Reinforcing Mechanism Of DJM Composite Foundation And Application On Petrol Storeroom Of Da Xing Port Engineering Project

With the development of national economy, It is so urgent to achieve project on bed foundation. In tbe same time, it is harder to get the foundation suitable to upper building by increasing load-bearing capacity of basement and decreasing settlement of ground. With the criticism sharply, more and more foundation treatment method appears. Among which DJM is widely used in domestic project because of its quick affection and good economical benefits.This paper discusses detail information of forming condition, reinforcing mechanism and applicable condition of DJM (Deep Jet Mixing of Dry Cement-soil Method) composite foundation. It also introduces design and calculation of single pile axial bearing power and composite foundation of dry cement-soil column, as well as check of substratum and several checking methods of sedimentation of composite foundation of dry cement-soil column. This paper gives a summing-up of designing steps of composite foundation of dry cement-soil column.Using an petrol storeroom of Da Xin port engineering project as example, the paper introduces overall designing, choice of construction method, construction technology and construction issues that needs attention. The quality detection of composite foundation was performed on the construction site. Methods being used include: low strain reflectivity dynamic testing of piles, static load test, lab test , Single pile axial bearing power, .... etc. An overall system analysis was given on the dry cement-soil column quality detection result in the aspects of pile body integration, bearing power and sedimentation, and it proves that the construction quality meets the requirements. However, from the actual bearing power point of view, it can bearing much more than the designed bearing power, and the actual quantity of sedimentation and differential settlement are smaller than the designed limitation. Thus, from the quality checking result, we can see that the construction design did not take advantage of the composite foundation, which caused unnecessary waste. In the field of the composite foundation design, it is a trend to use the combination of long and short pile composite foundation design, varied parameter composite foundation design, low load pile composite foundation design, combined material concrete design etc based on the economy efficiency, society efficiency, environmental efficiency and the overall efficiency for different geologycondition. It is our continuous effort to explore and research the construction technology of the composite foundation and quality detection.