Full Scale Experimental Study On Pile Supported Reinforced Embankment Of Ballastless Track In High Speed Railway

Geo-grid reinforced pile-supported embankment has the merits of rapid construction, small lateral displacement, and small after-construction deformation. It has been increasingly employed in the construction of high-speed railway in China. It is rather complicated for the function mechanism of pile-supported geogrid-reinforced embankment. Soil arching and reinforced mechanism of geogrid are the two key problems for pile-supported geogrid-reinforced embankment.In this paper, a full-scale experiment on high-speed pile-supported geogrid-reinforced embankment is conducted for the study of soil arching and reinforced mechanism of geogrid. An advanced loading system is equipped to the model test, which could simulate the train moving loads with a largest speed of360km/h. Water bags are distributed around the pile caps to model the subsoil and the settlement of the subsoil is modeled by the vertical deformation of the water bags. To measure the distribution of earth pressure in the embankment, earth pressure cells are arranged at different heights of the embankments over pile cap and subsoil. FBG sensors and distributed optical fibers based on PPP-BOTDA are employed to measure the tensile force of geogrid under different conditions.Soil arching under static condition is the base of studying soil arching. In this paper, soil arching under static condition is studied through embankment construction, static loading on the embankment and subsoil consolidation. The development of soil arching and earth pressure distribution under theses three conditions is analyzed. The transferring law of static loads in the pile-supported reinforced embankment is also analyzed. At last, the model test results are compared to the calculated results by three typical calculation methods. The comparison results show that the soil arching calculation methods all have their own application.The embankment would be suffered from the action of dynamic loads when it is under service. Train moving loads are generated to the model embankment by loading system. The development of soil arching and the dynamic stress distribution in the model embankment is studied. The influence of soil arching on dynamic stress distribution in the embankment is analyzed. At last, according to the model test results, a calculation method for dynamic stress in pile supported embankment is put forward.The reinforced behaviors and mechanism of geogrid is studied through the analysis of model test results. The tensile force distribution of geogrid under different conditions is analyzed. And the model test results are compared to the calculated results according to the current calculation methods.Finally, according to the dynamic stress calculation method and development mode of accumulative settlement of pile, a design method for controlling accumulative settlement of piles under embankment is put forward. And based on the practical engineering, the calculation method is calculated and analyzed.