Comparison of excavation-induced wall deflection using top-down and bottom-up construction methods in Taipei silty clay

This paper compares the excavation-induced wall deflection caused by the top-down method (TDM) and the bottom-up method (BUM). First, a total of 26 quality excavation case histories in Taipei silty clay were collected and analyzed. The field observations show that the maximum lateral wall deflection (delta(hm)) induced by the TDM were 1.28 times as large as that induced by the BUM. Factors affecting wall deflection are investigated and four of them are selected for further numerical experimentation to investigate the discrepancy of delta(hm) caused by the two methods. Analysis results showed that the average ratio of delta(hm) induced by the TDM over that induced by the BUM is approximately equal to 1.1, excluding the effect of thermal shrinkage of concrete floor slabs. Both observed data and analysis results revealed that greater delta(hm), is generally induced by the TDM despite its use of floor slabs with higher support stiffness. (C) 2008 Elsevier Ltd. All rights reserved.