Model Test Of Geogrid-Reinforced And Pile-Supported Embankment On Soft Ground Of Chaoshan Railway Station

Geogrid-reinforced and pile-supported embankment has been widely used in treatment of soft ground in the world for its perfect treatment,easy construction and highly cost-effective. In this dissertation, based on the prototype of treatment engineering for wide deep soft soil of ChaoShan station of Xiamen-Shenzhen railway, bearing property and mechanism of geogrid-reinforced and pile-supported embankment were studied by model test. The contents and results are showed as follows.(1)Status of research and application of geogrid-reinforced and pile-supported embankment in the world was outlined, and deficiency of model test was pointed out.(2)Definitions of soft soil in various domestic professions or departments were generalized. According to geological investigation, distribution of soft soil under ChaoShan railway station was discussed. The characteristics of soft soil, such as the high water content, the high void ratio, the high compressibility, the strong structure, the low permeability, the low shear strength and, the low deformation modulus, was elucidated.(3) According to the similarity theory of model test, a program of the model test was designed and the model test was carried out. Using the data obtained by the test, correlation curves were drawn and conclusions were shown as follows:①Axial force rises as increment of embankment load, varieties in different layer of soil, The maximal axial force appears in the segment of pile surrounded by silt.②As depth of pile increasing, skin frictional force on the pile is negative at top of the pile and turns to be positive at a certain depth.③Corresponding to each level of load, pile-soil stress ratio and pile efficacy both show ascents, tend to be smooth or decrease slightly until applying the next level of load. Closer to later part of load applying, margin of the ascent is smaller.④As increment of embankment load, whether settlement at top of the pile cap or settlement at top of the ground soil increases gradually, and the latter is greater than the former while settlement at top of the ground soil between two piles is greater than that among four piles.⑤As increment of embankment load, tensile strain of the geogrid increases gradually, the rate is slow initially and quick later. The maximal strain of geogrid locates at geogrid on top of the pile cap; the second largest strain of geogrid locates at geogrid between two piles; and the minimal strain of geogrid locates at geogrid among four piles.⑥As pile spacing increasing, the greatest axial force of pile rises; negative skin frictional force of pile decreases compared with positive skin frictional force of pile increases; pile-soil stress ratio rises significantly while pile efficacy rises indistinctly; differential settlement between pile and soil decreases slightly; function of geogrid coordinating deformation of geogrid-reinforced and pile-supported embankment reduces.