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Predicted and observed performance of motorway embankments on a soft alluvial clay in Somerset.

Roy, Malcolm. (1975) Predicted and observed performance of motorway embankments on a soft alluvial clay in Somerset. Doctoral thesis, University of Surrey (United Kingdom)..

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For 35km, the Birmingham to Exeter Motorway, M5, crosses the soft alluvial clays of the Somerset levels. This area extends from 15 to 50km south of Bristol and comprises alluvial sediments to an average depth of 26m. The sediments are so soft and unstable that the stability of the motorway embankments was low and large settlements were expected. The embankments were surcharged and allowed to settle for one year in order to reduce the post construction settlement. Instrumentation was installed at 24 locations along the motorway, to control the stability of the embankment during construction and to check the settlement and surcharge calculations. The stability of the surcharged motorway embankments was checked by observation of ground movements and that of the side road embankments by ground movements and effective stress analyses, because the main embankment was much lower than the side road embankments. The approach embankments to the side road overbridges, which reached a maximum height of 8.5m, were constructed over the higher section in pulverised fuel ash. Even using this lightweight fill, construction on all side road embankments was halted prior to completion, and stage construction and berms were necessary to reach the designed height in several cases. The observed performance of the motorway and side road embankments has been compared with the predicted performance, in order to assess the accuracy of the stability and the settlement and surcharge design calculations. The accuracy of these predictions has a considerable economic effect on the motorway expenditure in an area where the earthworks content of the work amounts to 30% of the total. Methods of improving the foundation soils by sand drains, vibro- floatation or relief piles were not considered suitable for these ground conditions.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Roy, Malcolm.
Date : 1975
Contributors :
Depositing User : EPrints Services
Date Deposited : 09 Nov 2017 12:17
Last Modified : 20 Jun 2018 11:34

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