Correlating EPB Chengdu Metro Settlement Data with Analysis Predictions in Sandy Cobble Stratum

摘要

Construction in urban areas, e.g., excavation, can generate negative impacts on the foundations of surrounding structures. In this study, based on the surface subsidence measurements due to earth pressure balance shield (EPB shield) tunneling in Chengdu Metro, displacement back-analysis was conducted for a typical cross section using the Peck formula and the stochastic medium theory. The engineering properties of a sandy cobble stratum in the Chengdu area, the settlement trough width (ⅰ), stratum loss rate (η), settlement trough effecting angle (β), and cross section contract value (AR) were analyzed statistically, and the ranges of these parameters under normal working conditions were corrected as: for the stochastic medium theory, tanp=1, AR=16mm (lower limit), and tanp=1, AR=5mm (upper limit); and for the Peck formula, k=0.3, η=0.9% (lower limit), and k=0.6, η=0.3% (upper limit). Comparison of the Peck formula and the stochastic medium theory formula, although composition and principle differ, show that the two methods can both be applied to the prediction of surface subsidence caused by tunnel excavation of sandy cobble formation through statistical experience, parametric inversion, and example verification.