Study On DJM Piles Used In Jing-Zhu Freeway In Hubei Province

The freeway in China has increased greatly since more than ten years ago, especially since 1998.Nowdays, the total length of it is near to 20,000 km, ranking second in the world, though it is until 1988 that the first freeway with 18.5 km was not built. How to strengthen soft ground in most freeway project is a common problem, which is difficult to resolve. A lot of methods have been used effectively by engineers in dealing with the problem of soft earth to economically have the possible settlements of the pavement be less than the permissible ones inscribed in the specifications. DJM(Dry-Jetted Method) Pile is one of them..It has been proved in practice that the road overlaid on soft ground strengthened by DIM Pile has a less settlement after construction, but the cost is relatively bigger. Therefore, this method is commonly used only to enforce the soft ground beneath embankment near to bridges, beneath culverts, or underpass structures. When DIM Pile is applied in work of a freeway project, it is conducted as a study issue, because both the theory about it is not very clear now and also the quality control is hard to demonstrate, in addition, there is a big difference among soft soils in different areas on the distribution, the ingredient of minerals and the physical and mechanical properties.There are several sections of Jing-Zhu(Beijing to Zhuhai) Freeway on soft ground. In these sections, the soft ground under embankment close to bridges and some culverts are strengthened with DIM Piles, and a good result has got. The writer, as a representative of employer in responsible for this work, took part in planning, conducting and inspecting it from beginning to end. An introduction of this work is given in this paper. The focus is on description the aspects of design and construction of DIM Piles used in the part of Jing-Zhu Freeway at Dong Xi Hu, Wuhan, Hubei. An detail analysis of the observed settlement is also presented.