Study Of Pile-Soil Interaction Of Soldier Pile Retaining Structure In Nanning Tertiary Mudstone

Tertiary mudstone mainly exposes in the northeastern part of the Nanning basin, including mudstone,silty mudstone,muddy siltstone and so on. Mudstone with characteristics of significant swelling, dehydration shrinkage is a typical swelling rock. Extensive research have been carried out by domestic and foreign scholars, and for the pile-soil interaction of supporting structure in expansion area is rarely reported.Based on foundation pit supporting pile of Nanning subway station, field monitoring and finite element numerical simulation analysis are utilized to research the characteristics of Tertiary mudstone by collecting and analyzing the research data of Nanning basin Tertiary expansive mudstone, obtaining the following conclusions:(1)Soil pit wall horizontal movement, soil stress releasing and pile earth pressure decreasing are found in pit Excavation, and earth pressure value is between the active earth pressure and the earth pressure;(2)There is a close relationship between changing of earth pressure and deformation of supporting pile;(3) The values of measured soil pressure is smaller than Rankine’s earth pressure;(4) The value of pile soil pressure rebound increasingly after excavation of the main structure, most of the earth pressure is greater than or equal to the static earth pressure;(5) Influenced by the atmospheric environment, the soil expansion shear caused by slow expansion of pile soil in the whole process of the foundation pit construction rises supporting pile which stops at the time of the construction of base plate and the plate, the rising value is quantity of the soil around pile;(6)With the analysis of excavation by MIDAS/GTS in which the impact of the expansion force is simulated by the additional horizontal earth pressure generated by uniform load, pile lateral soil pressure curve is a set of parallel curves when horizontal expansion force is40kPa,80kPa,120kPa,160kPa. The increasing of expansion forces significantly increase internal force and deformation of retaining pile.