An analysis of compressibility data from a deep borehole in Venice

Abstract

The Paper presents a brief synopsis of the problem of subsidence in Venice. It also includes summaries of the best information currently available on the settlements which have occurred during this century and of the rates at which piezometric levels in wells have declined. Most of the basic data used have been accumulated by the CNR laboratory in Venice which also commissioned a 1000 m deep borehole there in 1971. Extensive classification and œdometer test results have been obtained on soil samples from this borehole. The problem of reconciling the compressibility data with the piezometric level decline and surface settlement rates is discussed at some length and a tentative explanation is offered of the discrepancies found. Cette Communication présente un bref résumé des problémes d'affaissements á Venise. Elle comprend également une revue des meilleures données que l'on posséde actuellement sur les enfoncements qui se sont produits au tours de ce siécle et sur les vitesses d'abaissement des niveaux piézométriques dans les puits. La plus grande partie de ces données a été rassemblee par le laboratoire du CNR de Venise; qui a également donné un contrat pour le forage d'un trou d'une profondeur de 1000 m en 1971. On a obtenu un trés grand nombre de résultats déessais œdométriques et de classification sur les échantillons de sol obtenus dans ce trou de forage. On présente une discussion en profondeur des problémes de l'accord entre les résultats sur la compressibilité et l'baissement du niveau piézométrique et les vitesses d'affaissement de surface et on offre une tentative d'explication des divergences qui ont été observées.

An Improved Model of Soil Response to Load, Unload and Re-Load Cycles in an Oedometer

“…The resulting prediction, 146 mm, was much closer to the one generally accepted of about 140 mm -based on unusually goodˆeld data- (Ricceri and Butterˆeld, 1974;Buttereld, 2004), than Rowe's (1975) estimate of 205 mm derived from the same database and a conventional interpretation of the compressibility of the soil column.…”

Compression and Creep of Venice Lagoon Sands

“…Since the 1970's there have been extensive studies of the subsurface soil conditions in the lagoon in order to understand and predict the causes of subsidence (Ricceri and Butterfield, 1974). More recently the geotechnical investigations have focused on the foundation conditions at the three inlets (Ministero dei Lavori Pubblici, 1994;Ricceri, 1997).…”

Environmental Geomechanics

“…This behaviour, numerically calculated (Lewis and Schrefler, 1978b) and experimentally observed (Ricceri and Butterfield, 1974), in shown in Figure 11, where it is compared with the predictions made using the uncoupled model ofGambolati et al (1974). Before further data became available, the pumping rate was kept constant after 1969 and equal to its maximum value.…”

“…This information includes the material properties obtained from the analysis of core sample from test holes (Ricceri and Butterfield, 1974), the withdrawal rates of water at Marghera, Venice and Lido, and the records of piezometric decline and subsidence. This information includes the material properties obtained from the analysis of core sample from test holes (Ricceri and Butterfield, 1974), the withdrawal rates of water at Marghera, Venice and Lido, and the records of piezometric decline and subsidence.…”

“…They are located in the upper 350 m of the subsoil, as indicated in Figure 7. This data has been obtained from laboratory tests (Ricceri and Butterfield, 1974). A linear elastic constitutive relationship has been assumed for the skeleton along with a linear fluid flow regime.…”