes used for trout fishing, trout reduction by increased angling should be trialled, to see if this increases large-invertebrate abundance and scoter use.