Stability And Strengthening Test Research Of High Fill Abutment Soft Foundation For Cangzhou Section Of Coastal Freeway

Soft soil widely distributed in coastal wetlands, inland plain and mountain area in Hebei Province, which brought bad affect for freeway construction as its engineering geological properties of high water content, high void ratio, low permeability, high compressibility and low shear strength. Especially with the planning of freeway development layout in Hebei Province in 2020 is beginning, soft soil engineering is becoming the key problems of constrained freeway development.The Cangzhou section soft soil foundation of coastal freeway in Hebei Province is studied in this paper, and the correlation equation of physico-mechanical properties indexes in this soft foundation is established. On this basis, the stability of soft foundation is calculated and the sections which don't meet the stability requiremet are controled by diaphragm wall. At the same time, the stability of the coastal highway sections in filling stage and operation are calculated and the influence of water and earthquakes are analysised. The following conclusions can be obtained through the above research:(1) The stability factor of embankment is between 1.127～1.666 from stability calculation about coastal freeway. To ensure the safe use of embankment, the safety factor is F>1.3. The sections which don't meet the stability requiremet are controled by diaphragm wall.(2) The existence of diaphragm wall can cause redistribution of stress in internal and external side soil, which can effectively prevent the foundation soil settlement and lateral sliding in filling stage and operation. At the same time, the diaphragm wall has certain inhibitory effect for soil creep, where it could improve the foundation capacity and ensure the safe of embankment filling and operation. (3) The influence of groundwater on the soft ground are physico-mechanical properties indexes of soft foundation is reduceing and the seepage has bad impact on embankment stability. However, due to the poor permeability of diaphragm wall, N the seepage need to bypass the diaphragm wall. Seismic activity will also greatly reduce the safety performance of the foundation, so that the foundation would be destroyed. Thus the construction of embankment and groundwater need to be considered when the impact of the earthquake.