Although reliable and accurate prediction of ground movement has taken an essential role for economy and safety of major construction projects, it is known that current techniques for evaluation of soil properties and design procedure are showing considerable lack of accuracy when compared with the site instrumentation results and its main reason is attributed to misunderstanding of soil behavior under working load conditions. In order to reduce the discrepancy between the prediction and the instrumentation results in ground movement, this study has proposed an analysis procedure for ground and wall movement in deep excavation case considering small-strain nonlinearity of soils.
In this paper, the concept of nonlinear small-strain behavior of soils is reviewed and its evaluation techniques in both lab and field are described. And it was shown that the maximum shear modulus by downhole test and the normalized shear modulus reduction curve by resonant column test can be combined successfully to represent stiffness variation of soils in small-strain range. Also, procedures for interpretation, error correction and application in numerical analysis of field instrumentation results by inclinometer, pore pressure gauge, total earth pressure cell and steel strain gauge are explained and their reliabilities are verified using numerical parametric method. Numerical analysis is done using not only currently used methods such as subgrade modulus analysis based on SPT N value and linear finite element method, but also nonlinear finite element method which includes material nonlinearity of soil using methods proposed in this paper. As a result of series of numerical analyses, it was revealed that nonlinear finite element method using small-strain stiffness variation gives the best fit with the field instrumentation results when combined with consideration of confining pressure. And, when the load was applied directly on the wall instead of using gravity load on soil mass, exclusion of outer soil mass gave better result. Finally, it was shown that the coefficient of horizontal earth pressure is reduced to a value of active earth pressure, and strength and stiffness of concrete slurry wall are smaller than those of test specimens.
