Characteristic Analysis For Pile And Soil Stress Of Composite Foundation Under Station Embankment Load In Jinan West Railway Station Of Beijing-Shanghai High-speed Railway

CFG and PHC pile composite foundation are widely used in ground treatment for passenger dedicated line engineering. These composite foundation owns technical and economical advantages over other methods, for example convenient alternating construction, little post-construction and differential settlements fair consolidation, deep depth of ground improvement, high load capacity and savings of construction time and costs. Station subgrade is different from other common line Subgrade. Analysis for pile and soil stress of Composite Foundation under Station Embankment Load in Jinan West Railway Station of Beijing-Shanghai High-speed Railway has important significance on distributing load between pile and soil, and controlling settlement. It also has positive meaning in designing station subgrade of High-speed Railway in future. Based on subgrade field test research of Jinan West Railway Station, variation and distribution law of strss of pile and soil, and pile-soil stress ratio is studied via field test and numerical simulation. The main conclusions are follows:Firstly, earth pressure cells are placed on top of piles, caps and soil around piles to measureing stress. Pile and soil stress and its stress ratio variation law during embankment reclamation were obtained after analysising result of measurements. The main contents are follows: (1) It is obtained that the growth rate of strss on top of piles is lower than that on soil around pils when the embankment height is below about 1.2-1.5m. Contrarily, growth rate of strss on top of piles is higher when the embankment height is above 1.2-1.5m. Stress of pile caps has the same growth rate uring embankment reclamation. (2) Stress of piles increases with increasing pile length under same embankment load. This tendency shows obviously with increasing embankment load. Peak value of pile stress decreases form center of subgrade to lateral side. Pile stress at transition region of pile length has a sudden change. Soil stress at at transition region of pile length is lower than other regions. (3) Construction mode and consolidation time have a low effect on pile-soil stress ratio. These factors need not be considered when designing. (4) Pile-Soil Stress Ratio increases with increasing pile-soil settlement difference. Pile-soil settlement difference is a reason for this increasing. Secondly, a model of pile composite foundation is established by adopting plane strain FEM through ANSYS FEM software. Then a study on the factors affecting pile-soil stressratio of composite foundation has been done. The factors mainly include load level, pile-soilrelative stiffness, cusion thickness and module, pile whether with cap. The relationship between each influence factor and pile-soilstress ratio is given by the simulative results and the reason is analysed.Finaly, reinforcement mechanism of pile composite foundation and Function of cusion and pile caps is summarized in this dissertation based on field test and numerical simulation. Soil arching effect is verified.