Djm Applications And Research In The Jiangyin Port Railway Soft Foundation Treatment

Powder-spray pile has been commonly used in soft ground as a reinforcement technique.Due to advantages of low pollution, simple construction, short construction periods, low cost, it has been the more and more widely applicated in railway construction. Based on powder-spray pile soft foundation treatment engineering in the test section of Jiangyin harbour railway roadbed, research of pile composite foundation technology was carried out. Main contents are as follows:Based on the reinforcement mechanism of cement-soil and the work mechanism of composite foundation,the mechanism of application of powder-spray pile for reinforcement of soil was expound. The composite foundation design ideas, the content of calculation and requirements of the engineering geological survey were systematacially summaried and expound.To determine reasonable cement mixing ratio of powder-spray pile in the actual engineering, the main influence factors for soil-cement strength were studied through cement-soil mix proportions test. It was shown that the strength of cement-soil had two main factors of cement incorporation and age. The single pile bearing capacity was studied by single pile load test. The single pile ultimate bearing capacity was calculated using the hyperbolic method, the bearing capacity was evaluated analyzed. Through on-site load test,the bearing capacity of composite foundation was studied. The relation curve of composite foundation settlement and the load were obtainted and the bearing capacity of composite foundation of this project was determined applied the rebound method and the relative deformation method.The samples from drilling core of pile were used to carried out the unconfined compressive strength tests. It was shown that powder-spray pile strength discreased with the depth, but the strength could satisfy the design requirement. It was verified that the design method and the value of parameters were reasonable and reinforcement effect of powder-spray pile in test section was good. The six sections in the test section were selected and embankment settlement observations of were performed, the relation curves of load-settlement-time were obtained, the settlement development law of the powder-spray pile composite foundation was explored and the post-construction settlements were forecasted by exponential curve method and the hyperbolic method. It was showed that construction settlements and post-construction settlements were sall by measured and predicted results,settlement could satisfied design reqirement. Three-dimensional model for natural soft foundation and composite foundation were established by the finite difference software FLAC3D, the calculated embankments settlements of natural soft foundation and composite foundation were comparatively analyzed in the process of filling. Finally based on above jobs, the worthful studys of the subject were putted forward.