Monitoring Of Geogrid-Reinforced And Pile-Supported Embankment On Soft Ground And Settlement Prediction In Chaoshan Railway Station

Geogrid reinforced and pile-supported embankment is a new technique for foundation treatment developed in recent years. Compared with traditionnal techniques, it has numerous advantages in the reduction of the total and differential settlement, the control of the settlement after construction, the economical investment,etc, so it was widely used especially on soft ground.In this dissertation, through field monitoring on super-vast and deep soft ground in ChaoShan railway station, mechanisms and foundation settlement of geogrid reinforced and prestressed concrete pipe pile-supported embankment are researched. The main contents and conclusions are as follows:(1) Analysis are made on datas collected by field monitoring including the stress of pile and soil, the pore water pressure, the axial force of pile shaft, the layered settlement of the foundation, the strains of the geogrid and the lateral displacement, the conclusions are as follows:①The stress of pile and soil increase with the height of the embankment fill, in the middle and later period of the construction of the embankment, the increase of the soil stress on the top of the pile is far greater than that on the soil between piles.②The pore water pressure has frequent fluctuations, and the dissipation of the excess pore water pressure is slower in soft soil layer.③With the neutral point as a dividing point, the axial force of pile shaft shows a trend from ascent to descent along the depth, there is negative skin friction within certain depths along the pile.④The layered settlement of the foundation basically grows with the height of the embankment fill.⑤The strains of the geogrid increase with the height of the embankment fill, the strains of the geogrid on the soil between piles are lager than those on piles'.⑥The value of the lateral displacement is minor in general, it mainly focuses at about twenty meters below the ground.(2) Based on the the settlement datas of the representative magnet in the typical sediment-tube, the final settlement of the foundation is predicted with hyperbola method,exponential method,three point method and grey system method respectively. The final settlements of the second section predicted with the four methods are 132.130mm,124.810mm,125.140mm and 125.470mm respectively, the third section's are 220.840mm,218.820mm,218.690mm and 215.670mm respectively. The coefficients and the final settlements predicted meet the criteria for railways.(3) Based on the settlement datas of the representative magnet in the typical sediment-tube, the average consolidation degree of soil is calculated, and the process of the ground consolidation is analyzed briefly. The calculations show that the most settlement of the soft ground treated with geogrid reinforced and pile-supported embankment accomplishes during the construction of the embankment, which guarantees the settlement after construction being within the control standards.