للكاتبين
*Zeid Thabet Youssef , ** Ali A.S. Taleb
* Faculty of Engineering Emirates University of Aden, Aden-Yemen
** Hyder Consulting , Abu Dhabi, United Arab
ABSTRACT
Microtunnelling in soft soil may lead to ground surface settlement causing damage to structures,
existing roads, services and utilities. The present case study investigates the effectiveness of
preventive measures adopted to minimize ground surface settlement to within the permissible limits by
road authority of Abu Dhabi Municipality. The preventive measures undertaken include the use of
appropriate microtunnelling machine equipped with slurry system, continuous lubrication to the drive
during the microtunnelling to minimize the jacking force and the over cutting space between pipes and
soil media, immediate sealing to the gab between the pipe and soil after completing each drive,
maintaining continuous round the o’clock drive and minimizing the break time required to the
installation of subsequent pipes. For this purpose three microtunnelling drives of different lengths and
at different levels crossing beneath the existing roads were selected. Road surface movements above
each drive were monitored before, during and after completion of the tunneling works. The difference
in the levels was calculated, presented in graphical forms and discussed. The recorded values were
also compared with the calculated maximum anticipated settlement available in the literature. The
results have shown that the recorded road surface settlement for all drives falls within the allowable
settlements of 6.0mm.