The Application And Study Of Gravel Columns Pile In Ground Treatment

When the natural foundation can't meet the requirement of engineering construction, we must adopt some measures, one of which is to reinforce the foundation. There are many methods of foundation treatment in common use. According to the principle of reinforcement, they can be divided into the compaction method, displacement, composite foundation, adding tendons and grouting etc.. Each kind of methods has different principle of reinforcement and field of application. Gravel columns pile foundation, a complex foundation of incompact material pile, has such engineering characters as reducing subsidence, increasing bearing capacity, reforming drainage and improving shearing strength. It also has pile effect, buffer effect, drainage and decreasing pressure effect, packing dense body effect and reinforcement bar effect. The five effects above make gravel columns pile foundation have much potential and more flexible in the fields of increasing foundation bearing capacity, amending transformation, decreasing latent subsidence and uneven subsidence owing to burden impact, reforming liquefaction ability. The author generally introduces the reinforce mechanism of liquefaction resisting of gravel columns pile complex foundation and depict compaction, drainage, decompression and decouple of gravel pile in details. It also specifies the destroy mode of gravel. Based on the destroy mode, the author analyses bearing capacity calculation of single pile and complex pile foundation. It suggests adopt the formula recommending by Technical code of ground treatment of building (JGJ79-2002) or modifying equation on the basis of Brauns theory for calculation. Taking 12# building engineering in Clear Water Gulf and the River Shore Garden as examples, it represents the design, construction and monitoring of gravel columns pile foundation, evaluates the double effect of improving bearing capacity and erasing liquefaction in practical engineering. The main point is to discuss the problems be paid attention to in treating the liquefy soil layer by construction of sinking tube pack gravel columns pile. Though theory analysis and practical engineering , we conclude thefollowing points: 1.To reinforce the liquefaction layer foundation by using the treatment method of sinking tube pack gravel columns pile, it can get to the expected achievement of erasing liquefaction and subsidence and increasing bearing capacity of foundation. It's regarded as a feasible and economic method. 2. By using the gravel columns pile to handle the liquefaction foundation, lowering the liquid index number is valid. Generally, the gravel columns pile in order to raise the bearing capacity of the weak soil, can attain eliminating or reducing the liquefaction at the same time. 3.The gravel columns pile is classified as crowded soil pile. In order to prevent the chaos and un-formation of piles, we suggested construct piles from exterior to inside and twist to the center. This is different from traditional construction of crowded soil pile. 4.To use the gravel columns pile for reinforcement of foundation, the effect lies on the amount of gravel columns, namely the filling coefficient must satisfy the design requirement. In actual engineering, we should combine with the project condition and determine the constructiontechnology by testing. To guarantee the construction quality, the filling coefficient should be satisfied. 5.To reinforce the potential liquefaction soil, it has to adopt the repeated and reversal pile driving to make the filling coefficient satisfied and insure the quality of projection.