Modeling the effect of ground improvement on reducing movement during bermed excavation in clay

Abstract

To evaluate the effect of ground improvement on bermed excavation induced soil movement in clay, a 1‐g model test is proposed while keeping the base stability number (= γH/su ) equal to the full scale excavation in the field. The undrained shear strength of soil used in this model test is reduced according to size reduction from the prototype to the proposed model test. To verify the suitability of model test results, a three‐dimensional explicit finite difference program is adopted to perform numerical analyses for deducing the relationship between prototype and the proposed model test. In addition, a field case is compared with this model test. By comparing ground surface settlement associated with different ground improvement layouts, the buttress type arrangement has shown a better effect on controlling bermed excavation induced surface settlement than the column type arrangement. It is found that an increase of improved zone dimension will show more significant impact on reducing soil movement than an increase of improved soil's shear strength. Finally, apparent shear strength of buttress or column type improvement is determined by an empirical equation in terms of the unconfined compressive strength of treated material and the undrained shear strength of in‐situ clay.