Effect of an oak tree on seasonal ground movements in the Lower Lias Clay, Bristol, UK

摘要

Changes in ground elevation were monitored between 1990 and 1997 at depths of 0.4, 0.8, 1.2 and 1.6 m and distances of 1, 2.5, 5, 10, 15, 20, 25 and 50 m from a mature oak tree on the Lias Clay of Lower Jurassic age. Whilst movement was evident at all monitoring points, it was most pronounced within 5 m of the tree where in 1995 a maximum seasonal difference of 63 mm was recorded at 0.4 m depth, compared with only 14 mm at the same depth but 10 m from the tree. The influence of the tree on the geotechnical properties of the Liassic clays is reported.%Des modifications de cote des terrains ont t mesures entre 1990 et 1997 des profondeurs de 0,4m, 0,8m, 1,2m et 1,6m et des distances de lm, 2,5m, 5m, 10m, 15m, 20m, 25m et 50m d'un chne adulte enracin sur les argiles du Lias, d'ge jurassique infrieur. Alors que le mouvement tait vident pour tous les points de mesure, il tait le plus prononc des distances de l'arbre infrieures 5m o une diff-rence saisonnire de mouvement de 63mm a t enregistre 0,4m de profondeur en 1995, comparer avec seulement 14mm la mme profondeur mais une distance de 10m dernl'arbre. L'influence de l'arbre sur les proprits gotechniques des argiles liasiques est souligne.