Abstract: Although elastic beam-spring models are commonly employed to predict wall deflections in deep excavations, most existing models neglect the stiffness hardening behavior of soil. Moreover, the determination of model parameters heavily relies on laboratory tests, along with the inevitable errors due to sampling disturbance. To address these limitations, this study introduces an enhanced elastic beam-spring model that incorporates non-limit state earth pressure and soil stiffness hardening. A novel CPTU-based analytical approach is then proposed to estimate wall deflections in deep excavations by correlating in-situ piezocone penetration test (CPTU) parameters with the model inputs. The validity and accuracy of the proposed approach are confirmed through comparison with previous centrifuge test data. The proposed approach is further applied to a deep excavation project in the soft soil deposits of Taihu Lake, where the CPTU-based predictions show good agreement with field measurements. In contrast, solutions derived from laboratory tests overestimate the wall deflections, likely due to underestimated soil stiffness caused by sampling disturbance. This discrepancy underscores the practical advantages of the proposed CPTU-based approach. Finally, the influence of excavation depth, Young’s modulus of soil, stiffness of retaining structures, and strut stiffness on maximum wall deflections is explored through the proposed approach.

Key words: deep excavation, wall deflection, piezocone penetration test (CPTU), soil stiffness hardening, elastic beam-spring model