Tied-Back Excavations in Alluvial Soil of Taipei

In this paper we present monitored results of three tied-back excavations carried out in the alluvial soil of Taipei. All three cases involved large excavations and were supported by a diaphragm wall and multilevel tieback anchors. Based on the anchor loads measured during excavation, the apparent lateral pressure diagrams are calculated following Terzaghi and Peck’s method. It is found that the apparent lateral pressures increase approximately linearly with the depth. As the excavation reaches its final depth, the apparent lateral pressure diagrams tend to converge for the cases studied here. The measured lateral pressure diagrams for these tied-back excavations are close to the summation diagrams of groundwater pressure and lateral pressure calculated from the method of Terzaghi and Peck in 1967 or Tschebotarioff in 1973 for sandy soil but with a minor difference. The dominant sandy soil layer and groundwater pressure played a major role in determining the anchor load diagrams. The measured lateral wall movement for these tied-back excavations is found to be similar to that of cross-lot braced excavations in alluvial soil of Taipei both in magnitude and in profile.